Cormorants are water birds that are found around the world near water sources like rivers, lakes, coastlines and wetlands. They build nests in trees, on the ground, and on cliffs in colonies ranging from a few pairs to thousands of breeding pairs. Here are some key facts about where cormorants nest:
Tree Nests
Many species of cormorants build nests in trees near water. For example:
- Double-crested cormorants often nest in trees along coastlines, rivers and lakes throughout much of North America.
- Great cormorants build nests high up in trees on coastlines and islands around Europe, Asia and Africa.
- Indian cormorants nest in mangrove trees and other trees near waterways in India and Southeast Asia.
Cormorants that nest in trees typically build nests on branches or in forked branches using sticks, seaweed and other plant material. The nests are usually positioned above the water or ground below.
Cliffside Nests
Some species of cormorants nest on cliff faces and rocky outcrops near waterways and coasts, including:
- Brandt’s cormorants often nest on cliffs along the Pacific coast of North America.
- European shags nest on rocky coasts and cliffs in Europe.
- Rock shags build nests on rocky outcrops and cliffs near water in southern South America.
On cliffs, cormorants build nests on narrow ledges or crevices, anchoring them using guano and other materials to attach them to the rock face. These nests provide protection from predators.
Ground Nests
Some cormorant species nest directly on the ground near water, including:
- Flightless cormorants build nests directly on the ground on the Galapagos Islands off Ecuador.
- Red-faced cormorants nest on the ground on subantarctic islands near Antarctica.
- Bank cormorants nest in ground scrapes on Namibian islands along the southwestern coast of Africa.
For ground nesting, cormorants scrape out a shallow depression and line it with materials like twigs, grass and feathers. These nests are built close to the water’s edge.
Habitat and Materials
The specific habitat where cormorants nest depends on the species and geographic range, but they consistently choose areas that are:
- Near water for feeding and takeoffs/landings
- Elevated to provide protection from predators and flooding
- In areas with suitable nesting materials nearby such as sticks, seaweed, grass
Cormorants are resourceful in using local plant material and other items to construct their nests. Some other materials cormorants are known to use in nest building include moss, mud, guano, trash and debris.
Nest Sites
Some key types of sites where different cormorant species build nests include:
Nest Site | Examples |
---|---|
Coastal cliffs | European shags, Brandt’s cormorants |
Rocky outcrops | Rock shags, Red-faced cormorants |
Islands | Galapagos cormorants, Bank cormorants |
Trees | Double-crested cormorants, Indian cormorants |
Ground | Flightless cormorants, Bank cormorants |
Mangroves | Indian cormorants |
Nesting Colonies
Cormorants are colonial nesters, meaning they build nests close together in groups rather than solitary pairs. The size of cormorant nesting colonies varies by location and can include from just a few breeding pairs up to thousands of breeding pairs.
Some of the largest cormorant nesting colonies include:
- Middle Island, Lake Erie: Up to 25,000 double-crested cormorant nests
- Mandarte Island, British Columbia: Up to 15,000 Brandt’s cormorant nests
- Bird Island, Namibia: Up to 2,500 bank cormorant nests
Nesting in groups provides protection from predators. Cormorants use vocalizations and displays to establish nesting territories within the colony.
Seasonality
Most species have distinct breeding seasons during which they build nests and raise young. The exact timing varies across species and locations, but generally falls within the spring to summer months in each hemisphere.
Some examples of cormorant nesting seasons:
- Great cormorants in Europe: April – August
- Double-crested cormorants in North America: April – August
- Red-faced cormorants in Alaska: May – September
- Flightless cormorants in Galapagos Islands: Year-round
Cormorants tend to reuse nesting sites year after year, with some species known to use the same trees, cliffs or islands for nesting across many generations.
Threats to Nests
Several factors can threaten cormorant nesting areas and success, such as:
- Habitat destruction – Loss of nest trees and wetland foraging areas
- Human disturbance – Nests abandoned due to close human activities
- Predators – Eagles, gulls, ravens and others preying on eggs/chicks
- Weather – Storms, flooding and wave action destroying ground and tree nests
- Declining fish stocks – Reduces food availability for raising young
Conservation measures like protecting colonies, managing water levels and improving fish populations can help ensure suitable nesting habitats remain available.
Conclusion
In summary, cormorants are highly adaptable in selecting nesting sites, using locations ranging from mangrove trees to rocky cliffs and ground scrapes. The key requirements are proximity to water, elevation to protect from predators, and availability of nesting materials. Colonies can range from a few pairs to thousands of breeding birds, and pairs return to reuse nesting sites year after year. Protecting nesting habitats and managing threats is important for supporting cormorant populations into the future.