Predators such as American crows (Corvus brachyrhynchos), common ravens (Corvus corax), gulls, bald eagles (Haliaeetus leucocephalus), American coots (Fulica americana), raccoons (Procyon lotor), minks (Neovison and Mustela), and muskrats (Ondatra zibethicus) are known to feed on red-necked grebes eggs and chicks. When small and young are not upon their parent’s back, they may be in danger of being eaten by large fish such as northern pikes (Esox lucius) and largemouth bass (Micropterus salmoides).
Great horned owls (Bubo virginianus) and mink often attack adult birds while they are incubating their eggs. Parasites and roundworms can also infect this species. Some breeding pairs may also display aggressive behavior towards the young of other birds, occasionally killing another pair's chicks.
In response to predators, red-necked grebes are known to jab towards them with their bills or give a hissing call. They may also cover their eggs with nesting material before leaving their nests.
Known Predators:
During breeding season, red-necked grebes are a very vocal species. The most common call is the drawn out "whinny-braying" call, which is used by the grebes to declare territories and in the mating rituals. During these rituals they also perform a variety of physical displays and “crick crick”, and “teck teck” sounding vocalizations. Red-necked grebes are often silent in the fall and winter, although the generic “crick crick” and “teck teck” sounds are sometimes produced.
Dancing duets between potential mates are a critical part of courtship behavior.
Like all birds, red-necked grebes use visual, auditory, tactile, and chemical stimuli to perceive their environment.
Communication Channels: visual ; acoustic
Other Communication Modes: duets
Perception Channels: visual ; tactile ; acoustic ; chemical
Red-necked grebes are in the category of “least concern” on the ICUN Red List. Even though the population tends appear to be slightly decreasing, there has not been a significant amount of change to consider it a vulnerable species. An increase in unnatural predators and human recreational activities are hypothesized to be causing a decline among red-necked grebe populations throughout North America although no obvious trends have been observed that indicate a major declination of this species.
Human pollution is also having an effect on red-necked grebe populations. In a study done in Turtle Mountain Provincial Park in Manitoba it was found that organochlorides, the remains of certain pesticides, are affecting the reproductive success of red-necked grebes. These chemicals primarily affect the integrity of the eggs.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Red-necked grebes have no known negative impacts on humans.
Red-necked grebes have no significant economic importance for humans.
Red-necked grebes compete with other bird species for breeding territory and with fish for food sources. They also provide a food source to their previously mentioned predators. As their primary food source, fish populations are likely kept in check by red-necked grebes.
Red-necked grebes primarily eat small fish, crustaceans, land and aquatic insects, and occasionally amphibians. In smaller lakes that do not contain an abundance of fish, fish only make a minor contribution to the overall diet. Some specific fish species that red-necked grebes eat are: sticklebacks, Pacific herrings (Clupea pallasii pallasii), pilchards (Sardina pilchardus), sculpins, topminnows, lake shiners, perch (Perca), and eels. Some specific crustacean species they eat are: mud lobsters, shrimp, prawn, crayfish, and various other amphipods. Some insect species they eat are: damselflies, dragonflies, water boatmen, whirligig beetles, water scavenger beetles, black swimmers, water striders, crawling water beetles, flies, wasps, ants, bees, stink bugs, lamellicorn beetles, ground beetles, and billbugs.
When eating aquatic prey, red-necked grebes typically forage underwater, picking up their prey off the lake bed or off of vegetation and consuming them while remaining underwater. However, if the prey is too large or difficult to handle they may bring it to the surface before consuming it. They are also known to capture low flying insects out of the air.
Animal Foods: amphibians; fish; insects; terrestrial worms; aquatic crustaceans; other marine invertebrates
Primary Diet: carnivore (Piscivore )
Red-necked grebes (Podiceps grisegena) are native to portions of North America, Asia, and Europe. Their precise location within these biogeographic regions depends upon the time of year because they are migratory birds that move between breeding and wintering locations. In North America, during the breeding season, they are found in a region reaching from Alaska in the north, down through western Canada, across central Canada and the northern portion of the mid United States. For the winter season, North American populations of red-necked grebes migrate to the marine waters of the Pacific coast and the Atlantic coast, reaching as far south as California and North Carolina, but the majority of birds remain in the northern portion of the continent for wintering. A fraction of North American birds spend the winter in the Great Lakes region.
In eastern Asia, red-necked grebes breed in a large region that covers most of eastern Siberia and surrounding area. Eastern Asian populations winter along the Pacific coast of Asia and in some large inland lakes in the region.
In Europe and western Asia, red-necked grebes breed in a large portion of northern Europe that stretches from the Netherlands to western Siberia to southern Russia, eastern Kazakhstan, Turkey, and Bulgaria. This population winters off the coasts of the North, Baltic, Caspian, Black, Adriatic, and Aegean Seas. Although rare, some birds winter in the Mediterranean region and northern Iran.
Biogeographic Regions: nearctic (Native ); palearctic (Native )
Other Geographic Terms: holarctic
Red-necked grebes are predominantly water birds, that is, with the exception of the time spent in migration, they spend nearly all of their time on the water. During the summer breeding season, red-necked grebes typically live and nest on small inland freshwater lakes, shallow marsh areas, and bays of larger lakes. They are also found in more obscure locations, such as irrigation ditches and bogs. The subspecies Podiceps grisegena grisegena tends to make use of smaller and shallower waterbodies that have more surrounding vegetation than those used by P. g. holboellii. During the spring and fall migrations red-necked grebes make pit stops on rivers, large lakes and ocean coastlines that are along the way to their destined range. In winter all populations of both subspecies make use of the various topography of coastal waters or large inland seas and lakes. They typically winter in inlets, bays, or river estuaries and also venture miles away from land on the open ocean.
Habitat Regions: temperate ; polar ; terrestrial ; saltwater or marine ; freshwater
Aquatic Biomes: lakes and ponds; temporary pools; coastal
Wetlands: marsh ; swamp
Other Habitat Features: riparian
Over the years, populations of red-necked grebes have been banded in an effort to determine aspects of their lives including population locations, migratory routes and lifespan. However, recoveries from these studies have been insufficient to determine an estimated lifespan of this species. The little evidence that has been collected has shown that certain birds in Minnesota were still alive five years after being banded.
Range lifespan
Status: wild: 5 (high) years.
Red-necked grebes are relatively large in comparison to other species of grebes. They are 43 to 56 cm long and weigh 800 to 1600 g. Their bills are mostly black, with the exception of the base of the upper mandible and most of the lower mandible, which are orange-yellow or chrome-yellow. Their eyes contain a dark brown iris that is surrounded by a ring of yellow. Like all grebes, this species has lobed feet that they utilize as effective paddles for swimming and rudders for flying. Also, their legs are laterally compressed, which makes them more streamlined when passing through water.
This species has two different plumages depending on whether they are breeding or wintering. Their non-breeding winter plumage is marked by heads topped with black, followed by grey on the sides of the head and a white crescent reaching from the throat upwards to the lower lateral sides of the head. They have white or light gray on the anterior portion of their neck. Observing from anterior to posterior on the body of the bird, the light colors quickly darken to a gray-black; therefore the majority of the bird is dark, with exception of the sides of the head, throat, and anterior portion of the neck. The sides of the head become even lighter as a distinctive pale-gray patch develops in their breeding summer plumage. During this time, as their name suggests, the lateral portions of their neck and breast become a reddish-brown color. The rest of the bird remains relatively similar in color to its non-breeding plumage.
Male and female Red-necked grebes are alike in appearance, but on average males are larger. Juveniles resemble adults in breeding season plumage, with the addition of dark stripes on the cheeks.
On various continents, slight physical variations between populations are observed; therefore two subspecies of red-necked grebes have been identified. The populations that are native to Europe and western Asia are of the subspecies Podiceps grisenega grisegena and the populations of North America and eastern Asia are of the subspecies Podiceps grisenega holboellii. The P. g. grisegena subspecies is smaller and has relatively darker plumage on its back, cheeks, and neck than P. g. holboellii. The bill of P. g. grisegena is longer, slimmer, and not as yellow as the bill of P. g. holboellii.
Range mass: 800 to 1600 g.
Range length: 43 to 56 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike; male larger
Red-necked grebes breed every year and are seasonally monogamous. They are able to breed in their first year of life, yet they usually begin when they are two or more years of age. During mate selection, this species exhibit complex courtship rituals that include a large variety of displays. These rituals are similar to other species of grebes except they tend to be more vocal and contain extensive whinny-braying, which has been described as an eerie sound that resembles a screaming squeal of a scared young pig. One of these rituals involves the mates swimming around each other, then facing each other to make contact with their breasts while rising upright and making loud ticking sounds. Mating pairs have been observed diving to the bottom of the lake and pulling out vegetation with their bills and presenting it to each other.
The breeding patterns of red-necked grebes have some variation. In some areas it has been observed that a single breeding pair will isolate themselves from other birds and act aggressively to protect their claimed territory for breeding and feeding. In contrast, in other areas it has been observed that red-necked grebes breed in colonial groups. These birds engage in open interaction with other birds. Red-necked grebes nesting in a dispersed fashion is more common than in colonies.
Red-necked grebes also have a copulation ritual that includes a variety of actions that are accompanied by the whinny-braying call that is specific to this species. During copulation the female is present on the nest with her head low and the feathers on the back of her neck are erect. The male swims around behind the female and then hops up with his wings closed and his crest up and proceeds to make a number of steps on the female’s backside before making cloacal contact. After copulation has occurred the male then slides off the side of her and reenters the water. A common postcopulatory display involves the male diving down to the bottom of the lake, pulling out some vegetation, and presenting it to his mate.
Mating System: monogamous
Most breeding pairs form on wintering grounds prior to the spring migration. Because of this, most of the birds arrive at the nesting sites for breeding season already paired. If this is not the case, the birds are paired soon after.
Red-necked grebes have a breeding season that spans from May to September. Nest building typically occurs in May and most pairs lay their first clutch within the first two weeks. They often build their nests on vegetation that is floating on or anchored near the edge of bodies of water. Vegetation that forms thick mats or provides substantial cover and anchorage is preferred. Males initiate the nest-site selection process, but both sexes participate in nest building. The nest base is built out of partially decayed vegetation that is gathered from above and below the surface of the water. The rim of the nest is built out of primarily sticks and bulrushes.
Generally, a breeding pair of red-necked grebes only produces one brood per season. If the first clutch of eggs and or the nest becomes destroyed, the pair will often attempt a subsequent set. This may occur up to 5 times in one breeding season. Although rare, a pair may lay a second set even when the first set was a success. Each clutch usually consists of 4 to 5 eggs, but anywhere from 1 to 9 has been observed. The eggs are usually laid at 1 to 2 day intervals. Eggs are light blue when they are laid, but they often fade to white within one day of being laid. Over time, the wet nest material may stain them to a dark tan color. Hatching occurs 22 to 35 days after the eggs are laid. Chicks will fledge and reach independence between 9 and 10 weeks after hatching.
The behavior of red-necked grebe mating pairs differs depending on whether or not they are a part of a solitary pair or a colonial pair during the nesting season. Solitary pairs tend to leave their nest vacant and unguarded more often then colonial pairs. In the period prior to nesting, both female and male colonial birds are more aggressive towards other birds than are solitary birds. However, after the eggs have been laid and the nest has been fully established, the females of both colonial and solitary pairs lose much of their aggressive behavior. In both groups, the females spend more time near the nest during the egg-laying period than males. However, throughout the duration of the incubation period the colonial males spend much more time near the nest and their female than the solitary males do. It is believed that colonial nests are more likely to be exposed to predators because they stand out. Therefore, the nesting behavior of red-necked grebes depends on their social situation considerably. Regardless of this, they have been observed to successfully breed in both solitary and colonial aggregations.
Breeding interval: Red-necked grebes breed once yearly.
Breeding season: Breeding season for red-necked grebes is from May to September.
Range eggs per season: 1 to 9.
Average eggs per season: 4-5.
Range time to hatching: 22 to 35 days.
Range fledging age: 9 to 10 weeks.
Range time to independence: 9 to 10 weeks.
Average age at sexual or reproductive maturity (female): 1-2 years.
Average age at sexual or reproductive maturity (male): 1-2 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous
Both parents participate in incubating the eggs. The young red-necked grebes leave the nest via the parents' backs soon after the last egg hatches, although in some cases the parents will leave the nest before every egg has hatched. The chicks continue to ride on the parents back until they are ten to seventeen days old, the age at which they begin swimming themselves.
The parents feed the young for six to seven weeks. The primary food source of the hatchlings is insect larvae and other small prey items. The parents also feed feathers to the young birds. The young eat directly from the parents' bill. The young are typically completely independent from their parents at the age of nine to ten weeks and usually begin flying at about this time.
Parental Investment: precocial ; male parental care ; female parental care ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
Accidental visitor.
A large (18 inches) grebe, the Red-necked Grebe in summer is most easily identified by its dark back and head, brown neck, and conspicuous white chin patch. In winter, this species becomes dark gray above and light gray below, retaining some white on its chin. Male and female Red-necked Grebes are similar to one another in all seasons. The Red-necked Grebe occurs across wide area of the Northern Hemisphere. In North America, this species breeds across central Alaska, western Canada, and locally in the western United States, wintering along the Pacific coast from Alaska to California, along the Atlantic coast from Newfoundland to North Carolina, and locally in the Great Lakes. In the Old World, this species breeds in Northern Europe and East Asia, wintering along the coast as far south as the Mediterranean Sea, south China, and India. Red-necked Grebes breed in ponds, lakes, and shallow marshes, preferring areas with thick vegetation to more open water. In winter, this species may be found in shallow marine environments near the coast. Red-necked Grebes primarily eat small insects in summer, switching to small fish during the winter. In appropriate habitat, Red-necked Grebes may be observed floating low in the water, periodically diving down to capture prey. Like most grebes, this species must run and flap along the surface of the water in order to become airborne, subsequently flying swiftly low over the water. Also like most grebes, this species’ legs are positioned at the far end of its body, making it an adept swimmer but rendering it almost entirely unable to move on land. Red-necked Grebes are most active during the day.
A large (18 inches) grebe, the Red-necked Grebe in summer is most easily identified by its dark back and head, brown neck, and conspicuous white chin patch. In winter, this species becomes dark gray above and light gray below, retaining some white on its chin. Male and female Red-necked Grebes are similar to one another in all seasons. The Red-necked Grebe occurs across wide area of the Northern Hemisphere. In North America, this species breeds across central Alaska, western Canada, and locally in the western United States, wintering along the Pacific coast from Alaska to California, along the Atlantic coast from Newfoundland to North Carolina, and locally in the Great Lakes. In the Old World, this species breeds in Northern Europe and East Asia, wintering along the coast as far south as the Mediterranean Sea, south China, and India. Red-necked Grebes breed in ponds, lakes, and shallow marshes, preferring areas with thick vegetation to more open water. In winter, this species may be found in shallow marine environments near the coast. Red-necked Grebes primarily eat small insects in summer, switching to small fish during the winter. In appropriate habitat, Red-necked Grebes may be observed floating low in the water, periodically diving down to capture prey. Like most grebes, this species must run and flap along the surface of the water in order to become airborne, subsequently flying swiftly low over the water. Also like most grebes, this species’ legs are positioned at the far end of its body, making it an adept swimmer but rendering it almost entirely unable to move on land. Red-necked Grebes are most active during the day.
The red-necked grebe (Podiceps grisegena) is a migratory aquatic bird found in the temperate regions of the northern hemisphere. 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 nondescript 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, a 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. holboelii (formerly Holbœll grebe), in North America and eastern Siberia—is evaluated as Least Concern, and the global population is stable or growing.
The red-necked grebe was described by the French polymath Georges-Louis Leclerc, Comte de Buffon in 1781 in his Histoire Naturelle des Oiseaux.[2] 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.[3] 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.[4] The type locality was subsequently designated as France.[5] The red-necked grebe is now placed in the genus Podiceps that was erected by the English naturalist John Latham in 1787.[6][7] 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.[8] The species name grisegena is from Latin griseus (grey) and gena (cheek) and refers to the face pattern of the breeding adult.[9]
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 red-necked grebe's closest relative is the fish-eating great crested grebe of Europe and western Asia.[10] 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.[11] Fossils of the species dating to the middle Pleistocene have been found in Italy.[12]
The red-necked grebe has two subspecies, the nominate subspecies P. g. grisegena in Europe and western Asia, and P. g. holboelii (Holboell's grebe, named for Danish explorer of Greenlandic birds Carl Peter Holbøll) in North America and eastern Siberia. The east Asian birds have slightly smaller bills than the American form, although the differences are too small to merit separation as a third subspecies.[13]
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.[14][15] The adult of the nominate European subspecies is 40–50 cm (16–20 in) long with a 77–85 cm (30–33 in) average wingspan,[16] and weighs 692–925 g (24.4–32.6 oz).[16] 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.[17]
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.[17] Although the red-necked grebe is unmistakable in breeding plumage, it is less distinctive in winter and can be confused with similar species. It is larger than the Slavonian (horned) grebe, with a relatively larger bill and a grey, rather than white face.[18] It is closer in size to the Eurasian great crested grebe, but that species is longer-necked, has a more contrasting head pattern, and always shows white above the eye.[17]
The sexes are similar in appearance, although the male averages heavier than the female.[16] Chicks have a striped head and breast, and older juveniles have a striped face, diffuse blackish cap, pale red neck and extensive yellow on the bill.[17]
The subspecies P. g. holboelii is larger than the nominate race at 43–56 cm (17–22 in) length, with a 61–88 cm (24–35 in) wingspan, and a weight of 750–1,600 g (26–56 oz).[19] The plumages are the same as those of the nominate race, although the adult's bill is more extensively yellow.[18] The difference in size between the sexes is greater than for this subspecies that for P. g. grisegena.[13]
The red-necked grebe flies with its long neck extended and its large feet trailing behind the body, which gives it a stretched-out appearance.[20] The relatively small wings are grey with white secondaries, and beat very rapidly.[17] Its small wing area means that the grebe is unable to take off from land,[21] and needs a lengthy run across water to gain the speed needed for take-off.[22] 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.[23]
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.[16]
Breeding takes place in shallow freshwater lakes, bays of larger lakes, marshes, and other inland bodies of water, often less than 3 ha (7.4 acres) in extent and less than 2 m (6.6 ft) 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.[24] The best breeding habitat is fish-ponds, which have an abundance of food in addition to meeting the other requirements.[25] The American subspecies is less tied to a high aquatic plant density, and sometimes breeds on quite open lakes.[11]
All populations are migratory and winter mainly at sea, usually in estuaries and bays, but often well offshore where fish are within diving reach near shallow banks or islands.[13] The preferred passage and wintering habitat is water less than 15 m (49 ft) deep with a sand or gravel bottom, scattered rocks and patches of seaweed.[24] During winter, birds typically feed alone and rarely aggregate into flocks, but on migration, concentrations of over 2000 individuals may occur at favoured staging sites.[24] Migration is usually at night, but may occur during the day, especially when over water. This is particularly noticeable in autumn on the Great Lakes, when up to 18,000 birds may pass Whitefish Point on Lake Superior; these are thought to be Canadian breeders heading for the Atlantic Ocean to winter. This easterly route is longer than that to the Pacific, but avoids the Rockies.[13]
The breeding range of the red-necked grebe overlaps with that of the Slavonian grebe, although the latter species tends to be displaced from sites suited to both. The red-necked grebe prefers an inland temperate climate, and is less successful near coasts and in subarctic and warm temperate zones. It is usually a lowland bird, breeding below 100 m (330 ft), although has nested at up to 1,800 m (5,900 ft) in Turkey.[16]
The nominate subspecies breeds from southern Sweden and Denmark through central and eastern Europe east to western Siberia, and winters mainly in the North and Baltic Seas, with smaller numbers in the Adriatic, Black Sea, Caspian Sea, Mediterranean and on inland lakes.[26] P. g. holboelii 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.[26] This species occurs as a rare winter vagrant in Afghanistan, Pakistan[27] and parts of northern and western India.[28][29][30]
Red-necked grebes usually nest as isolated pairs with more than 50 m (160 ft) between neighbouring nests, although semi-colonial nesting may occur in suitable sites, where up to 20 pairs each defend a linear territory.[24] Semi-colonial breeding is more likely to occur in prime locations, such as large floating mats of vegetation with no connection to the shoreline. Such sites, safe from most predators and large enough to provide some wind and wave protection, have grebes nesting much closer than shoreline breeders, down to 10 m (33 ft).[31] Pairs nesting in these colonies produce larger clutches of eggs, which hatch earlier in the season and result in larger broods.[32] The territory is defended with various threat displays, including wing-spreading, hunching, and bill-thrusting;[18] pairs breeding in colonies are more aggressive, less likely to leave the nest unguarded and show a greater tendency to move out of sight of the colony when not incubating.[33] Breeding is often in loose association with gulls or other colonial water birds.[16]
The monogamous pair forms in April or May on migration or at the breeding water, and a highly vocal courtship ritual commences.[16] The elaborate breeding performance includes head-shaking, a head-lowered "cat" display, parallel rushes in an upright position and mutual presentations of green weeds, and culminates in a "penguin" dance in which pair members raise the whole body upright, breast to breast.[16][17][18]
Like all grebes, the red-necked grebe nests near water into which it can escape, since the position of the legs far back on the body prevents fast movement on land. It often breeds further within reed beds than other grebes. The nest is a floating platform of plant matter anchored to submerged or emergent vegetation,[16] in water 0.5–0.75 m (20–30 in) deep, and with the bulk of nest below the water line.[11] Egg-laying mainly takes place from mid-April to May in Europe,[14] and somewhat later, from mid-May to June, in North America.[11] Parents may leave the nest for significant periods of time during the night, possibly to evade nocturnal predators. It is unclear whether this is for self-protection or to protect the eggs by diverting attention from the nest; the clutch does not appear to suffer from this temporary abandonment, whatever the reason.[34]
The red-necked grebe lays four or five (range one to nine) dull white or pale blue eggs, which average 3.4 cm (1.3 in) in breadth, 5.1 cm (2.0 in) in length, and weigh about 30.5 g (1.08 oz), of which 10% is shell.[35] Parents take turns to incubate the eggs for 21–33 days until the precocial downy chicks hatch;[16] they immediately climb onto the parent's back, where they spend most of their time until they are 10–17 days old.[18][36] The young may be fed by the parents for up to 54 days after fledging,[11] and can fly at 50–70 days.[36] The parents do not interfere with the feeding of their chicks when they are still being carried. Later they care for the younger chicks for longer, and are aggressive with the older offspring. This equalises the post-fledging survival of all chicks, and encourages their independence.[37] The brood may be split, so that each parent feeds only some of the chicks. This spreads the feeding demand equally between the parents.[38]
After breeding the adults moult their wing feathers and are temporarily flightless; migration commences once the flight feathers have regrown.[24] The red-necked grebe is normally single-brooded, although second broods and re-nesting after a clutch has been lost may extend nesting into July or August.[16]
Eggs may be destroyed and chicks killed by a range of predators, including the raccoon in North America and the carrion crow in Europe.[11][39] Pike may take swimming chicks.[40] 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.[11]
On the breeding grounds, the red-necked grebe feeds mainly on invertebrates including adult and larval aquatic insects, such as water beetles and dragonfly larvae, crayfish and molluscs. Fish (such as smelt[41]) 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.[24]
Aquatic prey is obtained by diving or by swimming on surface with the head submerged, and terrestrial insects and their larvae are picked off vegetation.[16] A line slanting downward from the eye to the tip of the opened lower mandible may be used for sighting on prey before diving or when swimming under water. The grebe probably opens its bill and looks down the eye-line toward its target.[42] 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.[11] Birds of the nominate subspecies from the northernmost breeding populations in Finland and Russia, beyond the range of great crested grebe, have a longer and more slender bill than those further south, reflecting a greater proportion of fish in the diet where their main competitor is absent.[43] 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.[44]
Like other grebes, the red-necked grebe ingests large quantities of its own feathers, which remain in the bird's stomach.[18] Feathers are not only swallowed by adults, mainly during self-preening, but are often fed to the young, sometimes within a day of hatching. These feathers soon decompose into a felt-like, amorphous mass.[45] 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.[18]
The red-necked grebe has a large range, estimated at 1–10 million square kilometres (0.4–3.8 million square miles), and a global population of 150,000–370,000 individuals,[1] with P. g. holboellii about twice as numerous as the nominate race.[46] 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.[1]
The red-necked grebe is one of the species to which the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA) applies.[47] 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.[48]
The Red-necked Grebe was hunted by humans in northern Europe in the Mesolithic and Paleolithic periods,[49][50][51] but there is no evidence that there is any significant level of hunting at the present time.[1][39] In North America, there are potential threats from pollutants such as polychlorinated biphenyls (PCBs) and pesticides such as DDT which cause reduced reproductive success due to egg sterility and eggshell thinning. Breeding areas may be threatened by the modification and degradation of lakes and by human disturbance from water-based recreational activities.[24] There is no evidence to suggest that these threats could result in a significant risk to the overall population; more than 70% of North American red-necked grebes breed in Canada, where the population is stable or increasing.[39]
The red-necked grebe (Podiceps grisegena) is a migratory aquatic bird found in the temperate regions of the northern hemisphere. 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 nondescript 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, a 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. holboelii (formerly Holbœll grebe), in North America and eastern Siberia—is evaluated as Least Concern, and the global population is stable or growing.
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