Food and Feeding Behavior of the Black-faced Spoonbill
Abstract Feeding Black-faced Spoonbills (Platalea minor) were studied in four main areas along the coasts of South Korea, Taiwan, China and Vietnam. They fed on nekton, mainly fish and shrimps, varying in length between 2-21 cm that were caught by sweeping the bill in the water. The feeding behavior of a spoonbill is a chain of feeding and inter-feeding bouts. Each feeding bout started by putting the bill into the water and ended when the bill was taken out and any prey captured was swallowed. The times between feeding bouts were short and no or few steps were made. In a complete feeding bout, up to three functional phases were distinguished. These were successively (1) the attempt to locate a prey, (2) the attempt to catch the located prey, (3) the handling and swallowing of the prey. A feeding bout could end in any phase. A total of 1,684 feeding bouts were recorded of which 65% ended with swallowing prey. The mean outcome was 45.4 small (<5 cm long) and 1.3 large (>5 cm long) prey per 10 min. Tentative measurements indicated that a feeding spoonbill walked on average 3.87 m per 10 s, during which time the bill made 15.7 sweeps with a bill velocity of 5.8 km.h-1, meanwhile testing about 17% of the area within reach of their bill for the presence of food. Feeding by Black-faced Spoonbills often looked chaotic because they usually walk all over the feeding site at a variable speed, while showing a large variety of actions especially when large prey is present. However, analyses of the observations show that they behave efficiently and reduce time and energy spent in feeding in several ways, including giving-up times not much longer than the duration of bouts with success, pursuing only large prey, ceasing feeding and starting to rest or going to another site when no prey is caught in 5-10 min. With their tactile way of feeding on invisible prey, they also behaved efficiently by consuming all detected prey that could be caught and swallowed.