Abstracts

Presented by Joshua T. Ackerman - Email: jackerman@usgs.gov

For ground-nesting waterfowl, the timing of egg hatch and duckling departure from the nest may be constrained by the time required for ducklings to dry, to be developmentally ready to leave the nest, and to imprint on the hen, and influenced by predation risk. We determined the timing of hatch, nest departure, and predation on dabbling duck broods using small video cameras placed at the nests of mallard (Anas platyrhynchos; n=26), gadwall (Mareca strepera; n=24), and cinnamon teal (Anas cyanoptera; n=5). The onset of hatch differed by species, with cinnamon teal and gadwall nests starting to hatch during daylight hours (mean 7.5 hours after dawn) and mallard nests starting to hatch during daylight and night hours. Among all species, broods left the nest during daylight (98%), typically within 14 hours after dawn (53%). For mallard and gadwall, we identified 3 strategies for the timing of nest departure: 1) 9% of broods left the nest the same day that eggs began to hatch (612 hours after), 2) 81% of broods left the nest the day after eggs began to hatch, and 3) 10% of broods waited 2 days to depart the nest after eggs started to hatch, leaving the nest just after the second dawn (2742 hours after). Overall, eggs were depredated at 10% of nests with cameras in the 2 days prior to hatch and ducklings were depredated at 15% of nests with cameras before leaving the nest. The presence of predators at a nest and the death of multiple ducklings usually did not cause hens to flee the nest immediately with their broods. Our results suggest that broods prefer an early morning departure from nests, which may best balance developmental constraints with predation risk both at the nest and en route to wetlands.