Bird Database

Double-crested Cormorant

(Nannopterum auritum)

State of the Birds
At a Glance



Short distance




Human disturbance, Disease

Conservation Actions

Do not disturb nesting areas

Double-crested Cormorant

(Nannopterum auritum)

The iconic image of a Double-crested Cormorant is of a bird perched on a rock or pier with its wings spread wide to dry. Bird plumage is naturally waterproof, and other diving birds such as ducks and loons don’t stand around with their wings held out, so for a long time it was assumed that cormorants had a “deficient” oil gland at the base of their tail. All birds have this gland, which produces secretions that birds use to keep their feathers in good condition – but not necessarily waterproof them. Waterproofing instead results from the structure of feathers and the way they overlap across the body. Cormorants’ oil glands work just fine, and the real reason their wings get wet is because of structural differences that allow more water to pass through them; they are more wettable. This in turn allows cormorants to be less buoyant, which facilitates diving, but the downside is they also need to spend more time drying out after extended periods in the water.

The Double-crested Cormorant is found in both fresh and salt water across most of North America, where it nests in large colonies on islands, often with other waterbirds. Nests can be placed in trees or on the ground, and the latter become more prevalent within a colony as trees die back from accumulating guano. Loss of trees and increasing cormorant numbers have become conservation issues in some areas because of impacts to other colonial birds such as herons and terns. Growth in cormorant populations is also of concern to fisheries and aquaculture. Although there is limited evidence that cormorants compete directly with commercial or recreational fishing, there is no question that they can sometimes cause significant losses at fish farms in the southern United States. Ironically, increased protection in the 1970s enabled populations to rise to the point where wildlife managers now need to consider cormorant control measures for both ecological and economic reasons.

While Double-crested Cormorants are regularly seen statewide except in winter, the only New Hampshire nesting colony is at the Isles of Shoals. The summer cormorants you see inland are either immature birds or non-breeding adults. There are large colonies on lakes in neighboring states however, so it is only a matter of time before the species starts breeding in the Lakes Region or perhaps in Coos County. All they need is an island away from regular human disturbance, which given the high recreational use of many of our lakes may be hard to find.

Seasonal Abundance

Relative abundance based on eBird data. Numbers indicate likelihood of finding this species in suitable habitat at a given time of year, not actual numbers encountered.

Double-crested Cormorant
Range Map

Information for the species profiles on this website was compiled from a combination of the sources listed below.

  • The Birds of New Hampshire. By Allan R. Keith and Robert B. Fox. 2013. Memoirs of the Nuttall Ornithological club No. 19.

  • Atlas of the Breeding Birds of New Hampshire. Carol R. Foss, ed. 1994. Arcadia Publishing Company and Audubon Society of New Hampshire

  • Birds of the World. Various authors and dates. Cornell Laboratory of Ornithology.

  • Data from the Breeding Bird Survey

  • Data from the Christmas Bird Count