Juveniles have been found to eat caddis fly larvae. Reproduction Breeding generally occurs on the Alaskan coast and in northeastern Siberia. Pair bonds form at the beginning of each breeding season, during which there is constant contact between members of a pair. These bonds break immediately after the breeding season is over. To initiate breeding, females perform inciting movements and calls.
Males respond by performing ritualized displays that include exposing the blackened chest.
Nesting occurs in the grass flats or on the periphery of tundra ponds. The nest is built by the female and is lined with grass stems and a large amount of down. Once eggs are laid, the female is very protective of the nest and will often be extremely hesitant to leave, even allowing people to touch her. Clutch sizes average 4.5 eggs and range in number from one to eight. An egg is laid every other day.