STORM-PETRELS: Hydrobatidae

PHYSICAL CHARACTERISTICS

Storm-petrels are small seabirds that use their long legs to fend off the water as they snap up food from the surface. Like other procellariiforms (members of the order Procellariiformes), the storm-petrel has tubular nostrils that span almost half the length of the bill. The wings are rounded at the tip, and wing spans vary from about 12.6 inches to 22.4 inches (32 to 57 centimeters), depending on the species. They weigh from 0.7 ounces (20 grams) to 2.9 ounces (83 grams).

Their feathers are dark black or brown, and the storm-petrel's hind end is white. Tails are squared off at the end or forked, and all storm-petrels give off a musty smell characteristic of tubenoses. Females are larger than males.

GEOGRAPHIC RANGE

Though distributed throughout the world, storm-petrels are particularly plentiful in the Southern Ocean. While most species breed around Australasia (Australia and nearby Asian islands), five assemble around islands from Mexico to California. The birds can be found in all ocean waters.

HABITAT

Because they are small and dart around so quickly, it is difficult to identify the storm-petrel, so its habitats are not well known. All storm-petrels live solely in the ocean and retreat to land only during breeding season.

DIET

Crustaceans, freshwater or saltwater animals without backbones, are key foods in the storm-petrel's diet. Depending on where the petrels are, they may supplement their diet with other marine life as well. They tend to like oily foods, and their stomachs contain the oil found in most tubenoses. This oil is used not only for warding off intruders, but as a food source for adults and chicks when other food supplies are scarce.

They feed just below the surface of the water, and though they seem to prefer eating alone, they will gather together around larger food sources such as a dead squid. Storm-petrels follow fishing vessels, eating the food scraps that spray up from the propellers.

BEHAVIOR AND REPRODUCTION

The nests are burrows, holes in the ground, which, once built, are retained each season. The same pair returns to this nest year after year. Nests are visited at night, when there are fewer predators, animals that hunt them for food. Unlike some other procellariiforms, storm-petrels do not engage in fancy courtship displays or rituals.

Storm-petrels have a variety of calls that vary between males and females. These birds tend to be solitary, alone, though some flocking occurs.

Storm-petrels are monogamous (muh-NAH-guh-mus), having only one mate, and begin breeding at four or five years of age. Breeding sites are chosen according to their location in relation to water and food. Some female storm-petrels participate in what is known as the "prelaying exodus." During this period they feed at sea while producing their single egg, which allows them to reach the best feeding area before returning to the nest. Once back at the nest, she lays her egg within twenty-four hours.

RESURRECTION FROM THE DEAD

In late December 2003, two British men, Bob Flood and Bryan Thomas, announced that they had seen a New Zealand storm-petrel—believed to have been extinct since 1850.

The New Zealand storm-petrel had not been seen since 1850, when its population was decimated by rats. Experts later confirmed that the bird had survived undetected, on a predator-free island. According to BirdLife International, eleven more New Zealand storm-petrels were detected in mid-January 2004 and were filmed for television.

The burrow nests are usually made by the males. The burrow is usually at the end of a tunnel, and parents take turns sitting on the egg anywhere from two to four and a half days. This goes on typically for thirty-eight to forty-two days. The down-covered chick is hatched and attended to by its parents until it can control its own body temperature. At that point, parents visit the chick only to feed it. The chick can go six to seven days without food.

STORM-PETRELS AND PEOPLE

Seamen and fishermen have traditionally caught storm-petrels and used them as bait. This was easy to do since the birds tend to gather around fishing vessels. Native Americans were known to eat storm-petrels.

CONSERVATION STATUS

No storm-petrel is threatened, although a few of the harder-to-track species need further investigation. Predators have wiped out entire colonies, but this has not yet threatened the species.

WILSON'S STORM-PETREL (Oceanites oceanicus): SPECIES ACCOUNT

Physical characteristics: The feathers of this 7-inch (18-centimeter), 1.3-ounce (35-gram) bird are completely black except for a white hind-end. The pale coloring reaches across its lower thighs, and there is a band of it across each wing. Even the long legs and bill are black. There is no difference in coloration or size between the males and females.

Geographic range: Wilson's storm-petrels breed on the shores of Antarctica and nearby islands. They are common in the North Atlantic Ocean. Wilson's storm-petrels can be found in all oceans but they avoid the Arctic seas. They come ashore only to breed.

Habitat: Wilson's storm-petrels congregate, gather, along the ocean shelves during the northern summer, and most move back to southern waters to breed.

Diet: Although crustaceans are the preferred food, Wilson's storm-petrels will also eat fish, which has a higher energy content than crustaceans. They find their food by running on top of the water, wings outstretched, and pecking at prey swimming just below the surface. If necessary, the bird will immerse its entire head in the water to catch food.

Behavior and reproduction: Wilson's storm-petrels like to eat in groups, and they are notorious boat followers. These birds are highly migratory, move seasonally, and will travel thousands of miles each year in search of abundant food supplies. Although there is no evidence that petrel pairs remain together throughout migration, they do seem to maintain their bond for several seasons so that the same pair returns to the same nest year after year.

Most nests are built in rock crevices, and the single egg is laid on bare earth in a shallow "bowl" nest in mid-December. The eggs hatch after forty days of incubation, sitting on and warming the eggs for chick development, during which parents take forty-eight hour shifts. Chicks fly on their own for the first time between forty-eight and seventy-eight days old.

Wilson storm-petrels and people: The only interaction with humans occurs when the birds follow fishing boats. Early sailors used to kill Wilson's storm-petrels from the stern of the ship. The birds were attracted to the light, making it easy for them to be caught. Seal hunters would thread wicks through the birds to extract the stomach oil, which would then be used as a candle.

Conservation status: Wilson's storm-petrel is one of the most abundant birds, due in large part to its isolation from humans. When chicks die, it is usually due to snow covering the entrance to the nest, which makes it impossible for parents to get food to their chicks. ∎

FOR MORE INFORMATION

Books:

Enticott, Jim, and David Tipling. Seabirds of the World: the Complete Reference. Mechanicsburg, PA: Stackpole Books, 1997.

Harrison, Jim. Seabirds of the World: a Photographic Guide. Princeton, NJ: Princeton University Press, 1996.

Parkinson, Brian, and Tim Lovegrove. Field Guide to New Zealand Storm Birds. New Holland: Struik, 2001.

Web sites:

Kirby, Alex. "NZ Seabird Returns 150 Years On." BBC Online. http://news.bbc.co.uk/go/pr/fr/-/2/hi/science/nature/3344917.stm (accessed on May 13, 2004).

"New Zealand Petrel Causes Storm." BirdLife International. http://www.birdlife.net/news/news/2004/02/nz_storm-petrel.html (accessed on May 13, 2004).

"Storm-petrel." Science Daily. http://www.sciencedaily.com/encyclopedia/storm_petrel (accessed on May 13, 2004).

"Wilson's Storm-petrel." Australian Government, Australian Antarctic Division. http://www.antdiv.gov.au/default.asp?casid=1648 (accessed on May 13, 2004).

"Wilson's Storm-Petrel." eNature.com. http://www.enature.com/fieldguide/showSpeciesFT.asp?fotogID=568&curPageNum=3&recnum=BD0248 (accessed on May 13, 2004).