Deliver a Modern Day Message-in-a-Bottle
Story and photos by Susan Zaluski
The sun is setting as we slowly trudge up an inhospitable hillside on the westernmost end of the BVI on Great Tobago Island, which is not the kind of place where humans typically want to go. My long trousers are quickly covered with "jumping cactus", which have an effective, yet painful, reproductive strategy. The plants' barbs are designed to bury into whatever they touch – flesh or material – making it seem as if the landscape is reaching out to bite you. Each step requires careful contemplation so as to avoid cactus or slipping on loose rocks. After a long hike, we are met by the acrid scent of bird guano. The slope ahead of us appears like a moonscape, land that has been over-grazed by feral goats brought to the islands by early sailors and settlers as an emergency food source hundreds of years ago. Unfettered, the goats have eaten nearly everything in sight and reproduce wantonly, causing landslides that wipe out the trees where seabirds nest, while dumping piles of dirt with the ferocity of a bulldozer into the sea, smothering and killing once pristine adjacent coral reefs.
Nearly 1,000 nests pack the small stands of badly-weathered seagrape trees near where we stand. This site is home to the largest seabird colony in the BVI, which is the only Magnicificent frigatebird nesting site in the entirety of the Virgin Islands (USVI & BVI combined). Ranked as the third largest breeding site for frigatebirds in the Caribbean, the colony is regarded as both regionally and globally important. We are here to attach GPS and satellite devices onto these "Man-O-War" birds, as frigatebirds are known locally in the British Virgin Islands.
A large scissor-tailed bird with a seven foot wingpsan, Magnificent frigatebirds have no water-proofing on their wings like other seabirds, and must eat and drink entirely on the wing, snatching food from the water's surface. They are also known as the "pirates of the sky" and will chase other birds to steal food in mid-flight. True to their piratical nature, frigatebirds are often seen following fishing vessels and will sometimes swoop down – unwisely choosing a fishing lure or live bait as their meal. Many of the fishermen in the BVI will simply bring the bird into the boat and unhook the animal; however, many novice fishermen panic and cut the line – unaware of the deadly consequences. The still-hooked bird will fly off, still trailing several meters of invisible monofilament fishing line. When the bird returns to the colony, the fishing line becomes tangled throughout the nesting area. The hooked bird is usually either stuck or breaks its wing, and unable to fly or feed itself, dies. There is also the danger that more birds in the colony will unknowingly fly into the invisible but deadly web of line. This issue has been acute in the BVI, with dozens of birds perishing in the colony in recent years. Building maps of common foraging movement is a first step in helping to understand where birds might be exposed to this fisheries threat, and other environmental problems, such as oil spills, pollutions or other dangerous marine debris.
Silent in the sky, the birds noisily emanate a clattering noise with their beaks while in the colony. Each year, male birds arrive at the colony, ballooning out their red gular sacs (throat patch). Once a female is suitably impressed, a pair is formed that will work to care for a single egg that takes about two months to hatch. Newly born chicks are entirely naked and unable to feed themselves or even regulate their body temperatures against the cool night air or hot Caribbean sun, relying completely on their parents. Males will help their mate for the first three to four months of the chick's life, and will then depart, leaving the female to care for the chick for up to 18 months, one of the longest chick-rearing phases of any bird species on earth. Where the males go is not entirely clear, and is yet another puzzle that tracking technology may help to solve.
The GPS and satellite devices weigh about 22 grams, selected to be under 3% of the birds' bodyweight so as not to alter their flight capabilities. The GPS units are carefully fastened to the bird's tail feathers, while the satellite tags are attached via a harness system. We work with focus into the late night, and by midnight we are pleased to have retrieved GPS loggers from several birds that we had previously tagged. The GPS loggers have a limited battery life of about one week, and exactly like a message-in-a-bottle, we can only obtain information about the birds whereabouts from these devices when they are recovered with the re-capturing of a tagged bird – an exercise that takes patience and persistence, as the birds grow skeptical of our presence.
Spearheaded by the Jost Van Dykes Preservation Society (JVDPS) in the BVI, a small not-for-profit organization for which I serve as Director, our team is part of a research project funded by the UK's Darwin Initiative. Team members include staff and volunteers from the BVI Department of Conservation & Fisheries, The National Parks Trust of the Virgin Islands, The Royal Society for the Protection of Birds (RSPB), the University of Liverpool, and even volunteering staff from the BVI's Airport Authority.
On this particular trip, our project has received added support from the South Carolina Cooperative Fish & Wildlife Research Unit at Clemson University, the Avian Research & Conservation Institute in Florida and the UK's Foreign and Commonwealth Office to deploy three satellite tags onto frigatebirds in the colony. Equipped with tiny solar panels, these devices do not need to be retrieved and will be left on the birds continuously for a few years, allowing us to track longer term movement via satellite. This excursion has been the cumulative effort of months of planning, and we are relieved when we successfully attach the satellite devices. From South Carolina to Peru, researchers have solicited input from biologists familiar with these particular birds. Dozens of e-mails and phone calls have been dedicated to deliberating the safest and easiest methods of capturing birds and attaching the devices so that the "tags" both function properly and cause no disturbance to the animal's ability to fly and feed itself.
We leave the colony around midnight, and hike through the darkness covered in scratches and cuts from bird beaks, while bird excrement and regurgitated fish stain our clothing – common occurrences for working in a seabird colony – but relieved and excited about the information this project will generate.
The BVI is home to 15 species of breeding seabirds, a group of birds adapted to life within the marine environment. While seabirds are abundant globally, their numbers have been in severe decline in past decades due to both localized and global human and environmental disturbances. Today's populations are thought to be at a fraction of their historical levels. Most seabird species have a much longer lifespan than other birds (frigatebirds live an estimated 35 to 50 years), breed later in life and have just a few chicks, investing a great deal of care into in their nest as compared to other bird species. Sometimes an overlooked part of the marine environment, seabirds are an important indicator, often used to detect changes in the ocean. Fishermen have long known that "where there are birds, there are fish," and the movement of seabirds can be used to help identify hotspots for fish and other prey species.
Humans usually protect what we know and love, and we hope the project will raise the profile of seabirds. If you are considering fishing in the BVI, please familiarize yourself with the correct method of re-releasing a hooked bird. You can follow the movement of the three satellite-tagged frigatebirds – Atoya, Boyd and Clive – through an online system linked at the Jost Van Dykes Preservation Society's webpage: www.jvdps.org. You can also help sponsor a bird and ensure that the project has enough funding to continue to follow and learn about these frigatebirds.