January 16, 2013 | 31
Whenever I mention turkeys on Tet Zoo, it’s unavoidable that I (generally) mention or illustrate the turkey we know best: the domestic form of Meleagris gallopavo, the North American bird typically known as the Wild turkey. It’s big, with bronzy-brown plumage, a mostly pinkish head and neck and a wiry ‘beard’ that hangs down from the chest. This remarkable, charismatic, wonderful and familiar bird (hey, I really like turkeys) has been discussed on Tet Zoo a few times: see the links below. But I have turkey-guilt. There is…. another.
As you’ll know if you know your gamebirds, the second living turkey is the Ocellated turkey M. ocellata. Originally described (in 1820) as a species of Meleagris, it was regarded in 1896 as different enough from M. gallopavo to deserve its own ‘genus’, Agriocharis. This persisted until Steadman’s (1980) study of fossil turkeys showed that the species is not distinct enough from M. gallopavo to warrant ‘generic’ rank. Historically, several fossil species have been regarded as especially close to the Ocellated turkey and hence as members of Agriocharis as well.
Remember that these decisions about whether a species warrants its own ‘genus’ or not are wholly subjective; we accept the view for now that the species should be included in Meleagris (indeed, it is very similar in many skeletal details to M. gallopavo), but this might change in future. Bocheński & Campbell (2006) noted that “the osteological differences [between M. ocellata and M. gallopavo] are larger than previously thought” (p. 48) and they essentially recommended that further study is needed.
The Ocellated turkey is endemic to the Yucatán Peninsula, meaning that it mostly occurs in Mexico but is also present in parts of Belize and Guatemala. Its plumage is brighter and more glossy green and copper than bronzy-brown; it also differs from M. gallopavo in having far whiter remiges and a blue head decorated with orange, wart-like nodules.
Bands of small blue ocelli are present on the rump feathers and near the tips of the uppertail coverts and tail feathers. They’re most obvious, of course, when the bird fans out its tail in display (as in the photo below) and they explain the technical and common name. Prior to fanning the tail, a displaying male wags its tail from side to side. When displaying, it presses its neck against the top of its back (rather than pulling the neck into the chest, as is done in M. gallopavo) while drooping its wings.
Blue ocelli on the tail region are, elsewhere, famously seen in peafowl, and the superficial similarity between peafowl and the Ocellated turkey once led to the suggestion that the two might be especially close (Taylor et al. 2006). Today we’re confident that the Ocellated turkey really is a turkey, and for more on the probable position of turkeys within gamebird phylogeny see the previous article.
The fossil turkeys
Several Pliocene and Pleistocene species have been regarded as more closely related to the Ocellated turkey than to M. gallopavo: Martin & Tate (1970) recognised four fossil relatives of this species (they regarded all as part of Agriocharis): M. leopoldi, M. progenes, M. anza and M. crassipes. There are other Pleistocene fossil turkeys too, including M. alta, M. tridens and – best known of them all – the California turkey M. californica. The systematics and phylogeny of many of these species has been, and still is, controversial and unresolved. M. alta and M. tridens were both treated as synonyms of M. gallopavo by Steadman (1980) and the late Pliocene form M. progenes might be synonymous with M. leopoldi (Stidham 2011), as might M. anza.
The mostly Californian species M. californica was – ironically, in view of the previous Tet Zoo article – originally described as a peacock (Miller 1909). Its fossils are very abundant at Rancho La Brea where numerous specimens died after entrapment in the tar. The idea of numerous peacocks strutting about the woodlands and savannahs of Pleistocene California, alongside dire wolves, sabre-toothed cats and ground sloths, is perhaps amusing. However, its describer – Larry H. Miller – revised his view, later suggesting that the ‘California peacock’ was an evolutionary intermediate between peafowl and the Ocellated turkey, and warranting the new name Parapavo (Miller 1916). Later authors appreciated that Parapavo was a true turkey, either equally related to both living species, or closer to one or the other. Steadman (1980) eventually concluded that it should be sunk into Meleagris.
Proagriocharis kimballensis from the Pliocene of Nebraska was described as the smallest and oldest turkey (Martin & Tate 1970). Steadman (1980), in his major review of fossil turkeys, sank Proagriocharis into Meleagris. Olson & Farrand (1974) reinterpreted Rhegminornis calobates Wetmore, 1943 from the Early Miocene of Florida as a very early turkey. Named for a tarsometatarsus 29.6 mm long, it must have been a tiny turkey. If it is a turkey, it fits with the general trend of increasing body size otherwise seen in the fossil turkeys of the Pliocene and Pleistocene.
Some aspects of anatomy, biology, behaviour
The turkey we know best – M. gallopavo – has a reddish dewlap, a dangling structure that hangs over the side of the bill (called the snood), and thickly wrinkled skin over the top and back of the head. The Ocellated turkey lacks a dewlap but it does have a snood – a bluish one rather than a reddish one. A reddish eye-ring is present. Posterior to the snood, and projecting upwards from the top of the head, is a blunt blue horn, sometimes with a yellowish tip. Snoods and horns are absent in females. Ocellated turkeys also differ from M. gallopavo in having slimmer, shorter, redder legs. Long curved spurs (generally longer than those of M. gallopavo: Bocheński & Campbell 2006) are present in males. We don’t usually think of turkeys as birds that fight, but they do: google ‘fighting turkeys’ to see some great photos.
Relatively little information is available on the behaviour and biology of the Ocellated turkey and it’s one of those animals where you tend to see the same several facts trotted out again and again. Sources often say that it doesn’t produce a proper ‘gobble’ call like the other turkey; that’s apparently not true – males produce a series of drumming noises before producing a high-pitched gobble (Taylor et al. 2006). Diet-wise, it’s a generalist, eating the leaves and seeds of a diversity of plants as well as moths, beetles and ants. Sugihara & Heston (1981) reported an observation of two adult males “feeding intensively on a column of leaf cutter ants carrying flower parts” (p. 396).
Having mentioned insects, Sugihara & Heston (1981) also reported anting behaviour in members of this species. Three adult males were seen to deliberately lower their wings onto ant nest mounds. The ants they were using – Atta cephalotes – don’t produce formic acid, so were presumably just running about among the birds’ feathers, removing parasites and such. I have no idea how widespread anting behaviour is in gamebirds – I’m aware of anecdotes reporting possible anting behaviour in domestic chickens – and it raises the question of how widespread anting behaviour is in birds as a whole. Do waterfowl and palaeognaths do it too?
Moving on, the Ocellated turkey occurs in humid broadleaved forests as well as savannah-scrub mosaics, and it forms flocks that fluctuate in size throughout the year. During the early months of the year, males sing and fight with one another to claim dominance of a flock. As is typical for gamebirds with strong sexual dimorphism and ornate, showy males, females are solely responsible for eggs and chicks, and small groups of females and their poults may form ‘brooding flocks’ during September and October (Madge & McGowan 2002).
The small and localised nature of the population means that the species is listed as ‘Near Threatened’ and it’s thought to be in decline due to hunting pressure and habitat loss and degradation. It appears to be locally extinct in several Mexican regions. Declines that occurred during 1980 and 2000 were hypothesed by Kampichler et al. (2010) to be based on an influx of people into the region where it occurs and a concomitant increase in the obtaining of bushmeat.
Thanks to John Harshman, Markus Bühler, Simon Woolley and Sheri L. Williamson (of the excellent Life, Birds, and Everything) for providing the photos used here. For previous Tet Zoo articles on turkeys and other gamebirds, see…
Oh, remember the caption competition? This one wins, but only because a picture was created… and because I like Outkast. Well done, himitsunokare (if that is your real name).
Refs – -
Bocheński, Z. M. & Campbell, K. E. 2006. The extinct California turkey, Meleagris californica, from Rancho La Brea: comparative osteology and systematics. Natural History Museum of Los Angeles County, Contributions in Science 509, 1-92.
Kampichler, C., Calmé, S., Weissenberger, H., Arriaga-Weiss, S. L. 2010. Indication of a species in an extinction vortex: the ocellated turkey on the Yucatan peninsula, Mexico. Acta Oecologica 36, 561-568.
Madge, S. & McGowan, P. 2002. Pheasants, Partidges & Grouse, Including Buttonquails, Sandgrouse and Allies. Christopher Helm, London.
Martin, L. D. & Tate, J. 1970. A new turkey from the Pliocene of Nebraska. The Wilson Bulletin 82, 214-218.
Miller, L. H. 1909. Pavo californicus, a fossil peacock from the Quaternary asphalt beds of Rancho La Brea. University of California Publications, Bulletin of the Department of Geology 5, 285-289.
- . 1916. A review of the species Pavo californicus. University of California Publications, Bulletin of the Department of Geology 9, 89-96.
Olson, S. L. & Farrand, J. 1974. Rhegminornis restudied: a tiny Miocene turkey. The Wilson Bulletin 86, 114-120.
Sugihara, G. & Katherine Heston, K. 1981. Field notes on winter flocks of the Ocellated turkey (Agriocharis ocellata). The Auk 98, 396-398.
Steadman, D. W. 1980. A review of the osteology and paleontology of turkeys (Aves: Meleagridinae). Contributions in Science, Natural History Museum of Los Angeles County 330, 131-207.
Stidham. T. A. 2011. The carpometacarpus of the Pliocene turkey Meleagris leopoldi (Galliformes: Phasianidae) and the problem of morphological variability in turkeys. PaleoBios 30, 13-17.
Taylor, C. I., Quigley, H. B. & Gonzalez, M. J. 2006. Ocellated turkey (Meleagris ocellata). NWTF Wildlife Bulletin 6, 1-8.