Activity budgets and daily energy expenditure of black brant (Branta bernicla nigricans) during winter and spring along the Alaska Peninsula

Staging and migrating black brant (Branta bernicla nigricans) have one of the most specialized diets of geese, utilizing coastal habitats to feed on intertidal eelgrass (Zostera marina). Past studies suggest that black brant may not reach energetic requirements during diurnal foraging and must utilize other methods to acquire enough nutrients such as searching for and consuming drifting eelgrass, and foraging on eelgrass at night. I quantified time-activity budgets of black brant in Kinzarof and Izembek lagoons during winter and spring (February-May), 2011 during different tidal conditions, calculated daily energy expenditure (DEE), and described their use of alternate foraging strategies during periods of limited food availability. I conducted 577 instantaneous flock scans between 2 study sites to assess goose activity budget. When flock scans from all time periods and tidal situations were considered together, the predominant black brant activities were classified as vigilant (41.0 %), foraging (33%), comfort (16%) and locomotion (8%). Overall mean DEE based on time-activity budgets across months and locations was 1226 ± 610 kJ/day. Flight costs accounted for 23% -50% of expended energy in both winter and spring, roosting (22% - 27%) and cost of thermoregulation (13%- 18%) were the next most energetically expensive activities during winter, followed by foraging (8% -15%) and vigilance (10% -17%) in spring. Assessments of night foraging were made on 16 occasions. I observed black brant foraging at night nine times, as determined by the presence in the lagoons, coupled with observed foraging activities through night scopes. This study on energy expenditure will allow us to better understand and determine the ecological requirements for brant during winter and spring in Alaska, and to better manage the population in the future for sustainable yield.