Hormone changes triggered by aggression in a natural population of blackbirds

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Science  02 Mar 1979:
Vol. 203, Issue 4383, pp. 918-920
DOI: 10.1126/science.570304


The concentrations of hormones in the plasma of male red-winged blackbirds caught at the height of an aggressive encounter are significantly different from those in males that have not recently engaged in aggressive behavior. Concentrations of luteinizing hormone in the plasma are decreased in the aggressive males, whereas androgen concentrations are affected in a more complex manner. Concentrations of corticoids do not appear to be affected by aggressive behavior.