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Prolactin secretion in a brood parasite, the brown-headed cowbird, Molothrus ater

Authors

  • A. M. Dufty Jr,

    Corresponding author
    1. The Rockefeller University Field Research Center, Millbrook, New York 12545, USA
      *To whom all correspondence should be addressed
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  • A. R. Goldsmith,

    1. The Rockefeller University Field Research Center, Millbrook, New York 12545, USA
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    • **AFRC Research Group on Photoperiodism & Reproduction, Department of Zoology, University of Bristol, Bristol BS8 IUG

  • J. C. Wingfield

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    • ‡Department of Zoology, NJ 15, University of Washington, Seattle, WA 98195, USA


*To whom all correspondence should be addressed

Abstract

Blood samples were collected from a free-living population of male and female brown-headed cowbirds, Molothrus ater, during the breeding season and plasma levels of prolactin were measured by radioimmunoassay. Prolactin concentrations in both sexes increased significantly in mid to late May; peak levels were reached by June and were maintained throughout June and into July. Prolactin levels in juveniles were significantly lower than in adults but were still elevated. Prolactin has been implicated in parental care in several avian species; however, cowbirds are brood parasites with complete absence of parental behaviour, suggesting that prolactin must function in another capacity in cowbirds, or that cowbirds have developed target tissue insensitivity to this hormone.

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