- Clements, J. F., T. S. Schulenberg, M. J. Iliff, B.L. Sullivan, C. L. Wood, and D. Roberson. 2012. The eBird/Clements checklist of birds of the world: Version 6.7. Downloaded from http://www.birds.cornell.edu/clementschecklist/downloadable-clements-checklist
Habitat and Ecology
Behaviour This species is highly migratory (del Hoyo et al. 1992, Madge and Burn 1988) and breeds from mid-May onwards (Madge and Burn 1988) in solitary pairs or loose groups (del Hoyo et al. 1992, Kear 2005), occasionally nesting in association with gull or tern colonies (Kear 2005). Non-breeding birds spend the breeding season in flocks on open water (Flint et al. 1984). After breeding (from June onwards [Scott and Rose 1996]) the adults migrate to moulting sites(males travelling and moulting before the females) (Madge and Burn 1988), where they become flightless for 3-4 weeks (Scott and Rose 1996). When moulting and overwintering the species is highly sociable and can occur in large flocks (Madge and Burn 1988, Scott and Rose 1996) of several thousands of individuals (Scott and Rose 1996), although it is more common in small scattered groups of c.100 individuals (Snow and Perrins 1998). The species mainly forages by diving and may feed at depths of 30-40 m during the winter (del Hoyo et al. 1992). Habitat Breeding The species breeds on woodedcoastlines (Johnsgard 1978, Kear 2005), small freshwater lakes (del Hoyo et al. 1992, Snow and Perrins 1998, Kear 2005), pools and rivers (Snow and Perrins 1998) in northern coniferous forests (Johnsgard 1978, del Hoyo et al. 1992, Snow and Perrins 1998, Kear 2005), wooded Arctic tundra (del Hoyo et al. 1992, Snow and Perrins 1998) and alpine zones (Snow and Perrins 1998, Kear 2005), especially where there are boulder-covered or small rocky islands available for nesting with extensive herbaceous vegetation, shrubs and low trees (Johnsgard 1978, Kear 2005). Non-breeding The majority winter at sea on shallow inshore coastal waters (Madge and Burn 1988, del Hoyo et al. 1992), especially in estuaries or inlets where there are large mussel-beds (Snow and Perrins 1998). The species may also occur on freshwater lakes and estuaries during migration (Madge and Burn 1988, Kear 2005). Diet Its diet consists predominantly of molluscs, as well as crustaceans, worms, echinoderms (del Hoyo et al. 1992), amphipods, isopods (Kear 2005), small fish, and (in freshwater habitats) adult and larval insects (del Hoyo et al. 1992). The species may also consume plant material on its breeding grounds (del Hoyo et al. 1992) (e.g. leaves and shoots) (Flint et al. 1984). Breeding site The nest is a shallow depression positioned on the ground (del Hoyo et al. 1992) in tall grass, among hummocks or under bushes (Flint et al. 1984), usually within 100 m of open water (occasionally up to 2-3 km away) (Kear 2005). The species usually nests in solitary pairs (del Hoyo et al. 1992, Kear 2005), but it may form loose congregations (del Hoyo et al. 1992) (e.g. on islands [Kear 2005]) with neighbouring nests as close as 3 m apart (Snow and Perrins 1998), and will also nest in association with gull or tern colonies (Kear 2005).
IUCN Red List Assessment
Red List Category
Red List Criteria
- 2012Least Concern
Moulting and wintering concentrations of this species are very susceptible to oil spills and other marine pollutants (del Hoyo et al. 1992, Kear 2005) (an oil spill could destroy a large proportion of the global population if it occurred in a key moulting or wintering area [Madge and Burn 1988]). The species is also susceptible to the effects of commercial exploitation of marine benthic organisms and shellfish (Kear 2005), and is threatened by drowning in fishing nets (del Hoyo et al. 1992, Kear 2005). It is threatened by habitat degradation as a result of the human exploitation of natural resources in the taiga and lower tundra regions of its breeding range (Kear 2005). It is susceptible to disturbance from tourism in remote coastal and freshwater habitats in its breeding range (Kear 2005), as well as disturbance from wind farms (wind turbines) (Garthe and Huppop 2004). The species is susceptible to avian influenza, so may be threatened by future outbreaks of the virus (Melville and Shortridge 2006).
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The white-winged scoter is the largest of the three North American scoter species. It is characterised by its bulky shape and large bill. This is the largest species of scoter. Females range from 950–1,950 g (2.09–4.30 lb) and 48–56 cm (19–22 in), averaging 1,180 g (2.60 lb) and 52.3 cm (20.6 in). She is brown with pale head patches. The male ranges from 1,360–2,128 g (2.998–4.691 lb) and from 53–60 cm (21–24 in), averaging 1,380 g (3.04 lb) and 55 cm (22 in). He is all black, except for white around the eye and a white speculum. This scoter's bill has a black base and a large knob.
There are a number of differing characteristics of the Eastern Siberian race and the American race from Alaska and Canada to west of the Hudson Bay. Males of the American subspecies have browner flanks, dark yellow coloration of most of the bill and a less tall bill knob, approaching the velvet scoter. The Asian form has a very tall knob at the base of its mostly orange-yellow bill. Females are identical in the field.
The Latin binomial commemorates the French zoologist Dr. Côme-Damien Degland (1787–1856).
It was formerly considered to be conspecific with the velvet scoter, and some taxonomists still regard it as so. These two species, and the surf scoter, are placed in the subgenus Melanitta, distinct from the subgenus Oidemia, black and common scoters.
The white-winged scoter breeds over the far north of Asia east of the Yenisey Basin, and North America. It winters further south in temperate zones, on the Great Lakes, the coasts of the northern USA and the southern coasts of Canada, and Asia as far south as China. It forms large flocks on suitable coastal waters. These are tightly packed, and the birds tend to take off together.
The lined nest is built on the ground close to the sea, lakes or rivers, in woodland or tundra. 5–11 eggs are laid. The pinkish eggs average 46.9 mm (1.85 in) in breadth, 68.2 mm (2.69 in) in length and 82.4 g (2.91 oz) in weight. The incubation period can range from 25 to 30 days. After about 21 days, neighboring females may start to behave aggressively towards other nesting females, resulting in confusion and mixing of broods. By the time she is done brooding, a female may be tending to as much as 40 offspring due to the mixing from these conflicts. The female will tend to her brood for up to 3 weeks and then abandon them, but the young will usually stay together from another 3 weeks. Flight capacity is thought to be gained at 63 to 77 days of age.
In freshwater, this species primarily feeds on crustaceans and insects; while in saltwater areas, it feeds on molluscs and crustaceans. The favorite foods of the American (sub)species are an amphipod (Hyalella azteca) in freshwater, and rock clams (Protothaca staminea), Atlantic razor clams (Siliqua spp.) and Arctic wedge clams (Mesodesma arctatus).
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