Unusual Timing of Copulations in the Australian Brush-Turkey

Abstract

Recent studies of sperm competition have shown that the timing of copulations can be crucial to fertilization success. For example, in some birds copulations that occur near the time of laying are less likely to fertilize eggs than copulations that occur at other times. Thus, it was surprising to find that in Australian Brush-turkeys (Alectura lathami), most within-pair copulations (61.2%) occurred less than 1 h before laying, typically providing only 25 to 40 min for sperm to reach storage organs before potentially being flushed out by the descending egg. Brush-turkeys incubate their eggs in large mounds constructed by males; females lay an egg every few days and bury it within a chosen mound. Females usually solicited a copulation within 2 to 3 min after arriving at a mound to lay, but some males still forced copulations, particularly during the latter portion of laying visits. The unusual prevalence of copulations before laying probably results from males having little information about or control over female copulation behavior except when females need to lay in a males' mound. The prevalence of forced copulations during the latter part of laying visits may indicate conflict between the sexes over what constitutes adequate payment by females for use of a male's incubation mound. Neither sex showed any interest in copulating immediately after an egg was laid. This observation does not support the idea of a fertilization window after laying, but instead indicates that copulations at this time are probably ineffective in fertilizing eggs. Females also frequently made nonlaying visits to incubation mounds. The 38.8% of within-pair copulations that occurred during nonlaying visits may have been more likely to fertilize eggs, but the timing of these visits was controlled by females, who were probably less likely to be subject to male control when not laying.