Figure 3. Photos shows fish sizes in relation with the beak of M. squamatus. Fish size is used to estimate energy gain.
Energy expenditure Energy expenditure was calculated using the observed foraging activity profile and the Basal Metabolic Rate (BMR). The BMR was determined to use the Aschoff-Pohl equation (Aschoff & Pohl, 1970):
BMR=307.5 Body Mass0.734 (2)
The BMR coefficients of different behaviours were sourced from the published studies on Common Merganser Mergus Merganser , Lesser snow Goose and Black duck (Table 2). Because the BMR coefficient of other activities including socializing, preening and food handling varies greatly from literature, moreover, these activities account for only a small fraction of the total foraging time (less than 4.2% of the total, see Table 3 below), we excluded them in calculating energy balance. The weight data (i.e. male 1125–1400 g, female 870–1100 g) ofM. squamatus were obtained from (Kear & Hulme, 2005). Therefore, the BMR of male and female M. squamatus was calculated as 365.00 KJ/day and 304.12 KJ/day, respectively. We assumed that the mean BMR ofM. squamatus was 334.56 KJ/day and the energy expenditure was each foraging behaviour BMR by multiplying the behaviour time rate.
Table 2. Published basal metabolic rate (BMR) coefficients of different foraging activities