Extra-pair copulations and fertilizations are common among birds, especially in passerines. So far, however, only a few studies have examined genetic mating systems in socially monogamous shorebirds. Here, we examine parentage in the Western Sandpiper, Calidris mauri. Given that Western Sandpipers nest at high densities on the arctic tundra, have separate nesting and feeding areas, and show high divorce rates between years, we expected extra-pair paternity to be more common in this species compared to other monogamous shorebirds. However, DNA fingerprinting of 98 chicks from 40 families revealed that only 8% of the broods contained young sired by extra-pair males, in that 5% of all chicks were extrapair. All chicks were the genetic offspring of their social mothers. We found that males followed females more often than the reverse. Also, cuckolded males were separated from their mates (by more than 10 m) for longer than those that did not lose paternity. Although these results suggest a role for male mate guarding, we propose that high potential costs in terms of reduced paternal care likely constrain female Western Sandpipers from seeking extra-pair copulations.
Additional publication details
Genetic parentage and mate guarding in the Arctic-breedng Western Sandpiper