The use of social attraction techniques to restore seabird colonies on Desecheo Island, Puerto Rico

Desecheo Island (117 ha) was historically an important seabird island in the Caribbean with 15 species recorded of which seven are known to breed, including major populations of brown boobies and red-footed bobbies. The introduction of invasive mammals, plus the use of the island as a bombing range, contributed to the extirpation of five of the seven known breeding populations of seabird species and vastly reduced numbers of the remaining two species. The island became a National Wildlife Refuge in 1976 and major conservation interventions have included the eradication of invasive goats, rhesus macaques, and rats between 1976 and 2016. Removing these critical threats from the island has allowed other active restoration goals to be realized, including restoring seabird colonies to the island.

Here we report on the installation of social attraction equipment in 2018 to augment bridled tern and brown noddy colonies and establish a species of conservation concern, the Audubon's shearwater. We supported these actions through a review of historic seabird nesting and roosting on Desecheo. Motion-sensing cameras were installed to document activity at each social attraction site and evaluate the effectiveness of our methods.

During the two years of deployment and monitoring, a total of seven bridled tern nests were documented in new and historic sites for the species, two of them next to a decoy colony; however, no brown noddy visits or nests were detected. In 2018 and 2019, one and two Audubon's shearwaters, respectively, were attracted to one of the sound system speakers, representing the first record for this species on the island.

Social attraction efforts on Desecheo appears to be a feasible activity that may help support seabird recolonization and support conservation goals for this National Wildlife Refuge.