White-bellied Storm Petrel

The White-bellied Storm Petrel, Fregetta grallaria, is a small seabird with a distinctive coloration pattern. Its upper parts are dark while the underparts are light, with a white belly as its name suggests. This bird has a fine black bill, a square tail, and long legs that do not usually extend beyond the tail in flight. It measures approximately 18 to 20 centimeters in length and has a wingspan of 46 to 48 centimeters.

Identification Tips

To identify the White-bellied Storm Petrel, look for its contrasting plumage with black above and white below, including white upper tail coverts. The nasal tube is free at the end and upturned, and the bird exhibits a half culmen in length. Its tarsus is booted in front, with black webs, and the basal joint of the middle toe is flattened. The claws are blunt and flattened. There is no observed plumage variation between sexes or between adults and juveniles.

Habitat

This species is highly pelagic, spending most of its life on the open seas. It is rarely seen on land except near breeding colonies.

Distribution

The White-bellied Storm Petrel has a widespread range across the Southern Hemisphere's oceans, including the Pacific, Atlantic, and Indian Oceans. Its movements at sea are not well understood, and it is thought to migrate northward to some extent.

Behaviour

The White-bellied Storm Petrel is known for its low gliding flight, often pattering and dipping to feed. It is nocturnal on land and is thought to be generally silent at sea, becoming vocal only when nesting.

Song & Calls

The bird's voice is described as soft, high-pitched twittering calls, such as "pee-pee-pee-pee," repeated up to 20 times.

Breeding

Breeding colonies are found on offshore islands and rocky outcrops in the Pacific, Atlantic, and Indian Oceans. Nests are grass-lined and built in crevices and burrows. Breeding occurs in late summer and early autumn, with a single white egg laid between January and March. Both parents feed the young, which fledge from mid-April to May.

Diet and Feeding

The diet consists of small crustaceans, squid, and sea skaters. The White-bellied Storm Petrel feeds by skimming across the water's surface and dipping to catch prey near the surface.

Conservation status

The IUCN Red List classifies the White-bellied Storm Petrel as Least Concern. However, in New Zealand, it is considered nationally endangered, and in Australia, it is listed as vulnerable. The species faces threats from habitat loss, invasive species, and environmental changes such as climate change and pollution.

Climate change

Climate change is expected to affect the productivity of the sea surface, which could impact the White-bellied Storm Petrel's food sources and breeding success. The species is considered sensitive to climate change, particularly due to its small and localized population, slow breeding, and specialized feeding habits.

Similar Species

The White-bellied Storm Petrel can be confused with similar species of black and white storm petrels due to morphological differences and varied color phases. However, its long legs and the absence of toe projection beyond the tail are distinguishing features.