The red-necked grebe (Podiceps grisegena) is an aquatic bird found in the temperate regions of the northern hemisphere. A migratory bird, its wintering habitat is largely restricted to calm waters just beyond the waves around ocean coasts, although some birds may winter on large lakes. Grebes prefer shallow bodies of fresh water such as lakes, marshes or fish-ponds as breeding sites.
The red-necked grebe is a fairly drab dusky-grey bird in winter. During the breeding season, it acquires the distinctive red neck plumage, black cap and contrasting pale grey face from which its name was derived. It also has an elaborate courtship display and a variety of loud mating calls. Once paired, it builds a nest from water plants on top of floating vegetation in a shallow lake or bog.
Like all grebes, the red-necked is a good swimmer and particularly swift diver, and responds to danger by diving rather than flying. The feet are positioned far back on the body, near the tail, which makes the bird ungainly on land. It dives for fish or picks insects off vegetation; it also swallows its own feathers, possibly to protect the digestive system. The conservation status of its two subspecies, P. g. grisegena, found in Europe and western Asia, and the larger P. g. holbolii (sometimes called Holbøll's grebe), found in North America and eastern Siberia, is evaluated as Least Concern, and the global population is stable or growing.
Taxonomy
The red-necked grebe was described by the French polymath Georges-Louis Leclerc, Comte de Buffon in 1781 in his Histoire Naturelle des Oiseaux. The bird was also illustrated in a hand-coloured plate engraved by François-Nicolas Martinet in the Planches Enluminées D'Histoire Naturelle which was produced under the supervision of Edme-Louis Daubenton to accompany Buffon's text. Neither the plate caption nor Buffon's description included a scientific name but in 1783 the Dutch naturalist Pieter Boddaert coined the binomial name Colymbus grisegena in his catalogue of the Planches Enluminées. The type locality was subsequently designated as France. The red-necked grebe is now placed in the genus Podiceps that was described by the English naturalist John Latham in 1787. The genus name Podiceps comes from Latin podicis, "vent" or "anus", and pes, "foot", and is a reference to the placement of a grebe's legs towards the rear of its body. The species name grisegena is from Latin griseus (grey) and gena (cheek) and refers to the grey cheeks of the breeding adult.
Grebes are small to medium-large water birds with lobed, rather than webbed, toes. There are several genera, of which the most widespread is Podiceps with nine species, one recently extinct. The closest relative of the red-necked grebe is the fish-eating great crested grebe of Europe and western Asia. It is possible that the red-necked grebe originally evolved in North America and later spread to Europe, where a change of diet to include more insects helped to reduce competition with its larger cousin. Fossils of the species dating to the middle Pleistocene have been found in Italy.
Description
The red-necked grebe is a medium-large grebe, smaller than the great crested grebe of Eurasia, and the western and Clark's grebes of North America, but noticeably larger than other northern grebe species. In breeding plumage, it has a black cap that extends below the eye, very pale grey cheeks and throat, a rusty red neck, dark grey back and flanks, and white underparts. The eyes are dark brown and the long, pointed bill is black with a yellow base.
thumb|left|upright|Adult of American subspecies with chicks
The winter plumage of the red-necked grebe is duskier than that of other grebes; its dark grey cap is less defined, and merges into the grey face, and a pale crescent that curves around the rear of the face contrasts with the rest of the head. The front of the neck is whitish or light grey, the hind neck is darker grey, and the yellow of the bill is less obvious than in summer. The relatively small wings are grey with white secondaries, and beat very rapidly. and needs a lengthy run across water to gain the speed needed for take-off. Like all grebes, the red-necked is an expert swimmer; it uses its feet for propulsion underwater, and steers by rotating its legs, since its tail is too short for this purpose.
This is one of the most vocal grebes during the breeding season, but, like its relatives, it is mainly silent for the rest of the year. It has a loud, wailing or howling display call uooooh, given by a single bird or a pair in duet, by night or during the day, and often from cover. Long sequences of up to 60 consecutive notes may be delivered during singing encounters between rival territorial birds. A great variety of quacking, clucking, hissing, rattling and purring calls are also given, with much individual variation. || Nominate subspecies. Smaller, long with a average wingspan, and weighs . Longer, stouter bill with more extensive yellow.
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Holbøll's grebe was named after the Danish explorer of Greenlandic birds Carl Peter Holbøll. As Holbøll was Danish, under the International Code of Zoological Nomenclature Article 32.5.2.1, scientific names derived from his name treat the ø/ö as 'o', rather than 'oe' had it been derived from a German name, thus the correct spelling of the subspecies is Podiceps grisegena holbollii, and not "holboellii" as formerly often cited. The east Asian birds are in some aspects intermediate, with slightly smaller bills than the American birds, although the differences are too small to merit separation as a third subspecies. The difference in size between the sexes is slightly larger for this subspecies than for P. g. grisegena.
Distribution and habitat
Breeding takes place in shallow freshwater lakes, bays of larger lakes, marshes, and other inland bodies of water, often less than in extent and less than deep. The red-necked grebe shows a preference for waters in forested areas or, further north, in shrub tundra, and favours sites with abundant emergent vegetation, such as reedbeds. The best breeding habitat is fish-ponds, which have an abundance of food in addition to meeting the other requirements. The American subspecies is less tied to a high aquatic plant density, and sometimes breeds on quite open lakes. P. g. holbolii breeds in North America in Alaska, western and central Canada, and the northern US east to Minnesota; in Asia it nests in eastern Siberia from Kamchatka south to Hokkaido and west to Mongolia. The Asian birds winter at sea from Japan to the East China Sea, and American breeders winter in the Pacific, mainly from southern Alaska to British Columbia (with smaller numbers south to California), and in the Atlantic from Newfoundland and Labrador to Florida. Some birds remain on the Great Lakes if they are sufficiently ice-free. and parts of northern and western India.
Behaviour
Breeding and survival
thumb|Egg, Collection [[Museum Wiesbaden, Germany]]
Red-necked grebes usually nest as isolated pairs with more than between neighbouring nests, although semi-colonial nesting may occur in suitable sites, where up to 20 pairs each defend a linear territory. Pairs nesting in these colonies produce larger clutches of eggs, which hatch earlier in the season and result in larger broods. The territory is defended with various threat displays, including wing-spreading, hunching, and bill-thrusting; Breeding is often in loose association with gulls or other colonial water birds.
right|thumb|Chicks on a parent's back
The red-necked grebe lays four or five (range one to nine) dull white or pale blue eggs, which average in breadth, in length, and weigh about , of which 10% is shell. Parents take turns to incubate the eggs for 21–33 days until the precocial downy chicks hatch; The young may be fed by the parents for up to 54 days after fledging, The brood may be split, so that each parent feeds only some of the chicks. This spreads the feeding demand equally between the parents.
After breeding the adults moult their wing feathers and are temporarily flightless; migration commences once the flight feathers have regrown. Pike may take swimming chicks. On average, for each adult, 0.65 young birds are still alive by their fourth month, although the mortality rate for the adult is unknown. Red-necked grebes attempt to evade birds of prey by diving; when feeding, dives average less than 30 seconds, although escape dives are more prolonged.) may be important locally or seasonally, especially for the American subspecies, and crustaceans can constitute up to 20% of the grebe's diet. Birds breeding at the coast often make foraging flights to inland lakes or offshore areas to feed.
European breeders, which have to compete with the larger great crested grebe for fish, eat a greater proportion of invertebrates than the longer-billed American subspecies, although both races eat mainly fish in winter. If food is scarce, parents may desert unhatched eggs, or allow the smallest chicks to starve, although the latter strategy appears not to be particularly efficient in protecting the older chicks.
Like other grebes, the red-necked grebe ingests large quantities of its own feathers, which remain in the bird's stomach. The function of the feathers in the stomach is unknown, although it has been suggested that they help to protect the lower digestive tract from bones and other hard, indigestible material. The population trend has not been quantified, but it is not believed to meet the thresholds for the population decline criterion (declining more than 30% in ten years or three generations) of the IUCN Red List. For these reasons, the species is evaluated as Least Concern. Parties to the Agreement are required to engage in a wide range of conservation strategies which are describes in a detailed action plan. The plan is intended to address key issues such as species and habitat conservation, management of human activities, research, education, and implementation.
The red-necked grebe was hunted by humans in northern Europe in the Mesolithic and Paleolithic periods, but there is no evidence that there is any significant level of hunting at the present time.