Fork-tailed Storm Petrel

Identification

The fork-tailed storm petrel is a small seabird measuring 20 cm in length with a wingspan of 46 cm. Its most distinctive feature is its overall bluish-grey plumage, making it the only bird in its family with this colouration. The species typically has a paler underside that contrasts with the darker colours under its wings, a dark grey forehead, a black ear patch, and a small black bill. Despite its name, the forked tail is not always visible in flight. Other storm petrels are significantly darker; the similar-looking ashy storm petrel, for instance, is considerably more sombre. Southern populations appear somewhat darker than their northern counterparts. Males and females are virtually indistinguishable in colour and size, while juveniles resemble adults except for a less noticeable notch in their tails.

Range & Habitat

The fork-tailed storm petrel is the second-most abundant and widespread storm petrel globally, with an estimated range covering 22,400,000 km² and over 6,000,000 individuals occurring worldwide. During breeding season, they form dense colonies on islands throughout northern California, Oregon, Washington, British Columbia, Alaska, and northeast Asia off the Kamchatka Peninsula, with most of the population concentrated in Alaska, notably in the Bering Sea near the Aleutian Islands. Their southernmost colony is on Little River Rock in Humboldt County. Outside the breeding season, these pelagic birds spend up to eight months over the northern Pacific Ocean, with frequent sightings off the Californian coast during winter and sparse sightings indicating foraging as far south as Hawaii.

Behaviour & Diet

Fork-tailed storm petrels are generally silent birds, calling only when entering their breeding colony at night. Their most common call is a 3- to 5-note, raspy "ana-ana-ana", heard from both sexes and intensifying during courtship, accompanied by elaborate aerial displays. Males also emit a higher-pitched single note call to locate females and maintain pair bonds. The species mainly feeds on planktonic crustaceans, small fish, and squid, foraging by picking food off the water surface while in flight with characteristic short, stiff wingbeats close to the water. They are extremely opportunistic feeders with a well-developed olfactory system, often being the first birds to arrive at food sources and even scavenging on fatty tissue from dead marine mammals and trailing behind fishing boats.

Best Time & Places to See It

For breeding season encounters, visit islands and coastal regions of Alaska, British Columbia, or northern California from late spring through summer, when birds return to their colonies. The Bering Sea near the Aleutian Islands holds the densest populations. If visiting during winter months, the Californian coast offers the best chances of sightings, as fork-tailed storm petrels are the most northerly distributed storm petrel during this season. Birds only return to land to breed in single colonies, nesting in rock crevices or small burrows where a single egg is laid.

Photography Tips

Photographing fork-tailed storm petrels presents considerable challenges due to their pelagic nature and small size. Access to breeding colonies during the breeding season offers the best opportunities, though nesting birds are typically active at night when they call and engage in aerial displays. The distinctive bluish-grey plumage and contrasting paler underside are key identifying features to capture. At sea, their characteristic low, fluttering flight with short wingbeats close to the water surface is diagnostic. Patience and boat-based seabird trips off California or Alaska during appropriate seasons are essential for any serious attempt at photographing this species.