Cooperative display and relatedness among males in a lek-mating bird

McDonald, D.B., and W.K. Potts. 1994. Science 266: 1030-1032.

Long-tailed manakins mate in leks and cooperate in multi-year male-male partnerships. An alpha male is responsible for virtually all mating while a beta male assists in the courtship displays. Such altruism by the beta male poses a problem for evolutionary theory because most theoretical treatments and empirical examples of cooperative behavior involve kin selection or reciprocity.  Here we show that alpha and beta partners are not relatives and that reciprocity is not involved. Instead, we demonstrate direct, though long-delayed benefits to beta males, which include rare copulations, ascension to alpha status, and female lek-fidelity. These benefits maintain this unusual form of male-male cooperation.