Nest Site Selection by Laughing Gulls: Comparison of Tropical Colonies (Culebra, Puerto Rico) with Temperate Colonies (New Jersey)

Abstract

We examined nest site selection in Laughing Gulls (Larus atricilla) nesting on three islands in the Culebra National Wildlife Refuge, Puerto Rico, to determine if gull nest sites showed consistent characteristics differing from most of the available habitat, to compare nest site characteristics on islands with different vegetative cover, and to contrast nest site choices on these tropical island colonies with colonies that we have studied on the northern Atlantic coast of mainland United States. At Culebra, Laughing Gulls nested with Royal, Sandwich, and Bridled terns (Sterna maxima, S. sandvicensis, S. anaethetus), Brown Noddies (Anous stolidus), and Brown Boobies (Sula leucogaster), but their nearest neighbors were usually conspecifics. The gulls' nest sites generally differed from random points with respect to percent cover, vegetation height, visibility, and distance from clearings. Compared to the random points, gull nests were under denser vegetation of intermediate height with high visibility from their nests and with less cover around their nests. Their choice of nest sites provided protection and cover from predators and the sun. Dense and tall vegetation would hinder gulls from flying directly from their nests, and many nests were thus near rocks or clearings, which allowed the gulls to exit quickly. Laughing Gulls nesting on the Culebran cays generally nested in taller, denser vegetation than those nesting farther north along the Atlantic coast, which partially reflects temperature differences between the localities.