Breeding of the spotted shag at whitewash head, banks Peninsula

Breeding of spotted shags at Whitewash Head, Banks Peninsula, was studied in 1970 and 1971. The Whitewash Head colony consisted of a central area of breeding shags and peripheral areas largely of non-breeding birds. Male shags selected nest sites on ledges before pairing. Bath birds built the nest, and copulation took place at this time. Egg-laying started about the same time both years but varied within the colony. Most clutches were of three eggs and were laid within seven days. Incubation took from 28 to 31 days and was shared by mates. Development of the chick is described in detail and measurements of growth rates discussed. Nestlings were attended constantly until about 30 days old and were fed about four times daily by both parents. Clutch size and nestling mortality is discussed briefly. Nestlings fledged and left their nests when about 63 days old. No predation of shags occurred but red-billed gulls worried adults feeding chicks to obtain food. A method for ageing nestlings by measurements is given.