Black-Throated Diver Vs Great Northern Diver: Key Differences Explained
The Black-Throated Diver (Gavia arctica) and the Great Northern Diver (Gavia immer) are both species of Divers (also known as Loons) known for their distinctive appearances and aquatic habits. They can both be seen in the UK at certain times of the year and are both water birds.
However, there are enough differences between these two species to enable you to make a positive identification even from a distance. In this article we’ll be looking at these differences, keep reading to find out more.
Table of Contents
Key Takeaways
- Great Northern Divers are larger than Black-Throated Divers
- Black-Throated Divers are mainly silent outside of the breeding season
- Great Northern Divers are vocal all year round
- Some Black-Throated Divers breed in Scottish lochs and pools
- Whereas Great Northern Divers don’t breed in the UK at all
- Black-Throated Divers have grey heads and black necks
- Whereas Great Northern Divers have black heads and necks
What Is The Difference Between A Black-Throated Diver And A Great Northern Diver?
There are several differences between the Black-Throated Diver and the Great Northern Diver which will allow you to differentiate one from another. These differences include;
Visual Differences
Although Black-Throated Divers and Great Northern Divers are both members of the same bird family and have some similar features, they can be easily distinguished by their colours and markings.
Black-Throated Divers have a distinctive black throat with a purple sheen, white-spotted or chequered back, and thin white stripes on the neck. Their winter plumage is more grey and white with a lighter head and darker back.
Great Northern Divers have a grey or light black head, white spotted or chequered back and a greenish or blackish throat. In winter they take on a plain grey appearance with a white underside and a dark back.
Differences In Habitat
These two bird species inhabit similar, but different habitats at different times of the year.
Black-throated Divers prefer inland freshwater lakes and ponds for breeding, mainly in northern Europe and Asia. In winter, they migrate to coastal waters, often seen along European shores.
They can be seen on small lochs and pools in the Outer Hebrides and north west Scotland during the breeding season. In winter, they migrate to sheltered coastal water all round the UK as well as on some inland lakes and reservoirs.
Great Northern Divers are found in larger freshwater lakes across North America, Iceland and Greenland during the breeding season. In winter, they migrate to coastal waters, especially along the Atlantic and Pacific coasts of North America, as well as European coasts.
They favour shallow areas close to shore and can be seen off the coasts of eastern, southwestern and northern England and off the coasts of Scotland, Northern Ireland and Wales.
Nests & Eggs
It will typically take the Black-Throated Diver around 2 to 3 days to build a nest. The nest is constructed from localised plant materials by both the male and female bird.
The nest is often positioned right on the edge of freshwater lakes and ponds or on small islands. These nests are not large affairs and are purely designed to prevent their eggs from rolling into the water.
The brown-green coloured eggs are laid typically between March and April. Each egg is around 84 x 52 mm in size with an average weight of around 122 grams.
Great Northern Divers build their nests close to the water’s edge or on small islands or even on floating vegetation in marshy areas. These nests are constructed from localised plant matter and just like the nests of the Black-Throated Diver, it is a simple scrape in the ground.
They typically lay their eggs in May with each egg being olive green or dark brown in colour, covered with darker spots or blemishes. The eggs of the Great Northern Diver are larger than those of the Black-Throated Diver with each egg being around 90 x 58 mm in size and weighing around 167 grams.
Bird Calls
The call of the Great Northern Diver is quite distinctive and has been described as eerie. It consists of a series of yodels, wails and tremolos which vary in intensity and are used for communication and defending their territories.
Black-Throated Divers are usually silent during winter but are more vocal during the breeding season. The male is known to make a loud, rhythmic whistling sound which is quite unique.
Size & Weight
Black-Throated Divers are the smaller of the two with an average length of around 58 to 73 cm and a wingspan of around 110 to 130 cm. There is a variance in the weight of male and female Black-Throated Divers with females weighing around 2.3 kg while males typically weigh 3.4 kg.
Great Northern Divers are larger with an average length of around 70 to 90 cm and a wingspan of around 127 to 147 cm. Again, there’s a variance in weight between the sexes with females weighing around 3.6 kg while males weigh around 4.5 kg.
SEE ALSO: Magpie Diet and Size: Feeding Habits, Predators, and Measurements
Frequently Asked Questions
In the US, the Great Northern Diver is known as the Common Loon.
Black-Throated Divers are also known as Arctic Loons.
Black-Throated Divers mainly eat fish which they catch by diving underwater. They also supplement their diets with aquatic insects, crustaceans and molluscs.
