BREEDING HABITAT REQUIREMENTS AND SELECTION BY OLROG’S GULL (LARUS ATLANTICUS), A THREATENED SPECIES

PABLO GARCÍA BORBOROGLU; PABLO YORIO

AUK

American Ornithologists´ Union

Lugar: Winnipeg, Canada; Año: 2007 vol. 124 p. 1201 - 1212

0004-8038

We studied habitat requirements and selection of Olrog´s Gulls (Larus atlanticus) breeding at six colonies along 2,500 km of coastline in central Argentina that encompasses its entire distributional range. Colonies were located only on islands that ranged in size between 0.4 and 125.8 ha, and the islands’ distance to the mainland varied from 0.12 to 16.7 km. Colonies ranged in size between 12 and 341 nests. In three of the colonies, gulls nested in subcolonies (range: 8–239 nests). They nested at relatively high densities, with a mean inter-nest distance of 0.66 ± 0.25 m. Logistic regression analysis to compare nest and random-site characteristics at each colony showed that Olrog´s Gulls selected sites that were close to the hightide line, at a lower height above sea level, far from available vegetation, and had lower vegetation cover over the nest. Olrog´s Gulls showed a significant positive association with Kelp Gulls (L. dominicanus), an expanding generalist species that also nests in similar habitats. Current trends in coastal development, particularly in the Olrog’s Gulls’ main breeding grounds of southern Buenos Aires, indicate the urgent need for habitat-protection guidelines for this threatened species. Moreover, its breeding association with Kelp Gulls suggests a potential spatial conflict and highlights the need for increased monitoring and management actions.