You are here:
A NEW MODEL TO ESTIMATE DAILY ENERGY EXPENDITURE FOR WINTERING WATERFOWL
Citation:
McKinney, R A. AND S. R. McWilliams. A NEW MODEL TO ESTIMATE DAILY ENERGY EXPENDITURE FOR WINTERING WATERFOWL. WILSON BULLETIN 117:28-37, (2005).
Impact/Purpose:
To provide estimates of DEE that incorporate site-specific energetic costs of thermoregulation, and test its utility in assessing habitat quality
Description:
Activity budgets of wintering waterfowl have been widely used to assess habitat quality. However, when factors such as prey abundance or protection from exposure to cold or wind determine quality, measures of daily energy expenditure (DEE) may be more appropriate for this purpose. Here we propose an activity-based model to provide estimates of DEE that incorporate site-specific energetic costs of thermoregulation, and test its utility in assessing habitat quality. The model was used to estimate the DEE of bufflehead (Bucephala albeola) wintering at six habitats that afford differing degrees of protection from exposure within Narragansett Bay, RI (USA). We used bufflehead activity budget data collected during the winters of 2001-2002 and 2002-2003, along with average temperatures and wind speeds at the sites, to calculate DEE that ranged from 46.9 - 52.4 kJ h-1 and increased with increasing wind speed (r2 = 0.76, p = 0.02). The energetic cost of thermoregulation comprised as much as 28% of the total DEE and also increased with wind speed (r2 = 0.61, p = 0.06). Our DEE values were 11.8% higher, and thermoregulatory costs were up to two times higher than those calculated using an existing model that incorporates fixed thermoregulatory costs. This suggests that a model that incorporates the effect of environmental conditions on DEE may be better suited to assess habitat quality for waterfowl in cold environments. Using our model, we saw an increase in feeding activity at the sites with increasing DEE (r2 = 0.76, p = 0.02), resulting in a significant decrease in time spent in social (r2 = 0.71, p = 0.04) and maintenance (r2 = 0.96, p = 0.001) behaviors. The average abundance of bufflehead at the sites decreased as time spent feeding (r2 = 0.67, p = 0.04) and DEE (r2 = 0.18, p = 0.41) increased. These results suggest that estimates of waterfowl DEE that incorporate site-specific thermoregulatory costs may be useful in assessing habitat quality, particularly at sites where increases in feeding activity may result from increased thermoregulatory costs or from differences in prey availability.