Physical characteristics: Black-faced sheathbills range from 15 to 16.1 inches in length (38 to 41 centimeters) and from 19 to 32 ounces (540 to 900 grams) in weight. They have a wingspan, distance from wingtip to wingtip, of 29.1 to 31.1 inches (74 to 79 centimeters). They have black bills, black sheaths, and black carbuncles on their faces. The feathers are all white.
Geographic range: Black-faced sheathbills are found on a handful of subantarctic islands in the Indian Ocean. These include Marion, Prince Edward, Crozet, Kerguelen, Heard, and McDonald Islands.
Habitat: Black-faced sheathbills are found in the colonies of penguins and other seabirds, typically on rocky or sandy beaches. They may also occupy meadows and bogs close to shore.
Diet: Black-faced sheathbills eat the eggs, chicks, and excrement of seabirds. They also steal food that seabird parents bring back for their chicks. Black-faced sheathbills may also eat dead seal pups and seal milk. If these aren't available, they eat algae and invertebrates.
Behavior and reproduction: Black-faced sheathbills do not migrate, but remain in one place throughout the year. Pairs defend their territories from other sheathbills all year round. Black-faced sheathbills are most often associated with colonies of king penguins. Black-faced sheathbills are monogamous, with a single male breeding with a single female. The female lays two to three eggs in December or January, with breeding at the same time as that of the seabirds among which they live. Chicks hatch after twenty-seven to thirty-three days.
Black-faced sheathbills and people: Black-faced sheathbills have little interaction with people. They sometimes eat food scraps left by humans near research stations or eat human excrement.
Conservation status: Black-faced sheathbills are not considered threatened. ■
FOR MORE INFORMATION
del Hoyo, J., A. Elliott, and J. Sargatal, eds. Handbook of the Birds of the World. Vol. 3, Hoatzin to Auks. Barcelona: Lynx Edicions, 1996.
Parmalee, D. F. Antarctic Birds: Ecological and Behavioral Approaches. Minneapolis: University of Minnesota Press, 1992.
Perrins, Christopher, ed. Firefly Encyclopedia of Birds. Buffalo, NY: Firefly Books, 2003.
"Chionidae (Sheathbills)." The Internet Bird Collection. http://www.hbw. com/ibc/phtml/familia.phtml?idFamilia=64 (accessed on June 1, 2004).
"Family Chioniae (Sheathbill)." Animal Diversity Web. http:// animaldiversity.ummz.umich.edu/site/accounts/classification/ Chionididae.html#Chionididae (accessed on June 1, 2004).
"Sheathbills." Birds of the World, Cornell University. http://www.eeb. cornell.edu/winkler/botw/chionididae.html (accessed on June 4, 2004).
GULLS, TERNS, AND RELATIVES Laridae
Number of species: 105 species
Gulls, terns, and their relatives vary between 8 and 32 inches (20 to 81 centimeters) in length and between 1.6 and 74 ounces (46 to 2,100 grams) in weight. Gulls and terns generally have white bellies and gray or black backs. Males and females are similar in both size and coloration. Young birds, however, are usually spotted or streaked to help them blend in with their environments. During the breeding season, some gulls develop a pink or cream colored patch on the breast. Gulls have heavy bodies and long wings. Terns have narrower, longer bodies and long, slender, pointed wings. Their bills are slender and pointed. Many terns develop a black crown on top of the head during the breeding season.
Skimmers have heavy bodies and long, narrow wings. Their bills are large and laterally compressed, flattened from left to right. In skimmers, males are often significantly larger than females. Most skimmers have black backs and white bellies, although during the breeding season the legs may become cream colored.
Skuas and jaegers (YAY-gerz) have body shapes similar to that of gulls, but have heavy, hooked bills. They are exceptionally powerful fliers. Females are larger than males.
Gulls and terns are found in coastal regions worldwide. Skimmers are found in temperate, not too hot or too cold, and tropical regions in North America, South America, Africa, and Asia. Skuas and jaegers are found in temperate and polar areas.
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