The Red-billed Tropicbird (Phaethon aethereus) is a large majestic seabird that can often be seen flying over the waters of Saba and St. Eustatius. It actually spends most of its life flying over the open ocean, plunge-diving for fish and squid. It is rarely seen on land, and for good reason; it cannot stand upright or walk because its short legs are set too far back and its feet are paddle-shaped. It has to use its long wings to push itself forward on its belly.
Named after its large red bill, the Red-billed Tropicbird has a white head and body with fine dark barring on its upperparts, black wing edges and a distinctive black eye stripe. Its most characteristic feature is the two streaming long middle tail feathers, which can measure up to 56 centimeters long.
The Red-billed Tropicbird only comes to land to breed. It breeds in loose colonies, and the female lays just one egg a year onto a scrape in the ground, in a cliff crevice, or sometimes just under a large rock close to shore. Both Saba and St. Eustatius are especially important breeding habitats for the Red-billed Tropicbird. In fact, together these islands are home to the Caribbean’s largest nesting population of Red-billed Tropicbirds and may host the most significant breeding colonies in the world. BirdLife International has recognised Saba’s coastline as an Important Bird Area (IBA), notably because the cliffs around the island are important roosting and nesting sites for these tropicbirds. On St. Eustatius, estimates suggest that 100 to 200 Red-billed Tropicbirds breed each year on the cliffs around the island and on the steep slope of White Wall. The Red-billed Tropicbird is actually the only species of seabird known to nest on St. Eustatius.
The future of the Red-billed Tropicbird within the Lesser Antilles is however in jeopardy. The population of tropicbirds on Saba is particularly vulnerable due to poor breeding success (the rate at which offspring are produced); this is a significant problem for the long-term survival of the species as Saba is thought to be home to over 20% of the world population of Red-billed Tropicbirds. Following this alarming discovery, the Saba Conservation Foundation (SCF) and St. Eustatius National Parks Foundation (STENAPA), with the support of key volunteers, launched a monitoring programme to gain a clear picture of the population status of tropicbirds. It soon became evident that Saba’s population of Red-billed Tropicbirds is much more threatened than previously believed. Studies have confirmed that nest predation from feral domestic cats as well as rats are the biggest threat as they prey on tropicbird eggs and chicks.
To safeguard the future of this key species, the Saba Conservation Foundation and STENAPA are taking action. Nesting activities continue to be monitored to better understand why nesting success has been so poor. The use of geo-locators is also helping gain insight into the daily habits of this tropicbird. On St.Eustatius, STENAPA has been monitoring the abundance and breeding success of Red-billed Tropicbirds since early 2013. Monitoring programmes on both islands are now using similar methods for nest monitoring and peak attendance counts to ensure a coordinated approach. Research activities are also focusing on the predators of the Red-billed Tropicbird. The goal is to gather sufficient information to develop a plan to decrease and control predator populations quickly and efficiently. On Saba, Dutch researchers from IMARES have assisted SCF with the study of feral cats on the island; feral cats predate on tropicbird chicks because they suffer from starvation and go for any available food source. On St.Eustatius, rats were also confirmed as predators when a rat stealing a tropicbird egg was captured on a motion-tracking camera. While much has been learnt about the role of predators, further research on prey-predator dynamics will be necessary to maintain a conservation strategy that ensures the survival of Red-billed Tropicbirds on both Saba and St. Eustatius.
To find out more about the studies and conservation efforts mentioned above, click on the links below.
- Conservation Science: Red-billed Tropicbirds on Saba and St. Eustatius
- Tropicbirds on the Air
- Tropicbird Monitoring 2013 (Saba and St. Eustatius)
- Tropicbird Monitoring (STENAPA)
- Invasive Predator Research on Saba
- Cameras for Conservation
- BioNews 13 – February 2014
- BioNews 4 – April 2013
- Tropicbird Monitoring Manual (DCNA)