Fork-tailed Storm Petrel

The fork-tailed storm petrel, Hydrobates furcatus, is a small seabird belonging to the family Hydrobatidae. It is distinguished by its bluish-grey plumage and is the only member of its family to exhibit such coloration. This seabird is approximately 20 cm in length with a wingspan of 46 cm, and it exhibits a flight pattern characterized by short, stiff wingbeats close to the water's surface.

Identification Tips

When observed from above, the fork-tailed storm petrel's namesake feature, its forked tail, is more visible. The bird's underparts are paler, providing a contrast to the darker underwing colors. It has a dark gray forehead, a black ear patch, and a small, black bill. Juveniles are similar to adults but have a less pronounced notch in their tails.

Habitat

The fork-tailed storm petrel is a pelagic species, spending much of its life on the open ocean. It only comes ashore to breed, preferring isolated islands with varied nesting habitats, from bare rock to forested areas.

Distribution

This species has a broad range, estimated to cover 22.4 million square kilometers, with a global population exceeding 6 million individuals. It breeds along the coast of the northern Pacific Ocean, from northern California to northeast Asia, with dense colonies found on islands in Alaska and off the Kamchatka Peninsula.

Behaviour

The fork-tailed storm petrel is a nocturnal visitor to its breeding colonies, arriving under the cover of darkness to avoid predators. It is generally silent but engages in vocalizations and elaborate aerial displays during courtship.

Song & Calls

The most common vocalization is a raspy "ana-ana-ana" call, used by both sexes, particularly during courtship. Males emit a higher-pitched, single-note call to locate females within noisy colonies and maintain pair bonds.

Breeding

Breeding begins in late March to early April, with nests constructed in rock crevices or burrows. A single white egg is laid, incubated by both parents for around 50 days. Chicks are brooded for the first five days, then left alone, with parents returning to feed them sporadically until they fledge after two months.

Similar Species

The ashy storm petrel is similar in appearance but is significantly darker than the fork-tailed storm petrel.

Diet and Feeding

The fork-tailed storm petrel feeds on planktonic crustaceans, small fish, and squid, often scavenging offal and trailing fishing boats. It forages by fluttering across the water's surface and may dive to shallow depths.

Conservation status

The IUCN Red List classifies the fork-tailed storm petrel as Least Concern. However, it faces threats from oil and plastic ingestion, bioaccumulation of toxins, climate change, and introduced predators.