Summer distribution and foraging behavior of Histrionicus histrionicus around Cattle Point on San Juan Island, Washington

Abstract

Harlequin Ducks molt and winter in the San Juan Islands of Washington state. This study investigated habitat choice and feeding behavior of Harlequin Ducks around Cattle Point on San Juan Island by comparing time foraging versus resting in different habitats. In the water, ducks performed three behaviors while foraging: surface feeding, diving, or dabbling. Across observation periods, Harlequin Ducks spent on average 80% of the time foraging, and only 20% of the time hauled-out and resting. The ducks spent the more time foraging in areas of low current and high vegetation and the least time at areas high current and low vegetation. The mild climate in the San Juan Archipelago could allow the ducks to spend more time foraging to meet their in-molt energetic needs by reducing the need to thermoregulate.