Sooty Shearwater Life History

Habitat

Sooty Shearwaters nest on islands, mostly on forested or densely vegetated slopes near the ocean, although some nest on headlands or even well inland. When not at the nest site, they forage over marine waters, their great migrations taking them into all of the world’s oceans except the northern Indian Ocean. At sea, they spend about half their time over pelagic waters, mostly over the continental slope, and half of the time over shallower waters off the continental shelf. Some forage as far south as Antarctic pack ice, but Sooty Shearwaters do not generally forage in icy waters in the North Atlantic or North Pacific. Back to top

Food

Sooty Shearwaters eat fish and marine invertebrates. They are agile foragers, taking prey while swimming or, more often, diving beneath the sea surface and pursuing prey underwater using their wings for propulsion. They also dive into the sea while flying, like a tern or booby, from heights of 20 feet above the ocean. Their dives are usually less than 130 feet deep, but they have been recorded diving as deep as 220 feet. Like most “tubenoses” (shearwaters, storm-petrels, petrels, albatrosses, and allies), Sooties have a keen sense of smell that enables them to detect prey from great distances. When hunting schooling fish, however, they are visual predators, and their keen eyesight enables them to even feed at night. They gather wherever prey is abundant, often congregating with other seabirds in large flocks, sometimes around fishing vessels or feeding whales. Prey includes opalescent squid, clubhook squid, arrow squid, black-eyed squid, Pacific saury, anchovies, capelin, rockfishes, gurnard perches, lantern fishes, and tiny crustaceans (euphausiid and amphipods), also known as krill. Back to top

Nesting

Nest Placement

Nests are dug into grassy or forested hillsides on islands or headlands, usually near the ocean and often at high elevation.

Nest Description

Both adults excavate the nest burrow, which is up to 10 feet long. They may line the nest chamber at the end of the burrow with some grasses and feathers.

Nesting Facts

Behavior

In the Southern Hemisphere, Sooty Shearwaters begin returning to nesting colonies in spring (September and October). Males immediately begin advertising their presence, giving wild, catlike calls in the colony at night, usually while sitting on the ground near the nest site. They defend their nest burrows by sitting in the entrance and calling, and snap at potential intruders, including penguins in some places.

Although many birds that return to colonies are not yet old enough to breed (they generally start breeding between the ages of 5 and 9), they begin practicing courtship as early as age 2. Once partnered, they tend to be monogamous and reunite with their mate each year. Their keen sense of smell helps to locate their mate and burrow when they return to the colony in darkness.

Conservation

Numbers of Sooty Shearwater have been in decline for decades, with some colonies losing almost 40% of their numbers between 1970 and 2000 alone and some former colonies now gone. Surveys in the California Current since 2000 indicate a 90% reduction in counts. Partners in Flight currently estimates the global breeding population at 13 million and rates the species a 12 out of 20 on the Continental Concern Scale, indicating a species of relatively low conservation concern. As for most seabirds, heavy metals, pesticides, plastic particles, and other marine pollutants pose a risk to their populations, as do introductions of predators such as pigs, rats, and cats to their nesting areas. Thousands of Sooty Shearwaters are killed every year as bycatch in gillnets. As part of traditional cultural practices, local Maori In New Zealand kill an estimated 320,000–400,000 chicks per year to be sold as food. As for other seabird species, the negative impacts of climate change on habitats and food resources represent an additional, major conservation concern for survival of this species.

Credits

Partners in Flight. (2020). Avian Conservation Assessment Database, version 2020.

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

Back to top