Gavia arctica
Silhouette: Andy Wilson · PhyloPic
In 3 days ~20% in a week ~40%
The black-throated loon (Gavia arctica), also known as the Arctic loon and the black-throated diver, is a migratory aquatic bird found in the Northern Hemisphere, primarily breeding in freshwater lakes in northern Europe and Asia. It winters along sheltered, ice-free coasts of the north-east Atlantic Ocean and the eastern and western Pacific Ocean. This loon was first described by Carl Linnaeus in 1758 and has two subspecies. It was previously considered to be the same species as the Pacific loon, of which it is traditionally considered to be a sister species, although this is debated. In a study that used mitochondrial and nuclear intron DNA, the black-throated loon was found to be sister to a clade consisting of the Pacific loon and two sister species, the common loon and the yellow-billed loon.
The black-throated loon measures about 70 cm (28 in) in length and can weigh anywhere from 1.3 to 3.4 kilograms (2.9 to 7.5 lb). In breeding plumage, the adult of the nominate subspecies has mostly black upperparts, with the exception of some of the mantle and scapulars, which have white squares. The head and hindneck are grey, and the sides white and striped black. Most of the throat is also black, giving this bird the name "black-throated loon". The colour of the throat patch can be used to distinguish the two subspecies; the throat patch of the other subspecies, G. a. viridigularis, is green. The underparts are mostly white, including the bottom of the throat. The flanks are also white, a feature that can be used to separate this bird from the Pacific loon. When the bird is not breeding, the black patch on the throat is absent, replaced with white; most of the black lines on the throat are also missing, except those on the bottom sides, and the upperparts are unpatterned except for a few white spots on the upperwing. The juvenile is similar to the non-breeding adult, except that it is overall browner.
The timing of the breeding season is variable; in the southern part of its range, this loon starts breeding in April, whereas in the northern portion, it waits until after the spring thaw. It builds an oval nest about 23 centimetres (9.1 in) across, either near the breeding lake or on vegetation emerging from it. The black-throated loon usually lays a clutch of two, rarely one or three, brown-green eggs with dark splotches. After an incubation period of 27 to 29 days, the chick hatches and is fed a diet of small fish and invertebrates. The adult mostly eats fish. To catch this food, it forages by itself or in pairs, very rarely foraging in groups. Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Cairngorms National Park | 🇬🇧 United Kingdom | |
| 2 | Triglav National Park | 🇸🇮 Slovenia | |
| 3 | Kiskunság National Park | 🇭🇺 Hungary | |
| 4 | Wadden Sea National Park | 🇩🇪 Germany | |
| 5 | Olympic National Park | 🇺🇸 United States | |
| 6 | Biebrza National Park | 🇵🇱 Poland |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Tallinn Zoo | 🇪🇪 Estonia |
With luck
About 10% of wildlife watchers report an Arctic Loon sighting in Cairngorms National Park on a given day, based on 5 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 73rd most-seen of the 140 birds we can rate there. Over three days the chance rises to about 20%, and over a week to about 40%, if each day is a fresh chance.
May
In that month about 20% of wildlife watchers report an Arctic Loon in Cairngorms National Park on a given day, against under 5% in August to April, the lowest months.
Between 11 am and 2 pm
Across all the parks we cover, that three-hour window holds the most Arctic Loon sightings with a recorded time, and about 8 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
Yes
Of the 6 parks where we can rate Arctic Loon sightings, Cairngorms National Park has the highest daily chance: about 10%. Next come Triglav National Park (Slovenia, under 5%) and Kiskunság National Park (Hungary, under 5%).
GBIF citizen-science records
It is estimated from how often the Arctic Loon is recorded against all the birds logged in Cairngorms National Park (5 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
