Leach's Storm-Petrel Life History

Habitat

Leach’s Storm-Petrels breed on offshore islands that are free of mammalian predators. They typically excavate nesting burrows in habitats with well-drained soil, including open meadows, coniferous forests, and, in the eastern Pacific, talus crevices. During the breeding season, Leach’s Storm-Petrels in the northwest Atlantic travel long distances—ranging from 400 to 800+ km (250 to 500+ miles) from their nest sites to forage over deep pelagic waters at or beyond the continental slope (the offshore zone where the bottom begins to drop away to great depths). During the breeding season, Leach’s Storm-Petrels in the North Atlantic tend to occur in cooler waters than other storm-petrels, but in the North Pacific, they use warmer waters. On migration, they often concentrate at fronts and eddies, such as Gulf Stream eddies off the southeastern U.S., where water upwelling brings prey to the ocean surface.

Food

Leach’s Storm-Petrels are opportunistic feeders, with their diet varying geographically and by season. Important prey include fish (lanternfish, sandlance, cod, and rockfish), crustaceans (krill, decapods, amphipods, isopods, and copepods), squid, octopus, and jellyfish. They also consume fish offal and marine mammal feces. Leach’s Storm-Petrels forage primarily by hovering over the ocean surface and pecking at individual prey items, and they sometimes hover just above the surface and patter with their feet (like Wilson’s Storm-Petrel), or sit on the water.

Nesting

Nest Placement

Located inside a burrow excavated by the male, who uses his bill and feet to break ground and remove soil. Average burrow length at breeding sites in Newfoundland and Maine was 43 cm (17 inches), while average burrow depth was 13 cm (5 inches) and 23 cm (9 inches) respectively. Most burrows are straight, but some have a 45° turn in them.

Nest Description

A simple scrape, typically lined with some vegetation (e.g. twigs, moss, lichens, ferns, conifer needles and cones, leaves, feathers, and grass).

Nesting Facts

Behavior

Like many other storm-petrels, Leach’s Storm-Petrels approach and leave their nesting burrows at night to minimize the risk of predation by raptors and other avian predators. Birds at nests are generally quiet during daylight hours, but at night colonies come alive with distinctive chuckling and purring calls, which reach their peak intensity during the darkest part of the night.

Leach’s Storm-Petrels are socially monogamous, and most birds keep their same mate during successive breeding seasons, in part because individuals are very faithful to nesting burrows. Mate switching is more likely among failed nesters. The male excavates the burrow and builds the simple nest. Both sexes incubate the single egg, with a typical incubation bout lasting for three days (to allow for long-distance foraging trips by the other mate) and the total incubation period averaging about six weeks. The chick remains in the nest for about nine weeks. At one point during the nestling stage, it reaches a weight 1.5 times that of the adults, but then loses most of this fat before fledging.

Leach’s Storm-Petrels sometimes breed in huge colonies, including one in Newfoundland with nearly 2 million pairs, but at sea they tend to forage alone or in small groups. Millions of nonbreeding birds remain at sea throughout the year, but some make visits to active breeding colonies. On the ocean, Leach’s Storm-Petrels can be inconspicuous due to their small size, dark color, solitary nature, and lack of strong attraction to ships. They are best detected and identified at sea by their agile but erratic flight, which is reminiscent of a Common Nighthawk.

Conservation

Partners in Flight estimates Leach’s Storm-Petrel’s global population size at 13 million breeding individuals and rates the species a 9 out of 20 on the Continental Concern Scale, indicating a species of low conservation concern. However, the International Union for Conservation of Nature lists Leach’s Storm-Petrel’s conservation status as Vulnerable. This assessment is based on an apparent population decline of more than 30% over three generations, for unknown reasons.

Credits

BirdLife International. 2018. Hydrobates leucorhous. The IUCN Red List of Threatened Species 2018: e.T132438298A132438484. https://dx.doi.org/10.2305/IUCN.UK.2018-2.RLTS.T132438298A132438484.en.

Dunne, P. (2006). Pete Dunne’s essential field guide companion. Houghton Mifflin Harcourt, New York, USA.

Howell, S. N. G. (2012). Petrels, Albatrosses, and Storm-Petrels of North America: A Photographic Guide. Princeton University Press, Princeton, New Jersey, USA.

Partners in Flight (2024). Avian Conservation Assessment Database, version 2024.

Pollet, I. L., A. L. Bond, A. Hedd, C. E. Huntington, R. G. Butler, and R. Mauck (2021). Leach’s Storm-Petrel (Hydrobates leucorhous), version 1.1. In Birds of the World (S. M. Billerman, B. K. Keeney, P. G. Rodewald, and T. S. Schulenberg, Editors), Cornell Lab of Ornithology, Ithaca, NY, USA.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, NY, USA.

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