Capture of submerged prey by little egrets, Egretta garzetta garzetta: strike depth, strike angle and the problem of light refraction

How little egrets eatch submerged prey was observed in the field. The proportion of successful strikes was measured relative to the angle and depth of the strike and the water level in the pond. Prey capture success was significantly related to strike angle, being highest at the most acute angles. Strike depth had no effect on capture success. Strikes were more successful in shallow streams than in full or partly drained ponds. Adult breeding birds were as successful as non-breeders and uveniles, but performed deeper strikes more often. There was also significant variation between individuals in capture success. Light refraction had no apparent effect on the egrets' capture success.