Posted by Stuart Marsden
Recently, I have been working with Paul Watler of National Trust for the Cayman Islands and Dr Juliet Vickery of RSPB on a Darwin Initiative project looking at the status and conservation of the Near-threatened Cuban Parrot Amazona leucocephala and other birds on the tiny island of Cayman Brac in the Caribbean.
|Little Cayman from the tiny plane|
The parrot on Cayman Brac is an endemic sub-species (A. l. hesterna) which was thought by
Cayman Islands Department of Environment to have a population of around 570 in 2012. It is threatened both by natural events such as hurricanes, and rather unnatural clearance of the island’s forest for housing developments. The former can cause severe, but temporary, damage to the forest, particularly knocking down large old trees used by nesting parrots. The latter, of course, can destroy habitat for parrots and the island’s few other breeding landbirds, which, importantly, include the Near-threatened VitellineWarbler Setophaga vitellina, which is confined to the Caymans and the tiny Swan Islands, off Honduras.
|Above: Parrot Estates offering plots in Cayman Brac. Below: Much of the island is for sale it seems.|
The parrot surveys, nest searches and habitat measurements in the sweltering xeromorphic semi-deciduous forest of the Brac was just about the hardest fieldwork I have ever been involved with. It took us 20-30 minutes to cover just 100 metres. Nevertheless, Paul managed to accumulate a great dataset: nine active nests were found; forest birds were counted at 198 points; and potential nest site trees were recorded in forest across the island in an attempt to identify the best areas for the Trust to try to purchase, to safeguard the parrot, in the future.
All these data will allow us to estimate population densities for key bird species in different habitats on the island, generate island-wide population size estimates, and, we hope, to gauge the likely effects on the island’s birds of potential real estate development over the next 20 years or so. While we hope to publish our full results in due course, our preliminary analyses point to several important findings
|A pair of Cuban Amazons stands guard |
at an active nest cavity
- A high proportion of the island is owned by developers or potential developers
- Our initial population estimate for the parrot on the Brac is around 450 individuals, with the parrot occurring at a density of around 12 per sq km.
- Population densities of key landbirds were high – for example, perhaps in the order of 700 birds per sq km for Vitelline warbler, and 450 per sq km for Thick-billed Vireo Vireo crassirostris.
- The birds in general and the parrot in particular were not restricted to the least disturbed forests on the island.
Both high abundance and broad habitat use is something we would expect from birds on a small island with so few breeding land bird species. This is through processes known as ecological release and density compensation. It bodes reasonably well for the future of birds on the Brac – so long as real estate developments are not extensive, and those that do go ahead, retain native vegetation within the housing plots. Particularly important is retention of big old trees which contain cavities that may be used by the island’s parrots. Of course nobody can predict when the next big hurricane will strike the Brac, but the healthier the forest and its bird populations, the better they may be able to withstand its effects.
The project was coordinated by the National Trust for the Cayman Islands. For more information or to join, click here
The project was funded by Darwin Initiative
Photos: Stuart Marsden