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Saturday, 27 February 2010

Pigeons of Bristol 2: Pheasant?Pigeon?

One of the peculiarities of the bird life of the Australasian region is that it has, aside from two species of quail (which are migrants and therefore easily colonise new habitats), no native members of the Galliformes (the pheasants, quail and their allies). Instead, native groups such as the megapodes, button-quails, ratites, and even some songbirds like the Lyrebird, fill the ecological niche occupied by pheasants and grouse in other parts of the world. In the rain forests of New Guinea and the neighbouring islands these are joined by several species of pigeon, which have adopted a terrestrial lifestyle and a pheasant-like diet. In the last post I wrote about the Gallicolumba ground doves, this week I would like to introduce perhaps the most highly specialised of the surviving members of the pigeon family, the Pheasant Pigeon Otidiphaps nobilis.

The Pheasant Pigeon gets its name from its strong resemblance to a pheasant; including the long, compressed tail and reluctance to fly (it prefers to run through dense vegetation). It appears to feed mainly on seeds and fallen fruits, plus terrestrial invertebrates, although there have been few if any studies on the wild diet, and what information is available is based on observations of captive individuals.

The taxonomy of the Pheasant Pigeon is a little unclear, but there are several subspecies. The two most commonly seen in zoos are the White-naped Pheasant Pigeon O.nobilis aruensis (which we have in Bristol), and the Green-naped Pheasant Pigeon O.nobilis nobilis. As you might guess from their names, the chief visual difference is the colour on the back of the neck. The captive population of both the subspecies is small – ISIS lists only 44 O.nobilis aruensis in captivity, almost all in Europe, and 83 of the nominate form, also mostly in Europe. There are also 37 unidentified subspecies or hybrids, most of these in the US.

The closest living relatives of the Pheasant Pigeon seem to be the Nicobar Pigeon and the Crowned Pigeon (both of which we also have at Bristol. The extinct Dodo of Mauritius also appears to be part of this group. For an interesting paper on the origin and diversification of the pigeons, see this link: http://www.inhs.illinois.edu/~kjohnson/kpj_pdfs/Syst.Biol.2007a.pdf

The Pheasant pigeon is a very shy bird, and does not breed freely in captivity (only Barcelona Zoo in Europe has been consistently successful). The male has a display flight where he makes a distinctive wing-clap, and it is possible that most zoos hold their birds in aviaries that are too small and disturbed by passing members of the public to successfully encourage nesting. In addition, although it has a pheasant-like appearance, its reproductive rate is that of a pigeon, and it lays only 1 or two eggs at a time. When the young hatch they remain in the nest and ate fed at first on “pigeon milk”, which is produced from the crop and contains a similar composition of proteins, fats and minerals to mammalian milk (the belief that only mammals feed their young on parental secretions is untrue – pigeons, flamingos, and even many species of fish also produce food for their young from the parents bodies).

Although hard to study, the Pheasant Pigeon has a wide range and is presently classed by the IUCN as of least concern, although one subspecies, the Ferguson Island Pheasant Pigeon O.nobilis insularis may be threatened by deforestation.


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