Black-Throated Diver Life Cycle: Nest Building To Fledging (and everything in between)
The Black-Throated Diver (Gavia Arctica), also known as the Black-Throated Loon or the Arctic Loon, is a fairly large water bird being larger than the Great-Crested Grebe but smaller than a Cormorant. They are easily identifiable during the breeding season with their black throat, grey head and neck and white and black chequered back.
In winter their plumage changes to dark grey upperparts and white underparts with a distinct patch of white on the rear flanks. They breed in the far north of Scotland often in small pools and lochs. In winter the Black-Throated Divers migrate to coastal areas all round the UK to areas where large fish populations congregate.
In this article we’ll take a close look at the life cycle of the Black-Throated Diver from nest building through to the fledgling stage of development. Keep reading to find out more.
Table of Contents
How Long Does A Black-Throated Diver Live?
The Black-Throated Diver has a lifespan that ranges from around 12 to 20 years in the wild. The survival rate of this bird is closely linked to pollution and oil slicks in particular. This is because the Black-Throated Diver spends so much of its time at sea.
However, the oldest reported Black-Throated Diver reached an age of 28 years according to ring data.
How Fast Can A Black-Throated Diver Fly?
The Black-Throated Diver can achieve flight speeds of as much as 75 mph (120 km/h). These birds are strong flyers and can cover hundreds of miles during their migration period.
Their legs are positioned far back on their bodies which makes them awkward walkers. However, they are agile swimmers and can reach fast flight speeds. It’s just on land that they become awkward.
Are Black-Throated Divers Aggressive?
Black-throated divers are not generally considered to be aggressive birds. Like most loons, they tend to be more secretive and elusive, especially during the breeding season. However, they can show defensive behaviour if their nesting territory or chicks are threatened.
During the breeding season, they may become territorial and protective of their nests. In such cases, they can display aggression toward intruders, including other birds or animals that come too close. This aggression usually takes the form of warning calls, lunges, or splashing, but physical contact or fights are rare.
Generally, they are more likely to avoid conflict by diving underwater and swimming away rather than engaging in direct aggression.
What Is A Black-Throated Diver’s Habitat?
During the breeding season, the Black-Throated Divers habitat is on small pools and lochs in the Outer Hebrides and north west Scotland. They prefer lochs with small islets that they can build their nests on.
Once the breeding season has finished, during winter, Black-Throated Divers migrate to coastal waters all around the UK. They are often spotted in sheltered bays and beaches but many are seen on large lakes and reservoirs.
How Long Does It Take For A Black-Throated Diver To Build A Nest?
It takes a relatively short time for a Black-Throated Diver to build a nest, typically just 2 or 3 days. Both the male and female take part in the construction of the nest.
The nest is typically built on the edges of freshwater lakes or ponds, often close to the water’s edge or on small islands. They choose sites that allow easy access to water, due to their clumsiness on land.
The nest is constructed primarily from plant material gathered from around the site. They typically use aquatic vegetation like reeds and grasses as well as moss, mud and sometimes small twigs and leaves
These nests are not elaborate but are functional, providing just enough structure to support the eggs and keep them from rolling into the water.
Eggs
Once the pair are satisfied with their nest, they will move on to the next stage of the life cycle of the Black-Throated Diver, the eggs.
When Do Black-Throated Divers Lay Eggs?
Black-Throated Divers lay their eggs in the spring typically returning to their breeding grounds in March or April. In the southern range of their habitats, Black-Throated Divers lay eggs at the beginning of May but the exact time eggs are laid will depend on the temperature locally.
How Many Eggs Does A Black-Throated Diver Lay?
The female will lay 1 to 3 eggs with a typical clutch containing 2 eggs. The number of eggs laid depends on the health, age and experience of the female.
What Do Black-Throated Diver Eggs Look Like?
Black-Throated Diver eggs are oval shaped and brown-green coloured with darker speckles. Each egg is around 84 x 52 mm in size and weighs around 122 grams with 9% of that weight being the weight of the shell.
How Long Do Black-Throated Diver Eggs Take To Hatch?
The eggs are incubated by both parents but the female does the bulk of the incubating. The eggs are incubated for around 27 to 29 days with the eggs being turned regularly.
If the pair successfully raise at least one chick, they will not renest that season. However, if their first attempt ended in failure and there’s still enough warm weather to achieve a second laying, the pair will renest and try again.
Chicks
After the incubation period has ended, the next stage in the life cycle of the Black-Throated Diver is the rearing of the chicks.
How Many Chicks Does A Black-Throated Diver Have?
The survival rate for Black-Throated Diver chicks isn’t great. In fact it is estimated that the eggs have a 50% chance of hatching if 2 or more eggs were laid. If a single egg was laid, it has a 60% chance of survival.
This means that a typical nest will produce one chick per season. Even then, some are lost due to predation or nest flooding.
When Do Black-Throated Diver Chicks Open Their Eyes?
Black-Throated Diver chicks hatch with their eyes open. These semi-precocial chicks spend the first day of their lives in the nest being fed and cared for by both parents.
They are able to swim by days 2 to 4 but often hitch a ride on one of their parents’ backs to avoid predators and prevent having to return to the nest. The younglings are fed by their parents for around 2 to 3 weeks before they start to feed themselves.
When Do Black-Throated Diver Chicks Fledge?
The young chicks grow and develop at a rapid rate but don’t actually fly until they reach about the age of 8 to 9 weeks. It’s at this point that they are considered to be fledglings.
However, they spend much of their early life in water and only really fly when it’s time to migrate.
SEE ALSO: Swift Diet and Size: Feeding Habits, Predators, and Measurements
Frequently Asked Questions
The average lifespan of the Black-Throated Diver is around 12 to 20 years in the wild. The oldest reported Black-Throated Diver reached an age of 28 years according to ring data.
The eggs of the Black-Throated Diver are oval shaped and brown-green coloured with darker speckles. Each egg is around 84 x 52 mm in size and weighs around 122 grams.
Black-Throated Divers can be seen along much of the coastline of the UK especially during winter months. During the breeding season however, they can be seen in the north west of Scotland, particularly in the Hebrides, Orkneys and Shetland Islands.
