Disruption, Dispersion, and Dominance in Lek-Breeding Birds

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Abstract
Disruption is any behavior that interferes with male-female courtship interactions of copulation and leads to a decrease in the number of copulations completed by a male, or an increase in the time and energy required to complete them. The origin and maintenance of disruption, its effects on the fitness of the individuals involved and its influence on dominance relationships and spacing of males at leks are examined. Disruptive behavior is most common among lek-breeding birds, probably because its frequency is proportional to the amount of contact between members of the same sex. Amount of contact is inversely proportional to distance between males so that clustering of males on leks may result in increased disruption. Disruption usually is performed by a rival male who, as a result of his actions, may be able to mate with the female disrupted. Such behavior should be highly advantageous if, on average, the disruptor is able to decrease his age of first reproduction or to obtain more copulations. It is disadvantageous to the disrupted pair. Disruption also may occur as a by-product of high levels of male aggressiveness that are favored by selection because they increase the ability of a lek male to obtain and hold a high quality court or a high rank in a dominance hierarchy and to attract and excite females for copulation. Selection should operate to minimize the amount of disruption at leks through the evolution of strict dominance hierarchies among lek males, or by increasing the separation of lek males which may result in the formation of exploded leks.