GREBES: PodicipediformesGREAT CRESTED GREBE (Podiceps cristatus): SPECIES ACCOUNTS
WESTERN GREBE (Aechmophorus occidentalis): SPECIES ACCOUNTS
Grebes stand anywhere from 8.7 to 29.9 inches (22 to 76 centimeters) tall and weigh between 3.5 and 56 ounces (100 to 1,600 grams). The appearance and color in both sexes of these diving birds are similar, though the female is usually smaller. Their coloration varies, depending on whether or not they are breeding. Their wings are rather short and skinny. Their eyes may be yellow, red, or brown, and their bills are short. Because their feet have adapted, changed over time, to swimming, they are unable to walk well on land and can do so only for short distances.
Although their weight remains basically the same throughout their lives, their body mass distribution changes on a yearly cycle. When flight is needed, breast muscle is built up. When frequent diving is required, leg muscle is developed. And when flight feathers are shed each year, huge quantities of fat are deposited because grebes eat feathers. Eating these feathers gives their stomachs a protective lining against the many parasites that inhabit the grebes' bodies. As many as thirty thousand parasites have been counted on one grebe.
Grebes live throughout the world but not in the Antarctic or high Arctic regions where temperatures are frigid.
Grebes live in freshwater ponds and lakes as well as slow-moving rivers. Northern populations migrate, travel from region to region seasonally, to inland lakes and coastal waters during winter months.
In addition to feathers, grebes eat many kinds of fish, including perch, herring, eels, minnow, pipefish, goby, and cod. They also eat water bugs, crayfish, shrimp, and snails.
Grebes are powerful divers and can feed just below the surface or in greater depths.
BEHAVIOR AND REPRODUCTION
Grebes like to sunbathe and preen, groom, themselves and spend a lot of time doing so. Many grebes have ten to twelve calls that they use, primarily during breeding season, while other grebes are almost completely silent year-round. Their vocalizations range from whistles to beeps to wails.
Grebes fly at night when moving between various regions. They sometimes fly in groups and loose flocks. The grebe is seasonally monogamous (muh-NAH-guh-mus), has only one mate each year. Nests are built by both parents on the water so that they float, but often they are attached to plant life. These birds build several other platforms besides the nest which they use for resting, mating, and sunbathing. Two to four eggs, or three to eight eggs at higher latitudes, are laid and incubated, warmed, by both parents for twenty-two to twenty-three days. After birth, both parents care for and feed the chicks, which take their first flights between six and twelve weeks of age. They are ready to breed at one year. Some species lay eggs two or three times each year.
OIL SPILLS: WHAT'S THE BIG DEAL?
When oil tankers spill oil into the ocean, rivers, and bays, aquatic wildlife and the environment are harmed. Spilled oil floats on the surface of the water and spreads out into an "oil slick." Animals that pass through the slick can be seriously injured. Feathers lose the ability to repel water, and fur is no longer able to keep mammals warm. Also, animals swallow the poisonous oil as they attempt to clean themselves, and die.
The largest spill in the United States happened in 1989 when the Exxon Valdez spilled eleven million gallons of oil off the coast of Alaska. Two-hundred-sixteen thousand gallons (818,000 liters) of oil ended up on shore, affecting approximately 1,300 miles (2,090 kilometers) of shoreline.
The Exxon Valdez Oil Spill Trustee Council estimates that the spill killed 250,000 seabirds, 2,800 otters, 300 harbor seals, 250 bald eagles, up to 22 killer whales, and billions of salmon and herring eggs.
Predators of the grebe, animals that hunt them for food, include weasels, mink, ferrets, crows, hawks, gulls, and pike. Grebes live to be anywhere from eleven to fifteen years old.
GREBES AND PEOPLE
Though once hunted for their plumage, feathers, and as food, grebes are considered bad-tasting in most parts of the world today. In China, the little grebe's meat is used for medicine.
Although no species of grebe is immediately threatened, two species, the giant pied-billed grebe and Colombian grebe, became Extinct, died out, in the 1970s. The Alaotra grebe is listed as Vulnerable, facing a high risk of extinction in the wild. The numbers of the Madagascar grebe have declined recently to the point of concern, due primarily to habitat destruction and the introduction of exotic fish.
Physical characteristics: Great crested grebes are 18 to 24 inches (46 to 61 centimeters) tall and weigh between 1.25 and 3.3 pounds (0.57 to 1.5 kilograms). During breeding, the adult's crown is black while the sides of the head are white blending to a light brown fan at the back of the head. Their undersides are white. Nonbreeding adults have no fan. Immature birds are similar, but sport numerous black stripes on the side of the head. Their eyes are red and the bill is pink.
Geographic range: These birds live in Europe, in Asia south to the Himalayas, and in North Africa north of the Sahara Desert. They spend the winters in warmer coastal waters.
Habitat: Great crested grebes breed on large lakes and in brackish, slightly salty, waters. They can also be found in environments such as city parks.
Diet: Great crested grebes eat mostly large fish, but also eat squid, frogs, snails, and other invertebrates, animals without backbones.
Behavior and reproduction: Great crested grebes can be found in groups of up to ten thousand, although they are also found alone or in pairs. This species participates in elaborate mating rituals. Nests are built on the water, and although females can lay up to nine eggs, they are more likely to lay between three and five eggs. Incubation lasts twenty-five to twenty-nine days. Parents carry their young on their backs for three to four weeks. Chicks are able to fly at ten weeks.
Great crested grebes flee from danger by diving under water rather than taking flight. They can live to the age of eleven years.
Great crested grebes and people: This bird was once extensively hunted for its feathers and as a result nearly became extinct in Europe in the 1800s.
Conservation status: Although once nearly extinct in Europe, this species has made an impressive comeback thanks to the eutrophication (yoo-troh-fih-KAY-shun), the aging process, of lakes—the lakes contain more food for the grebes as they age. Populations are stable in all ranges. ∎
Physical characteristics: Western grebes stand 21.6 to 29.5 inches (55 to 75 centimeters) tall and weigh 1.8 to 4 pounds (0.8 to 1.8 kilograms). Females are smaller than males. The body is narrow, the neck and bill long. Breeding adults are black from the top of the head to below the eye. The rest of the top part of the body is blackish with sides being spotted with gray. Undersides are white. Nonbreeding adults are similar but with less contrast between the black/gray and white areas. Eyes are red and the bill is green.
Habitat: Western grebes breed on lakes and marshes with large areas of open waters, both fresh and brackish. They like the reedy shores for building their nests. These birds winter on salt lakes or in coastal waters.
Diet: Western grebes eat almost nothing but fish. They often spike fish with their pointed bills. Western grebes can dive for periods of up to forty seconds.
Behavior and reproduction: Western grebes form colonies, sometimes up to several thousand birds. They have well-developed courtship displays, including the ability to "dance" on water in pairs. Females lay eggs just once each year, and the timing depends more on the availability of food than on the seasons. Females usually lay two to six eggs in nests that are 3 to 12 feet (2 to 4 meters) apart and built out of wetland vegetation. The nests are found in the protective environment of the reedy waters.
Incubation lasts from twenty-two to twenty-four days, and both parents raise the chicks and carry them on their backs. Chicks are independent at eight weeks.
Western grebes and people: These birds often fall victim to oil spills while wintering in the coastal waters. They also have had reduced breeding success in areas where insecticides used for agriculture wash into their wintering habitats.
Conservation status: Western grebes are not threatened. ∎
FOR MORE INFORMATION
Konter, Andre. Grebes of Our World. Barcelona: Lynx Edicions, 2001.
Ogilvie, Malcolm, and Chris Rose. Grebes of the World. New York: Bruce Coleman, 2002.
Simmons, K. E. The Great Crested Grebe. Buckinghamshire, U.K.: Shire Publications, 1999.
Seago, Michael J. "Great Crested Grebe." Birds of Britain (May 2004). Online at http://www.birdsofbritain.co.uk/bird-guide/g-c-grebe.htm (accessed on July 13, 2004).
American Birding Association. http://www.americanbirding.org (accessed on July 13, 2004).
"Great crested grebe." Royal Society for the Protection of Birds. http://www.rspb.org.uk/birds/guide/g/greatcrestedgrebe/index.asp (accessed May 27, 2004).
"Order Podicipediformes." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Podicipediformes.html (accessed May 27, 2004).
"What's the Story on Oil Spills?" National Oceanic and Atmospheric Administration, Office of Response and Restoration. http://response.restoration.noaa.gov/kids/spills.html (accessed on May 27, 2004).