Nestled along the rocky shores and cliff tops of the eastern bluff of Cayman Brac are what remains of the Cayman Islands’ only Brown Booby colony (Sula leucogaster). Established long before human settlement, the colony was once thousands strong according to historical accounts from the early 20th century, yet the 2021/2022 nesting season saw a record low of just two chicks surviving to fledge along the Lighthouse Trail.
Though the once common practice of harvesting Booby eggs likely facilitated the population to dwindle, scientists consider the exponential rise in feral populations of invasive predators such as domestic cats, dogs and black rats as the primary cause of their steep decline from the 80’s through to the present day. Despite their increasing scarcity over the last 30 years, the Brown Booby has remained one of the national treasures of Cayman Brac, being fully protected (along with all birds) under the first Animals Act in 1976 and now under the National Conservation Act (2013). Anyone who lives in, or has visited Cayman Brac will know what a joy it is to watch them coast majestically in the wind along the bluff, squawking as they swoop to their nests and beak wrestle with their goofy, fluffy fledglings.
When monitoring first began in 1983 only 170 Brown Booby nesting pairs were recorded in five subgroups along the coastline. By 2001 just 61 pairs were recorded at four active sites and in 2019, the number of nesting pairs recorded had declined to 46 across three active sites.
As an open-ground nester, the Brown Booby is particularly vulnerable and in the Cayman Islands, breeds only on Cayman Brac in increasingly small numbers. The Brown Booby should not be confused with its tree-nesting wetland cousin in Little Cayman, the Red-footed Booby (Sula sula) who’s 6000-strong nesting colony in the Booby Pond Nature Reserve (owned and managed by the National Trust) is the largest in the Caribbean. Though similar in name, Cayman’s Brown and Red-footed Boobies occupy completely different habitats, on separate islands and rarely interact. In fact, tracking studies reveal that while our Red-footed boobies travel as far as Jamaica on their regular fishing expeditions, Brown Boobies are primarily coastal foragers.
Brown Boobies mate for life, usually rearing just one chick per year. Courting begins as early as October with playful chatter and stick trading, as the foundations of the open-ground nest are laid. Their (often) lone chick emerges in early spring and will have fledged by late August – if it survives the myriad of challenges it will face from deathly cliff falls, predation, human disturbance, and the ever increasing strength of storms in a climate changing world. To raise the stakes even higher, if one parent perishes during nesting or rearing, the remaining adult cannot sustain the chick on his or her own and will abandon the nest, leaving the chick to starve.
All three of the remaining active nest sites on Cayman Brac – along the upper ridge of the eastern half of Long Beach, around the eastern tip of the bluff edge (including all of the Lighthouse Trail), and on the beach and bluff edge along the south shore – have been severely disturbed in recent years by an increased density of feral predators including feral cats and Black Rats.
During the 2018 nesting season it was concluded, based on evidenced reports, that cats had attacked and killed at least 16 Brown Boobies, the majority being adult birds. With only 23 nesting pairs recorded in 2022, concerns over the ability of the population to recover from sustained predation or a natural disaster became more critical than ever.
In an attempt to address the mounting vulnerabilities of these iconic seabirds, the Department of Environment partnered with the RSPB and the National Trust, supported by funding through DarwinPlus, to launch a predator control program during the 2023 nesting season which placed cat and rat traps inside the most densely populated nesting site along the Lighthouse Trail running from the eastern most tip of the bluff top, westerly along the bluff’s northern edge. The results were undeniable. After removing 17 feral cats (unowned, living in the wild) and 231 rats from just this area alone, the 2023 nesting season saw a 77.8% nest success compared to just 12.5% of the previous year. These results mirror the successes of predator control programs from similar island nations also struggling to protect their delicate ecosystems from unmanaged, invasive threats and have prompted control measures to continue.
The 2024 nesting season saw even greater success with all of the nests that had eggs achieving 100% fledgling success. Brown Boobies begin mating around 3 years of age so scientists are hopeful to observe the colony as the 2023 cohort reaches maturity in the 2026/27 seasons.
As the global biodiversity crisis continues to swell, localized conservation efforts become a crucial piece of the puzzle. Recognizing the native animals and plants which existed long before human settlement, such as the Brown Booby colony on Cayman Brac, and promoting their survival through education and conservation measures, means the ecosystems they rely on, and which rely on them in return, are also maintained.
Though living on the edge quite literally and figuratively, with dedicated effort, time, and some luck, Cayman Brac’s colony can recover and perhaps even flourish, allowing our future generations to experience the magic of our Brown Booby.
Learn more about Cayman’s Brown Booby colony and other nesting seabirds at www.conservation.ky/seabirds