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.

Saturday, 20 February 2010

Pigeons of Bristol 1: The Bleeding heart Doves and their relatives

One of the most important elements of Bristol’s bird collection is our range of pigeon and dove species. We currently hold thirteen different species, including the highly endangered Mauritius Pink pigeon. Most of the species we hold originate from south east Asia and Indonesia, so I will begin this series with a genus widely held in zoos and in private ownership, the Bleeding heart doves and their relatives.

Scattered across the islands of Indonesia, the Philippines and further out into the Pacific is a group of small terrestrial pigeons classed in the genus Gallicolumba (“Chicken-Pigeon”). Several species have a crimson blotch on their breast, which has given these species the English name of Bleeding Heart Doves (in fact, I have had visitors to the zoo reporting the birds we have as injured!). Not all species have this red patch however, and these tend to be termed Ground Doves instead.

About 20 species survive today, but several are threatened for the usual reasons of island endemic birds – introduced predators (especially rats and cats), and habitat destruction. All indications are that many more have become extinct without being recorded – the surviving species have a patchy distribution across the islands, with species present on two islands with none on intervening ones.

Bristol currently holds three species of Gallicolumba – The Luzon Bleeding Heart G.luzonica and the Mindanao Bleeding Heart G.criniger, plus the Sulawesi Quail Dove G.tristigmata. We are also working with a local organization in the Philippines which holds the only captive population of the Negros Bleeding Heart Dove G. keayi

Sunday, 14 February 2010

Compare the mongoose

New arrivals in the diurnal carnivore exhibit in Twilight World are a pair of Yellow Mongooses. Cynictis penicillata. This is the first time in recent years that Bristol has exhibited this species, which is becoming increasingly common in zoos in Europe (there are none currently in North America according to ISIS).

Yellow Mongooses have an extensive range in southern Africa, and at least 11 subspecies have been defined, although whether these are all valid is debatable. There is however a tendency for northern animals to be smaller and greyer than those to the south. This probably is an effect of the average colour of the habitat – Yellow Mongooses have numerous natural enemies, especially birds of prey, and need to match their background as closely as possible. Their natural habitat is dry grassland to semi-desert, where they live in burrows. The diet is mainly insects, but they will also catch rodents, reptiles, and birds. In general, they could be considered the ecological equivalent of the smaller species of North American fox.

Sunday, 7 February 2010

February Research Colloquium - Partula, past, present, and future

Some decades ago, at the start of the introduction of biochemistry to the study of animal diversity, a research project was undertaken on the endemic live-bearing snails of French Polynesia belonging to the family Partulidae, especially to the widespread genus Partula. The studies were aimed at disentangling the primary engines of evolution of diversity, in other words was the multiplicity of species due to natural selection, random events, genetic drift or something else entirely? Unfortunately, while the debate was raging disaster struck the study populations.

The Giant African Snail (seen in many pet shops in the UK) was introduced by a misguided local entrepreneur as a potential food source. Finding that no one wanted to eat his livestock, he let them go, with disastrous results for the local peoples crops. That was only the prelude however. The real disaster was a misguided attempt at biological control, which took the form of the introduction of the Rosy Wolf Snail Euglandina rosea. Euglandina originates from Florida, where it is a generalist predator of snails and slugs (it is also sometimes cannibalistic). However, it has a preferred size of prey, and Giant snails are simply too big for it once adult. What was the right size however, was the different species of Partula. As with many island species, Partula has a low reproductive rate, only managing a potential 7 fold increase in a year, compared to Euglandinas’ 57 and the Giant snails 500. The result was a mass extinction event, and it was believed that all the Partula in the wild were either extinct in the wild or headed that way.