Notornis, 33 (4), 233-245
Article Type: Paper
Time-activity budgets and feeding rates were compiled for White-faced Herons (Ardea novaehollandiae) on pasture near Pukepuke Lagoon, Manawatu, from March 1980 to February 1981. Indices of the hourly strike, catch and step rates were calculated. The direction of the bill during strikes was recorded to indicate the kind of prey being hunted.
Time spent foraging increased from summer through to spring. Feeding rates were highest in spring, less in summer and winter, and lowest in autumn. Herons fed most actively early and late in the day. Adults were more efficient at foraging than juveniles. Herons spent longer foraging and fed at a faster rate when energy demands were high owing to cool temperatures, breeding or moult, and when more food was available.
Areas of pasture in which herons fed, and some that they avoided, were sampled with a sweep net and soil quadrat to determine the seasonal availability of potential prey. Earthworms were most abundant in winter and scarcest in summer, whereas larger insects were common in summer and autumn. Herons fed on whatever prey was most available, taking earthworms in winter and less often in autumn and spring, but concentrating more on insects in summer and autumn.