High frequency of polyandrous trios in an endangered population of lammergeiers Gypaetus barbatus in Northern Spain

Abstract

In the Pyrenees, between 1979 and 1986, six trios of lammergeiers Gypaetus barbatus, all consisting of a female and two males, occupied breeding territories formerly inhabited by pairs. In 1988 the frequency of polyandrous females in the population was 11·5%. Both males copulated, shared nest building and incubation, and fed the young. Aggressive behaviour between males was not detected. Trios had similar reproductive success as pairs which formerly occupied the same territories and as neighbouring pairs. Polyandry may have important implications for the conservation of this endangered lammergeier population.