Female perception of cowbird song: a closed developmental program.

To investigate the modifiability of the brown-headed female cowbird's (Molothrus ater ater) response to male song, we reared M.a. ater females with either M.a. ater or M.a. obscurus males, whose songs differ in geographic origin. The females were later tested for their responsiveness to playbacks of M.a. ater and M.a. obscurus song. Rearing with M.a. obscurus males had no effect on the female's preference for her native song variant, suggesting a closed program for receptive development. The data on song perception are contrasted with those previously obtained for male production and indicate different constraints on song perception as opposed to song production.