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Research Spotlight: Ducklings Leave Nests in Early Morning, Suggesting Predator Avoidance

In a study published in the journal Ecology and Evolution, U.S. Geological Survey (USGS) biologists put small cameras next to duck nests to determine what time of day wild ducklings began hatching, when the hen and ducklings departed the nest, and if any predators came to the nest when ducklings were present.

Gadwall ducklings in nest
Gadwall ducklings in nest, Suisun Marsh, CA. 

Some species of ducks, including mallard (Anas platyrhynchos), gadwall (Mareca strepera), and cinnamon teal (A. cyanoptera), nest in dry, upland habitat in California, with ducklings leaving the nest for wetlands shortly after hatching. The timing of egg hatching and duckling departure from the nest is critical for egg and brood survival. Eggs and ducklings risk being eaten by predators like coyotes, raccoons, skunks, birds of prey, and snakes while in the nest and en route to wetlands. At the same time, for the journey from the nest to wetland to be successful, ducklings need enough time in the nest to fully dry, develop motor skills, and imprint on their mother. 

To study hatch and departure timing, USGS scientists placed cameras next to the nests of mallard, gadwall, and cinnamon teal ducks at the Grizzly Island Wildlife Area, near San Francisco Bay. Grizzly Island is one of many state wildlife areas that provides important nesting habitat for these species.  The videos showed that the onset of hatch differed by species, with most gadwall and cinnamon teal nests starting to hatch during daylight hours and mallard nests starting to hatch during both daylight and night hours. Both gadwall and mallard broods demonstrated a clear preference for leaving the nest in the early hours of the morning, usually the day after hatching.

Predators ate eggs at 10% of nests in the two days prior to hatch and ducklings in 15% of nests prior to departure. Gopher snakes (Pituophis catenifer) were the most common predator of ducklings at the nest, with striped skunk (Mephitis mephitis), coyote (Canis latrans), and an unidentified predatory bird species was also observed eating ducklings. In one case, ducklings were crushed by a Tule elk (Cervus canadensis nannodes) stepping on a 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. 

These results indicate that timing of hatch and nest departure is influenced by a variety of factors, including species, predator risk, and duckling readiness.

This spotlight refers to:
Peterson, SH, Ackerman, JT, Herzog, MP, Hartman, CA, Croston, R, Feldheim, CL, and Casazza, ML. 2019. Sitting ducklings: Timing of hatch, nest departure, and predation risk for dabbling duck broods. Ecology and Evolution.

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Photo: Gadwall ducklings in a nest at the Grizzly Island Wildlife Area, shortly after hatch and before departure of hen and brood to a nearby wetland. (Credit: Sarah Peterson/USGS)


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