The cosmopolitan genus Phalacrocorax of the Suliformes family includes thirty-five species frequenting coasts and islands. The face and throat are naked; the bill is long, and the upper mandible much curved at the point, while the lower supports a dilatable membrane which forms a gular pouch. The legs are short, strong, and abdominal, with three toes in front and one behind, all united; the claw of the middle toe is pectinated and probably used to dress the plumage and to free the bird from insect pests. The wings are of moderate length, and the tail-feathers stiff and rigid. Many of the species develop crests or wattles in the breeding season. These birds feed exclusively on fish. All Cormorants, Shags and Darters have a small bone at the back of the skull, the occipital style. This bone is flexibly attached to the skull and is supposed to have a function for the grasping ability of these birds. The ramphotecal coating of the bills of the cormorants are divided in plates, very much like those of the tubenoses, without visible nostrils.
Males are slightly bigger than females. Juveniles are much duller in color than adults. They are usually dark brown with grayish or whitish coloring underneath.
Listen to the sound of Double-crested Cormorant
Copyright remark: Most sounds derived from xeno-canto
|wingspan min.:||125||cm||wingspan max.:||130||cm|
|size min.:||70||cm||size max.:||90||cm|
|incubation min.:||25||days||incubation max.:||28||days|
|fledging min.:||21||days||fledging max.:||28||days|
Double-crested cormorants do not defend a large territory around the nest. They defend a small area immediately around the nest that is less than one meter in diameter.
Double-crested cormorants breed between April and August, with peak activity occurring in May through July. The males arrive at the breeding colony first and chose a nest site. They then advertise for a mate. The male and female work together to repair an old nest or to build a new one of sticks, twigs, vegetation and flotsam and jetsam found nearby, including rope, fishnet, buoys and deflated balloons. The male brings most of the material to the female who builds the nest and guards it from other colony members who would otherwise steal the nest materials. The nests typically built on the ground, but are occasionally built in trees. After nest construction is complete, the female lays 1 to 7 (usually 4) pale bluish-white eggs with a chalky coating. The eggs are laid 1 to 3 days apart. Both parents incubate the eggs, which hatch asynchronously after 25 to 28 days. The newly hatched young are altricial, and are cared for by both parents. Both parents feed the chicks regurgitated food. The young begin to leave the nest when they are 3 to 4 weeks old. They can fly at about 6 weeks and dive at 6 to 7 weeks. The chicks become completely independent of their parents by 10 weeks of age. Double-crested cormorants do not breed until they are at least 2 years old.
Both parents incubate the eggs and care for the altricial chicks. The parents feed the chicks regurgitated food 2 to 6 times per day. On hot days, parents fetch water and pour it directly from their beak into the open mouths of the chicks.
When feeding on schooling fish, cormorants may feed together in flocks. They have a hook-like tip on the upper maxilla of their bill and specialized muscles that aid them in grasping their slippery prey.
Double-crested cormorants breed across North America, as far north as southern Alaska. They winter in North America as far south as Sinaloa, Mexico, and are common on marine and inland waters throughout their range.