Brood Size, Hatching Order and Hatching Date: Effects on Four Life-History Stages from Hatching to Recruitment in Western Gulls

We examined survival and recruitment (into the breeding population) in three cohorts of western gulls Larus occidentalis (Audubon) in relation to brood size at hatching, hatching order and hatching date. We divided the pre-breeding period into four stages: (i) the natal stage ― «pre-fledging» from hatching to independence; (ii) the juvenile stage ― the period from independence to age 1 year; (iii) the subadult stage ― the second and third years of life; and (iv) the recruitment stage ― the period when adults breed for the first time. Hatching date and hatching order (in order of importance) each had a strong, negative effect on survival in the natal stage. Brood size had little effect on natal survival; however, after controlling for hatching date there was a significant negative effect