Grebes

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Grebes

Grebes are aquatic birds that make up the family Podicipedidae. This is the only family in the order Podicipediformes, a rather unique group of birds that is not closely related to other living orders, and has a fossil lineage extending back 70 million years. The 22 species of grebes range in size from the least grebe (Podiceps dominicus ), with a body length of 9.9 in (25 cm) and weight of 4 oz (115 g), to the great crested grebe (Podiceps cristatus ), 18.9 in (48 cm) long and weighing 3.1 lb (1.4 kg). The winter color of grebes is brown, gray, or black on top and white below, but during the breeding season most species develop a rather colorful plumage, especially around the head and neck.

Grebes are well adapted to swimming, with feet placed far back on the body, and paddlelike, lobed toes that provide a greater surface area for propulsion and a very short tail. The dense plumage of these birds provides waterproofing and grebes are strong, direct flyers. However, once they are settled in a particular place for breeding or feeding, grebes tend not to fly much.

Grebes breed on freshwater lakes and marshes on all of the continents except Antarctica. Some species winter in coastal marine waters or on large lakes. Grebes have a noisy courtship behavior, often accompanied by a spectacular display. For example, courting western grebes (Aechmophorus occidentalis ) run in tandem over the water surface, each bird striking a symmetric, ritualized pose known as the penguin dance.

The nests of most grebes are made of anchored, piled-up mounds of vegetation in shallow water. The young chicks often ride on the back of their parents, where they are brooded. The prey of these birds includes fish and aquatic invertebrates.

Species of grebes

Most species of grebes are found in the Americas, especially in Central and South America. Three species are flightless and confined to single lakes, these

being the short-winged grebe (Rollandia microptera ) of Lake Titicaca in Bolivia and Peru, the Junin grebe (Podiceps taczanowskii ) of Lake Junin in Peru, and the giant pied-billed grebe (Podilymbus gigas ) of Lake Atitlan in Guatemala. The latter species probably became extinct in the mid-1980s as a result of hunting and development activities around its lake.

Six species of grebes occur regularly in North America. The largest species is the western grebe (Aechmophorus occidentalis ) of the western United States and southwestern Canada. The western grebe breeds on lakes and marshes, and winters in near-shore waters of the Pacific Ocean and on some large lakes. This is the only species of grebe that spears its prey of fish with its sharp beak. Other grebes catch their food by grasping with the mandibles.

The red-necked grebe (Podiceps grisegena ) breeds in northwestern North America, and winters on both the Atlantic and Pacific coasts. The horned grebe (Podiceps auritus ) also breeds in the Northwest and winters on both coasts. A similar looking species, the eared grebe (Podiceps caspicus ), breeds in southwestern North America. The pied-billed grebe (Podilymbus podiceps ) has the widest distribution of any grebe in North America, breeding south of the boreal forest and wintering in Mexico and further south.

Conservation of grebes

Small species of grebes are not often hunted, because their meat is not very tasty, but the larger grebes have been hunted for their plumage. “Grebe fur” is the patch of breast skin with plumage attached, which can be stripped from the dead bird. Grebe fur from the western grebe and great crested grebe was used to make hand muffs, capes, and hats for fashionable ladies, while that of the short-winged grebe was used locally around Lake Titicaca to make saddle blankets.

Grebe populations also suffer from pollution. Species that winter in coastal waters are highly vulnerable to oil spills, and grebes can be killed in large numbers when this type of pollution occurs.

Grebes may also be affected by pesticides. One of the earliest, well documented examples of birds being killed by exposure to chlorinated-hydrocarbon insecticides occurred at Clear Lake, California. This lake is important for recreational use, but there were numerous complaints about a non-biting midge (a tiny, aquatic fly) that could sometimes be extremely abundant. In 1949, this perceived problem was dealt with by applying the insecticide DDT to the lake. This chemical was used again in 1954, and soon afterward about 100 western grebes were found dead on the lake. It took several years of study to determine that the grebes had been killed by the insecticide, which they had efficiently accumulated from the residues in their diet of fish, achieving unexpectedly large, toxic concentrations in their bodies. This case study proved to be very important in allowing ecologists and toxicol-ogists to understand the insidious effects that persistent chlorinated hydrocarbons could achieve through food-web accumulation.

Status of North American Grebes

Western grebe (Aechmophorus occidentalis). Plume hunters devastated the population in the beginning of the twentieth century. The species has apparently recovered, taking up residence in areas not historically used. The population in Mexico may be declining.
Clark’s grebe (Aechmophorus clarkii). Plume hunters contributed greatly to the decline in population. Past population counts are unreliable because of confusion of this bird with the western grebe. The population in Mexico may be declining due to loss of nesting habitat (i.e., tules on lakes).
Red-necked grebe (Podiceps grisegena). Declines in population have resulted from damage to eggs and eggshells by pesticides and PCBs, and by raccoon predation. This species continues to be vulnerable to polluted wintering areas along the coast. In 2002, the global population was estimated at 150,000-370,000 birds.
Horned grebe (Podiceps auritus). Population may be declining, but is still large.
Eared grebe (Podiceps nigricollis). Feathers were once used for hats, capes, and muffs; and eggs were gathered for food. Today the populations appear stable, but the species is considered vulnerable because large numbers depend on a very few lakes at certain seasons (for example, the Great Salt Lake, Mono Lake, and the Salton Sea).
Pied-billed grebe (Podilymbuspodiceps). This species has proven adaptable, and is now found in developed areas. In 2002, the global population was estimated at 110,000–130,000 individuals.
Least grebe (Tachybaptus dominicus). Normally found in southern Texas in the United States. Sometimes killed by exceptionally cold Texas winters.