Great Northern Diver Diet and Size: Feeding Habits, Predators, and Measurements

The Great Northern Diver or Common Loon as it is known in North America is the largest Diver we ever see here in the UK. They are easily recognisable when in their breeding plumage with their black backs with white spots, glossy black heads and necklace-like pattern on their necks.

They have a black bill, deep red eyes and dark legs. Outside of the breeding season they have brownish grey upper bodies with white underbellies. Juveniles resemble non-breeding adults but have buff coloured scales on their upperparts.

In this article we’ll be looking at the dietary habits, breeding habits, the size and weight as well as the conservation status of these interesting birds. Keep reading to find out more.

The Dietary Habits Of The Great Northern Diver

The Great Northern Diver mainly eats fish but they also eat other aquatic organisms when fish are in short supply.

What Does A Great Northern Diver Eat?

Great Northern Divers are skilled hunters and dive underwater to catch their fish prey. They eat perch, bass and trout. They supplement their diets with amphibians, crustaceans and insects.

What To Feed A Baby Great Northern Diver? 

The chicks are fed with a variety of prey starting with small fish and other soft bodied aquatic animals that are easy for the chicks to eat and digest.

As the chicks grow and develop, the parents will gradually increase the size of the fish they provide, making sure that the chicks get the necessary nutrients to grow strong and healthy. 

Breeding Habits Of Great Northern Divers

Breeding usually occurs in late spring to early summer, depending on the region. In North America, this often spans from May to July. They prefer clear, freshwater lakes and ponds with abundant fish. 

Courtship often involves a series of vocalisations. The haunting, wailing calls of the Diver are a key part of this process. These calls are used to establish territory and attract a mate. There are different types of calls used, including the “yodel” of males, which can signify territorial claims and attract potential mates.

During courtship,they also take part in a variety of visual displays. These can include synchronised swimming, where the pair moves together at the same time, and specific postures like head-bobbing or stretching, which help reinforce their bond. They might also take part in mutual preening which is also a good way for the Great Northern Diver pair to strengthen their bond.

Do Great Northern Divers Mate For Life?

Great Northern Divers form monogamous partnerships that typically last for life. The pair are both responsible for nest building, egg incubation and chick rearing.

They often separate at the end of the breeding season but reunite the following year to raise another brood. However, in some cases, older partners can be forced off their nesting site by younger, more aggressive birds who will often then mate with the remaining partner.

This behaviour tends to be a problem for older Great Northern Divers of around 15 years of age and above.

The Size & Weight Of Great Northern Divers

Great Northern Divers are large members of the diver family and are often compared to Cormorants as they are a similar size.

How Much Does A Great Northern Diver Weigh?

Although there is little difference in the colouration and markings of these birds, males tend to be the larger and heavier of the two. The average weight of the Great Northern Diver is around 3.6 to 4.5 kg.

How Big Is A Great Northern Diver?

The average length of an adult Great Northern Diver is around 70 to 90 cm with a wingspan of around 127 to 147 cm. Again it’s the male that tends to be the larger of the two.

Are Great Northern Divers Under Threat?

Although considered to be a species of least concern by the International Union for Conservation of Nature (IUCN) and the Species of European Conservation Concern (SECC) the Great Northern Diver is Amber listed in the UK.

This is due to some evidence of concern due to a downward trend in population numbers locally. The main threats to the Great Northern Diver include habitat loss due to the destruction or alteration of their freshwater lake habitats, pollution which can cause a shortage of food, human disturbance either from construction sites, or recreational activities like boating or fishing can disturb nesting sites.

There is also the threat posed by climate change that can affect fish populations and water levels. All of which can affect the timing of breeding and the availability of adequate food for the development of both chicks and adult birds.

What Eats A Great Northern Diver?

The Great Northern Diver also faces the threat of predation from a number of creatures. The eggs and chicks are particularly vulnerable from mammals such as raccoons and rats as well as from birds like Gulls and Crows. In some areas snapping turtles can also take eggs from nests.

Adult Great Northern Divers have few natural predators but can sometimes be taken by large birds of prey like Eagles or large Hawks. However, their main threats are environmental and human-related rather than predation.

Where Can I See Great Northern Divers In The UK?

In the UK, the Great Northern Diver is a winter visitor rather than a breeding bird. There are reported sightings each year in the following places;

Scotland

• The Scottish Highlands (particularly Loch Ness & Loch Awe)
• The Moray Firth
• The Outer Hebrides

England

• The Lake District
• The Northumberland Coast

Wales

• Snowdonia National Park (particularly coastal areas)

Great Northern Divers are generally seen from late autumn through to early spring. They are most commonly spotted between October and March.

 Look for them in large, open bodies of water, especially coastal areas and large lakes. They are more likely to be seen in deep, clear waters where they can dive for fish.

SEE ALSO: Shelduck Diet and Size: Feeding Habits, Predators, and Measurements

Frequently Asked Questions