Double nesting behaviour and differences between sexes in breeding success in wild Red-legged Partridges Alectoris rufa

Abstract

Double nesting behaviour, a rare breeding system where females 21 lay in two nests, one incubated by herself and the other one by her male, could be considered an intermediate stage in the evolutionary trend from biparental to uniparental care of single clutches. We examined the occurrence and success of double nesting behaviour of Red-legged Partridges Alectoris rufa in central Spain. We recorded clutch size and hatching success, and the variation in these among years and between the sex of the incubating bird. Participation in incubation was higher for females (94.66 %) than males (40.97 %), and the proportion of incubating males varied markedly between years with no incubating males in a dry year while approximately 50% of males incubated in other years. There was significant variation among years and between sexes in laying date, clutch size and hatching success. Also, clutch size decreased with later laying date in both sexes. The probability of clutch loss to predation differed between sexes, being much higher for nests incubated by females. Our results suggest that both rainfall and predation influence the occurrence and success of double nesting.