Fasola M. (1984) Activity rhythm and feeding success of nesting Night Herons Nyciticorax nycticorax. ARDEA 72 (2): 217-222

Activities of the Night Heron were observed over the whole daily cycle, at the nest site in the pre-laying period and during incubation, and both at the nest and on the feeding grounds in the nestling period. The distribution of activities over time changed from a sharp day (roosting)-night (feeding) rhythm in the pre-laying period to an even distribution of activities (movement from colony, attendance at nest, feeding and resting in feeding grounds) in the nestling period when total time devoted to feeding increased. The Night Herons switched from 'standing feeding' to 'walking feeding' when feeding success on smaller prey items increased. The rhythm of activities and of feeding efficiency are different from those observed elsewhere, suggesting that the activity pattern of the Night Heron is adapted to food availability and to avoid interference by other diurnal herons. However, the peak of feeding activity at dawn did not coincide with the peak of food intake at noon; a result of the high number of tadpoles available. Calculations show that during the nestling period, the amount of food that can be obtained by a bird feeding continuously at night, would be insufficient for the adult plus its brood. Consequently, the extension of the foraging period into the day is due to the increased food requirements of the nestlings.