Diving-petrels

(Pelecanoididae)

Class Aves

Order Procellariiformes

Family Pelecanoididae

Thumbnail description
Small-sized, black-and-white colored, stocky, short-winged, tube-nosed seabirds with nostrils pointing upwards. Diving-petrels dive and swim for their food

Size
7–10 in (18–25 cm); 4–8 oz (120–220 g)

Number of genera, species
1 genus; 4 species

Habitat
Cool and cold oceans

Conservation status
One species is Endangered

Distribution
Occurs in cool and cold oceans of the Southern Hemisphere, usually close to breeding sites

Evolution and systematics

Diving-petrels (family Pelecanoididae) are in a group of seabirds known as tubenoses (order Procellariiformes), all of which have a distinctive pair of tube-like, salt-excreting, external nostrils on the top or sides of the upper mandible. Other families in this group are the albatrosses (Diomedeidae), storm-petrels (Oceanitidae), and fulmars, petrels, shear-waters, and prions (Procellariidae).

With their rapid wing beats and stocky, short-necked appearance, diving-petrels resemble the little auks of the Northern Hemisphere (family Alcidae). This resemblance represents an example of convergent evolution between unrelated species occupying similar ecological niches in widely separated parts of the world.

Physical characteristics

Diving-petrels are small, stocky-bodied, short-winged, tube-nosed seabirds that dive and swim to catch their food. Their body length is 7–10 in (18–25 cm) and they weigh 4–8 oz (120–220 g). Their bill is small, short, broad, and slightly hooked at the tip. The nostril tubes on the upper bill are parallel, short, have a thin partition between them, and are directed upward. Diving-petrels are the only tubenoses in which the nostrils project upward rather than forward, which may be an adaptation to diving. The wings are relatively short and wide and the flight is consequently swift, direct, fluttering, and whirring. When diving and swimming, the wings are used as flippers to achieve forward propulsion. The plumage is gray, blue-gray, or black on top and whitish on the underside. The primary feathers all molt simultaneously, rendering the birds temporarily flightless.

Distribution

Diving-petrels are restricted to waters of the Southern Hemisphere, generally between latitudes 35° south and 60° south. They usually occur in coastal waters but may sometimes be found well offshore.

Peruvian and Magellan diving-petrels (Pelecanoides garnotii and P. magellani) inhabit South American waters. Common and South Georgian diving-petrels (P. urinatrix and P. georgicus) are circumpolar species.

Habitat

Diving-petrels breed on remote oceanic islands. They feed in cool and cold oceans, usually rather close to their breeding sites.

Behavior

Diving-petrels characteristically fly low, direct, and fast over water, occasionally diving and swimming to catch their prey. In rough weather, they may fly right through the crests of waves rather than around or over them. Diving-petrels are the only tubenoses that swim underwater using their wings for propulsion. Diving-petrels only come to land to breed, and they will do so only at night. This wariness is an adaptive response to predation by larger seabirds, such as skuas. Diving-petrels are not migratory, but they may wander during the nonbreeding season.

Feeding ecology and diet

Diving-petrels catch their prey of small fishes and crustaceans by flying directly into the water and then using their wings to swim underwater to pursue their food. They emerge

from the water in a similar manner, by flying directly out into the air. Diving-petrels usually feed in flocks.

Reproductive biology

Diving-petrels breed in colonies. They nest in burrows excavated in organic turf and also in cavities among rocks and tufts of grass. Each female lays only one relatively large white egg that weighs 10–15% of the female's body weight. The incubation period is about eight weeks, and both parents tend the egg during one-day-long watches. Egg laying generally occurs between July and December. The newly hatched chick is brooded closely for its first two weeks of life. After about eight weeks the chick fledges and begins to fend for itself. After the breeding season ends, adults molt all flight feathers and are flightless until this plumage has regrown. Diving-petrels reach sexual maturity in two or three years, which is considerably faster than other tubenoses.

Conservation status

The Peruvian diving-petrel is listed as Endangered. This rare species has an extremely small breeding range on only four islands off the west coast of South America, and all of its subpopulations are declining, some quite rapidly. The declines in abundance have been caused by excessive hunting of these birds for food, disturbance of their habitat during guano collection, predation on eggs, nestlings, and adults by introduced mammals, and diminishment of their food supply by commercial overfishing of the waters around their breeding colonies.

Significance to humans

Diving-petrels are not of much importance to humans, except for the economic benefits of marine ecotourism related to birdwatching.

Species accounts

List of Species

Common diving-petrel

Pelecanoides urinatrix

taxonomy

Pelecanoides urinatrix Gmelin, 1789, New Zealand. Six subspecies.

other common names

English: Subantarctic diving-petrel; French: Puffinure plongeur; German: Lummensturmvolgel; Spanish: Potoyunco Común.

physical characteristics

8–10 in (20–25 cm); wingspan 13–15 in (33–38 cm). Coloring similar to other Pelecanoides species; differentiated by configuration of its bill and nostrils.

distribution

This is the most widespread of the diving-petrels, occurring in the Southern Ocean between about latitudes 35° south and 55° south. It breeds on islands off Australia, New Zealand, Chile, Argentina, and in the south Atlantic Ocean and south Indian Ocean.

habitat

Breeds on oceanic islands and feeds in cool and cold oceans, usually close to breeding sites.

behavior

Flies low, direct, and fast, both through the air and in the water.

feeding ecology and diet

Dives and swims to feed on small fish and crustaceans.

reproductive biology

Lays a single egg in a burrow or crevice. The egg is incubated by both parents.

conservation status

Not threatened. Locally widespread and abundant.

significance to humans

None other than through economic benefits of birdwatching and ecotourism.

Magellan diving-petrel

Pelecanoides magellani

taxonomy

Pelecanoides magellani Gray, 1871, Strait of Magellan. Mono-typic.

other common names

English: Magellanic diving-petrel; French: Puffinure de Magellan; German: Magellan-Lummensturmvogel; Spanish: Potoyunco Magallánico.

physical characteristics

7.5–8 in (19–20 cm), side of neck bears a crescent-shaped half collar.

distribution

Occurs only in extreme southern South America, off southernmost Argentina and Chile.

habitat

Breeds on oceanic islands and feeds in cold oceans, usually close to breeding sites.

behavior

Flies low, direct, and fast, both through the air and in the water.

feeding ecology and diet

Dives and swims to feed on small fish and crustaceans.

reproductive biology

Lays a single egg in a burrow or crevice. The egg is incubated by both parents.

conservation status

A locally abundant species.

significance to humans

None other than through economic benefits of birdwatching and ecotourism.

Resources

Books

BirdLife International. Threatened Birds of the World. Barcelona: Lynx Edicions and BirdLife International, 2000.

Carboneras, C. "Family Pelecanoididae (Diving-petrels)." Handbook of the Birds of the World. Vol. 1, edited by J. del Hoyo, A. Elliott, and J. Sargatal. Barcelona: Lynx Edicions, 1992.

Harrison, P. Seabirds. An Identification Guide. Beckenham, U.K.: Croom Helm Ltd., 1983.

Warham, J. The Behaviour, Population Biology and Physiology of the Petrels. San Diego: Academic Press, 1996.

Organizations

BirdLife International. Wellbrook Court, Girton Road, Cambridge, Cambridgeshire CB3 0NA United Kingdom. Phone: +44 1 223 277 318. Fax: +44-1-223-277-200. E-mail: [email protected] Web site: <http://www.birdlife.net>

IUCN–The World Conservation Union. Rue Mauverney 28, Gland, 1196 Switzerland. Phone: +41-22-999-0001. Fax: +41-22-999-0025. E-mail: [email protected] Web site: <http://www.iucn.org>

Bill Freedman, PhD