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Bird behaviour, the ‘deep time’ perspective

The views expressed are those of the author and are not necessarily those of Scientific American.

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The behaviour of long-extinct animals remains an area of major public and scientific interest – the great perennial problem being that we’re always massively constrained, if not crippled, by a frustrating lack of data. Think of all the things we want to know, versus the things that we actually do know. In a paper recently published in Journal of Zoology, I aimed to review what we know about the behaviour of fossil birds (Naish 2014).

Composite cladogram of Avialae - topology and names based mostly on Yuri et al. (2013), and with many lineages excluded for reasons of space – showing where the fossil record gives us key insights into behaviour. From Naish (2014): this diagram is a much-updated version of the tree published in Naish (2012). The name Insolitaves has been applied to the wrong branch, whoops.

Simply knowing about the behaviour of fossil animals is neat and interesting. It allows us to better imagine the daily lives and lifestyles of given species, and thus firm-up hypotheses about their ecology, the timetables of their lives, and the selection pressures that might have acted on their evolution. But it can also give us hard data on the antiquity or novelty of given bits of behaviour, and indicate which behaviours were inherited from ancestral groups, and which were or are specific to certain groups. It is often astonishing how little we know. Conversely, there are areas where key pieces of evidence, or key analyses, can allow us to make fairly detailed statements.

‘Form leads to function’… except where it doesn’t

Where do we start in reviewing a subject as broad as the behaviour of fossil birds? (and keeping in mind that I’m keen not to re-write the paper I’m talking about). To start with, basic indications as to a fossil bird’s ecology and lifestyle can of course be determined by looking at its anatomy, the basic tenet ‘form leads to function’ being an important guiding principle. So, if we look at a fossil bird that combines long limbs with a long, slender bill (both sets of features resembling those of modern wading birds), we can reasonably assume that the bird was an aquatic forager; if it has both a reinforced, strongly curved rostrum and enlarged, strongly curved foot claws, it was almost certain raptorial, and so on.

Anatomical features present in fossil birds allow us to make inferences about behaviour. (a) Probable wading stem-flamingo Juncitarsus; (b) potoo-like Paraprefica; (c) marine, pseudo-toothed Pelagornis; (d) vertebrate predator Phorusrhacos; (e) slender-billed forager Rhychaeites; (f) icterid-like gaper Chascacocolius (surprisingly, a mousebird). Images not to scale. From Naish (2014).

Compared to many animal groups, birds are relatively well studied, and a huge amount of work has been done on how their proportions and skeletal and soft tissue anatomy correlate with specific lifestyles and ecologies. This whole field is termed ecomorphology and enough is known about ecomorphological correlations in living birds (e.g., Baker 1979, Leisler 1980, Leisler & Winkler 1984, Miles & Ricklefs 1984, Winkler & Leisler 1985, Bairlein et al. 1986, Miles et al. 1987, Carrascal et al. 1990, Hertel 1995, Piersma et al. 1998, Barbosa & Moreno 1999, Nebel et al. 2005) for us to say very specific things about ecology and lifestyle when enough is known about mass, proportions, wing-loading, and about bill, wing and hindlimb anatomy, and so on. Consider that ornithologists can say, for example, that a given bird is not just an insectivore, but that it’s a forest-adapted insectivore that forages for small insects at and underneath branch tips (Carrascal et al. 1990).

The gigantic Paleogene galloanserine Gastornis (= Diatryma) nicely illustrates some of the problems we have when fossil taxa lack extant analogues. Was it an arch-predator, scavenger, nut-cracker, folivore, frugivore, or some combination of these things? Photo by Darren Naish.

Alas, when it comes to fossil taxa, a number of problems erode our confidence. Firstly, some fossil taxa possess anatomical features that don’t precisely resemble those of modern ones, or possess unusual combinations of features not present within living species. The large-bodied, flightless gastornithids of the Eurasian and North American Paleogene and the Australian dromornithids or mihirungs of the Paleogene and Neogene, for example, differ from extant birds in combining robust hindlimb bones with deep, massive crania. As you’ll know if you’ve followed the literature on these birds, there has consequently been much disagreement as to whether they were arch-predators, bone-cracking ‘hyaena-birds’, dedicated herbivores, or omnivores that did a bit of everything.

Secondly, we’re often missing key bits of information when it comes to the anatomy of fossil species. We might be looking at the shapes of the skull bones, for example, while lacking the all-important rhamphotheca; likewise for claws where the keratinous sheath is absent or incomplete.

Anatomy is not destiny. With only bones to go on, would we know that Gypohierax (image by Hans Hillewaert) is predominantly frugivorous, or that Cinclus (image by Mark Medcalf) is an aquatic forager? Apparently not. Gypohierax image licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license; Cinclus licensed under Creative Commons Attribution 2.0 Generic license.

Thirdly, the ‘form leads to function’ tenet is not always as reliable as we might like. Some living animals do things that we almost certainly wouldn’t predict if we only knew of them from their bones. My favourite examples come from the world of armadillos (Smith & Redford 1990) and fruit-eating crocodylians (Brito et al. 2002). And there are quite a few examples of this sort of thing within birds. The Palm-nut vulture Gypohierax has a predatory bauplan but is almost exclusively frugivorous [adjacent image by Hans Hillewaert]; dippers (Cinclidae) routinely practice aquatic behaviour yet apparently reveal no trace of this in the skeleton [adjacent image by Mark Medcalf]; and several auks nest in trees yet appear anatomically ill-suited for perching or indeed frequenting trees at all.

Despite these problems, people have of course used data on proportions and inferred wing-loading and so on to make a huge number of inferences about the behaviour of fossil birds (e.g., Brathwaite 1992, Hertel 1995, Hopson 2001, Noriega 2001, Elzanowski 2002, Worthy & Holdaway 2002, Tambussi & Hospitaleche 2008, Hinic-Frlog & Motani 2010, Wang et al. 2011; Nudds et al. 2013).

Feeding behaviour and dietary preferences

How might we confirm the predictions about lifestyle and ecology made based on anatomy? Stomach and gut contents provide pretty good answers: I tabulated all the examples I was aware of at the time of submission (Naish 2014) (needless to say, new specimens have been published since, including Piscivoravis from the Jiufotang Formation of China).

Stomach contents show that the long-tailed Cretaceous bird Jeholornis ate seeds (or, rather, fruiting bodies that contained seeds). Reconstruction by Matthew Matyniuk, used with permission.

Many fossil birds with stomach or gut contents confirm the ideas already arrived at on the basis of anatomy: there are hesperornithines and fossil loons with fish remains in their guts, and numerous moa with leaves and twigs in their stomachs, for example. Mesozoic birds – conventionally assumed to be faunivorous animals that preyed on arthropods and fish – have proved more diverse in diet and ecology than previously thought (Naish 2014), however, with evidence for seed-eating and sap-eating known in addition to faunivory.

Among Paleogene crown-birds, early members of some living lineages seem to be very different from the modern species: Eocene rollers were seemingly omnivorous or herbivorous whereas living ones are mostly faunivorous, for example, while Strigogyps – apparently a Middle Eocene member of the seriema-phorusrhacid clade – preserves evidence of a plant diet, a surprise in view of its affinities.

FEA analysis of the Andalgalornis skull (at far left) compared to that of living sea eagles and seriemas. From Degrange et al. (2010).

Additional support for behaviour comes from the bones of prey species damaged by vultures and eagles, and shells transported in the bodies of seabirds. We can also say things about the behaviour of fossil birds based on the functional studies that have been done: work on limb-bone strength in moa and phorusrhacids provides insight into locomotory abilities and perhaps (in the phorusrhacids) predatory behaviour. Finite element analysis of the phorusrhacid Andalgalornis allowed Degrange et al. (2010) to devise hypotheses about how this animal tackled prey.

There are also fossil feeding traces, some of which indicate modern-style dabbling and sediment probing occurring as far back as the Paleogene and even Early Cretaceous. The idea that we might detect the ecology and feeding behaviour of certain extinct birds by looking at the plants and animals they co-evolved with – the idea that we are sometimes seeing the ‘ghosts of predators past’ – was covered in the recent Tet Zoo article The ‘ghosts’ of extinct birds in modern ecosystems. As you might have guessed, the text that appeared in that article was excised from the submitted manuscript that became Naish (2014). The submitted manuscript was more than twice as long as allowed, so I had to axe a lot of material.

Display, combat, vocalisation

Finally, what do we know about the social and reproductive behaviour of fossil birds? Extravagant structures (like elaborate tail feathers) indicate the presence of sexual display in several fossil bird lineages, including the jeholornithids and confuciusornithids located right at the base of the avialan radiation. The long tail plumes known for confuciusornithids seem to be sexually dimorphic (Chinsamy et al. 2013) (something that some researchers had already been saying for years, and something that had been strenuously resisted by others), suggested social polygyny in these birds. Evidence for intraspecific combat in some fossil birds is strongly suggested by the presence of carpometacarpal spurs, clubs and other structures highly similar to structures used in combat in living species. Hume & Steel’s (2013) analysis of the evidence for combat in the Solitaire Pezophaps solitarius appeared too late for me to include reference to it in the paper.

Long, looping tracheae in moa (this one belongs to Euryapteryx: the looped section alone is c 1 m long) indicate that some of these birds made loud, resonating calls. Image from Worthy (1989).

Long, looping tracheae in some moa and enlarged syringeal bullae in some extinct waterfowl are almost certainly linked with unusual vocalisations in these birds but frustratingly little is known about the distribution and antiquity of the syrinx. Did it evolve within birds, or was it present in older dinosaur lineages? We still don’t know.

Considering what we know of nesting and parental behaviour in non-bird dinosaurs and other archosaurs, we might predict that birds inherited nest-building from their ancestors as well as brooding (perhaps involving substantial male involvement) and precociality among hatchlings. Fossils show that colonial nesting and the creation of scrape-type terrestrial nests were present in Upper Cretaceous enantiornithines (Dyke et al. 2012, Fernández et al. 2013, Naish 2014), but that these stem-birds were unlike modern ones in some aspects of nesting behaviour (they did not turn their eggs, for example).

Where are all the nests?

Living birds are remarkable for the diverse nests they construct, many incorporating vegetation and located in trees. What does the fossil record tell us about the origin and antiquity of arboreal and vegetative nest-building behaviour? Well, pretty much nothing: only a handful of vegetative nests are known, and none (so far as I can tell) come from arboreal settings. A few Eocene and Oligocene nests suggested to be those of ducks have been mentioned or illustrated but not described in any detail. More recently, a mass of twigs and leaves, associated with five eggs, was described from the Miocene of Spain and identified as that of a stem-flamingo (Grellet-Tinner et al. 2012).

Evidence for a large nesting colony of Late Cretaceous enantiornithines comes from Romania in (a) the form of tightly packed masses of eggshell as well as a few near-complete eggs (marked with arrows); (b) reconstruction of the colony by Julio Lacerda, used with permission. From Naish (2014).

It makes some sense that vegetative nests of the sort most abundant in the modern world – masses of twigs and/or leaves, usually located high up in trees – are very rare as fossils, since they have a very low preservation potential. But the fact that they aren’t represented at all seems odd, especially when we consider how numerous nests must have been throughout the history of avian evolution, and especially when we consider how many nests there are that incorporate sediment and are actually quite durable. I mean, shouldn’t the South American Neogene fossil record be full of ovenbird nests, at least?

Part of John Gould's illustration of Vogelkop bowerbirds (Amblyornis inornata), with the large hut-like bower in the background. Will the fossil record ever reveal preserved examples of bird-built structures of this sort? Image in public domain.

On that note, there are several structures made by birds that have high theoretical preservation potential and remain unknown from the fossil record: “Examples include the bowers of bowerbirds, mud nests of ovenbirds, nest cavities of hornbills, giant (sometimes colonial) nests of hammerkops, weaverbirds and monk parakeets, and cache sites of corvids and woodpeckers” (Naish 2014).

Needless to say, as always, there’s lots and lots more that could be said – there’s lots more that’s covered in the paper – but I hope that this brief discussion of some of what we know about the behaviour of fossil birds shows that, while we know something about some areas, there are other areas where we essentially know next to nothing. And that’s annoying.

Several previous Tet Zoo articles have covered some of the subjects discussed here. See…

Refs – -

Bairlein, F., Leisler, B. & Winkler, H. 1986. Morphological aspects of habitat selection of small migrating birds in a SW-German stopover site. Journal of Ornithology 127, 46-73.

Baker, M. C. 1979. Morphological correlates of habitat selection in a community of shore birds (Charadriiformes). Oikos 33, 121-126.

Barbosa, A. & Moreno, E. 1999. Evolution of foraging strategies in waders: an ecomorphological approach. The Auk 116, 712-725.

Brathwaite, D. H. 1992. Notes on the weight, flying ability, habitat, and prey of Haast’s eagle (Harpagornis moorei). Notornis 39, 239-247.

Brito, S. P., Andrade, D. V. & Abe, A. S. 2002. Do caimans eat fruit? Herpetological Natural History 9, 95-96.

Carrascal, L. M., Moreno, E. & Tellería, J. L. 1990. Ecomorphological relationships in a group of insectivorous birds of temperate forests in winter. Holarctic Ecology 13, 105-111.

Chinsamy, A., Chiappe, L. M., Marugán-Lobón, J., Gao, C. & Zhang, F. 2013. Gender identification of the Mesozoic bird Confuciusornis sanctus. Nature Communications 4 (1381). doi:10.1038/ncomms2377

Degrange, F. J., Tambussi, C. P., Moreno, K., Witmer, L. M. & Wroe, S. 2010. Mechanical analysis of feeding behavior in the extinct “terror bird” Andalgalornis steulleti (Gruiformes: Phorusrhacidae). PLoS ONE 5 (8): e11856. doi:10.1371/journal.pone.0011856

Dyke, G., Vremir, M., Kaiser, G. & Naish, D. 2012. A drowned Mesozoic bird breeding colony from the Late Cretaceous of Transylvania. Naturwissenschaften 99, 435-442.

Elzanowski, A. 2002. Biology of basal birds and the origin of avian flight. In Zhou, Z. & Zhang, F. (eds) Proceedings of the 5th Symposium of the Society of Avian Paleontology and Evolution. Beijing, Science Press, pp. 211-226.

Fernández, M. S., García, R. A., Fiorelli, L., Scolaro, A., Salvador, R. B., Cotaro, C. N., Kaiser, G. W. & Dyke, G. J. 2013. A large accumulation of avian eggs from the Late Cretaceous of Patagonia (Argentina) reveals a novel nesting strategy in Mesozoic birds. PLoS ONE 8 (4): e61030. doi:10.1371/journal.pone.0061030

Grellet-Tinner, G., Murelaga, X., Larrasoaña, J. C., Silveira, L. F., Olivares, M., Ortega, L. A., Trimby, P. W. & Pascual, A. 2012. The first occurrence in the fossil record of an aquatic avian twig-nest with Phoenicopteriformes eggs: evolutionary implications. PLoS ONE 7 (10): e46972. doi:10.1371/journal.pone.0046972

Hertel, F. 1995. Ecomorphological indicators of feeding behavior in recent and fossil raptors. The Auk 112, 890-903.

Hinic-Frlog, S. & Motani, R. 2010. Relationships between osteology and aquatic locomotion in birds: determining modes of locomotion in extinct Ornithurae. Journal of Evolutionary Biology 23, 372-385.

Hopson, J. A. 2001. Ecomorphology of avian and nonavian theropod phalangeal proportions: implications for the arboreal versus terrestrial origin of bird flight. In Gauthier, J. & Gall, L. F. (eds) New Perspectives on the Origin and Early Evolution of Birds: Proceedings of the International Symposium in Honor of John H. Ostrom. New Haven: Peabody Museum of Natural History, Yale University, pp. 211-235.

Hume, J. P. & Steel, L. 2013. Fight Club: A unique weapon in the wing of the solitaire, Pezophaps solitaria (Aves: Columbidae), an extinct flightless bird from Rodrigues, Mascarene Islands. Biological Journal of the Linnean Society 110, 32-44.

Leisler, B. 1980. Morphological aspects of ecological specialization in bird genera. Okol. Vögel 6, 119-126.

Leisler, B. & Winkler, H. 1984. Ecomorphology. In Johnson, R. F. (ed) Current Ornithology, vol. II. New York, Plenum Press, pp. 155-186.

Miles, D. B. & Ricklefs, R. E. 1984. The correlation between ecology and morphology in diciduous forest passerine birds. Ecology 65, 1629-1640.

Miles, D. B., Ricklefs R. E. & Travis, J. 1987. Concordance of ecomorphological relationships in three assemblages of passerine birds. American Naturalist 129, 347-364.

Naish, D. 2012. Birds. In Brett-Surman, M. K., Holtz, T. R. & Farlow, J. O. (eds) The Complete Dinosaur (Second Edition). Bloomington & Indianapolis, Indiana University Press, pp. 379-423.

- . 2014. The fossil record of bird behaviour. Journal of Zoology doi:10.1111/jzo.12113

Nebel, S., Jackson, D. L. & Elner, R. W. 2005. Functional association of bill morphology and foraging behaviour in calidrid sandpipers. Animal Biology 55, 235-243.

Noriega, J. I. 2001. Body mass estimation and locomotion of the Miocene pelecaniform form Macranhinga. Acta Palaeontologica Polonica 46, 247-260.

Nudds, R., Atterholt, J., Xia, W., Hailu,Y. & Dyke, G. J. 2013. Locomotory abilities and habitat of the Cretaceous bird Gansus yumenensis inferred from limb length proportions. Journal of Evolutionary Biology 26, 150-154.

Piersma, T., van Aelst, R., Kurk, K., Berkhoudt, H. & Maas, L. R. M. 1998. A new pressure sensor mechanism for prey detection in birds: the use of principles of seabed dynamics? Proceedings of the Royal Society, London B 265, 1377-1383.

Smith, K. K. & Redford, K. H. 1990. The anatomy and function of the feeding apparatus in two armadillos (Dasypoda): anatomy is not destiny. Journal of Zoology 222, 27-47.

Tambussi, C. P. & Hospitaleche, C. A. 2008. Skull shape analysis and diet of South American fossil penguins (Sphenisciformes). Oryctos 7, 137-145.

Wang, X., McGowan, A. J. & Dyke, G. J. 2011. Avian wing proportions and flight styles: first step towards predicting the flight modes of Mesozoic birds. PLoS ONE 6 (12): e28672. doi:10.1371/journal.pone.0028672

Winkler, H. & Leisler, B. 1985. Morphological aspects of habitat selection in birds. In Cody, M. L. (ed). Habitat Selection in Birds. Orlando, Academic Press, pp. 415-434.

Worthy, T. H. 1989. Aspects of the biology of two moa species (Aves: Dinornithiformes). New Zealand Journal of Archaeology 11, 77-86.

- . & Holdaway, R. N. 2002. The Lost World of the Moa. Bloomington, Indiana University Press.

Yuri, T., Kimball, R. T., Harshman, J., Bowie, R. C. K., Braun, M. J., Chojnowski, J. L., Han, K.-L., Hackett, S. J., Huddleston, C. J., Moore, W. S., Reddy, S., Sheldon, F. H., Steadman, D. W., Witt, C. C. & Braun, E. L. 2013. Parsimony and model-based analyses of indels in avian nuclear genes reveal congruent and incongruent phylogenetic signals. Biology 2, 419-444.

Darren Naish About the Author: Darren Naish is a science writer, technical editor and palaeozoologist (affiliated with the University of Southampton, UK). He mostly works on Cretaceous dinosaurs and pterosaurs but has an avid interest in all things tetrapod. His publications can be downloaded at He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at! Follow on Twitter @TetZoo.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. BonesBehaviours 8:03 am 01/27/2014

    I don’t buy the argument that gastroliths predict herbivory given that they are attested for a suliform and a rather sunbittern-like Yanornis. What was the wear upon the gastroliths consistent with?

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  2. 2. naishd 8:11 am 01/27/2014

    I agree that the distribution of gastroliths sometimes looks confusing. They do appear, however, to correlate with herbivory in living birds, hence the suggestion that their presence in Protoplotus (the suliform you have in mind) is suggestive of seasonal diet-switching. Ditto for Yanornis – these birds could well be switching from a fish-based diet during part of the year to a herbivorous one at other times. Why do you refer to Yanornis as ‘sunbittern-like’?

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  3. 3. BonesBehaviours 8:56 am 01/27/2014

    When I saw the skeletal reconstruction of Yanornis, I simply thought of a sunbittern right away – sort of heron-like with long pointy jaws, but looking in proportions much more like a terrestrial skulker than a wader. As you know sunbitterns are terrestrial predators of forest floor invertebrates, dendrobatid frogs and sometimes small fishes in very shallow water rather than at all herbivorous. As such Yanornis likely between a ‘normal’ terrestrial insectivore and shallow water wader, with an overall emphasis upon terrestrial prey items despite the presence of a fish in the gut contents.

    Now Protorosaurus shows that facultative herbivory is sometimes undetectable from morphology alone, but claims are made for an ecologically drastic seasonal switching of diet in Yanornis with no study of gastrolith or tooth wear to my knowledge, and I don’t find this especially convincing.

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  4. 4. BonesBehaviours 9:17 am 01/27/2014

    Darren, you may be the tetrapod oracle but I bet you can’t name me a fish eating seabird that seasonally switched to herbivory as is predicted for Protoplotus. I expect you might suggest a modern day Yanornis analog that changes diet throughout the year, but not a penguin that eats so much salad.

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  5. 5. ekocak 9:23 am 01/27/2014

    Wait wait wait, back up. There is a bird that eats dendrobatid frogs? As in, enough toxin to kill a busload of people dendrobatid frogs? Really? Does the toxicity transfer? How do they accomplish this??

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  6. 6. ViktorNilssonOrtman 9:26 am 01/27/2014

    Growing up, I was told by my father that dippers are one of very few birds with solid bones, as an adaptation for staying submerged. A quick google scholar search, however, turns up very little to support this idea (but a web search suggest that I was not the only person in the world that had been told so). Is this just a myth?

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  7. 7. BonesBehaviours 10:01 am 01/27/2014


    At a certain zoo in the US a keeper tried to introduce dendrobatids into the same mixed exhibit as sunbitterns. The sunbitterns treated them as live food. The conclusion is that the only insectivorous birds safe with such small frogs are those that east the same grade of prey size as the frogs themselves.

    This is the short but unambiguous text posted over in the Birdfkeepers Yahoo! Group.

    “We actually tried some dendrobates in our rainforest exhibit in a small area. The sunbittern loved them. So I would say anything along the lines of bitterns, egrets, ibis, or other wading birds would be out.”

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  8. 8. naishd 10:04 am 01/27/2014

    Thanks all for comments, some interesting stuff there. Some responses…

    – regarding the idea of a partially/seasonally herbivorous Protoplotus – the idea that the gastroliths might be to do with buoyancy control has also been mooted (by the way, I don’t think you’re meant to be ‘convinced’ by any of the ideas published about the lifestyle or ecology of Protoplotus: rather, they’re speculative attempts to explain the data). I agree that the idea of a partially herbivorous member of Suliformes seems unlikely.

    – I’m not convinced that Yanornis is at all sunbittern-like! Sunbitterns have heron-like skulls, for one thing.

    – dippers and solid (= non-pneumatic) bones: yes, the limb bones in dippers are non-pneumatic, but this is not a special feature of this group – non-pneumatic limb bones are the norm across most passerine groups. In birds in general, big species are the most pneumatic, small species the least so.

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  9. 9. BonesBehaviours 10:14 am 01/27/2014

    But a heron like skull can’t be predicted for an ecologically similar toothed bird, since a modern bird’s prey capture must compensate for its lack of teeth. As far as I can see the jaws and teeth of Yanornis do appear adapted for biting invertebrates, small fish and micro-tetrapods (a size category likely poorly represented as fossils.)

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  10. 10. albertonykus 10:48 am 01/27/2014

    The National Zoo does keep both sunbitterns and (mythical*) poison-dart frogs in their Amazon exhibit. I wonder if they’ve ever had any issues there.

    *Mythical because they only come out at night and so are almost never seen by visitors, though sometimes they can be heard.

    While we’re on the subject, isn’t it thought that poison-dart frogs get their toxins from eating poisonous arthropods? Captive specimens might not have access to those and may be thus non-toxic.

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  11. 11. ekocak 10:53 am 01/27/2014

    I can confirm from experience that captive bred dendrobatids are not toxic. Was just going to raise this point. So maybe sunbitterns are indiscriminate eaters, some of which die in the wild from eating poisonous frogs?

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  12. 12. naishd 10:56 am 01/27/2014

    Dendrobatids: there are indeed studies which show that wild species are becoming less toxic than they used to be since they’re no longer able to consume the same toxic arthropods they sequester their toxins from, apparently.

    While we’re here, it’s worth saying that ‘only’ a third or so of dendrobatids secrete deadly toxins – the group is not homogenous (the colostethines and hyloxalines are not toxic, and the aromobatids – traditionally included in Dendrobatidae – are not toxic either). Having said though, zoos only tend to keep the brightly coloured, ubertoxic dendrobatine dendrobatids…

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  13. 13. naishd 10:58 am 01/27/2014

    … which aren’t ‘ubertoxic’ when bred in captivity, of course :)

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  14. 14. BonesBehaviours 11:03 am 01/27/2014

    It would indeed be odd if the sunbitterns did not instinctively recognise sympatric, toxic frogs that might be confused with prey items.

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  15. 15. BrianL 11:49 am 01/27/2014

    This article raises a number of questions for me:
    - Are captive Palmnut Vultures fed with fruit? I’ve only twice seen a captive individual. One of these was an immature taking part in a flight demonstration and if I recall correctly, it was fed little bits of meat like the other raptors were. I know the birds eat some meat in the wild, but are captive ones kept on a carnivorous diet?
    - Is *Juncitarsus* still considered a stem-flamingo? I believe Mayr considered it likely basal to modern Mirandornithes in general. Of course, that does make it a stem-flamingo of sorts but…
    - What do TetZoo commenters think of the idea that dromornithds and gastornithids do not really have proportionally large beaks, but simply heads that befit a herbivorous galloanseraean/neognath of their size? The arguments of the authors of ‘Magnificent Mihirungs were quite convincing to me.
    - Is there any theory as to how the weird nesting habits of auks that nest in trees far inland evolved?
    - Given how sunbitterns seem to be fairly easy to keep alive in captivity, does the same apply to the kagu? I’ve seen it in capitivity once and once read they are fairly robust and easy to care for, but is this thought to be true still?
    - Do the species of dipper differ in how good and often they swim, as far as is known?

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  16. 16. David Marjanović 12:40 pm 01/27/2014

    The submitted manuscript was more than twice as long as allowed, so I had to axe a lot of material.

    Why didn’t you submit to another journal? Impact factor?

    As far as I can see the jaws and teeth of Yanornis do appear adapted for biting invertebrates, small fish and micro-tetrapods (a size category likely poorly represented as fossils.)

    Hardly anything is poorly represented as fossils in the sites where Yanornis comes from. :-)

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  17. 17. MMartyniuk 1:39 pm 01/27/2014

    Re: Yanornis, note that one specimen may preserve evidence of webbed feet ( If confirmed, this would be pretty good evidence it was partially aquatic rather than sunbittern-like. Superficially, the long jaws with slightly hooked toothless premaxilla and teeth restricted to the maxilla and dentary are reminiscent of Ichthyornis etc. and suggest a mainly piscivorous diet.

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  18. 18. Tayo Bethel 1:44 pm 01/27/2014

    Howdid the presence of teeth affect the feeding behavior of toothed birds? Did the presence of teeth make the diverse bill shapes of modern birds unnecessary?

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  19. 19. Spironis 2:35 pm 01/27/2014

    Dendrobatids bred and fed within captivity are not toxic. Their wild forebears apparently eat something (ants, centipedes, mites) to acquire the toxins. In turn, toxin molecular structures are exotic as arthropod metabolites (e.g., halogenated pyridine in epibatidine), suggesting a fungal or plant (re nicotine) origin.

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  20. 20. ekocak 2:44 pm 01/27/2014

    That’s interesting. So what you’re saying is, based on the chemical makeup of the toxins, it seems to be a plant or fungus ingested by insects, which are then ingested by the frogs?

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  21. 21. ekocak 2:52 pm 01/27/2014

    Followup question related to the initial discussion: Would there be any indication whatsoever that dendrobatid frogs were toxic if we only had fossils to go on? I’m going to guess not, which makes me wonder what other species in the past may have been poisonous but left no traces. (I immediately thought of the baboon reconstruction in All Yesterdays). Would something like extremely gracile skeletons be an indicator that an animal was relying on some form of chemical defense? Maybe as molecular analysis of preserved chromatic information gets better and better we could hope for finding animals with “warning coloration”. (Although how you’d separate that from sexual displays is beyond me) Is there just 100% no way to ever know?

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  22. 22. BonesBehaviours 4:45 pm 01/27/2014

    I can imagine ie. microsaurs being toxic but I’ve no idea how anyone might prove it. Its just that they seem like the kind of animal to benefit from toxicity.

    And if Yanornis were a diver then the stones may as in Protoplotus have represented ballast. Does Cinclus perhaps swallow grit?

    About the kagu, yes, they laid in captivity when they were more readily available to western collections but tragically for that reason there was no real interest in maintaining a captive gene pool. I think Chester is interested in getting some to share a building together with mountain gorillas.

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  23. 23. BonesBehaviours 4:58 pm 01/27/2014

    I’ve no idea about the palmnut vultures, but in the wild they are dependant upon oil palm, which is cultivated widely in the tropics but I doubt its readily available in ie. western Europe.

    There is actually a theory that fruits mimic meat so as to attract carnivores first to prey on pesdts and then to assist seed dispersal, so depending on how you look at it, the palm nut vulture is either more or less interesting for its strong frugivorous tendencies. This works in reverse with the duikers switching to hypocarnivory through increasing their dependence upon fruit, and a frugivorous dove (Ptilinopus coralensis) evolving raptorial tendencies in French Polynesia.

    Because they are a bird of prey that is switching to the consumption of fruit, the palm nut vulture is a parallel to the likely evolution of parrots from birds of prey during the Cretaceous or Paleogene. Its easy to imagine the same thing happening to a kite or something in the future.

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  24. 24. Yodelling Cyclist 5:47 pm 01/27/2014

    @BonesBehaviours: I think Chester is interested in getting some to share a building together with mountain gorillas.

    Is that still going ahead? I’ve been a member of Chester Zoo for ~27 years, and I remember the vast gorilla enclosure plans, but the last I heard on that was that funding fell through post 2008 and I don’t think that plan has been resuscitated (there were plans for an integrated hotel!). Currently work is under way on the Islands site – which will be very spectacular! “Islands” will lack gorillas but would be a wonderful site for kagu.

    Chester used to have western lowland gorillas, but the last one (a big silverback) died over 20 years ago. For those who know Chester Zoo well, but are younger, the gorillas used to be housed in the tropical house, where the Indian and Rhinoceros Hornbills are now (it was a single enclosure), behond the waterfall, with access to the out side moated paddock which (when I was last there) held the Red River Hogs.

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  25. 25. BonesBehaviours 5:55 pm 01/27/2014

    I don’t know whether its still going ahead just that there is still interest, I noticed it on ZooChat. The problem with Chester is the entry price which is necessary for upkeep but still unfortunate.

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  26. 26. Yodelling Cyclist 5:55 pm 01/27/2014

    Some further research through a huge pile of gently mouldering zoo news letters has been prompted after in-house allegations that my memory may be less than perfect.

    Alas these have proven true.

    Some corrections.

    A.) Eastern lowland gorillas.
    B.) The last individual (which was a silverback) died in 1986, so I must have seen him very much at the end.
    C.) Funding for “Heart of Africa” was lost in 2010, although hope for the project has never completely died, and it may, one day, come to pass.

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  27. 27. Yodelling Cyclist 5:57 pm 01/27/2014

    I have the zoo to blame for my love of zoology and palaeontology. I’d pay the membership with my life’s blood if need be. It’s an incredibly important part of my childhood and indeed “life”.

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  28. 28. David Marjanović 7:06 pm 01/27/2014

    Dendrobatids bred and fed within captivity are not toxic. Their wild forebears apparently eat something (ants, centipedes, mites) to acquire the toxins.

    The source for hemibatrachotoxin has been identified, IIRC: some beetles I’ve forgotten. Closely related beetles are eaten by the pitohui, a few species of poisonous birds in New Guinea that have hemibatrachotoxin in their feathers, skin and muscles, IIRC.

    In turn, toxin molecular structures are exotic as arthropod metabolites (e.g., halogenated pyridine in epibatidine), suggesting a fungal or plant (re nicotine) origin.


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  29. 29. Tayo Bethel 7:59 pm 01/27/2014

    Parrots evolving from birds of prey?

    Interesting. I know that the latest phylogenetic analyses link parrots, falconids and (if my memory serves) passerines. I’ve never heard of the hypothesis that parrots evolved from predatory ancestors.

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  30. 30. vdinets 12:21 am 01/28/2014

    BrianL: I don’t think switching from rocks to trees was particularly difficult for auks, since switching either way seems to be easy for birds (think nuthatches, ibises, swifts, condors, etc.). Murrelets (the auks in point) nest on large horizontal branches near the trunk, in places generally similar to rock shelves. To me a more interesting thing is Tringa sandpipers nesting in trees.

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  31. 31. Dartian 3:11 am 01/28/2014

    Darren (OP):
    several auks nest in trees

    Several? I thought it was just the marbled murrelet Brachyramphus marmoratus that nested in trees. Are there others?

    I’ve no idea about the palmnut vultures, but in the wild they are dependant upon oil palm, which is cultivated widely in the tropics but I doubt its readily available in ie. western Europe.

    This species can be successfully kept in captivity by offering it alternative (mainly meat-based) foods. Jacksonville Zoo, Florida, for example, has kept palm-nut vultures on such a diet.

    Speaking of zoos, placing birds and amphibians (of any species) together in a mixed-species enclosure sounds like a spectacularly bad idea. I doubt that the amphibians enjoy that kind of ‘enrichment’.

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  32. 32. Richard Hing 4:55 am 01/28/2014

    “…A frugivorous dove (Ptilinopus coralensis) evolving raptorial tendencies in French Polynesia.”

    Any more information on this?

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  33. 33. Dave Unwin 5:13 am 01/28/2014

    Admirers of your column might like to take a look at Falk et al.’s paper: “A behavioral analysis of fossil bird tracks from the Haman
    Formation (Republic of Korea) shows a nearly modern avian
    ecosystem”, which has just appeared in the latest volume of Vertebrata PalAsiatica, dedicated to one of the palaeornithological greats: Larry Martin. The entire volume is available for free on the IVPP website.

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  34. 34. Chabier G. 6:34 am 01/28/2014

    Gastroliths can be a good indicator for the diet of a bird, but, looking at modern examples, the inference can be far from evident.
    Some of my favourite examples are: Panurus biarmicus, who substitutes a thin grit, when spring comes, for its winter one, fairly thicker, as summer diet relies on arthropods, instead of seeds eaten in winter; Stone Curlews uses to have curious gastroliths, 2 or 3 rather big (7 mm or so) angular stones, I think it’s related to a high consumption of small snails, but not all the stone curlews have grit; Ravens can eat a lot of corn, but they never have grit, perhaps the highly keratinized gizzard epitelium is enough for a facultative granivore.
    It wouldn’t be easy to suspect how did these birds eat, were they not living species.

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  35. 35. Gigantala 6:53 am 01/28/2014

    So, if gastroliths correlate with herbivory, does that mean Pterodaustro was an herbivorous pterosaur?

    Certainly explains the huge torso…

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  36. 36. Jerzy v. 3.0. 7:05 am 01/28/2014

    Sounds like interesting paper. Pity that you axed a lot of material, rather than eg. split it in two, eg. one on feeding, another on social and breeding behaviour.

    Speaking of evidence: it would be interesting to see a numerical analysis, how surely characters predict behaviour traits. I know Darren is fond of unusual one-off counterexamples, but that would be pretty revealing. For example, do raptorial characteristics distinguish raptors from parrots – also with curved beaks and claws? What about kea?

    One group you may pay close attention is Anatidae. Geese and ducks vary from filter-feeders, algae feeders, grass grazers, invertebrate feeders, shellfish eaters, piscivores and omnivores. They could be interesting model in food switching and feeding specialization.

    One question: is there a fossil evidence of bird migration, and how long?

    Another thing – bird bills are often modified for social display. Any such structures in non-avian dinosaurs or mesozoic birds?

    Re 1: palm-nut vulture: they are sometimes kept and bred in zoos and thrive on meat-based diet. Apparently their feeding specialization didn’t go far (and they eat fair amount of animal diet in the wild).

    Re 2: Kagus have currently a captive breeding program based in Walsrode zoo, and it seems pretty succesful. The problem is very small founder base exported from New Caledonia, and perhaps not enough interest from other zoos (fewer and fewer zoos are interested in any animals not popular in cartoons and blockbuster movies).

    Re 3: auks on trees – murrelets nest on thick branches of old-growth trees which are wider than cliff ledges used by other auks.

    Re 4: something even stranger is lack of vegetation or even feathers or protofeathers in nests of non-avialan dinosaurs. Only mineral material. Or is it overlooked?

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  37. 37. Percival 7:07 am 01/28/2014

    The comments are as interesting as the article (for me at least)- I’ve always wondered how frogs were supposed to produce toxins with their own metabolism. Now I know they get them second-hand.

    As for where all the fossil nests might be, it seems to me that such nests, once abandoned, would be virtual supermarkets for detritovores. I’m slightly surprised that any fossil nests at all have been found.

    For that matter, what happens to bowerbird bowers and such today? If something doesn’t come along and disassemble them for whatever reason you’d think their nesting grounds would be hip-deep in them.

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  38. 38. David Marjanović 9:44 am 01/28/2014

    Re 4: something even stranger is lack of vegetation or even feathers or protofeathers in nests of non-avialan dinosaurs. Only mineral material. Or is it overlooked?

    Do you really think organic material in a ground nest would be preserved in the kind of environment that preserves eggshells?

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  39. 39. BonesBehaviours 9:45 am 01/28/2014

    Chabier, I never knew that about the stone curlews, and its surely of importance that they are essentially vertivores and predators of invertebrates. As good analogs for compsognathids and small coelophysoids, they seem to confirm the possibility of carnivorous theropods possessing gastroliths.

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  40. 40. BonesBehaviours 9:57 am 01/28/2014

    Richard there is mention of the atoll fruit dove in this paper.

    “The Atoll Fruit-dove (Ptilinopus coralensis) who lives in treeless atolls has been observed feeding on lizards (Baptista et al. 1997).”

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  41. 41. naishd 11:11 am 01/28/2014

    Lots of comments worthy of responses: I’ll try to say things as opportunity allows.

    On gastroliths and herbivory: nobody says that you can, or should, heap too much significance on things when the sample size is small (n = 1, as it usually is with vertebrate fossils), since we need multiple specimens before arriving at firm conclusions. There are, after all, tyrannosaurids and megalosaurids and so on with gastroliths (see Varricchio 2001). Accidental ingestion and use of stones as ballast also explain gastrolith presence in some animals. At the moment, I would think that, when sample size is ‘reasonable’ (I can’t say ‘large’, since, again, we’re talking about vertebrate fossils) – that is, when all specimens do preserve a large number of gastroliths (not just 1, 2 or 3) – they probably are indicative of herbivory. The ingestion of fine grit is not necessarily linked to herbivory: specialised insectivores do this, as do some detritivores.

    Ref – -

    Varricchio, D. J. 2001. Gut contents from a Cretaceous tyrannosaurid: implications for theropod dinosaur digestive tracts. Journal of Paleontology 75, 401-406.

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  42. 42. Jerzy v. 3.0. 11:39 am 01/28/2014

    I think there are enough dinosaur nests known already fossilized in different conditions, some preserving fine details like minute embryonic bones. Also, presence of vegetation could be seen on eg. imprints on the sand, or position of the eggs.

    Birds and crocodilians build nests with lots of vegetation. Lack of published accounts in non-avian dinosaur nests is surprising.

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  43. 43. Jerzy v. 3.0. 11:43 am 01/28/2014

    Re: lizard-eating dove.
    Interesting! However, birds on oceanic islands might be unusual. On the oceanic islands, niches occupied by non-dispersing animals are open, and exploited by species which are poorly adapted to them. Eg. scavenging South Georgia Pintail, Kerguelen Tern pecking at land insects, and all the weird examples from Galapagos, New Zealand etc.

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  44. 44. Jerzy v. 3.0. 11:44 am 01/28/2014

    I wonder if coprolites of prey animals could be swallowed by tyrannosaur?

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  45. 45. Jerzy v. 3.0. 11:44 am 01/28/2014

    AAAA! Gastrolites! Time to log off ;)

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  46. 46. Yodelling Cyclist 12:01 pm 01/28/2014

    You guys are all idiots, see these big dinosaurs were nesting in stone nests on the ground. Likely stones were swallowed, stored in a special internal “stone crop” and regurgitated at the nest site. Some got stuck in the stone crop and were still present at the time of death. Modern avian dinosaurs lost the stone crop to save weight.


    Well, it’s a fun speculation. Nothing more.

    Best wishes,

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  47. 47. Yodelling Cyclist 12:02 pm 01/28/2014

    Of course that may well all be a load of crop….

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  48. 48. MMartyniuk 12:57 pm 01/28/2014

    #18 – I think we have a good enough sample size to say the presence of teeth made the diverse bill shapes of modern birds sort of unnecessary, yes. Especially in enantiornithians, there is a pretty big amount of diversity when it comes to tooth morphology, and so far only a single lineage (gobipterygids) are known to have had any sort of beak at all.

    That said, among lineages that DID evolve beaks, they seem to have been good at partially replacing or at least supplementing the function of teeth. All known non-avian euornithians had beaks (though we’d expect there to be at least a few primitive beakless forms yet to be discovered), and right around the base of that clade we start seeing loss of or extreme reduction of teeth (Archaeorhynchus, Schizooura, hongshanornithids), which implies once beaks arrived on the scene they quickly took over the role of teeth at the business end of the jaws, maybe by being more plastic in an adaptational sense.

    Still, a lot of advanced non-avians did retain maxillary and dentary teeth while also employing a premaxillary and predetnary beak. It could be the survival of only the completely toothless avian lineage is a random fluke of extinction rather than representing a “better” evolutionary strategy.

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  49. 49. vdinets 1:46 pm 01/28/2014

    Dartian (#31): also the long-billed murrelet.

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  50. 50. BrianL 1:53 pm 01/28/2014

    I want to react to the notion of parrots descending from birds of prey, because I think that is a rather misleading statement.
    Firstly, ‘bird of prey’ means, AFAIK, either ‘falconiforms’ or owls. Shrikes, ground hornbills or indeed seriemas are not birds of prey, even if they habitually hunt vertebrates. Saying that parrots descended from birds of prey when you mean predatory birds is therefore misleading.
    Secondly, I presume this statement referred to pseudasturids, stem-parrots that likely were predatory. This ignores the fact that these birds were likely sister to a clade (crown Psittaciformes + Quercypsittidae + *Psittacopes* in whatever topology). The stem-parrots here were likely finch-like granivorous species and modern parrots are expert granivores too. The likely concestor of this clade was thus presumably a granivore (or at least an omnivore) as well. Pseudasturid habits were therefore presumably derived relative to the ancestral stem-parrot and their predatory habits say nothing about modern parrots descending from a dedicated predator. It’s worth noting that crown parrot-like beaks are known from *Oligocolius*, *Didunculus* and some Hawaiian honeycreepers. This suggests that the peculiarity of such beaks did not evolve from a raptorially adapated beak but rather from a more typically granivorous one.
    The outgroups of pan-Psittaciformes are not particularly suggestive of predatory habits in the concestor either. Passeriforms aren’t ancestrally predatory birds. Falconids are very raptorial, but the modern clade is highly derived, fairly recent and fossil falconids are very poorly known. We do not know how far their raptorial habits and adaptations go back. Seriemas are omnivores with some adaptations and a predilection for carnivory but not very raptorial all in all. Darren himself pointed out in the article that the very basal cariamaean *Strigogyps* was likely (mostly) herbivorous so Cariamae is not neccessarily ancestrally raptorial either, phorusrhacids notwithstanding.
    So to sum things up: I’d consider ‘parrots evolved from birds of prey’ to be misleading and perhaps flat out wrong.
    The outgr

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  51. 51. BrianL 1:54 pm 01/28/2014

    Sorry, I forgot to remove that last word-and-a-half.

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  52. 52. Tayo Bethel 5:22 pm 01/28/2014


    I agree with you. You cleared things up tremendously. Is there information on the probable predatory stem parrots? On the presence of premaxillary and predendary beaks: both Hesperornis and Ichthyornis possess,according to the literature,both a beak and teeth–in the case of Hesperornis, the teeth seem to have been quite functionaland specialized. Where do these birds fit on the avian tree?

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  53. 53. naishd 5:24 pm 01/28/2014

    Some more random responses…

    Those wondering why I decided to keep the paper short might like to know that it was an invited paper that I didn’t want to appear elsewhere, plus I like to have stuff in Journal of Zoology (IF = 2.043).

    – On bulk of data vs the exceptions (comment # 36): yeah, I suppose it’s true that I do like to point to “unusual one-off counter-examples” (the importance of reading too much from small sample sizes is usually on my mind, in part because we palaeontologists are often forced to make bold conclusions from single specimens; and this can be dangerous and misleading), but I wouldn’t expect to say anything confident about behaviour unless sample size was decent. As for doing things like distinguishing raptors from parrots – I can’t point to a specific study, but I think it’s obvious that the sorts of bill and claw shapes we see in these groups are not similar in detail. Raptors and parrots plot well apart in claw curvature, for example.

    – Evidence for migration in fossil birds (comment # 36)? There are two pieces of evidence indicating migration in ancient bird populations. (1) ‘Alien’ sediment, transported regularly (annually?) on the feathers of birds. (2) Evidence from phylogeography and palaeogeographical reconstructions have been combined to show the routes that migratory species might have taken in the past. This has been done for some waders and cranes.

    – Regarding the expectation that we should find vegetation preserved in association with fossil dinosaur nests (comment # 42), one of the problems is that the nests present in the fossil record have of course been covered with sediment washed in by floodwaters. I think that the nests in questions were subjected to a lot of weathering before they were buried. Nevertheless, the apparent lack of evidence for associated vegetation does seem odd. People have said that seeds and pollen are present in some of these nests – the assumption has been that it represents the remains of food transported to the juveniles, but I wonder if alternative ideas have been eliminated? In case it’s not obvious, I’m doing this without checking the literature.

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  54. 54. John Harshman 9:08 pm 01/28/2014

    The source for hemibatrachotoxin has been identified, IIRC: some beetles I’ve forgotten.

    Isn’t that homobatrachotoxin? At least it is in pitohuis.

    The source you’re probably thinking of is here:

    Dumbacher, J. P., et al. 2004. Melyrid beetles (Choresine): A putative source for the batrachotoxin alkaloids found in poison-dart frogs and toxic passerine birds. PNAS 101:15857–15860.

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  55. 55. Chabier G. 3:43 am 01/29/2014

    About predatory habits in doves, odd as it seems, I’ve found twice pigeon crops plenty of little snails, both were feral pigeons (Columba livia), one of them had swallowed Cochlicella barbara, a tiny gastropd, the other one had eaten Theba pissana, some of them about 10 mm wide. I think these birds were looking for a good amount of proteins and minerals, as both were females at the beginninig of breeding. Switching for small lizard consumption wouldn’t be too difficult, and poor islands ecosystems can elicit such behaviours.

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  56. 56. Chabier G. 4:06 am 01/29/2014

    I’ve been revising my data about stone curlew grit, of 55 individuals, only 9 had got gastroliths, 4 of the birds had got 3 stones, 2 of them carried 2 stones, and the other 3 carried only 1. All the stones were pyramidal or tetraedric in shape, and 3-8 mm wide. Then, it seems that the birds look actively for this kind of pebbles, discarding an accidental ingestion. The gizzard of the 55 stone curlews contained mainly insects (Coleoptera and Dermoptera), centipedes and little snails, but two of them had eaten a good load of wheat (!), and two other olives (!).

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  57. 57. David Marjanović 7:11 am 01/29/2014

    I think there are enough dinosaur nests known already fossilized in different conditions, some preserving fine details like minute embryonic bones. Also, presence of vegetation could be seen on eg. imprints on the sand, or position of the eggs.

    Plants and mineralized tissues are usually not preserved equally well in the same environments. Plants seem to preserve better in acidic soil that dissolves first eggshells, then bones and teeth. Without eggshells, a nest that consists of a mound of sediment with a crater is difficult to recognize at best.

    and right around the base of that clade we start seeing loss of or extreme reduction of teeth (Archaeorhynchus, Schizooura, hongshanornithids)

    A paper that appeared in the last few days shows that Hongshanornis did have plenty of teeth; only the premaxilla was toothless as apparently usual.

    Isn’t that homobatrachotoxin? At least it is in pitohuis.

    …It is. The things my memory does sometimes…

    The source you’re probably thinking of is here:

    Oh, thanks! I had only read secondary literature and didn’t know the paper. :-)

    On the presence of premaxillary and predendary beaks: both Hesperornis and Ichthyornis possess,according to the literature,both a beak and teeth–in the case of Hesperornis, the teeth seem to have been quite functionaland specialized. Where do these birds fit on the avian tree?

    They’re all very close to the crown-group; and they have teeth in the maxilla and the dentary but not the premaxilla, like the songlingornithids (Yanornis most famously) and Hongshanornis.

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  58. 58. BonesBehaviours 9:00 am 01/29/2014

    Chabler, do you remember whether the wheat or olive eating stone curlews possessed the stoned? Fruit eating by a well known predator is inexceptional, but the wheat eating is odd.

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  59. 59. vdinets 9:33 am 01/29/2014

    I’m just looking at the cladogram and trying to estimate how many times has arboreal nesting evolved. At least six, perhaps?

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  60. 60. BonesBehaviours 12:31 pm 01/29/2014

    Given that flight allows most birds to nest at any vertical level, more important is the nest structure and composition than where it is located. Likely small maniraptors were always somewhat fluid about nesting location even before the evolution of flight.

    A good All Yesterdays might be an Ichthyornis nesting in a tree like it was a cliff ledge? why not?

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  61. 61. John Harshman 1:07 pm 01/29/2014

    Nest location seems to be a pretty labile character, making it difficult to come up with a good count. Transitions in both directions are probably frequent. Are you counting fairy terns and tree swallows, for example?

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  62. 62. Tayo Bethel 4:39 pm 01/29/2014

    Some thoughts.

    Would nest location be more dependent on environment and the presence or absence of egg predators rather than phylogeny? Which maniraptorans outside of Aves might be likely to be facultative arboreal nesters? Ground-nesting birds today typically have precocial or superprecocial offspring. As this seems likely to have been the primitive condition,it would seem likely that most maniraptorans nested on the ground and that arboreal nesting might be restricted to crown-group Aves which have altricial young.

    Is there anything known about the ground locomotion of Ichthyornis?

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  63. 63. Jerzy v. 3.0. 6:25 pm 01/29/2014

    Nest location is extremely labile. Consider eg. Great Cormorant which can nest on trees, bushes, cliffs or on ground… Or Common Kestrel which can nest in tree hollows, rock cracks, roof cracks or open nests of other birds.

    I think tree nesting evolved more likely 60 times than 6…

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  64. 64. Augray 9:53 pm 01/29/2014


    In #8 you write that

    dippers and solid (= non-pneumatic) bones: yes, the limb bones in dippers are non-pneumatic, but this is not a special feature of this group – non-pneumatic limb bones are the norm across most passerine groups. In birds in general, big species are the most pneumatic, small species the least so.

    I thought that a pneumatic humerus was a trait shared by all extant birds…

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  65. 65. vdinets 9:54 pm 01/29/2014

    Jerzy: that’s totally possible, yes. Or it could evolve just once and then have countless reversions ;-)

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  66. 66. Chabier G. 2:34 am 01/30/2014

    BonesBehaviours: Sorry, I’ve checking my files more accurately. Indeed, the two birds with wheat in the gizzard (without any grit)were two poor yearlings near dead by starvation when they were caught by misinformed citizens (or non informed at all), who give them wheat as the only fodder, a starving, desperate, carnivorous bird can eat any thing (even wood sticks or stones). I can’t believe a stone curlew could digest seeds at all. Otherwise, the two animals with olives were adults in good condition (without grit, too), olives provides good fat, and are sought actively by foxes, badgers,and introduced swans, for example.

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  67. 67. Dartian 3:45 am 01/30/2014

    In Charadriiformes alone, tree-nesting has evolved at least five times: Tringa ochropus + T. solitaria, Bonaparte’s gull, fairy tern, the noddies, and the Brachyramphus/i> auklets (this is assuming that Gygis and Anous do not form a clade). And other charadriiforms such as Tringa glareola and Larus canus may occasionally nest in trees too. So yes, tree-nesting is a pretty widely distributed trait.

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  68. 68. Dartian 3:46 am 01/30/2014

    Oh crap, forgot to close the italics tag properly.

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  69. 69. naishd 4:27 am 01/30/2014

    Augray (comment # 64): I didn’t say all limb bones.

    Regarding the lability of nesting in trees: it is indeed one of those behavioural traits that (I think) animals do “because they can”, not because there is some fundamental hardwired behavioural constraint. Remember also that habitual tree-nesters will nest on the ground when conditions require (this is seen in various raptor and owl species usually thought of as tree-nesters).

    I also want to mention the fact that cavity nesting is all over the place in birds – the cavities can be holes in trees and downed branches or trunks, but also burrows and tunnels. If we were to analyse this in a phylogenetic context, would we see multiple independent derivations and reversals, or is there some sort of pattern (perhaps evolved repeatedly in different lineages) involving transitions from ground-nesting to cavity-nesting, and from there to both burrow-nesting and ‘vegetative’ nesting? Someone should analyse this, given that we now have reasonably good phylogenetic trees to hang our hypotheses on. I hung out with Walter Jetz a while back and John Harshman is a regular here… hmm…

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  70. 70. Jerzy v. 3.0. 10:46 am 01/30/2014

    In the old literature there are some theories and graphs illustrating how the evolution of nests and nest sites proceeded. But I think that such generalizations are not justified. Plus, many those graphs were using outdated phylogeny.

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  71. 71. naishd 10:52 am 01/30/2014

    Yes, trying to link nesting behaviour with phylogenetic trends and trees remains a popular topic. Among recent papers, the following are worth checking…

    Dial, K. P. 2003. Evolution of avian locomotion: correlates of flight style, locomotor modules, nesting biology, body size development, and the origin of flapping flight. The Auk 120, 941-952.

    Isles, T. E. 2009. The socio-sexual behaviour of extant archosaurs: implications for understanding dinosaur behaviour. Historical Biology 21, 139-214.

    Wesołowski, T. 2004. The origin of parental care in birds: a reassessment. Behavoural Ecology 15, 520–523.

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  72. 72. Jerzy v. 3.0. 10:52 am 01/30/2014

    And a memo for paleontologists: ;) If you find a dinosaur or enantiornithine egg, look if the material around can be interpreted as a fossilized vegetation from a nest.

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  73. 73. naishd 10:57 am 01/30/2014

    In response to comment # 72, it should be noted, in fairness, that people have done this, with the sediment so far not revealing evidence for preservation of vegetation (as per other comments above). We did it with the Romanian enantiornithine eggshell assemblage. No vegetation present at all.

    I should also add that some workers (e.g., Charles Deeming) have used eggshell porosity to determine incubation style: Deeming says that the dinosaurs he’s examined (these include non-avialan maniraptorans, like oviraptorosaurs) mostly indicate burial under sediment. This contradicts the idea that these dinosaurs were transferring body heat to their eggs – so far I haven’t seen his argument responded to in print.

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  74. 74. Yodelling Cyclist 12:11 pm 01/30/2014

    So how basal a group are megapods? Is their behaviour likely to be reversion to or conservation of an ancestral state?

    Also, as I have made good and clear, I’m one of the enthusiasts rather than pros around here, so pardon my ignorance, but am I right in stating that anseriformes are amongst the earliest clades of birds (hoping I’m using the correct terminology!) and have highly precocial young (when compared with later passerines etc.). Maybe nesting can’t be tracked precisely, but precocial vs. altricial might be a better path to go down. Once that’s been addressed (or has it already?) then maybe nesting may form a more reasonable pattern (more vegetative nests amoungst the more derived altricial groups, for example). How do tinamous nest/develop?

    Oh, and btw. many thanks to the knowledgeable contributors. I’m thoroughly enjoying this thread!

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  75. 75. BonesBehaviours 1:04 pm 01/30/2014

    Megapodes are nested in Neornithean birds. Their parental care, or absence of, is plesiomorphic.

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  76. 76. BonesBehaviours 1:05 pm 01/30/2014

    Sorry, is a reversal to a plesiomorphic state. I got distracted, sorry.

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  77. 77. John Harshman 1:07 pm 01/30/2014

    Megapodes are the sister group of other galliforms. In order for mound-building to be the primitive state you would need three origins of incubation (Anseriformes, Neoaves, Palaeognathae). Conceivable, though hardly parsimonious. And that’s without considering such evidence as we have for nesting in non-Aves dinosaurs.

    Given that both paleognaths and galloanserines are all precocial, that seems the most parsimonious assumption for the base of Aves, though that’s only slightly more parsimonious than the alternative. (I use a crown-group definition for Aves; substitute Neornithes if you prefer.)

    Tinamous are pretty standard paleognaths: the male builds the nest and incubates the eggs all by himself, and the chicks are precocial.

    “Earliest clades of birds” doesn’t have a clear meaning. Anseriformes, if by that we mean the crown group, appears to be Cretaceous in origin, based on fossil presbyornithids. Molecular clocks claim that there are quite a few more groups of similar age, i.e. Cretaceous lineages with modern descendants.

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  78. 78. Yodelling Cyclist 1:16 pm 01/30/2014

    Thanks for the response, and apologies for the inaccurate phrasing.

    I wasn’t so much dwelling on the mounds themselves, these would presumably be quite environment specific (it would be impossible to build rotting vegetation mounds in a desert, and certainly challenging on short grass prairie) as the precociality (if such a term may be used). Obviously this is a tough concept to quantify. Possibly in terms of number of days until the young are independent, with the extremes such as kiwis and megapodes on one side, and say eagles on the other.

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  79. 79. ekocak 4:37 pm 01/30/2014

    I’m reminded of Douglas Adams’s writings about megapode nest building as analogy for working somewhat fruitlessly:

    I’ve just spent a cheerful hour of my time writing a program on my computer that will tell me instantly what the volume of the mound was. It’s a very neat and sexy program with all sorts of pop-up menus and things, and the advantage of doing it the way I have is that on any future occasion on which I need to know the volume of a megapode nest, given its basic dimensions, my computer will give me the answer in less than a second, which is a wonderful saving of time. The downside, I suppose, is that I cannot conceive of any future occasion that I am likely to need to know the volume of a megapode nest, but no matter: the volume of this mound is a little over nine cubic yards. […]

    So all the megapode has to do to incubate its eggs is to dig three cubic yards of earth out of the ground, fill it with three cubic yards of rotting vegetation, collect a further six cubic yards of vegetation, build it into a mound, and then continually monitor the heat it is producing and run about adding bits or taking bits away.

    And thus it saves itself all the bother of sitting on its eggs from time to time.

    Douglas Adams and Mark Carwardine Last Chance to See

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  80. 80. Tayo Bethel 5:07 pm 01/30/2014

    What’s interesting about megapodes is that they use an incubation strategy broadly similar to that of some modern crocodilians. It seems, though, that wecant really know whether moundbuilding is a primitive trait which megapodes reverted to, or a derived behavior adapted to the environment in which they live.

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  81. 81. imhennessy 7:26 pm 01/30/2014

    I’d like to propose Hennessy’s Law:
    The quality of a conversation is inversely proportional to the number of interactions before an on topic Douglas Adams reference.

    That conversational quality is measured in Naishs, with 1 Naish equal to 79 interactions.

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  82. 82. John Harshman 9:56 pm 01/30/2014

    Some megapodes don’t use rotting vegetation, just naturally hot (volcanic) earth. But the process is similar.

    Anyway, again based on tree topology we can suppose that the ancestral Aves state is to be precocial, leaving the nest within a day of hatching, but not to be capable of flight until considerably later.

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  83. 83. Mark Robinson 11:03 pm 01/30/2014

    #81 – that’s just what Hitler would have said!

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  84. 84. Jerzy v. 3.0. 6:06 am 01/31/2014

    Yes, I now remember this study of eggshell pores. This makes absence of evidence of vegetation even more surprising.

    I agree that megapodes are probably descendant of standard incubating birds.

    One other trait of megapodes I find interesting. Chicks freshly hatched from the mound disperse long distances. There are even reports of them found on ships tens of kilometers on the open ocean. Apparently they are propelled by yolk sac.

    It is possible that hatchings of herbivorous dinosaurs which nested in enormous colonies behaved the same way. That is now they would avoid the problem of all the vegetation being eaten by incubating adults, or colonies located in an area with low predation pressure.

    And another pet theory of mine (this one is really a pet theory, not any direct evidence here) – that flight evolved first in juvenile maniraptorians, with the better area-volume ration. Juveniles could be flying or fluttering and arboreal, adults ground-living and flightless.

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  85. 85. Yodelling Cyclist 7:07 am 01/31/2014

    So only (but not all) altricial species invest in arboreal vegetative nests (not counting the megapode mound which I think we can all agree is something special in itself)?

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  86. 86. John Harshman 10:07 am 01/31/2014

    No, I wouldn’t say that. Many ducks, for example, nest in trees.

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  87. 87. Yodelling Cyclist 10:30 am 01/31/2014

    …and build nests from vegetation? Are these examples (struggles to save idea) perhaps the more altricial of ducks?

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  88. 88. Heteromeles 10:40 am 01/31/2014

    On the question of precocial galliformes, I’ve seen quail, turkey, and pheasant chicks fly when they’re tiny, a small fraction of adult size. How young can they fly?

    It appears that the key weirdness, excuse me, key innovation, of megapodes is their mound-building. Perhaps it started when some stupid galliform started burying its nest for protection (rather than simply closing it up with vegetative matter), and then evolution kicked in when they raised more offspring that way?

    Knowing very little about megapodes, my other question is, what’s the function of the nest? According to good ol’ Wikipedia, the mound-building clade tends their mound for most of the year, even though they don’t care for their offspring at all. To me, that sounds more like a bower or some other social structure than an incubator, but I’m perfectly willing to be wrong.

    They’re not alone, either. Humans, after all, tend their nests for years before they have offspring and years afterwards, so moundbuilders aren’t the most extreme animals out there.

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  89. 89. Yodelling Cyclist 10:48 am 01/31/2014

    Don’t involve humans. They’re just far too behaviourly weird.

    Further, we can be fairly sure that many of their behaviours are modern, and not reversions. AFAIK to date, no fossil primates have been found fossilised hunched over a laptop.

    I may yet be the first to something….

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  90. 90. John Harshman 1:22 pm 01/31/2014

    Yes, they build nests from vegetation. At least as much as any other hole-nester does. And all ducks are about equally precocial, unless you want to count the (non-arboreal) black-headed duck Heteronetta atricapilla as special.

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  91. 91. Tayo Bethel 9:29 pm 01/31/2014

    Yodeling Cyclist:

    Perhaps the arboreal-nesting ducks descended from a clade of ducks that originally nested on the ground like most other precocial birds and for whatever reason–perhaps just because they could?–moved their nests into tree cavities. BTW, dont ducks use vegetation in nest building?

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  92. 92. imhennessy 10:25 pm 01/31/2014

    Megapode mounds are prominent when in use, but it sounds like their functional benefits come from the fact that they’re decomposing. Not only are they decomposing, but they’re doing it in an anaerobic manner. (Unless there’s evidence that there’s another mechanism, but anaerobic sends like the standard compost-heap method of decomposing.) No wonder there’s little our no fossil evidence of them.
    David mentioned that conditions for preserving bone or eggshell are different than those which preserve vegetation, but are there any conditions we could expect too be favorable to both? Perhaps a pyroclastic flow?

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  93. 93. David Marjanović 8:48 am 02/1/2014

    Deeming says that the dinosaurs he’s examined (these include non-avialan maniraptorans, like oviraptorosaurs) mostly indicate burial under sediment. This contradicts the idea that these dinosaurs were transferring body heat to their eggs – so far I haven’t seen his argument responded to in print.

    Maybe the idea of sitting on a nest was to shield it from rain instead? It was warm in the Campanian anyway…

    Megapodes are the sister group of other galliforms.

    Other crown-group galliforms – but that doesn’t matter, because the nesting modes of stem-group galliforms are all unknown.

    In order for mound-building to be the primitive state you would need three origins of incubation (Anseriformes, Neoaves, Palaeognathae).

    Four: Palaeognathae, Neoaves, Anseriformes, rest-of-Galliformes.

    Yes, I now remember this study of eggshell pores. This makes absence of evidence of vegetation even more surprising.

    I told you bones and plants aren’t often preserved in the same places. :-) I’m not aware of any plant fossils from the Cretaceous of the Gobi!

    Perhaps a pyroclastic flow?

    Yes! The petrified forest in Chemnitz*, Germany, is just such a thing: it preserves leaf litter with tetrapods in it! :-)

    Pyroclastic flows are just exceedingly rare.

    * That’s right: in the city. The center even.

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  94. 94. John Harshman 10:14 am 02/2/2014

    Other crown-group galliforms

    Ha! That’s what “galliforms” means. stem-group galliforms aren’t galliforms; they’re pan-galliforms.

    Four: Palaeognathae, Neoaves, Anseriformes, rest-of-Galliformes.


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  95. 95. David Marjanović 2:16 pm 02/3/2014

    The crown-group “convention” is not some kind of universal standard. If you use it, you have to say so. :-)

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  96. 96. John Harshman 9:57 am 02/4/2014

    Shan’t. It’s part of my effort to mandate a universal standard. Crown groups for everyone!

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  97. 97. John Harshman 9:57 am 02/4/2014

    Sorry, forgot to add the “Mwah-ha-ha-ha-ha”.

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  98. 98. Metridia 10:41 pm 02/16/2014

    >The idea that we might detect the ecology and feeding behaviour of certain extinct birds by looking at the plants and animals they co-evolved with – the idea that we are sometimes seeing the ‘ghosts of predators past’ – was covered in the recent Tet Zoo article The ‘ghosts’ of extinct birds in modern ecosystems.

    Darren, I have to take issue with the idea that it was previously “covered”!

    The article you wrote there didn’t really do the subject justice. For example, the overall tone of the bits about ghost adaptations in NZ was given in the title: “Anti-moa browsing adaptations…. or not.” This really implies to me that you are going to argue against it- or at least, we’re going to hear details about why or why not, what were the cases made by different authors, and maybe some synthesis thereof. Instead, you basically cite some opposing literature with a minimum of contextualization. As a piece of science writing, to me this most reminds me of articles with titles like like “Scientists Differ on Existence of Climate Change” with even quotes from “both sides”. By giving both sides equal space and minimal context/evaluation, you create false equivalency where it might not be justified.

    Merely citing literature might work in a scientific review paper, but it’s not sufficient for an opinion/synthesis work of science writing- “some say this, while others say the opposite” is poor journalism for the reason that the reader should not be left to go read the primary literature themselves to get some sense of how the field lies. Especially since the existence of “ghosts” is the main topic of that post, and the citations are not just a name-check aside for further reading by interested readers.

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  99. 99. naishd 5:04 am 02/17/2014

    Metridia: wow, you really seem to have a problem with this. Here’s the exact same comment I left at the ‘ghosts of predators past’ article…

    Metridia: the article here is meant to be a review – the section on alleged coevolution between moa and flora is brief and not intended to provide detailed, in-depth coverage. My idea is that, should you want to read such, you should look at the literature I cited – Worthy & Holdaway (2002) for starters. So, yes, I left a lot unmentioned, sorry about that.

    As for ‘not making a strong case’, well, I can’t see that I’ve made (or tried to make) any case of any sort – I basically say what’s been suggested, then say that it’s been doubted, and, personally, I don’t have strong feelings either way on this particular subject. In other words, there’s a controversy here, with different people favouring different interpretations of the data. I think I get the point that I didn’t write the article you thought I should have. Sorry about that.

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  100. 100. Metridia 8:41 pm 02/17/2014


    Before I shut up about it, I might as well try to make it as clear as possible. It’s not really that you “didn’t write the article that I wanted”, it’s that, to me at least, your article sold itself as something different- and that by saying stuff like this topic was “covered”, you continue to do so. This is an argument about structure and convention in writing, and how they are used to support or disparage an idea; it is not just that you didn’t include my personal viewpoints.

    Before going further I will say it makes sense that you mention above that the ‘ghosts’ article was excised from a review manuscript- where it’s fine and common to name-check references to make sure you’ve covered your bases, and allow the reader to access these papers via their institutional subscriptions; further, it ostensibly wasn’t the main part of your published paper, and so name-checks are fine, as you aren’t expected to digest every ancillary point for your reader. However, as a science journalism piece, most of the readers won’t have access to the journal articles you reference, and won’t have time or the inclination to dig into them to provide their own synthesis of the arguments. Additionally, generally the purpose of science journalism is to provide some measure of synthesis for the reader, and so it’s different from primary literature.

    But let me address what I objected to about the structure of the piece, and how it seems to mislead the reader, since I kept feeling like I wasn’t being understood.

    The first section builds toward increasing ambivalence about the reality of the hypothesized coevolutionary ghosts. You finish the long introductory part by saying “We’ll start with New Zealand” as a place where you will “talk specifically about pieces of evidence that – so it’s been suggested – represent the incomplete leftovers of co-evolutionary relationships that specifically involve birds. “ The reader is then expecting a discussion, not a name-check; moreover, by building towards increasing skepticism, one expects some measure of debunking. The sense that you are going to in some way “debunk” these ideas is heightened by the bolded title of the NZ section that ends with “…or not.” Ending with doubts like that suggests to the reader you are coming down on the side of “not”. Yet, coming to the relevant two paragraphs, we don’t have any real synthesis of the arguments that could lead one to doubt the hypotheses. We just have equal space given to a few scattered “cons” as to the exposition of the hypotheses themselves. For the reader, all of this suggests the existence of a complete lack of consensus, leaning towards doubt; and no sense for the merits of the ideas themselves is conveyed.

    This doubt/skepticism about coevolutionary “ghosts”, it would appear, is in fact your own viewpoint on the matter. Contrary to your assertion that you “ don’t have strong feelings either way on this particular subject”, in the comments on that article you say:

    “Regarding comment # 17 (and some other comments here), I feel pretty sceptical about most or all of the suggested co-evolutionary scenarios discussed here – I was hoping that this was properly conveyed throughout the text.”

    The thing about this is that if you actually went into specifics and provided a synthesis, one could argue against that – or agree with it; but as it is, you are just “teaching the controversy” and expressing doubt by giving both sides equal space, regardless of their merits. Now I have to make my point about the structure of your piece, instead of the substance; this is harder to do, and I seem nitpicky in perservering. By the way, I am not alone in being a little disappointed in this article- see other comments.

    So, I would say my objections come down to: making the reader hunt down inaccessible journal articles instead of providing synthesis of what was ostensibly the main topic of discussion; and, hiding your skepticism of a hypothesis by saying you are just providing “references,” when in fact, providing unsynthesized references in equal amount to a brief exposition of a hypothesis creates the impression of more doubt of that hypothesis than what might be warranted. While you may say that you “didn’t try to make a strong case”, the promotion of the existence of “controversy,” as you do, is equivalent to endorsing the opposition without actually making this viewpoint explicit. The fact that you do endorse that particular viewpoint is revealed when you say you feel “pretty skeptical.”

    Maybe it isn’t fair criticism of your writing style, which tends more towards the scholarly than journalistic. Anyway, thanks for reading, and I hope this isn’t unwelcome discussion.

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  101. 101. naishd 4:20 am 02/18/2014

    Metridia (congrats on getting comment # 100): ok, I apologise if I’ve seemed aggressive in my responses, since your comments really have come across as those of someone saying “But you didn’t write the article I wanted you to!”. As I’m sure you can appreciate, that’s something that can come across as extremely annoying.

    Anyway… re-reading the article with your criticisms in mind, I’m afraid I still don’t appreciate your expectation of a lengthy critique, maybe because I’m more on-the-fence about this issue (moa coevolution with camouflaged and/or divaricating foliage) than you are (am I? Read on). The second paragraph [we're talking here about the 'ghosts of predators past' article; not the one above] explains that the suggested coevolutionary anti-browsing adaptations might actually represent adaptation to “low air temperatures and to the minimisation of damage caused by either frost or bright sunlight”; I also note that moa “weren’t demonstrably interested in consuming the ‘protected’ foliage anyway” (this meaning, supposedly, that there’s no evidence for selection pressure from moa on the evolution of the divarication habitus). I end by stating that “it remains controversial as to whether the floral peculiarities seen on New Zealand really do represent anti-moa adaptations or not… maybe they don’t”.

    To reiterate, my thought process went like this: (1) some people have argued for anti-browsing adaptation in flora, (2) some other people have then argued that these aren’t anti-browsing adaptations at all, and (3) this issue is not resolved, I don’t know what the ‘truth’ is, and maybe those ‘anti-browsing adaptations’ are not anti-browsing adaptations after all.

    You keep saying that I’m being lazy or unsatisfactory in not providing more finely honed coverage (despite your statement, I cannot find comments from other people indicating that they were as disappointed in the article as you are), but I just don’t understand what else you expected me to do – I’m sceptical about the issue, don’t have a firm idea as to what the answer is, and hence finished that section with an open-ended, sceptical last line. Of course, I should also add that I didn’t particularly want to expand on the floral adaptations issue, since a lengthy discussion would prevent me from covering the other material I summarised in the article (time limitations being what they are; I also try and keep articles to within a certain approximate length most of the time). Your comparison of what I did to a ‘teach the controversy’ style of reporting/writing is not appropriate, since those are cases where journalists give equal time to unequal or unmatched schools of thought, one of which warrants less serious consideration than the other.

    To conclude, given that I tried to review what people have said about this subject, given that I can’t see that an answer is obvious but that reasonable scepticism about the initial hypothesis is warranted, and given that you really wanted me to come down firmly on one side of the debate, I can only disappoint. I’m sorry that you didn’t appreciate, or agree with, what I wrote – I’m left wondering if you have a firmer view on this issue than I do, and hence wanted me to write in favour of the view you prefer. Or is it just that you wanted me to write lots and lots more about the subject, in which case: sorry, I’m the one who decides what I write about, not you!

    So, I’m sorry I didn’t do what you expected, but – to make it clear – maybe this is because your expectations are unrealistic in this instance. Nevertheless, I hope you can appreciate and understand where I’m coming from, and I hope you will keep visiting and reading Tet Zoo.

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