Radar surveys of Audubon’s Shearwater

This article is from BioNews 18 – August 2015  See all BioNews issues here.


Radar (Kai Wulf Saba Conservation Foundation)

Audubon’s Shearwater [Kai Wulf, Saba Conservation Foundation]

Audubon’s Shearwater (Puffinus Iherminiera) is a tropical seabird that lives throughout the Caribbean. On Saba and Sint Eustatius this charismatic species is locally known as “Wedrego”, because of its mating call, interpreted as “where do we go?” The “Wedrego” symbolizes Saba’s National Bird and is prominently represented on Saba’s coat of arms.

These birds have an extraordinary behavior. During the day they are far out on the sea catching food. However, by night, they return to their island breeding areas where their nests consist of burrows or natural cavities located on steep “cliffs”. On land, introduced predators such as feral cats, rats and goats threaten them. Their nocturnal behavior and inaccessible nesting sites make it difficult to study them with standard bird monitoring techniques and this behavior is the main reason why so little is known about this seabird. However, basic knowledge on their breeding status and threats to the species are crucial to safeguard Saba’s National Bird.

To better protect Audubon’s Shearwaters, Adam C. Brown from Environmental Protection in the Caribbean (EPIC), in partnership with the Saba Conservation Foundation (SCF), completed a pilot study on Saba to get more insights on the density, nesting areas and flights paths of Saba’s national bird.

The goal of their pilot study was to record the seabirds as they flew from the sea to their nests. The researchers made use of an innovative technique: marine radar. This method has already proven to be an effective tool for other nocturnal seabirds, such as the Black-capped Petrel on Dominica, that are difficult to observe using traditional techniques. Each night during the survey period, radar monitoring started at sunset, when Audubon’s Shearwaters return to their nesting areas. The survey areas focused around potential and historic nest activity centers. During the three hours after sunset, all targets that appeared on the radar’s monitor within a radar of 1.5 km were examined. Researchers noted time, flight direction, flight behavior, velocity and, if possible identified species and number of individuals detected.

More than 450 Audubon’s Shearwater were recorded over seven nights of surveys at seven sites around Saba: The Bottom, Sulpher Mine/Pirate Cliffs/ Past Lambee Pullout, Agricultural Station/Spring Bay, St. Johns, Well’s Bay and Windwardside. Data showed that Audubon’s Shearwaters are widespread, with the largest densities detected near Hell’s Gate and above The Bottom.

This project demonstrated that the radar technique is an efficient tool to study birds like the elusive Audubon’s Shearwater. Recommendations included follow-up monitoring on Saba, a pilot study of Audubon Shearwaters on St Eustatius and the mapping of communication towers on nest islands as these pose a potential threat to shearwaters where they are located on or near their flight paths.




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