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Author: Gilardi, James D.
Year: 1992
Title: Sex-Specific Foraging Distributions of Brown Boobies in the Eastern Tropical Pacific
Journal: Colonial Waterbirds
Volume: 15
Issue: 1
Pages: 148-151
Keywords: Brown Booby; foraging; parental investment; sexual dimorphism; Sula leucogaster

Abstract: This study investigates sex differences in the distribution of foraging Brown Boobies (Sula leucogaster) near Clipperton island in the eastern tropical Pacific. Females tended to forage farther from shore than males: e.g., the sex ratio varied from strongly male-biased near the colony (within 20 km) to to female-biased away from the colony (beyond 90 km). Males also return to the colony earlier in the evening than females, again suggesting more proximate foraging locations in males. An hypothesis linking these foraging differences to sex role partitioning and sexual size dimorphism is proposed. Selection on females for increased chick provisionning may have lead to increased size and foraging range. Conversely, males are selected to remain close to the colony to maintain territories and prevent or acquire extra-pair copulations, thus reducing their foraging range and body size.