Breeding systems, climate, and the evolution of migration in shorebirds

Migratory behavior incurs energetic costs that may influence the time and energy available for reproduction including territory establishment, courtship, pair formation, incubation, and brood care. Conversely pair formation and parental care may leave less time and energy available for migration and other nonbreeding behaviors. Therefore, natural selection favoring migratory behavior may influence breeding system evolution and vice versa. We used phylogenetic comparative methods to investigate relationships between migration distance and the wide diversity of breeding systems in shorebirds (sandpipers, plovers and allies). Consistent with previous studies, we show that long-distance migration is associated with reduced male care across shorebird species. We then use directional phylogenetic analyses to test whether migration distances have tended to increase or decrease over time and whether such evolutionary changes have preceded or followed changes in parental care. We show that evolutionary transitions from short-distance migration to long-distance migration have coevolved with changes from full biparental care to reduced male care. Furthermore, our directional analyses suggest that increments in migration distance are more likely to have preceded reductions in male care than vice versa. We also show that male polygamy is associated with northern breeding latitudes when the nonbreeding latitude is controlled statistically. Although this suggests that mating systems, parental care, and migration have more complex relationships than previously thought, our results are consistent with the hypothesis that migration influences breeding system evolution. Copyright 2009, Oxford University Press.