2.4 Energy budget
Energy gain We estimated the energy gain of every successful fishing event. First, the prey size was determined by comparing the catch with the beak volume of M. squamatus , and was assigned to one of the five following classes: 0.5 volume, 1 volume, 1.5 volume, 2 volume, 2.5 volume of beak (Fig 3). Based on the fish survey at Shangqing River, the average weight of the fish with one beak size was 14.1 g. As the energy content of the fish is approximately 4.0 KJ/g (Gremillet, Schmid, & Culik, 1995) and the assimilation efficiency is assumed to be 80% (Feltham, 1995), the energy gain can then be calculated as:
Energy gained=45.12 x fish size (1)