TIME OF BREEDING IN RELATION TO FOOD AVAILABILITY OF FEMALE GREAT BLUE HERONS (ARDEA-HERODIAS)

I examined the hypotheses that Great Blue Herons (Ardea herodias) bega n breeding in spring shortly after acquiring enough food to make eggs, or so that chicks were in nests when food was most plentiful. Egg lay ing began about nine days after a female's daily food intake crossed a n estimated energy threshold of 1,715 kJ/day. In contrast, the peak in availability of food energy to adults occurred at least 26 days befor e the peak food demands of their chicks. The estimated food energy int ake by adults increased gradually in March and April with increasing d uration of low tides and the inshore movement of fishes. Adult food en ergy intake reached a peak in May when shiner seaperch (Cymatogaster a greggata) were most abundant, and diminished through June and July.