Variation in brood behavior of Black Brant

We studied behavior of broods of Black Brant (Branta bernicla nigricans) during five summers between 1987 and 1993, a period in which the local breeding population increased >3-fold. Goslings spent more time foraging than adults of either sex, while adult males spent more time alert and less time foraging than adult females. Percentage of time spent alert was positively correlated with brood size for adult males but not adult females. Foraging time for all age and sex classes increased with date following hatch within years. Foraging time increased and time spent alert decreased between 1987 and 1993 for both adult males and adult females. The trend in foraging behavior for adults is consistent with an hypothesis of declining food availability at higher brood densities and declining alert behavior by adults has implications for prefledging survival of young.