Work

Hormonal Correlates of Parental and Helping Behavior in Cooperatively Breeding Harris' Hawks (Parabuteo unicinctus)

Year: 1991

Type: article

Abstract: We measured plasma levels of progesterone and prolactin in free-living adult breeders, adult-plumaged helpers, and juvenal-plumaged helpers of the cooperatively breeding Harris' Hawk, Parabuteo unicinctus, at different stages of the nesting cycle. Overall, progesterone levels did not vary significantly with sex, nest stage, or behavioral role, but they increased significantly with handling time. Progesterone levels were highest (2-4 ng/ml) in breeding females just before egg laying. Prolactin levels did not vary with handling time but were significantly elevated in breeding females during the nest-building stage (14.1 ng/ml) and in both breeding males (8.4 ng/ml) and females (25.5 ng/ml) during incubation. Both sexes of breeders incubate the eggs, but the females do the bulk of incubation and only they develop a brood patch. Prolactin levels in the breeders declined immediately after the eggs hatched, in contrast to the pattern seen in many other altricial species. Prolactin levels in the adult-plumaged male helpers rose significantly after the eggs hatched (9.1 ng/ml). At this time these birds bring more food items from group kills to the nestlings than any other group members. The elevated prolactin levels in the adult-plumaged helpers may facilitate the helping behavior that they exhibit toward the nestlings and fledglings.

Source: The Auk

DOI: 10.2307/4088104

Authors: Carol Masters Vleck, Arthur R. Goldsmith

Institutions: University of Arizona, Biotechnology and Biological Sciences Research Council, University of Bristol

Language: English

Topic: Animal Behavior and Reproduction

Subfield: Ecology, Evolution, Behavior and Systematics

Field: Agricultural and Biological Sciences

Domain: Life Sciences

Open Access status: green

Funders: National Science Foundation, University of Bristol

Award: Hormone Levels and Behavior