Nest Site Selection by Masked and Blue-Footed Boobies on Isla Espanola, Galapagos

Abstract

On Punta Suarez, Isla Española, Galápagos Islands, Masked Boobies (Sula dactylatra) nested at the edge of a cliff while Blue-footed Boobies (Sula nebouxiz) nested farther inland. Elsewhere in the Galápagos, Blue-footed Boobies nested near cliff edges at seven of eight sites where Masked Boobies were absent. Masked Boobies appeared to have difficulty taking flight except from the cliff edge, while Blue-footed Boobies were able to take off from the interior. Neither species appeared dominant in interspecific interactions or could displace the other from occupied nest sites. Blue-footed Boobies may avoid nesting near cliff edges where Masked Boobies are present in order to avoid more frequent conflicts caused by a restricted habitat. Any such competition which occurs seems to involve only a small percentage of either species and breeding birds or the total population.