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Because the world belongs to petrels (petrels part I)

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


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Short-tailed shearwater (Puffinus tenuirostris) megaflock, photographed in Unimak Pass, Alaska. Photo by USGS.

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Seabirds are fascinating (as I often say: hey, just like all the other tetrapods). To me, they’ve always seemed to be one of those groups that requires a lifetime of immersion and specialisation should you hope to become properly acquainted with them. I just don’t feel that you can get to know them via books and published articles – you have to actually be out there, at sea, in diverse latitudes, armed perpetually with binoculars and a telescope. My chances to become immersed in the ‘seabird experience’ have been few and far between, but I have done my fair share of watching gulls, terns, auks, gannets and shearwaters as and when possible. [Awesome photo above from USGS.]

Seabirds of many species are phenomenally abundant, and data shows that they play major roles as predators, planktivores and scavengers in various marine ecosystems. But as everyone interested in the natural world should know, seabird populations today are beleaguered by such problems as plastic and oil pollution, climate change, human disturbance, alien predators that exploit them on their nesting grounds, declines in sea ice, and depletion of fish and plankton stocks. There’s therefore a rush to better understand their ecology in an effort to minimise the population losses and the general degradation of the marine ecosystems that these birds are part of.

Introducing petrels

Montage showing representatives of the five main petrel clades. Top left: Great shearwater (Puffinus gravis). Top right: Black-capped petrel (Petrodoma hasitata), both images by Patrick Coin. Below, top to bottom: Southern giant petrel (Macronectes giganteus) by Brocken Inaglory; Broad-billed prion (Pachyptila vittata), by Rosemary Tully; Westland Petrel (Procellaria westlandica), by Mark Jobling.

Here I want to talk about one of my favourite seabird groups, the petrels, also known as true petrels or procellariids. [Adjacent photos by Patrick CoinBrockenInaGlory*, Rosemary Tully and Mark Jobling, all from wikipedia.]

* Licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.

For people who like the same sort of thing that I do – recently discovered species, species known from just a few (or even single) specimens, species about which just about nothing is known, species with remarkable life histories, and species capable of really surprising bits of behaviour – petrels are where it’s at. Numerous short articles have been published reporting sightings of petrel species outside of their normal ranges and some species have been reported on so few occasions that any additional sightings are worthy of publication. Other species have disappeared and reappeared throughout history. And major contributions have been made by people able to identify and differentiate species at sea and hence report new, distinguishing characters. There are some excellent field guides to the petrels of the world. I especially recommend Tuck & Heinzel (1978) and Harrison (1983).

The main aim here – and, by “here” I mean “over the next several articles” – is to cover petrel diversity (there are about 75 living species, grouped into five main clades), to overview their biology, ecology and behaviour, and also to discuss how certain aspects of petrel behaviour and ecology match with morphology. I tried hard not to get bogged down in tedious discussions of phylogeny and systematics. As usual, however, you need to understand at least a bit about the phylogeny and systematics of the group before you can hope to realistically understand the evolutionary patterns within the group. In the end I’ve tried to combine everything in the hope that it presents a coherent picture of petrel diversity, ecology and form-function correlation. Completing these petrel-themed articles has not been easy – I started writing them in 2009 or earlier but they’ve been on the backburner.

Petrels (Procellariidae) are tubenosed seabirds, or tubenoses: part of the same neornithine clade as albatrosses (Diomedeidae), storm-petrels (Hydrobatidae) and diving-petrels (Pelecanoididae). The way I’ve just listed those groups – I mean, with all four being recognised as distinct taxonomic ‘families’ – represents the way tubenoses have been classified in mainstream 20th (and 21st) century literature. However, this ‘four family system’ does not match the phylogeny of the group as recovered by recent studies. More on this later.

Wilson's storm-petrel (Oceanites oceanicus) doing the 'water walking' thing. Image by Patrick Coin, from wikipedia.

I should note that ‘petrel’ is supposed to be pronounced in similar fashion to the name Peter, since it apparently originated as a diminutive form of that name (and hence started out as ‘peter-el’). The books say that petrels are named after St. Peter since he “walked (somewhat fearfully) on the stormy sea of Galilee at Christ’s invitation” (Lockley 1983, p. 8). The irony here is that the ‘water walking’ behaviour referred to here is practised by storm-petrels, not by petrels proper (storm-petrels don’t really walk on the water; rather, they patter across the surface with their large webbed feet while flying) [Adjacent image, showing this behaviour, by Patrick Coin]. So, petrels – most of which are speedy soarers – are named after the idiosyncratic behaviour practised by storm-petrels.

Totally tubular (external) nostrils

Labelled section of a tubenose compound rhamphotheca, from Hieronymus & Witmer (2010).

Tubenoses are united by such distinctive morphological features as their tubular nostrils and strongly reduced hallux (it consists just of a single phalanx, or is absent altogether). They also share a terminal hook on the bill. The tubenose bill is composed of a series of distinct plates rather than a continuous rhamphothecal covering and hence is referred to as a ‘compound rhamphotheca’. These different bill plates all have names (Coues 1866). The naricorn, latericorn, culminicorn and maxillary or premaxillary unguis (or nail) are all on the upper jaw; the ramicorn and mandibular unguis (or nail) are on the lower.

The persistence of prominent grooves between these plates might be due to their role in helping to drain unwanted saline fluid from the salt glands. As is typical for seabirds, the glands are located in bony depression over the eye sockets, but the fluid that drains from them is discharged through the nostrils and drips away from the end of the bill (Schmidt-Nielsen 1960). If you’re wondering, in the seabirds that have sealed external nostrils (gannets, cormorants etc.), the fluid is discharged via the internal, palatal nostrils and then runs along the dorsal surface of the palate before being released at the bill tip.

Short-tailed shearwater (Puffinus tenuirostris), photo by J. J. Harrison.

In petrels, the nostrils are united in a single, dorsally positioned tube, and this is also the case in diving-petrels and storm-petrels [see adjacent photo of Short-tailed shearwater, photo by J. J. Harrison]. Albatrosses, however, differ in having two tubes, one on either side of the bill. Given that (virtually all) phylogenies nest albatrosses somewhere within the clade that includes all other tubenoses, you might like to wonder what sort of transformation occurred during the evolution of these birds. Did albatrosses have a single, dorsally placed tube ancestrally, or have albatrosses retained a primitive condition while members of the other lineages convergently evolved the single, dorsally-placed condition?

Incidentally, there are no clear indications from the tubenose skull that tubular nostrils – let alone a single, dorsally located tube – would be present in life. In a tubenose skull, the bar located between the long, oval bony nostrils is raised relative to the sides and more anterior parts of the rostrum, but I can’t see that anyone would link this with the presence of a united tube in the absence of other information. As I write this, I have Northern fulmar Fulmarus glacialis skulls right in front of me.

Northern fulmar skulls - would you think from these skulls that a single, dorsally located nasal tube was present in place of paired external nostrils? Note also the depressions for the salt glands and the hooked premaxillary tip.

The nostril tube may help in channelling scent and it’s well known that storm-petrels and true petrels at least are attracted to dimethyl sulphide (DMS) (Nevitt et al. 1995), a compound released by phytoplankton when it’s subjected to grazing by zooplankton. The tubenoses that have so far exhibited high sensitivity to DMS are nocturnal foragers, so it seems logical that they might respond to olfactory cues more than visual ones when foraging (Nevitt et al. 1995). However, in view of their nocturnal habits, it’s not surprising that many petrels have highly acute night-time vision, with a flattish cornea and a lens that does most of the work in focusing light being among several specialisations for improved vision in the dark (Martin 1990).

I just mentioned that the nostril tube might help to channel scent. It has also been suggested that the tubular (laterally placed) nostrils of albatrosses contain pressure receptors that help them negotiate and exploit shifting air masses over waves (Kaiser 2007).

Next: Oil, squirting oil, using oil, and why contain oil in the first place?

For previous Tet Zoo articles on seabirds, see…

Refs – -

Coues, E. 1866. Critical review of the family Procellariidae: Part V; embracing the Diomedeinae and the Halodrominae. With a general supplement. Proceedings of the Academy of Natural Sciences of Philadelphia 18, 172-197.

Harrison, P. 1988. Seabirds: an Identification Guide. Houghton Mifflin Company, Boston.

Hieronymus, T., & Witmer, L. (2010). Homology and Evolution of Avian Compound Rhamphothecae The Auk, 127 (3), 590-604 DOI: 10.1525/auk.2010.09122

Lockley, R. M. 1983. Flight of the Storm Petrel. David & Charles, Newton Abbott & London.

Kaiser, G. W. 2007. The Inner Bird: Anatomy and Evolution. University of British Columbia, Vancouver.

Martin, G. 1990. Designer eyes for seabirds of the night. New Scientist 128 (1741), 46-48.

Nevitt, G. A., Veit, R. R. & Kareiva, P. 1995. Dimethyl sulphide as a foraging cue for Antarctic procellariiform seabirds. Nature 376, 680-682.

Schmidt-Nielsen, K. 1960. The salt-secreting gland of marine birds. Circulation 21, 955-996.

Tuck, G. & Heinzel, H. 1978. A Field Guide to the Seabirds of Britain and the World. Collins, London.

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 darrennaish.wordpress.com. He has been blogging at Tetrapod Zoology since 2006. Check out the Tet Zoo podcast at tetzoo.com! 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. C.M. Kosemen 9:10 am 03/12/2012

    The tube nose is obviously a biological machine-gun turret that petrels use to shoot down flying gorgonopsians…

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  2. 2. naishd 9:50 am 03/12/2012

    In all seriousness, the idea that the nasal tube does function as a nozzle for squirting oil at enemies, or for squirting food into the mouths of chicks, is mentioned enough in the older literature. It’s not correct – squirting and baby-feeding is done through the mouth. More on this in the next article.

    Darren

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  3. 3. Heteromeles 10:03 am 03/12/2012

    It’s bizarre on the face of it that a group that nests in compact colonies could at the same time produce a number of cryptic species. I assume the groups that have most of the cryptic species tend to nest in holes and fly to them after dark?

    I also wonder if the birds use oceanic bioluminescence as a way to find their prey at night. Flashes from disturbed algae might highlight a school of fish, for example.

    The final point came from a biologist who explained why a young elephant seal had washed up on one of our beaches, starving. His observation was that seal pups have to learn to hunt apparently on their own once they leave the rookery, and not all of them learn fast enough. Weird way to teach the kids, isn’t it, especially for a deep diver like the elephant seal? AFAIK, tubenoses do the same thing, which makes me wonder how fledgling tubenoses learn to feed themselves.

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  4. 4. marky 10:08 am 03/12/2012

    Brings back happy days in Aberdeenshire 40 years ago ! Since those days studying Redshank I’ve become a biology teacher and , while teaching evolution, always use the absence of colored plumage in sea birds as opposed to the plumage of birds in other ecosystems ( jungle for example) as a talking point – hte students are always intriged by this but we new arrive at an agreed “reason” for this – could you comment ?

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  5. 5. naishd 10:12 am 03/12/2012

    Heteromeles – some good questions there. Many of the super-abundant species nest in enormous colonies (consisting of literally millions of birds), but even these are (often) nocturnal burrow-nesters. Sensitivity to disturbance by introduced predators, human hunting, sea level rises etc. have all contributed to the rare status of some species. Others do seem naturally rare and/or widely dispersed.

    I mostly wanted to respond because I liked your elephant seal comment. Burney Le Boeuf and colleagues wrote a paper about the recruitment of juveniles into the adult population and basically argued that juveniles have a super hard time in learning how to hunt and make a living. Elephant seal behaviour is something else I’ve been planning to write about for ages.

    Darren

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  6. 6. naishd 10:14 am 03/12/2012

    Marky (comment 4) – I’ve written some hundreds of words on the subject of seabird pigmentation and colouring, we’ll come back to it real soon, ok?

    Darren

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  7. 7. Andreas Johansson 10:58 am 03/12/2012

    However, in view of their nocturnal habits, it’s not surprising that many petrels have highly acute night-time vision, with a flattish cornea and a lens that does most of the work in focusing light being among several specialisations for improved vision in the dark

    If the later is remarkable, what’s the norm?

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  8. 8. naishd 11:14 am 03/12/2012

    Normal condition for birds, so I understand, is to have a strongly convex cornea that does more work than the lens in terms of refraction. In cross-section, the eye of a nocturnal petrel is far more spherical than the eye of a diurnal bird.

    Darren

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  9. 9. Andreas Johansson 11:21 am 03/12/2012

    Thanks. Is a more petrel-like condition typical for mammals? If so, is that thought related to ancestral nocturnality?

    And why is lens-refraction good for night vision anyway?

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  10. 10. John Harshman 2:01 pm 03/12/2012

    Regarding abundance: once on the California coast I watched a flock of shearwaters fly past. It took at least 15 minutes, and I estimated the numbers at around 35,000. I was impressed.

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  11. 11. psweet 2:04 pm 03/12/2012

    Heteromeles — the fact that they breed in compact colonies is probably one of the reasons that they have cryptic species. If site fidelity is high enough, each colony can become a reproductively isolated population, even though those populations mix thoroughly in terms of foraging and non-breeding habitats. As long as mate choice doesn’t depend strongly upon visual cues, there would be no reason for obvious phenotypical divergence.

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  12. 12. Heteromeles 2:58 pm 03/12/2012

    Actually, I think people have pointed to the central paradox: when the birds fledge, they do it more or less individually, but in some species at least, they form massive flocks. Similarly, elephant seals leave their pups, spend most of their lives at sea, but can integrate navigation data well enough to get back to their rookeries whenever it’s the right time.

    The birds are obviously pretty social and I wouldn’t be surprised if the same isn’t true for elephant seals. Perhaps the seals are as social as domestic cats, for example. The young may learn, not by trial and error, but by finding adults out in the ocean and learning from them.

    That might be one function of the tubenoses–finding conspecifics as well as food. Since elephant seals can’t smell under water, I do wonder whether they’re following their taste buds around. Adult elephant seals don’t call underwater, do they?

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  13. 13. Jerzy New 3:09 pm 03/12/2012

    Many those so-called cryptic species exist because a shortage of nesting sites on remote islands. So there are discrete summer-nesting and winter-nesting populations which don’t mix. Also, one season is normally much more productive than another. So good season nesters are more productive than poor season nesters.

    There is a caveat, though. On Dutch island of Schermonikoog, there nest well-known Eurasian Oystercatchers. They traditionally nest on seashore. Recently a population of oystercatchers grew, and some were forced to establish territories behind the shore. These “leapers” fly over territories of shore-nesters to feed at low tide, and are doubly disadvantaged: first, their feeding territories are exposed by low tide shorter, second, oystercatchers are ineffective in carrying food. So breeding success of these leapers is several times lower.

    What is interesting, that these populations from the start became reproductively isolated – practically none of leaper pairs managed to fight their way and take over shoreline territory.

    So you see how easily bird populations can become separated by nesting site shortage. I wonder if these “separate” petrel “species” really deserve their status.

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  14. 14. Biology in Motion 3:31 pm 03/12/2012

    Fun and somewhat odd fact that relates to the discussion on feeding ecology: some petrels (particularly shearwaters) aquafly to capture prey. This is interesting because 1) it runs contrary to the common notion that the short, stout wings of alcids are a necessary adaptation to aquaflight and 2) there are very few morphological differences, if any, between petrels that aquafly and those that do not. As a result, the transition to aquaflying can be very subtle indeed, and that means that reconstructing the likely feeding ecology of more cryptic species is near impossible.

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  15. 15. naishd 5:38 pm 03/12/2012

    Thanks for all the comments – don’t have time to deal with them all. But…

    Jerzy (comment 13) – ah, always with the over-zealous attempts at lumping :) There are indeed many petrel taxa that are of controversial status – that is, are they really ‘species’, or are they ‘subspecies’ (whatever those terms mean)? Controversies like that continue, but I would remind that you that the taxonomic/phylogenetic status of any taxon is not (these days) based on reproductive isolation alone, but also on distinctive morphological and molecular characters. Petrel workers have been conservative and cautious about this sort of thing.

    Biology in Motion (comment 14): stay tuned for a later article, where there’s quite a bit about aquaflying. Some authors (well, Gary Kaiser in The Inner Bird) say that aquaflying taxa have thicker-walled humeri than non-aquaflyers. Don’t say any more for now – you’ll spoil all the ‘surprises’ :)

    Darren

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  16. 16. falcon121 5:42 pm 03/12/2012

    Another series of articles on a highly diverse and interesting group of tetrapods …looking forward to it. I still have the vesper bat articles…

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  17. 17. naishd 6:14 pm 03/12/2012

    Oh, and, yes, I wrote comment 15 before reading Habib (2010).

    Darren

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  18. 18. CS Shelton 8:07 pm 03/12/2012

    Regarding the title: “The World Belongs to…,”

    I’ve often said the world belongs to seabirds (usually meaning gulls or terns), for a couple of reasons, so this title excited my interest. Seabird ability to range over huge distances in search of food gives them the run of the whole damn world. The more specialized ones can be vulnerable, of course, but in the apocalypse my money is on seagulls to be the only survivors. That idea is also supported by the fact that coastal animals fared best in previous extinction events, though I don’t know whether any shorebird-like animals made it through the K-T event.

    Anyhow, as an artist my favorite thing about seabirds is the razor-sharp appearance of their wings, and the way long-winged seabirds fold those things up like origami sails. So cool.

    -

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  19. 19. albertonykus 3:27 am 03/13/2012

    Speaking of weaponized nasal tubes, The Future is Wild (yeah, I know) had a speculative petrel descendant that could spray burning chemicals out of its nasal tubes to repel predators.

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  20. 20. Dartian 3:38 am 03/13/2012

    Darren:
    Totally tubular (external) nostrils

    I was kinda expecting that you’d pay homage to Mike Oldfield by using the sub-title Tubular Bills

    CS Shelton:
    Seabird ability to range over huge distances in search of food gives them the run of the whole damn world.

    Most of them are pretty helpless not just on, but also over, land though. Procellariiforms, in particular, rarely venture far inland – unless they happen to be carried there by storm winds (and such dislocated birds usually perish). Which means that land areas, including narrow isthmuses, may prove insurmountable barriers to dispersal for many seabirds.

    The more specialized ones can be vulnerable

    Actually, the fact that many (most?) seabirds concentrate their nesting to just a few specific places makes them – and especially their eggs and young – quite vulnerable to predation, disease, and adverse weather conditions. If disaster strikes, even large populations can crash rapidly (which has happened to several procellariiform species).

    in the apocalypse my money is on seagulls to be the only survivors

    Sorry to rain on your parade (and, for the record, I like gulls too!), but even the gulls’ adaptability has its limits. Gulls are notably scarce in the tropics and the subtropics. They are also not particularly numerous in the entire Southern Hemisphere, even at the high latitudes.

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  21. 21. Dartian 3:48 am 03/13/2012

    Crap, I pressed ‘Submit’ too soon.

    I meant to add that the gulls are at their most successful in the Northern Hemisphere. The reason for that may be partly ecological (e.g., a larger landmass than in the Southern Hemisphere, creating more gull-suitable habitats), but my personal hunch is that the most important single factor explaining the gulls’ success on a global scale is human activity. Many gull species have been able to adapt and to exploit the habitats and the opportunities created by us Hairless Beach Apes. If the apocalypse wipes us out, I’d expect the gulls to suffer too.

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  22. 22. Jerzy New 4:13 am 03/13/2012

    @naishd
    In cryptic seabirds, scientists ran into typological problem. They are really best described as “morphs” but scientists don’t like the term. So they suggested “subspecies” except that subspecies should be geographically separated (which are not). So the obscure creatures are proposed to be full species – for lack of better term.

    Another thing is conservation of these morphs. I think we protect species not because of some fetish associated with the name “species” but because they are different and irreplaceable once extinct. Those forms are neither one or another.

    And oystercatchers – a population with a different behaviour, ecology and not interbreeding can pop up just so easily!

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  23. 23. naishd 4:16 am 03/13/2012

    Jerzy – I don’t wish to be rude, but I find this constant scepticism naive in view of what the experts say.

    Ok – please list some petrels that might be mere ‘morphs’ rather than phylogenetically distinct entities. I _guarantee_ that someone has done the work to work out exactly what they are. Eurasian oystercatchers = yes, different cultures and bill forms arise quickly and easily (partly as an accidental by-product of their ridiculously rapid bill-tip growth I think)… is this really similar to the situation with all those poorly known petrel forms? I don’t think so.

    Darren

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  24. 24. Dartian 4:58 am 03/13/2012

    Jerzy:
    Those forms are neither one or another.

    Wait, wait, wait! What publications are we referring to here? Please provide the citations, and then please explain what, exactly, is wrong with the data/methods/results in those papers.

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  25. 25. RaMas 5:02 am 03/13/2012

    Jerzy, inland and shore breeding Oystercatchers could only ever be called “reproductively isolated”, if the offspring of any group could be shown not to mate with that of the other group. This is certainly not the case.

    The recently described, hot-season breeding storm-petrel Oceanodroma monteiro on the other hand has not mixed up with the sympatric cold-season breeding Oceandroma castro for at least 70,000 years, according to molecular clock analyses. Even under the least restrictive species concepts they cannot be called morphs.

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  26. 26. Biology in Motion 9:55 am 03/13/2012

    Oh fine, I won’t post an spoilers about aquaflying. Stoked that you’re covering it, though :) –Mike H.

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  27. 27. Jerzy New 12:30 pm 03/13/2012

    @RaMas
    Lets put aside methodological weaknesses of such study.

    You put only one and the most distict example. O. castro is present on multiple islands and often has two seasonal populations. Of them only monteiro and jabejabe are so distinct. Cold and warm season morphs on other islands are more similar.

    So status of such forms is a bit weakened by the fact that every island group has separate populations and there is a spectrum from similar morphs to two distinct oddballs.

    Interesting situation, anyway.

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  28. 28. RaMas 1:54 pm 03/13/2012

    @Jerzy: I don’t know of any other seasonal cryptic forms of Procellariiformes that have yet been considered as distinct species, so what do you actually criticize?

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  29. 29. David Kelly 4:07 pm 03/13/2012

    Western Europe has a pretty restricted Procellarid avifauna but it appears this is at least partly due to human influence. There is archealogical evidence that at least one, possibly two, species of Gadfly Petrel Pterodroma was historically present in north western European waters.

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  30. 30. naishd 4:18 pm 03/13/2012

    David (comment 29): the eastern Atlantic was also home to additional shearwater species that became extinct in recent centuries… and must not mention presence of Cahow in eastern Atlantic… stay tuned, it’s all in later articles.

    Darren

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  31. 31. David Marjanović 5:58 pm 03/13/2012

    Schermonikoog

    Schiermonnikoog.

    I don’t know whether any shorebird-like animals made it through the K-T event

    Apparently none did. If you depend on the ocean surface, and the ocean surface dies, you die.

    In cryptic seabirds, scientists ran into typological problem. They are really best described as “morphs” but scientists don’t like the term. So they suggested “subspecies” except that subspecies should be geographically separated (which are not). So the obscure creatures are proposed to be full species – for lack of better term.

    It seems like you are a proponent of one of the two Biological Species Concepts.

    Let me just say that there are (as of February 2009) 147 species concepts out there. They have nothing in common except the word “species”; depending on the species concept, there are from 101 to 249 endemic bird species in Mexico.

    You seem to approach the question as “there are species; what is the best definition for ‘species’”? In reality, the question is: “which one of these 147 or more concepts, if any, should we call ‘species’”?

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  32. 32. Heteromeles 6:52 pm 03/13/2012

    I’m not a paleozoologist of course, but my impression, on reading the lists of fossil birds from the Paleocene, is that it was heavily slanted towards bird groups that we today consider shorebirds or wetland birds. I’m not sure whether that’s the vagaries of fossilization or that shorebirds are preadapted to survive asteroid strikes. Still, so many clades made it through the K-T transition that some paleontologists quibble with the whole mass extinction concept. I’m not as extreme as them, but I do know that species lists are available online to check this out.

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  33. 33. Jerzy New 6:27 am 03/14/2012

    @RaMas
    Over the years, lots of local and seasonal forms were suggested as species. Originally it was an idea that warm and cold season storm-petrels anywhere in North Atlantic were one species each.

    @David
    I don’t want to blew Darren’s next articles, but there is a paradox here. Tubenoses fly widely and were directly observed to colonize new nesting sites. However, genetic studies often suggest incredible isolation of breeders from different locations and seasons. I wonder what factors may confuse those genetic studies? Too small sample size?

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  34. 34. Heteromeles 9:21 am 03/14/2012

    Perhaps tubenoses identify appropriate mates on the basis of smell, as much as feather color?

    The other thing about breeding in huge colonies is that when those colonies collapse (and don’t forget that islands are ephemeral over evolutionary time), the few survivors may be forced to colonize new areas. This will tend to create bottlenecks and drive allopatric speciation, especially if young birds prefer to breed where they were born.

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  35. 35. Jerzy New 9:52 am 03/14/2012

    (one post apparently was eaten by cybermonster)
    #32
    Wetland birds, in theory, could well survive K/T extinction. They eat invertebrates feeding on decaying organic matter accumulating on shorelines, and there should be plenty of that after K/T event.

    That is, if one believes that K/T extinction was caused primarily by disruption of photosynthesis and food chains. If one believes that K/T extinction was caused directly by radiant heat or poisonous gases, shorebirds and most other birds are verysensitive to both.

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  36. 36. RaMas 3:00 pm 03/14/2012

    “I wonder what factors may confuse those genetic studies? Too small sample size?”
    Maybe the fact that those forms don’t usually interbreed despite being capable of reaching each others nesting sites confuses you?

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  37. 37. David Marjanović 8:27 am 03/16/2012

    so many clades made it through the K-T transition

    No – except if you trust badly calibrated molecular-dating studies way too much.

    I don’t want to blew Darren’s next articles, but there is a paradox here. Tubenoses fly widely and were directly observed to colonize new nesting sites. However, genetic studies often suggest incredible isolation of breeders from different locations and seasons. I wonder what factors may confuse those genetic studies? Too small sample size?

    They colonize new nesting sites, but do they ever enter nesting sites that are already occupied?

    If not, and if they simply don’t mate except on nesting sites, there’s no paradox here at all.

    And in that case, yes, every nesting site is a new species under one of the two “Biological Species Concept”s, the one that says species don’t interbreed (resulting in fertile offspring) in the wild but could in captivity – as well as under all species concepts that equate cladogenesis with speciation, because the colonization of a new nesting site is cladogenesis if populations with different nesting sites don’t interbreed.

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  38. 38. Heteromeles 10:40 am 03/16/2012

    so many clades made it through the K-T transition

    No – except if you trust badly calibrated molecular-dating studies way too much.

    Go check out the lists on http://www.paleocene-mammals.de/, particularly http://www.paleocene-mammals.de/pal_vertebrates.htm, and get back to me. Note that this doesn’t even include invertebrates, plants, or any other group. To repeat, quite a lot of clades made it through the K-T.

    Link to this
  39. 39. Heteromeles 11:05 am 03/16/2012

    As for the “quibbles about the K-T mass extinction,” here’s the quote: “Brysse (204) did another survey of vertebrate paleontologists. Of those surveed, 72% felt that the K/T extinctions were caused by gradual processes followed by an impact. Only 20% felt that the impact was the sole cause. (The remaining 8% had no opinion as to its cause, or questioned whether it was really a mass extinction at all).”

    Source: Prothero, D.M. 2006. After the Dinosaurs. Indiana University Press. p. 39. The Brysse citation is to a PhD thesis, and I don’t know if it’s available.

    Link to this

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