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Double-crested Cormorant - BirdForum Opus

(Redirected from Nannopterum auritum)
Adults in breeding plumage
Photo © by Steve Messick
St. Vrain SWA, Weld County, Colorado, USA, 25 April 2004
Nannopterum auritum

Phalacrocorax auritus

Identification

Immature with extensive whitish underparts
Photo © by Joseph Morlan
Rodeo Lagoon, Marin County, California, USA, 15 March 2020

Length 74–91 cm (29–36 in)
Wingspan up to 132 cm (52 in)
Adults: This is a large, black bird that may have green sheen in some lighting. It has a long tail, a chin patch of bare orange skin, and variably white or dark double head plumes for a short period during breeding. Eastern birds are duller.
Juveniles: Variable plumage; overall dark brown, with paler face, foreneck, and breast.

Similar Species

Photo © by fuzzhead
Richland, Washington, USA, 21 October 2009

The Brandt's Cormorant lacks the orange chin, and has a shorter tail. The Neotropic Cormorant is a bird of southern latitudes but has expanded its range into Arizona and Southern California. It can be distinguished by its smaller size, longer tail and angled gape line forming a pointed gular. In breeding plumage it has a white outline to the gular.

Distribution

Photo © by STM
Murrells Inlet, South Carolina, USA, 24 March 2021

A very common and widespread species, it winters anywhere that is ice-free along both coasts of North America, as far north as southern Alaska (on the west coast) and southern New England (on the east coast). It can be found as far south as Mexico and the Bahamas.

It migrates from the coldest parts of its breeding range, such as eastern Canada, and has occurred in Europe as a very rare vagrant, for example in Great Britain, Ireland and the Azores.

Taxonomy

Photo © by Joseph Morlan
Golden Gate Park, San Francisco, California, USA, 26 March 2021

Formerly placed in the genus Phalacrocorax

Subspecies

There are 4 subspecies[1]:

Dark-crested

  • N. a. auritum:
  • Gulf of St. Lawrence to Cape Cod and locally west to Utah
  • N. a. floridanum:

White-crested

  • N. a. albociliatum:
  • N. a. cincinatum:

A 5th subspecies, heuretum, endemic to San Salvador in the Bahamas, is not recognised by all authorities[2]. It may be a junior synonym of P. a. floridanum.

Habitat

Oceans and fresh water ponds and lakes. This is the only cormorant in the US that is commonly found on fresh water.

Behaviour

Actions

In flight, note crooked neck. Flies in wavy, loose flocks. The Double-crested Cormorant swims low in the water, often with just its neck and head visible, and dives from the surface. It uses its feet for propulsion and is able to dive to a depth of 1.5–7.5 m (5–25 feet) for 30–70 seconds. After diving, it spends long periods standing with its wings outstretched to allow them to dry, since they are not fully waterproofed. This species flies low over the water, with its bill tilted slightly upward, sometimes leaving the colony in long, single-file lines.

Breeding

Colonial. Nest is a twig platform either in a tree or on the ground. Clutch is one to seven pale blue eggs. Average clutch is four.

Diet

Almost exclusively fish: over 250 fish species from more than 60 families recorded in diet. Also crustaceans, amphibians and insects.

Vocalisation

Usually silent away from breeding colonies, but occasionally gives low guttural calls.

Movements

Northern and inland populations migratory, although North Pacific birds only slightly so.

References

  1. Clements, J. F., T. S. Schulenberg, M. J. Iliff, S. M. Billerman, T. A. Fredericks, B. L. Sullivan, and C. L. Wood. 2019. The eBird/Clements Checklist of Birds of the World: v2019. Downloaded from http://www.birds.cornell.edu/clementschecklist/download/
  2. Lepage D. (2021) [Avibase - https://avibase.ca/3AC46C54 ]. Retrieved 30 March 2021
  3. Dorr, B. S., J. J. Hatch, and D. V. Weseloh (2020). Double-crested Cormorant (Phalacrocorax auritus), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.doccor.01
  4. Orta, J., Jutglar, F., Garcia, E.F.J., Kirwan, G.M. & Boesman, P. (2020). Double-crested Cormorant (Nannopterum auritus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/52626 on 16 March 2020).

Recommended Citation

External Links


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