Podicipediformes

Grebes

(Podicipedidae)

Class Aves

Order Podicipediformes

Family Podicipedidae

Number of families 1

Thumbnail description
Medium-sized, swimming and diving birds, recalling ducks, gallinules, or finfoots. Head small, bill pointed, neck medium to long. Rear end of body fluffy and appearing tail-less. Wings not used during diving. Most species dull-colored, a few with golden head plumes

Size
7.9–31 in (20–78 cm); 0.25–4.0 lb (112–1,826 g)

Number of genera, species
7 genera; 22 species

Habitat
Freshwater lakes, in winter also on coast

Conservation status
Two species recently Extinct, two Endangered, one Near Threatened; two with restricted range, one of them seriously declining

Distribution
Worldwide except for Antarctic and high Arctic regions

Evolution and systematics

For a long time grebes were thought to be related to loons, but it is now known that the similarity is merely owing to convergence. Despite their fairly similar lifestyle and shape, the two have very different tongues, knees, toe webbing, tail, and wing structure. DNA comparisons show that grebes have evolved independently since the early Tertiary, whereas loons branched off from the penguin-tubenose lineage much later, in mid Tertiary. The details of neck musculature, shape of sternum, and some special muscles that pull the skin of the nape forwards to raise the cheeks and crown, might link the grebes to coots (Rallidae) and finfoots (Heliornithidae). Seven genera with 22 species are currently recognized. Three species, Atitlán (Podilymbus gigas), Colombian (Podiceps andinus), and Alaotra grebes (Tachybaptus rufolavatus) are fairly poorly differentiated and have at some time been treated as subspecies of pied-billed (Podilymbus podiceps), eared (Podiceps nigricollis), and little grebes (Tachybaptus ruficollis), whereas others currently treated as subspecies might deserve status of full species. These latter include the large and nearly flightless Malvinas race of the white-tufted grebe (Rollandia roland), two or even three populations of silvery grebe (Podiceps occipitalis), and perhaps the yellow-eyed forms of the little grebe.

Physical characteristics

Grebes have rather flattened, round bodies, long necks that are nearly twice the length of the body and composed of 17–21 vertebrae, pointed bills, vestigial tails, and fluffy rear ends. Their feet are flattened, lessening resistance, and are the birds' only means of propulsion during swimming and diving. The feet are placed far back on the body, beat parallel to the water surface, and function as a rudder. The feet have become so adapted for swimming and diving that grebes are barely able to walk, doing so only for short distances and with a labored waddle and the body held upright. During relaxed swimming grebes only use one leg at a time, but during dives they move them simultaneously. Each toe has a large, unilateral swimming lobe and the three large front toes are only slightly webbed. The hind toe is small, but also lobed. The rear edge of the tarsus is serrated in adults. Serration is most pronounced in the genera Tachybaptus and Rollandia, and might serve to cut through entangling submergent vegetation. Some species have very long necks and long bills used for darting during rapid pursuit of fish, a characteristic that has evolved independently three times in the family. Most species have moderately long necks and shorter bills that also serve for feeding on small arthropods and other invertebrates. To handle fish grebes have evolved a strong bite,

but unlike several other diving birds, they have no serrated bill. Body feathers are more numerous than in any other group of bird and may amount to 20,000 or more. The feathers are downy at the base and are frequently oiled with secretion from the tufted uropygial gland. The dark skin absorbs heat during frequent sunbathing on the water, often with the bird attaining an awkward sidewise posture to expose the belly. The rectrices are strongly degenerate and barely differ from the fluffy feathers of rump and vent. The flank feathers are modified for absorbing water to decrease buoyancy during dives. The wings are fairly short and narrow, with 11 functional primaries that are somewhat curved. The number of secondaries varies interspecifically and is presumably correlated with size. There is only a single downy plumage, in which the head and neck are striped in a distinctive pattern and, in some species, also show patches of colored bare skin. The striped pattern on the downy neck is retained for months after the rest of the body has become feathered, and probably serves to appease the adults. Adults of most species shift between a breeding plumage and a duller winter plumage. The body mass changes drastically through the year in many species and is shifted between different parts of the body. Breast muscle is built up when flight is needed, leg muscle when frequent diving is needed, and during wing molt, when all the flight feathers (remiges) are shed simultaneously, enormous quantities of fat may be deposited, increasing the body mass twofold or more. Body feathers, especially the flank feathers, are molted all year round and eaten to fill half the stomach with a felt-like lining, possibly to avoid attacks by spiny-headed worms (Acanthocephala) and perhaps other parasites, which are common in grebes owing to the great diversity of food ingested. It has also been suggested that the feathers help protect the stomach from puncture by fish bones. Most grebes are heavily infested, and several species of parasites are dependent on grebes. As many as 33,000 parasites, mostly flukes, tapeworms, and nematodes have been counted in a single individual. Flight is of relatively little importance, and grebes need a running start to get airborne. Young grebes cannot fly until they are six to nine weeks old. Several resident species have evolved near or total flightlessness, and the heavy build-up of fat deposits in winter quarters, together with the time of wing molt, render many other grebes flightless for a large part of the year. The oldest known grebe was 15 years old (western grebe, Aechmophorus occidentalis) and the little grebe is known to reach 12 years of age.

Distribution

Grebes have a nearly worldwide distribution, missing only in the Antarctic and high Arctic regions. They occur from sea level to over 13,000 ft (4,000 m). The greatest diversity is found in the Americas with 15 species representing all but one of the seven recognized genera.

Habitat

Grebes breed on shallow freshwater lakes or brackish water, often rich in submergent plants, but many winter along sea coasts. During molt and migration some species gather on larger, often saline or even super saline, lakes.

Behavior

Grebes spend a lot of time preening and sunbathing. Most species are aggressive while breeding, especially during pair formation, notably the horned grebe (Podiceps auritus), which will attack not only grebes, but also several other species of birds within its territory and was once observed to drive away a whole flock of the much larger greylag goose (Anser anser) by spiking their bellies from below. Intraspecifically grebes also keep apart, and most of those that nest colonially are territorial on the feeding grounds. Among the exceptions is the hoary-headed grebe (Poliocephalus poliocephalus), which both feeds and nests socially, and the Junín grebe (Podiceps taczanowskii) feeds in organized groups, moving forward in a lateral line and diving synchronously. The courtship of many species is spectacular and among the most complex in birds. It comprises ritualized aggressive behavior with hunched postures, head turning, running on the water side by side, synchronous diving followed by surfacing with weeds in the bill and rising breast to breast while shaking heads, and several other acts. Vocalizations accompany most displays, but are especially developed in the smaller grebes, in which the members of a pair give remarkably well-synchronized duets. Other displays are poorly developed.

When moving between breeding, staging, and winter quarters grebes fly at night. They sometimes congregate in large groups, largest in the eared grebe in North America with over two million molting on just a few supersaline lakes.

Feeding ecology and diet

The larger grebes regularly dive to depths of 80 ft (25 m), exceptionally 130 ft (40 m), but catch most of their food within 26 ft (8 m) of the surface, and some, such as the little grebe, do not dive below 7 ft (2 m). Grebes sometimes pick prey from the surface, but for the most part they feed underwater and only occasionally bring a fish to the surface before swallowing it. The importance of fish in their diet has thus been overestimated. Invertebrates, mainly insects and crustaceans but also snails and annelid worms, are important for some species, at least seasonally, and some do not eat fish at all. Other known prey include squid, tadpoles, frogs, and leeches. Even when fish form the bulk of the diet, the large numbers of invertebrate prey that may be found in their stomachs are evidence that they spend much more time catching invertebrates than fish. Prey are usually pinched, but Clark's (Aechmorphorus clarkii), western, and apparently sometimes great crested (Podiceps cristatus), and possibly great grebes (Podiceps major) spike fish with a quick dart of the neck during rapid pursuit. In turbid water grebes spot their prey from below. Grebes show a remarkable division of resource use between species. Generally two similar-sized species are not found in close proximity on the breeding grounds. Species that do occur in the same lakes are adapted to exploit different food items, usually in different parts of the lakes. Larger, mostly fish-eating species forage in the deeper parts, whereas smaller species that rely more on invertebrates and small fish feed closer to shore. Some of the most convincing examples of character displacement in birds is found in grebes and mainly involve change in bill size where two or three species occur in the same place.

Undigested food is regurgitated in pellets together with feathers after drinking. The hoary-headed and New Zealand grebes (Poliocephalus rufopectus) do not drink before regurgitating and also do not eat feathers, perhaps owing to their special diet.

Reproductive biology

The nest is almost invariably floating, but often attached to vegetation. It is built of rotting plant material and varies from small platforms to rather bulky structures, the latter most common in grebes of wind-swept habitats. Some grebes place their nest near that of a coot or other aggressive bird, presumably for protection against predators.

Besides the nest, several more platforms are often constructed. These are used for mating (which never occurs on the water), resting, and sunbathing. The fairly small, biconical eggs are light blue at first, but soon become white and then stained. They are usually 2–4 in number, at high latitudes 3–8, and have an outer layer of calcium phosphate, allowing them to breathe when wet. The incubation period is 22 to 23 days, but because of asynchronous hatching a nest may hold eggs for up to 35 days. The young can swim but

are carried on the back of the parents for weeks except during dives. After about ten days the parents may separate, more or less permanently, with one or two chicks each. The young of horned grebe are independent at two weeks, but young of most species are cared for much longer. The young can fly at six to nine weeks, but in double-brooded species they often stay even longer and help their parents feed younger siblings. Breeding success is usually two to four, but the hooded grebe (Podiceps gallardoi) apparently never raises more than one chick.

Conservation status

No entire genus of grebe is immediately threatened. Two species, Atitlán and Colombian (Podiceps andinus) grebes have gone extinct within the last two decades, and one, the Alaotra grebe, is on the brink of extinction and probably cannot be saved. Luckily all three of them have close living relatives of which they were once considered subspecies. The most critically threatened of the others is the Junín grebe, endemic to a single Peruvian lake that is subject to pollution from mining and changing water levels controlled by a hydroelectric power plant. During dry periods polluted water is fed into the lake, and with current practices a few years of drought could wipe out the entire ecosystem. The lake is declared a national reserve, but unless the intake of polluted water is cut off (which is technically possible) and the electricity for the local mines bought somewhere else, so the hydroelectric plant can cease to function, there seems to be little hope of saving the grebe from extinction.

Another species, the Madagascar grebe (Tachybaptus pelzelnii) is cause for concern, but its status is not critical. Its numbers have declined steadily for the last half of the twentieth century, owing to reduction of habitat and introduction of exotic herbivorous fish, which change the habitat sufficiently for a competing grebe to establish.

Significance to humans

Until the early twentieth century, grebes were hunted extensively for their silky-white belly feathers. These were used to make shoulder capes and muffs for women's clothes. Great crested grebes were nearly extirpated in Western Europe, but "grebe-fur" was then imported from other parts of the World.

Archaeological studies in the Great Salt Lake basin suggest that eared grebes, which gather there in millions to molt, were an important food in the past, but today grebes are barely hunted for food anywhere on the globe, and in many places are considered ill-tasting. Locally they are believed to harm freshwater fisheries, and are shot.

In China, the little grebe has found various uses: its fat is used as an anticorrosive; its feathered skin for fur hats; and its meat as medicine.

Species accounts

List of Species

Titicaca flightless grebe

Rollandia microptera

taxonomy

Podiceps micropterus, Gould, 1868, Lake Titicaca.

other common names

English: Short-winged grebe, flightless grebe; French: Grèbe microptère; German: Titikakataucher; Spanish: Zampullín de Titicaca.

physical characteristics

15.3–17.7 in (39–45 cm); 1.4 lb (635 g). Adult breeding: Above blackish brown, shaggy crown chestnut with greenish-black streaks, lower cheeks white with black streaks, throat and fore-neck white, breast and thin line on sides of neck rufous, belly mottled drab, rufous and gray, flanks with most rufous. Secondaries mostly white with black shaft streak. Bill dark suffused with yellow, eye-ring yellow, eyes dark. Nonbreeding birds with more or less whitish central underparts, immatures considerably paler both above and below.

distribution

Endemic to Lake Titicaca and adjacent Lake Uru-Uru at 12,100–12,600 ft (3,700–3,800 m) in southeast Peru and west Bolivia.

habitat

Breeds among patches of bulrush (Scirpus totora) or floating waterweeds, always with easy access to open water.

behavior

Usually alone. Flees to open water rather than seeking cover in the vegetation.

feeding ecology and diet

Feeds nearly entirely on large fish caught in relatively open and deep water. Sometimes peers from surface.

reproductive biology

Courtship elaborate, usually beginning with assembly of several birds. Breeds throughout year. Lays 2 eggs several times a year, sometimes using the same nest. Large young sometimes help feed chicks from later broods. Incubation period unknown.

conservation status

Population size unknown. Estimated to between 2,000 and 10,000 birds in the 1980s, but has declined dramatically in recent years, probably mostly owing to increased use of fishing nets with fine mesh, but local eutrophication and the introduction of trout and silverside (Odonthestes bonariensis), which has caused disappearance of many native fish, may also have played a role. Classified as Near Threatened but situation possibly critical.

significance to humans

None known.

Little grebe

Tachybaptus ruficollis

taxonomy

Colymbus ruficollis, Pallas, 1764, Holland. Nine subspecies.

other common names

English: Common grebe, red-throated little grebe, dabchick; French: Grèbe castagneux; German: Zwergtaucher; Spanish: Zampullín Común.

physical characteristics

9.8–11.4 in (25–29 cm); 0.26–0.53 lb (117–241 g). Adult breeding: breast, chin, lores, cap and rest of upperparts blackish, cheeks, throat and side of neck rufous. Sides and flanks dusky more or less washed with rufous, belly variable according to subspecies, ranging from silvery white to black. Most forms have no white in wing, some a small patch on inner secondaries. Bill black-tipped white and with pale yellow wattle at base, eyes red in most of range, yellow in east Asia. Nonbreeding dull brownish, throat and belly whitish, immature similar but with striped neck.

distribution

T. r. ruficollis: Europe and northwest Africa; T. r. iraquensis: Iraq and southwest Iran; T. r. capensis: Africa south of the Sahara, Madagascar, Caucasus and eastwards through India to Myanmar; T. r. poggei: southeast and northeast Asia; T. r.

philippensis: northern Philippines; T. r. cotabato: southeast Philippines; T. r. tricolor: Sulawesi to north New Guinea; T. r. vulcanorum: Java to Timor; T. r. collaris: northeast New Guinea to Solomon Islands.

habitat

Mostly small and shallow lakes and ponds, but also along vegetated shores of larger lakes. When not breeding, sometimes on more open water, rarely on coast.

behavior

Pairs may reside on the same pond all year, but non-breeding birds may assemble in loose groups of 5–30, occasionally hundreds.

feeding ecology and diet

Usually feeds within 3.3 ft (1 m) of surface, often just peering and picking with head and neck under water or picking from the surface. Diet variable, but mainly insects. Also takes small fish and, unlike most grebes, substantial numbers of snails.

reproductive biology

Courtship display poorly developed and partly replaced by vocal duetting given with remarkable synchrony. Eggs 2–7, usually 4; often two, sometimes three broods a year. Incubation 20–25 days, young stay in nest for a week and can fly when 44–48 days old. They sometimes help feed older siblings.

conservation status

Not threatened. Widespread and generally common.

significance to humans

None known.

Least grebe

Tachybaptus dominicus

taxonomy

Colymbus dominicus, Linnaeus, 1766, Santo Domingo. Five subspecies.

other common names

English: American dabchick, least dabchick; French: Grèbe dominicain; German: Schwartzkopftaucher; Spanish: Zampullín Macacito.

physical characteristics

8–11 in (20–27 cm); 0.25–0.40 lb (112–182 g), female decidedly smaller than male, T. d. eisenmanni smallest. Adult breeding: above blackish, sides of head, and neck gray. Breast and sides dusky, breast washed with buff, belly whitish mottled with gray. Eyes pale yellow to orange-yellow; bill black with pale tip. Nonbreeding duller with white throat, immature with striped head, brown eyes and pale bill.

distribution

T. d. dominicus: northern Caribbean; T. d. bangsi: Baja California; T. d. brachypterus: west central Mexico to Panama; T. d. speciosus: most of South America, including northern Argentina and southern Brazil; T. d. eisenmanni: western Ecuador.

habitat

Usually in water almost overgrown with floating vegetation. Mostly temporary ponds, but also swamps, shallow lakes and ditches. Occasionally in mangroves.

behavior

In pairs or loose groups, territories sometimes grouped close together.

feeding ecology and diet

Mainly feeds on insects.

reproductive biology

Multi-brooded, nesting at any season if conditions are suitable. Eggs usually 4–6. Incubation period 21 days.

conservation status

Not threatened and locally common. Total population at least 20,000.

significance to humans

None known.

Pied-billed grebe

Podilymbus podiceps

taxonomy

Colymbus podiceps, Linnaeus, 1758, South Carolina. Three subspecies.

other common names

French: Grèbe à bec bigarré; German: Bindentaucher; Spanish: Zampullín Picogrueso.

physical characteristics

12–15 in (30–38 cm); 0.6–1.3 lb (253–568 g). Adult breeding: above blackish, headside gray in contrast to black throat, sides of neck, breast, and sides of body grayish buff grading to mottled whitish and sooty gray on belly. Rump white. Bill short and thick, bluish white with distinct black vertical bar, eyes dark. Nonbreeding similar but throat pale, cheeks, neck, and flanks more buffy brown, bill usually fleshy pink without black bar. Immature: Head and neck boldly striped rufous, black and white, body rather uniform gray.

distribution

P. p. antillarum: Greater Antilles; P. p. podiceps: central Canada to Panama, in winter in southern part of range and Caribbean; P. p. antarcticus: eastern Panama and large parts of southern America.

habitat

Lakes, marshes, and ponds, usually with abundant reeds, floating and submergent vegetation and often with little open water.

behavior

Alone, in pairs or family groups.

feeding ecology and diet

Eats a great variety of prey, but more than other grebes may take armored or spiny fish, crayfish, and crabs, the latter forming a substantial part of the diet in the Neotropics.

reproductive biology

Courtship display poorly developed. Highly territorial. Eggs 2–10. Often double-brooded. Incubation period 21–27 days, shortest for last egg, fledging 35–37 days.

conservation status

Not threatened and common over much of its range. Often killed on rainy nights during migration when they mistake wet asphalt roads and parking lots for ponds and dive in from some height.

significance to humans

None known.

Hoary-headed grebe

Poliocephalus poliocephalus

taxonomy

Podiceps poliocephalus, Jardine and Selby, 1827, New South Wales.

other common names

English: Hoary-headed dabchick; French: Grèbe argenté; German: Haarschopftaucher; Spanish: Zampullín Canoso.

physical characteristics

11–12 in (27–30 cm); 0.4–0.7 lb (190–311 g). Adult breeding: entire head and upperparts dark, head covered with long, fine streaks of white plumes except on black mid-crown and upper throat. Neck and breast light rusty to whitish, belly white, sides mottled with gray. Eyes buffy, bill black prominently tipped white. Nonbreeding: duller, with fewer and shorter head plumes, throat white, neck and breast whitish, bill horn; immature similar, but after shedding striped head and neck, head without any white plumes; bill pinkish with dark ridge.

distribution

Australia and Tasmania, recently also locally on South Island, New Zealand.

habitat

Mainly semi-permanent open swamps with relatively little floating vegetation, but also on open temporary ponds. In drought years non-breeders congregate in permanent wetlands and coastal lagoons.

behavior

Gregarious, even when feeding. Semi-nomadic, sometimes appearing suddenly in groups of up to ten thousand.

feeding ecology and diet

Feeds within 6.6 ft (2 m) of surface, almost entirely on small arthropods, fish consituting less than 3% of diet.

reproductive biology

Courtship display poorly developed. Nest fairly exposed, but inaccessible, in colonies with up to 400 nests. Single-brooded. Eggs 3–5.

conservation status

Not threatened and locally common. Population may exceed half a million.

significance to humans

None known.

Great grebe

Podiceps major

taxonomy

Colymbus major, Boddaert, 1783, Cayenne. Two subspecies.

other common names

French: Grand Grèbe; German: Magellantaucher; Spanish: Somormujo Macachón.

physical characteristics

22–31 in (57–78 cm), P. m. navasi largest, Peruvian birds smallest; 3.5 lb (1600 g). Slender with very long neck and thin, slightly upturned bill. Adult breeding: face gray to blackish, small median crest on hindcrown black, hind-neck dark gray to black, back blackish with pale feather edges, neck, breast, flanks, and vent rufous, flanks with dusky wash, belly, secondaries, inner primaries and base of outer primaries white. Eyes brown, bill black. Nonbreeding either similar, but with pale gray lores and throat, or duller, or with cap black, upper lore pale, cheeks graybrown, neck gray with some rufous, and sides gray. Immature: sides of head with bold black lines and spots, neck dull rufous, body rather uniform sooty gray, belly white.

distribution

P. m. major: western Peru, central Chile and all of Argentina north to southern Paraguay and southeastern Brazil, many winter on coast; P. m. navasi: southern Chile, in winter on coast.

habitat

Large open lakes and marshes, in winter in kelp zone along coast.

behavior

Alone or in loose groups, often nesting in colonies.

feeding ecology and diet

Mainly eats fish, but also some arthropods and mollusks, locally many crabs. Feeds in fairly deep water.

reproductive biology

Courtship display rather poorly developed. Large nest, often close to each other in colonies. Sometimes double-brooded. Eggs 1–6, usually 2–3.

conservation status

Common in southern part of range and not at risk. Total population estimated at 50,000.

significance to humans

None known.

Great crested grebe

Podiceps cristatus

taxonomy

Colymbus cristatus, Linnaeus, 1758, Sweden. Three subspecies.

other common names

French: Grèbe huppé; German: Haubentaucher; Spanish: Somormujo Lavanco.

physical characteristics

18–24 in (46–61 cm), P. c. infuscatus smallest; 1.3–3.3 lb (568–1,490 g), heaviest while staging. Adult breeding: crown black elongated to two posterior "horns" that can be raised and spread; rest of upperparts blackish; sides of head white (upper lores and supercilium black in infuscatus) grading to chestnut on large posterior fan with black rear edge; underparts white, upper sides washed with dusky; secondaries, tips of inner primaries,

lesser wing-coverts and scapulars white. Eyes red, bill pink with dusky ridge. Nonbreeding: crest short, sides of head white with no fan, immature similar but with several black stripes on headside.

distribution

P. c. cristatus: Palaearctic, in winter in southern part of range, mainly on coasts; P. c. infuscatus: Africa locally south of Sahara;P. c. australis: Australia, Tasmania, and South Island, New Zealand.

habitat

Mainly large lakes with expanses of open water and reedy bays, but also brackish water, and tolerates heavily eutrophicated and disturbed environments such as city parks.

behavior

Alone or on pairs, in staging areas in groups of hundreds, occasionally up to 10,000 together.

feeding ecology and diet

Mainly feeds on relatively large fish, usually in fairly deep water, but also takes frogs, crustaceans, squid and other invertebrates.

reproductive biology

Courtship display well developed. Nest often placed near that of a coot. One or two broods per year. Up to 9 eggs, but usually 3–5. Incubation period 25–29 days. Young carried 3–4 weeks, associated with parents until 8–10 weeks old, able to fly at 10 weeks.

conservation status

Nearly extirpated from parts of Europe in the 1800s owing to hunting for the plume trade, but now common in Palaearctic region, where increasing owing to eutrophication of lakes and where the population is estimated at around 700,000 birds. Less common in other parts of range and decreasing in parts of Africa, probably owing to drowning in monofilament gill nets. In New Zealand a drastic decline occurred since the arrival of Europeans, but population now stable.

significance to humans

Formerly extensively hunted for "grebe fur."

Eared grebe

Podiceps nigricollis

taxonomy

Podiceps nigricollis, C. L. Brehm, 1831, Germany. Three subspecies.

other common names

English: Black-necked grebe; French: Grèbe à cou noir; German: Schwartzhalstaucher; Spanish: Zampullín Cuellinegro.

physical characteristics

11–13 in (28–34 cm); averages 0.7 lb (325 g) while breeding, but may weigh over 1.3 lb (600 g) while staging. Females with smaller bills than males. Adult breeding: back blackish, crested head, neck and upper breast black with tuft of golden plumes behind eye, sides chestnut, rest of underparts, and secondaries white. Eyes bright red, bill black. Nonbreeding with less developed crest, blackish crown reaching to below eye where grading with white cheeks and throat, neck and sides gray;

immature similar, but more brownish, especially on neck; striped pattern of head soon wearing off.

distribution

P. n. nigricollis: Europe and western Asia, in winter in southwestern part of range; P. n. gurneyi: South Africa; P. n. californicus: southwestern North America, in winter south to Guatemala.

habitat

Small, shallow, eutrophic lakes with open water and scattered patches of reed. Molts and winters on saline lakes and on coasts.

behavior

Gregarious. In small groups where breeding, in large flocks when molting. In North America over two million stage on just a few lakes.

feeding ecology and diet

Sometimes feeds in organized groups. Eats tiny arthropods, only rarely fish.

reproductive biology

Courtship display well developed. Monogamous, but nests colonially, often far from shore, usually a few together but occasionally up to 2,000 pairs in one colony, often in association with marsh terns and smaller gulls, but away from coots and other grebes. Usually single-brooded, eggs 2–4, incubation period 20–22 days.

conservation status

Not threatened. The most numerous of all grebes, with a world population exceeding 5 million birds, most occurring in North America. Numbers fluctuate greatly and species at risk while molting, when large parts of the population are concentrated on just a few lakes in flightless condition.

significance to humans

None known.

Hooded grebe

Podiceps gallardoi

taxonomy

Podiceps gallardoi, Rumboll, 1974, Argentina.

other common names

English: Mitred grebe; French: Grèbe mitré; German: Gold-scheiteltaucher; Spanish: Zampullín Tobiano.

physical characteristics

12.6 in (32 cm); 0.9–1.6 lb (420–740 g). Adult breeding: head and hindneck black with white forehead grading into orange-rufous semi-crest; back blackish, rest of body and most of wings white. Eyes bright re d, bill bluish gray. Nonbreeding similar, occasionally with some white feathers on cheeks. Immature soon loses striped head to become like adult, except for black instead of rufous on crown, and white lower cheeks and throat.

distribution

Patagonia, main breeding grounds on meseta between Lake Stroebel and Lake Cardiel.

habitat

Nests in fish-free, steep-sided potholes on volcanic tablelands, water with abundant submergent and floating carpets of water milfoil (Myriophyllum elatinoides). After breeding gathers on large upland lakes, in winter perhaps only on coast.

behavior

Gregarious and peaceful. In small dispersed flocks while breeding, in large flocks at other times.

feeding ecology and diet

Feeds entirely on invertebrates, perhaps mainly insects, but also snails, crustaceans and leeches, mainly caught diving.

reproductive biology

Courtship display well developed, more complex and stereo-typed than in any other grebe. Single-brooded. Nest large. Eggs 1–2, but only one young reared.

conservation status

Population estimated at 3,000–5,000 birds. Not threatened owing to inaccessibility of habitat.

significance to humans

None known.

Western grebe

Aechmophorus occidentalis

taxonomy

Podiceps occidentalis, Lawrence, 1858, Fort Steilacoom, Washington. Two subspecies.

other common names

French: Grèbe élégant; German: Renntaucher; Spanish: Achichilique Común.

physical characteristics

21.6–29.5 in (55–75 cm); 1.8–4.0 lb (823–1826 g), A. o. ephemeralis smallest, females decidedly smaller than males. Body narrow, neck very long, bill long and sharply pointed. Head with slight crest. Adult breeding: cap to below eye black, rest of upperparts blackish with faint gray scales on back; underparts white, sides spotted gray. Wings with variably sized white bar across remiges. Eyes red, bill buffy green with black ridge. Nonbreeding: similar, but crown duller, less crested and less clearly demarcated from white. Immature: like non-breeding, but crest even shorter, back without scales, and facial pattern more diffuse, sometimes with white on lores.

distribution

A. o. occidentalis: west to North America, in winter on coast of Texas and Pacific coast south to Baja California; A. o. ephemeralis: resident in central Mexico.

habitat

Breeds on large lakes and marshes with large expanses of open fresh or brackish water and with reedy shores. In winter mostly on salt lakes or in deep offshore waters on coast.

behavior

Colonial, sometimes several thousand together.

feeding ecology and diet

Feeds almost entirely on large variety of fish, often spiking them, usually in fairly deep water, but on average closer to shore than Clark's grebe.

reproductive biology

Courtship display well developed. Nests 3–12 ft (2–4 m) apart in colonies. Eggs 3–4, incubation period 22–24 days. Young independent at 8 weeks.

conservation status

Not threatened. Population estimated at 70,000–100,000 birds, only few in Mexico.

significance to humans

None known.

Resources

Books

Cramp, S., and K.E.L. Simmons, eds. The Birds of the Western Palearctic. Vol. 1 of Handbook of the Birds of Europe, the Middle East and North Africa. Oxford, London, and New York: Oxford University Press, 1977.

del Hoyo, J., A. Elliot, and J. Sargatal, eds. Ostrich to Ducks. Vol. 1 of Handbook of the Birds of the World. Barcelona: Lynx Edicions, 1992.

Ilychev, V.D., and V.E. Flint, eds. Handbuch der Vögel der Sovjetunion. Vol. 1. Wiesbaden: Aula-Verlag, 1985.

Marchant, S., and P.J. Higgins, Coordinators. Handbook of Australian, New Zealand and Antarctic Birds. Vol. 1, Ratites to Ducks. Oxford: Oxford University Press, 1990.

O'Donnell, C., and J. Fjeldså. Grebes—Status Survey and Conservation Action Plan. Gland, Switzerland, and Cambridge, United Kingdom: IUCN/SSC Grebes Specialist Group, IUCN, 1997.

Sibley, C.G., and J.E. Ahlquist. Phylogeny and Classification of Birds. A Study in Molecular Evolution. New Haven: Yale University Press, 1990.

Periodicals

Appert, O. "Die Taucher (Podicipedidae) der Mangokygegend in Südwest-Madagaskar." Journal of Ornithology 112 (1971): 61–69.

Boertmann, D. "Phylogeny of the Divers, Family Gaviidae (Aves)." Steenstrupia 16 (1990): 21–36.

Fjeldså, J. "Comparative Ecology of Peruvian Grebes—A Study of the Mechanisms of Evolution of Ecological Isolation." Vidensk. Medd. Dansk Naturh. Foren. 144 (1981): 125–249.

Fjeldså, J. "Displays of the Two Primitive Grebes Rollandia rolland and R. microptera and the Origin of the Complex Courtship Behaviour of the Podiceps Species." Steenstrupia 11(1985): 133–155.

Geiger, W. "Die Nahrung der Haubentaucher (Podiceps cristatus) des Bielersees." Ornithologische Beobachter 54(1957): 97–133.

Moum, T., D. Johansen, K.E. Erikstad, and J.F. Piatt. "Phylogeny and Evolution of the Auks (Subfamily Alcinae) Based on Mitochondrial DNA Sequences." Proceedings of the National Academy of Sciences of the United States of America. 91 (1994): 7912–7916.

Voous, K.H., and H.A.W. Payne. "The Grebes of Madagascar." Ardea 54 (1965): 9–31.

Organizations

IUCN/SSC Grebes Specialist Group. Copenhagen, DK 2100 Denmark. Phone: +45 3 532 1323. Fax: +45-35321010. E-mail: [email protected] Web site: <http://www.iucn.org>

Wetlands International. Droevendaalsesteeg 3A, Wageningen, 6700 CA The Netherlands. Phone: +31 317 478884. Fax: +31 317 478885. E-mail: [email protected] Web site: <http://www.wetlands.agro.nl>

Niels K. Krabbe, PhD