A new project collecting data on the seabirds of the Sister Islands is already yielding some interesting results.

Last month, the Cayman Islands Department of Environment began work on the Sister Islands to gather comprehensive data on regionally and globally important seabird populations in the Cayman Islands. This project is primarily funded by the Darwin Initiative, a U.K. government grant scheme aimed at helping to protect biodiversity and the natural environment within the U.K. Overseas Territories.

Over the next two years, the DoE will work in partnership with the National Trust of the Cayman Islands and seabird experts from the Universities of Liverpool and Exeter, U.K., to collect urgently needed information on the movements, ecology and status of resident seabird populations.

It is hoped that the knowledge gained through this work will contribute to conservation management around the Cayman Islands.

The project will focus largely on red-footed boobies (Sula sula) on Little Cayman and brown boobies (Sula leucogaster) on Cayman Brac. While these species breed in colonies on the Cayman Islands that are recognized as globally and regionally important, they remain poorly understood throughout much of their foraging range.

“At the moment, we have more data on the activities of these birds on shore regarding breeding activities, but we don’t have as much information on what they are doing at sea,” said researcher Rhiannon Meier, who began working on the project in April.

“How are they using the marine environment? Where do they go when they fly out to sea? These are the types of questions we are looking to answer,” said Ms. Meier.

A brown booby roosts.
A brown booby roosts.

A combination of electronic tags and biogeochemical markers are being used to provide insights into the habitat use, foraging strategies and dietary habits of the birds.

Breeding adults at the Booby Pond Nature Reserve (red-footed boobies), and at multiple sites on Cayman Brac (brown boobies), have been fitted with miniaturized GPS loggers that trace their movements as they travel over the ocean to find food.

The data collected from these devices should help to reveal the strategies that these animals use to exploit their surrounding environment, and will enable the DoE to identify appropriate conservation measures on land as well as at sea.

“We have already noted that it looks like the brown boobies stay closer to home, while the red-footed boobies go out to sea sometimes for up to five days, at night sleeping on the water,” she said.

She said the GPS loggers stay on the birds for about two weeks, and while all efforts are made to recover the loggers from the tagged birds, they will fall off on their own at about the two-week mark.

“Some birds are quite skittish, but overall we have not found it too difficult to approach them and attach the loggers,” said Ms. Meier.

The data from about 20 of the birds which were fitted with trackers is now being analyzed, providing researchers with some valuable baseline information.

Using visual survey methods, information on breeding behavior and population biology is also being collected at seabird colonies. This information, in combination with previous data recorded by volunteers, will allow scientists to assess the status of populations, as well as develop longer-term seabird monitoring programs.

“We are trying to gain an understanding of the general ecology of these birds’ habitat and their diet,” said Ms. Meier.

“We do this by analyzing blood samples from the birds. The biogeochemicals can tell us what they are eating, and where they go, by comparing them to samples of fish in the region.”
Ms. Meier said the researchers are also looking at the population statuses of red boobies, magnificent frigate birds and tropic birds.

During the study period, the researchers are hoping they will be able to build on the work already done to develop robust population monitoring programs and test out a few possible methods.

The outputs of this project will feed directly into the development of Species Conservation Plans that are required under the National Conservation Law of the Cayman Islands.

For more information, contact the DoE by phone at 949-8469 or by email at
[email protected] or [email protected]