March 2, 2013 | 45
New Zealand is home to several highly peculiar endemic parrots, with three similar-looking species being of particular interest: the Kakapo Strigops habroptila, Kea Nestor notabilis, and Kaka N. meridionalis. Here are taxiderm specimens of all three on display together (with other New Zealand endemic birds*) at Bexhill Museum, Bexhill, East Sussex. I can’t pretend to have seen all three in life.
* A massive sense of smug satisfaction to whoever can identify all 16 species shown here.
I’ve written about the Kakapo before (see links below), but not about Kea and Kaka. Of the three, the Kakapo is the most extraordinary, and indeed it’s one of the most extraordinary of parrots. It’s a giant among the group (reaching 3.6 kg) and is nocturnal, cryptically coloured, flightless, and highly specialised for a lifestyle of bulk-processing low-quality plant food. For its body size, it has a proportionally small brain when compared to other parrots (Iwaniuk et al. 2004). It’s also – uniquely among parrots – a polygynous lek-breeder. It’s restricted today to offshore islands but formerly occurred across the New Zealand mainland. Many of its anatomical details are interesting, including its vaguely owl-like facial disc (hence the name Strigops: it means ‘owl face’) and moss-like appearance to the plumage.
As a strongly terrestrial member of a predominantly arboreal clade, the proportions and anatomy of the Kakapo’s feet and legs are of special interest to those of us who aim to test the correlations we see between morphology and climbing abilities in birds and other maniraptorans. As always, there’s very little in the way of work on this sort of thing. However, we do know that the Kakapo’s hindlimb proportions are unusual compared to those of other parrots: its femora are especially long and its tarsometatarsi are especially short (Livezey 2005). In its feet, the penultimate phalanges are comparatively short, whereas they are typically long in parrots (Hopson 2001: appendix). This is exactly what we’d predict for a bird that mostly walks on the ground. The Kakapo can, however, still climb trees.
A dedicated conservation effort involving captive breeding and supplementary feeding has allowed Kakapo to slowly build their numbers. The last time I wrote about Kakapo (January 2009) there were 90 individuals worldwide. As of February 2012, the number was 126 (graph above by KimvdLinde). Whenever Kakapo are mentioned these days, the first thing people seem to mention is the scene from Last Chance to See where a Kakapo raised by humans takes a particular liking to Mark Carwardine and proceeds to mate with his head. You can find that clip online if you search for it (I won’t add it here, since I struggle to get our blogging platform to embed video clips).
Kea are famous for being playful, intelligent and destructive, and I’m sure you’ve seen photos of them sliding down snowy slopes, destroying windscreen wipers on cars, raiding picnic tables and that sort of thing [image of flying Kea above by klaasmer]. A captive Kea once bit through the strap attached to my camera. Today, Kea are mostly regarded as mountain-dwelling parrots, restricted to South Island but with occasional vagrants reported from North Island. However, they do still occur in some lowland forests; indeed, fossils show that they were previously common in the lowland forests and shrublands of the east (Worthy & Holdaway 2002). They’re known to indulge in at least some nocturnal behaviour and some authors describe them as semi-nocturnal.
Their notorious habit of latching on to sheep and then biting into the soft tissues of the back (thereby resulting in blood loss and/or infection and eventual death for the sheep) may – suggested Worthy & Holdaway (2002) – be the modern incarnation of a more ancient bit of natural behaviour. Kea fossils are found in association with moa and the extinct goose Cnemiornis that apparently died after becoming mired in swamps, and the bones of some of these birds exhibit damage that could have been caused by Kea beaks. Maybe Kea learnt to take advantage of mired birds by biting into their backs, and later transferred this behaviour to large domestic mammals (Worthy & Holdaway 2002).
The Kaka is the least well known of these New Zealand parrots (remember that, compared to the majority of reptiles, amphibians and non-tetrapods, all birds are extremely well known… by which I mean that they’re familiar to the public, well studied, and easy to source information on). It’s a brownish parrot with a pale cap, reddish collar on the back of its neck and reddish underparts. South Island is home to the subspecies N. m. meridionalis; North Island to the smaller, duller N. m. septentrionalis (in which the cap is less prominent). Again, they are often active at night.
Another Kaka taxon, the Norfolk Island or Long-billed kaka N. productus (regarded as a ‘subspecies’ by some authors, and hence named N. m. productus), is now extinct, the last specimen dying in London in 1851 or thereabouts. It possessed a particularly long and strongly curved upper mandible and several freak individuals with remarkably ‘over-curved’ jaws were recorded. Very little is known of its behaviour in the wild but some sources say that it spent a lot of time on the ground. What seems to be an additional (as yet unnamed) kaka species is known from bones found on the Chatham Islands. The population here seems to have become extinct within the last 150 years or so.
Several features of these parrots make them unusual and interesting compared to the members of other lineages. It used to be intimated that New Zealand was a predator-free environment where birds evolved flightlessness and unusual body shapes and lifestyles due to an absence of the selective pressures created by predation. If that were so, the nocturnal habits of these birds and their cryptic patterning and colouration seem incongruous (though note that birds are sometimes nocturnal because they can be, not necessarily because they’re avoiding activity in the daytime). Of course, New Zealand was actually inhabited by a giant eagle as well as by a giant harrier, an Accipiter hawk and some owls, so there are good reasons for thinking that many or all of its birds actually evolved within the context of constant danger from predation. The terrestrial mammals and large geckos that previously occurred on New Zealand might have represented additional predation threats for small vertebrates, but that’s a blatant speculation on my part.
These parrots are also unusual in exhibiting fairly obvious sexual dimorphism: males are definitely bigger than females in Kakapo and Kea, and male Kea have weakly curved bills relative to females (Bond et al. 1991). It has been suggested that island-dwelling birds exhibit more sexual dimorphism than ones on big landmasses: one hypothesis is that the smaller land area means that the sexes are more likely to be in competition due to a smaller resource base (and hence need to evolve in different directions to avoid competition); another is that a lower number of competitors allows members of a single species to diversify to fill niches that – in the more packed assemblages of continental habitats - are typically occupied by members of other species (Selander 1966).
Phylogenetic work on these parrots shows that they represent the sister-group to remaining crown-parrots (de Kloet and de Kloet 2005, Tokita et al. 2007, Wright et al. 2008, Schweizer et al. 2010), though note that some of these studies included onlyNestor or Strigops, and not both taxa. Some old classification systems do position Nestor and Strigops well apart (see Sibley & Ahlquist 1990 for a review); however, because they all look somewhat alike, because they’re all endemic to New Zealand, and because they group together in molecular phylogenies, it’s universally thought today that they form a clade, termed variously Nestoridae, Nestorinae or Nestorini. However, Strigopini, Strigopinae and Strigopidae have been used for Strigops alone (both Nestoridae and Strigopidae were first used by Charles Lucien Bonaparte in 1849). Most recently, Joseph et al. (2012) have advocated the use of a clade called Strigopoidea that includes both Nestoridae and Strigopidae. Several fossil relatives of the Kea and Kaka – included together within the genus Nelepsittacus – are known from the Early Miocene St Bathans Fauna of Otago (Worthy et al. 2011).
Several of these studies also show that cockatoos – that is, the clade Cacatuini (conventionally considered a ‘Tribe’), Cacatuinae, Cacatuidae or Cacatuoidea (see Joseph et al. 2012) – then represent the sister-group to the rest of crown-parrots. So, strigopoids represent the sister-group to a cockatoo + all other crown-parrots clade.
Mayr (2010) looked at the anatomy of parrots within a phylogenetic context and argued that strigopoids differ from most other crown-parrots in having a broad, bifurcated anterior spine on the sternum: cockatoos have this condition too, but all other crown-parrots have a narrow, non-bifurcate process (Mayr 2010). In strigopoids and cockatoos, the first few rings on the bronchi (the two tubes that extend between the syrinx and the lungs) are “weak and cartilaginous”, and well separated by thick tracts of membrane, whereas the rings are ossified and in close contact in other crown-parrots. The implication from the distribution of these characters is that strigopoids and cockatoos possess the plesiomorphic condition for parrots, with all other crown-parrots possessing derived conditions. Suggestions that strigopoids might be close relatives of the superficially similar night parrots (Pezoporus) and ground parrots (Geopsittacus) are not correct based on what we currently think.
Because parrot lineages endemic to New Zealand (strigopoid) and Australasia (cacatuine) have been recovered as outside the clade that includes all the remaining crown-parrots of the world, it has been suggested that Australasia represents the ancestral home for these birds (Wright et al. 2010). The ancestors of all other parrot lineages must have moved northwards during various dispersal events. While this scenario of Gondwanan origins and later dispersal has, understandably, been quite popular, it should be noted that other possibilities are still on the cards. Fossil stem-parrots are (so far) from the north, not the south, so it remains plausible that strigopoids and cacatuines dispersed southwards from a northern centre of origin (Naish 2012).
For previous Tet Zoo articles on parrots, on birds endemic to New Zealand, and on some of the other topics mentioned here, see…
Refs – -
Bond, A. B., Wilson, K.-J. & Diamond, J. 1991. Sexual dimorphism in the Kea Nestor notabilis. Emu 91, 12-19.
de Kloet, R. S. & de Kloet, S. R. 2005. The evolution of the spindlin gene in birds: sequence analysis of an intron of the spindlin W and Z gene reveals four major divisions of the Psittaciformes. Molecular Phylogenetics and Evolution 36, 706-721.
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. Peabody Museum of Natural History, New Haven, pp. 211-235.
Iwaniuk, A. N., Nelson, J. E., James, H. F. & Olson, S. L. 2004. A comparative test of the correlated evolution of flightlessness and relative brain size in birds. Journal of Zoology 263, 317-327.
Joseph, L., Toon, A., Schirtzinger, E. E., Wright, T. F. & Schodde, R. 2012. A revised nomenclature and classification for family-group taxa of parrots (Psittaciformes). Zootaxa 3205, 26-40.
Livezey, B. C. 1992. Morphological corollaries and ecological implications of flightlessness in the kakapo (Psittaciformes: Strigops habroptilus). Journal of Morphology 213, 105-145.
Mayr, G. 2010. Parrot interrelationships – morphology and the new molecular phylogenies. Emu 110, 348-357.
McDougall, A., Porter, G., Mostert, M., Cupitt, R., Cupitt, S., Joseph, L., Murphy, S., Janetzki, H., Gallagher, A. & Burbridge, A. 2009. Another piece in an Australian ornithological puzzle – a second Night parrot is found dead in Queensland. Emu 109, 198-203.
Naish, D. 2012. Birds. In Brett-Surman, M. K., Holtz, T. R. & Farlow, J. O. (eds) The Complete Dinosaur (Second Edition). Indiana University Press (Bloomington & Indianapolis), pp. 379-423.
Schweizer, M., Seehausen, O., Güntert, M. & Hertwig, S. T. 2010. The evolutionary diversification of parrots supports a taxon pulse model with multiple trans-oceanic dispersal events and local radiations. Molecular Phylogenetics and Evolution 54, 984-994.
Selander, R. K. 1966. Sexual dimorphism and differential niche utilization in birds. Condor 68, 113-151.
Sibley, C. G. & Ahlquist, J. A. 1990. Phylogeny and Classification of Birds. New Haven: Yale University Press.
Tokita, M., Kiyoshi, T. & Armstrong, K. N. (2007). Evolution of craniofacial novelty in parrots through developmental modularity and heterochrony. Evolution & Development 9, 590-601.
Worthy, T. & Holdaway, R. N. 2002. The Lost World of the Moa. Indiana University Press, Bloomington, Indiana.
- ., Tennyson, A. J. D., Scofield, R. P. 2011. An early Miocene diversity of parrots (Aves, Strigopidae, Nestorinae) from New Zealand. Journal of Vertebrate Paleontology 31, 1102-1116.
Wright, T. F., Schirtzinger, E. E., Matsumoto, T., Eberhard, J. R., Graves, G. R., Sanchez, J. J., Capelli, S., Müller, H., Scharpegge, J., Chambers, G. K. & Fleischer, R. C. 2008. A multilocus molecular phylogeny of the parrots (Psittaciformes): support for a Gondwanan origin during the Cretaceous. Molecular Biology and Evolution 25, 2141-2156.