Birds of Midway Atoll
Christmas Shearwater / Puffinus nativitatis
A population of approximately 166 nesting pairs was observed on Eastern Island (1998), along with a small number of Christmas Shearwaters heard and seen on Sand Island. Christmas Shearwaters breed in low numbers on small islands throughout the central Pacific.
Vocalization takes place throughout the night, often continuing 1-2 hours after sunrise. Birds can often be observed calling in paired flights. Their sounds are similar to the Wedged-tailed Shearwaters: moans and groans, but with a more nasal gurgling quality at the beginning of their call.
Feeds primarily in association with large predatory fish such as skipjack tuna. These fish drive the larval forms of fish to the surface. Christmas Shearwaters locate larval food such as mackerel scad, flying squid, goat fish and squirrel fish most likely by using their sense of smell. Christmas Shearwaters capture prey by plunging into water and chasing it.
Birds are believed to be monogamous. Birds return at dusk and are active in courtship around dawn. They are active at night but quiet during the day and thus, are rarely seen. They arrive at breeding grounds in late February and begin to lay eggs by the end of April.
A simple nest is built with small twigs or leaves on the ground-surface under dense vegetation, such as native naupaka (Scaevola sericea). A single, white egg is laid. Incubation period ranges from 50 to 54 days. Both parents share in the incubation, taking about a five day shift on the nest, while the mate is feeding at sea.
Chicks are fed stomach oil and partially digested fish as frequently as once every 24 hours for about the first two months. It takes about 100-115 days for chicks to grow and fledge. Adults will not desert their chicks before fledging. Shearwaters depart their breeding grounds by November.