NEST PREDATION AS A SELECTIVE FACTOR IN THE EVOLUTION OF DEVELOPMENTAL RATES IN ALTRICIAL BIRDS

Birds develop rapidly compared with other vertebrates, and it has been proposed that such rapid development serves to minimize the period of exposure to predators of eggs and nestlings. Evidence is, however, scant. We test the proposition that nest predation has been an important selective factor in the evolution of the rapid developmental rates characteristic of altricial birds. We compare the incubation and nestling periods of altrical land birds from islands that lack native mammalian and reptilian nest predators with those of phylogenetically related species from areas with predators. We show that open-nesting native species from islands take longer to hatch and fledge than related species from continents, controlling for body mass. In contrast, species that have been recently introduced to islands have similar incubation and nestling periods there compared to those in their region of origin. In addition, we show that statistically different regression equations describe the interspecific allometric relationships between incubation and nestling period and body mass in hole-nesting and open-nesting species, the latter of which presumably face higher predation pressure. We confirm that, in relation to body mass, hole-nesting species develop more slowly. We conclude that predation has been an important selective factor in the evolution of developmental rates in altricial birds.