Black-throated Diver or Arctic Loon
Length: 58-73 cm
Wingspan: 110-130 cm
Weight: 1300-3400 g
Black-throated Diver is a large swimming and diving bird. Relatively similar to grebes, the diver differs by its webbed feet with the three front toes joined by the membrane, and its short tail.
The name “diver” is given in Eurasia, whereas the name “loon” is usually used in North America.
In breeding plumage, the Black-throated Diver has dark upperparts, almost black, but with broad white-streaked areas with scaled effect.
Head and hind neck are grey. Fore neck and throat show black patch, vertically white-streaked on the sides.
We can see a short collar of small white spots which separates the throat from the upper neck. Breast is white finely streaked black.
Underparts are very pale, almost white.
PROTECTION / THREATS / STATUS:
The Black-throated Diver is vulnerable to human disturbances on the breeding areas. Changes in the habitat, alterations of water levels, acidification of these waters and oil and heavy metal pollution are important threats for this species.
However, populations are probably fairly large but with progressive decline throughout the southern part of the range.
Usually, the male selects the nest-site always close to the water. They are highly territorial on the breeding areas. They use aggressive postures and do not tolerate any intruder within their field of vision.
The bird raises its neck in order to display the throat patch and the neck pattern. Some displays are similar to courtship behaviour with in addition, several water chases with flapping wings. Territorial calls are uttered during these displays.
Fights are not frequent, but they may be intense and violent, using bill and wings, and occasionally, one bird, or both, may die.
The Black-throated Diver has slender silhouette when in flight, and performs wing-beats with flexible wing tips. It runs over water to take off because even with its large wingspan, the wing surface is small compared to the body size.
Breeding season starts in May in the southern parts of the range, and depends on the spring in the northern parts.
The Black-throated Diver is solitary nester. The nest varies from a scrape in the ground to a heap of plant matter close to the water.
Female usually lays 1-3 olive-brown eggs with dark brown spots. Incubation by both adults lasts about 28-30 days. Chicks are covered in sooty brown down above and paler below. They grow during 12-13 weeks reared by both adults. They are able to feed themselves at this moment. They can fly at two months, and they reach their sexual maturity at 2-3 years.
The Black-throated Diver feeds almost exclusively on fish of several species. Sometimes, some aquatic insects, crustaceans and molluscs may be consumed, and plant matter too.