Determinants of nest repair in laughing gulls

Laughing gulls Larus atricilla , nesting in saltmarshes subject to tidal inundations, build substantial nests and continue adding material throughout the reproductive cycle. Under normal conditions, nest size increased until gulls had 5-day-old chicks. I manipulated nests at various stages in the reproductive cycle. Until their chicks reached 14 days of age, gulls added material to artificially wetted nests, making them significantly deeper and wider than before treatment. During all reproductive stages examined, gulls repaired nests having half of the material removed. The adaptive significances of nest building and relative nest size are discussed in terms of washouts and the requirements of the eggs and chicks at different stages in the reproductive cycle.