Fork-tailed Storm-petrel

Fork-tailed Storm-petrel exhibit monogamous pairing, often reuniting with their previous season's mate upon returning to breeding islands. They engage in aerial courtship displays and remain in close proximity to their nesting sites, extensively vocalizing and preening each other. Notable for their longevity in nest-site fidelity, fork-tailed Storm-petrel may reuse the same site for consecutive years. Both partners share incubation duties and chick provisioning, after which the fledgling independently departs. In the nonbreeding season, fork-tailed Storm-petrel form small foraging flocks, sharing in rest and communal feeding on the sea surface.

The range of the fork-tailed storm petrel is estimated to cover 22,400,000 km with over 6,000,000 individuals occurring globally, making it the second-most widespread and abundant storm petrel. During the breeding season, the fork-tailed storm petrel form dense colonies on islands throughout northern California, Oregon, Washington, British Columbia, Alaska, and northeast Asia off the Kamchatka Peninsula. Most of their population is concentrated in Alaska, notably in the Bering Sea near the Aleutian Islands. Their southernmost colony is on Little River Rock in Humboldt County, with a population of 200 individuals. Their nesting habitat varies, ranging from bare rock to forests. They typically build their nests under rock crevices or roots, or burrow into soft ground with low-growing vegetation. As they frequent the open ocean, little is known about fork-tailed storm petrels outside of the breeding season. They have been frequently sighted off the Californian coast, making them the most northerly distributed storm petrel during the winter. Sparse sightings also indicate that they forage as far south as Hawaii.

Being widespread and abundant, the fork-tailed storm petrel is not threatened with extinction. However, humans impact their life history in many ways. As a species that feeds on surface material and follows ships, this storm petrel often ingests oil and plastic with their food items. Surprisingly, the fork-tailed storm petrel is relatively unaffected by the toxicity of oil, as their natural diet contains substances that are very chemically similar. Plastics also do not severely affect the birds because they can be regurgitated after ingestion. In contrast, being a top marine predator, fork-tailed storm petrels are susceptible to bioaccumulation. High lead concentrations have been found in the bones of petrels, and DDT can cause eggshells to become dangerously thin. The greatest threats that face fork-tailed storm petrels today are global climate change and introduced species. An increased severity of storms makes foraging more dangerous, decreasing the chances that an adult will return to the colony. The introduction of mammals also adversely affect storm petrels, where raccoons and river otters prey upon nests, and rabbits increase soil erosion and compromise the structural integrity of burrows.