Reproductive success, growth of nestlings and foraging behaviour of the Great Blue Heron (Ardea herodias herodias L.)

Reproductive success, nestling growth, and adult and juvenile foraging behaviour of Great Blue Herons (Ardea herodias herodias L.) were studied on Boot and Bon Portage Islands, Nova Scotia in 1977 and 1978. Numbers breeding dropped from 42 to 50 pairs in 1977 to 26 and 10 pairs in 1978 on Boot and Bon Portage Islands respectively. Average clutch sizes ranged between 4.5 and 5.0 for both locations in each year. With the exception of Bon Portage Island in 1978 from which an average of 1.0 young fledged per pair, an average of 2.5-3.1 young fledged per pair in the two colonies. Approximately 1 wk prior to fledging, 96% of nestling tarsal growth is complete while 86, 83 and 78% of body weight, wing chord and culmen growth respectively are attained. Growth of culmen and tarsus varied little between years. Both are good indicators of age. Pace and strike rates of adults and newly fledged juveniles are similar while capture and probe rates are markedly different. Adults are more successful in capturing prey than juveniles but the ability of the latter improves with age.