Maintenance of plumage polymorphism in red-footed boobies in the Galápagos archipelago: Observations of mate choice and habitat association

Abstract

The Red-footed Booby (Sula sula) is considered one of the most polymorphic seabirds, with three adult plumage types recognized: white, white-tailed brown, and brown, as well as several degrees of intermediates. Here we show that there is no evidence of deviation from random mating according to plumage color in the largest population of Red-footed Boobies in the Galápagos Archipelago, based on a random sample of approximately 300 pairs, which agrees with previous results found in the Indian Ocean. We also found that the ratio of color morphs varies among islands within this archipelago, with the populations of Islas Genovesa and Wolf presenting a reversed ratio (90% brown, and 10% white) when compared to the majority of Red-footed Boobies populations worldwide. Furthermore, there was no indication of differential habitat association among morphs. We concluded that plumage color does not play an important role in mate choice, and as a result, nonrandom mating based on plumage color is likely not a selective mechanism maintaining the plumage polymorphism in this population. © The Cooper Ornithological Society 2008.