Coastal cormorants make their nest on rocky ledges or islands out of seaweeds; inland tree-nesting birds construct their nest from twigs. The faeces are so acidic that nest-trees usually die within about three years (3). Either 3 or 4 pale blue, chalky eggs are laid, these are incubated for 28-31 days during which time they are placed on the adult's feet and warmed by the body (3). In the first few days of life the chicks feed on liquid regurgitated by the parents, they then take solid food from the parent's throats (3). After 50 days of life the young fledge, and return to the colony to breed at 2-3 years of age (3). During the winter, they roost together each evening, sometimes in their hundreds (9). Cormorants feed exclusively on fish (6), which are caught by means of dives from the surface of the water (6). A wide range of fish is taken, and this bird's efficiency as a predator has brought it into conflict with anglers (3). The cormorant has special feathers, which allow the water to penetrate, enabling the bird to swim well under water. After fishing, cormorants stand in a characteristic pose, with wings out and neck extended (3). This was thought to be to dry their wings, but is now considered to help digestion (9).