Tetrapod Zoology

Tetrapod Zoology

Amphibians, reptiles, birds and mammals - living and extinct

Turkeys vs peafowl, the great debate


Photo by Darren Naish.

Galliforms – gamebirds – are among the most spectacularly flamboyant of birds; the males of many lineages are provided with an abundance of elaborate display structures. I’ve written about turkeys and their snoods, wattles, caruncles and showy feathers before. I like the photo above because it depicts two of the showiest gamebirds – Meleagris gallopavo (domestic turkey) and Pavo cristatus (Indian peacock) – together. Turkeys and peafowl are not especially close relatives, or are they? We have conflicting trees.

Peafowl supposedly belong together with the Congo peacock (Afropavo congensis), argus pheasants (Argusianus and Rheinardia) and peacock-pheasants (Polyplectron) in a group typically called Pavoninae. You can understand why these birds are usually regarded as close relatives: they share feathery head crests and gigantic, showy wing and tail covert feathers, marked with ocelli. Behaviourally, they’re birds where the males are polygonous or promiscuous and play no role in parental care. As always, these generalisations don’t go for all members of the group. Some peacock-pheasants (like the Sumatran peacock-pheasant Po. chalcurum) and the Congo peacock lack giant ocellated feathers, and the Congo peacock is monogamous and practises biparental care. Nevertheless, genetics and anatomy show that these species are deeply nested within the group, so their unusual morphology and behaviour probably represent reversals relative to the ancestral condition (Kimball et al. 1997, 2001).

Captive pair of Congo peacock at Antwerp Zoo; photo by Frank Wouters, licensed under Creative Commons Attribution 2.0 Generic license.

The evolution of monogamous, biparental Afropavo from polygynous ancestors where males did not provide parental care might be unique among birds. Afropavo – often regarded as one of the most sensational ornithological discoveries of the 20th century – was famously recognised by James Chapin in 1936 when he realised that two discarded taxiderm specimens (labelled as juvenile Pavo cristatus) possessed feathers matching those brought back from Liberia by an American Museum of Natural History expedition in 1913 (Chapin 1936, 1937) [adjacent photo of Afropavo pair by Frank Wouters]. These weren’t juvenile Indian peafowl at all, but representatives of an entirely new, peacock-like gamebird from the Congo. Chapin regarded Afropavo as a peafowl but it was argued by later authors to be a close relative of the African francolins or the guineafowl. Chapin was right, however: the classification of Afropavo among the pavonines is well supported (de Boer & van Bocxstaele 1981, Kimball et al. 1997, Dyke et al. 2003, Ksepka 2009).

Substantially simplified segment of gamebird phylogeny based on the topology recovered by Bonilla et al. (2010): the key thing to note is that turkeys and peafowl belong to different clades. Images by Naish (Meleagris), in public domain (Afropavo), or licensed under Creative Commons Attribution-Share Alike 3.0 Unported (Footwarrior: Lophura; Bjørn Christian Tørrissen: Chrysolophus; Doug Janson: Tragopan; Dinesh Kannambadi: Pavo; Dante Alighieri: Polyplectron) and 2.0 (Gary Noon: Phasianus; David Galavan: Perdix; Lip Kee Yap: Gallus) and 2.5 Generic (André Karwath: Coturnix) licenses.

Some recent molecular phylogenies find pavonines to belong in a clade that also includes junglefowl (Gallus) and quails (Coturnix) (Kimball & Braun 2008, Bonilla et al. 2010). This pavonine + junglefowl + quail clade is the sister-group to a clade that includes tragopans, turkeys, partridges, northern pheasants, gallopheasants and others. A much simplified version of that sort of topology is shown here.

Kriegs et al. (2007) and Kimball et al. (2011) found pavonines to be outside a clade that included quails, gallopheasants, partridges, turkeys and grouse (Kimball et al. (2011), incidentally, didn’t find pavonines to be monophyletic). The point is that – according to these results – turkeys and peafowl are not close at all, but members of clades that have been distinct for a substantial amount of time: probably since, say, the Late Miocene or earlier.

Morphological studies don’t recover the same shape to the tree though. According to the work concerned, pavonines do not necessarily group with junglefowl and quails; instead, they are close to, or form part of a poorly resolved group that includes, gallopheasants and turkeys (Dyke et al. 2003, Kspeka 2009). According to these sorts of topologies, peafowl and turkeys might only have diverged within the past 10 million years or so.

So, peafowl and turkeys are definitely not close if you follow the molecular results, but they might be close if you follow the morphological ones. Ksepka (2009) produced an analysis where molecular and morphological results were combined, and turkeys belonged to the same clade as northern pheasants, gallopheasants, grouse and grey partridges; pavonines grouped with junglefowl, quails, snowcocks, Alectoris partridges and others. For now, I favour the idea that turkeys and peafowl do indeed belong to long-separate gamebird clades: they are not close relatives.

The section of Ksepka's (2009) combined analysis that we're especially interested in. Turkeys (Meleagridinae) are part of the same major clade as northern pheasants and kin (Phasianinae) and grouse (Tetraoninae) while peafowl and kin (Pavoninae) are part of the same clade as junglefowl and kin (Gallinae) and quails and kin (Coturnicinae).

Strange as it may seem, peafowl inhabited the Pliocene of eastern Europe where their fossils are found alongside those of ptarmigan (Boev 1998). Presumably, these extinct peafowl were denizens of fairly open habitats where the flora included cold-adapted, broadleaved shrubs and small trees. The species concerned – P. bravardi – was apparently bigger than living peafowl (Boev & Koufos 2000) but, for now, we can only speculate as to whether it had the giant showy trains of modern species. Don’t go thinking that all fossil peafowl were like this, however. The Miocene-Pliocene species P. aesculapi from southwestern and central Europe lived in warm, forested places, while an as-yet-unnamed species of Early Pliocene peafowl from Kenya comes from a humid, forested environment and lived alongside chevrotains and hominids (Pickford et al. 2004).

And now we come to the whole reason for this article. UNBELIEVABLY, it started out as a caption competition. Provide a caption for the photo used at the top. Of course, if you have anything else useful to say, especially if it concerns turkeys, peafowl, or their relatives or evolutionary histories… now would be a good time.

For previous Tet Zoo articles on gamebirds, see…

That's not much. I must do better.

Refs - -

Boev, Z. 1998. Peafowls (g. Pavo Linnaeus, 1758) and ptarmigans (g. Lagopus Brisson, 1760): an unique coexistence in North Bulgaria over 3 m.y. ago. Biogeographica 19, 220-222.

- . & Koufos, G. 2000. Presence of Pavo bravardi (Gervais, 1849) (Aves, Phasianidae) in the Ruscinian locality of Megalo Emvolon, Macedonia, Greece. Geologica Balcanica 30, 69-74.

Bonilla, A. J., Braun, E. L. & Kimball, R. T. 2010. Comparative molecular evolution and phylogenetic utility of 3’-UTRs and introns in Galliforms [sic]. Molecular Phylogenetics and Evolution 56, 536-542.

de Boer, L. E. & van Bocxstaele, R. 1981. Somatic chromosomes of the Congo peafowl (Afropavo congensis) and their bearing on the species' affinities. Condor 83, 204-208.

Chapin, J. P. 1936. A new peacock-like bird from the Belgian Congo. Revue de zoologie et de botanique africaines 29, 1-6.

- . 1937. A remarkable new gallinaceous bird from the Belgian Congo. Proceedings of the Linnean Society of London 149, 37-38.

Dyke, G. J., Gulas, B. E. & Crowe, T. M. 2003. Suprageneric relationships of galliform birds (Aves, Galliformes): a cladistic analysis of morphological characters. Zoological Journal of the Linnean Society 137, 227-244.

Kimball, R. T. & Bruan, E. L. 2008. A multigene phylogeny of Galliformes supports a single origin of erectile ability in non-feathered facial traits. Journal of Avian Biology 39, 438-445.

- ., Braun, E. L. & Ligon, J. D. 1997. Resolution of the phylogenetic position of the Congo peafowl, Afropavo congensis: a biogeographic and evolutionary enigma. Proceedings of the Royal Society of London B 264, 1517-1523.

- ., Braun, E. L., Ligon, J. D., Kucchini, V. & Randi, E. 2001. A molecular phylogeny of the peacock-pheasants (Galliformes: Polyplectron spp.) indicates loss and reduction of ornamental traits and display behaviours. Biological Journal of the Linnean Society 73, 187-198.

- ., St. Mary, C. M. & Braun, E. L. 2011. A macroevolutionary perspective on multiple sexual traits in the Phasianidae (Galliformes). International Journal of Evolutionary Biology 2011, Article ID 423938, 16 pp., doi: 10.4061/2011/423938

Kriegs, J. O., Matzke, A., Churakov, G., Kutizin, A., Mayr, G., Brosius, J. & Schmitz, J. 2007. Waves of genomic hitchhikers shed light on the evolution of gamebirds (Aves: Galliformes). BMC Evolutionary Biology 2007, 7:190 doi:10.1186/1471-2148-7-190

Pickford, M., Senut, B. & Mourer-Chauviré, C. 2004. Early Pliocene Tragulidae and peafowls in the Rift Valley, Kenya: evidence for rainforest in East Africa. C. R. Palevol 3, 179-189.

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

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