Double-crested Cormorant with aberrant pale plumage in Barrie, Ontario

This Double-crested Cormorant with an aberrant pale plumage is with a normal Double-crested Cormorant on the Barrie waterfront. It lacks pigments that would give it the normal plumage, legs and bill coloration. Aberrant plumage expert, Hein van Grouw, Senior Curator at The Natural History Museum in Tring, UK, advised me that "The aberrant plumage colour of this Cormorant is the result of a mutation which affects the melanin synthesis and therefore original black remains dark-brown (as the melanin synthesis is incomplete)." He explained that it could be either of two mutations. "One is the mutation Brown, although that mutation normally does not affect the skin colour (bill and feet) as much as in this individual. Another ‘candidate’ is a dark form of Ino. Both mutations, Brown and Ino, are sex-linked so this bird is most likely a female." Feathers resulting from both of these mutations are easily bleached by sunlight, causing them to turn whitish. 7 October 2018.

 

ACTION VIDEO: Aberrant pale Double-crested Cormorant swimming, fishing, flying and preening

This pale Double-crested Cormorant`s eye is a pale bluish-brownish. It's not an albino because all the black and brown areas of its plumage are not completely white and the eyes are not red. It's also not leucistic, which means white, because in this condition a variable number of dark feathers would be completely white. The mutation affecting this cormorant caused its feathers to be brown, not white, and subsequently they have bleached unevenly from brown to white. Brown patches are visible under the wing and on the flanks for example. To learn more about aberrant plumages, please Hein van Grouw's excellent article:

What Colour is that bird: the causes and recognition of common colour aberrations in birds

 

When Double-crested Cormorants hold their wings open it's called "Wing-spreading". This important posture is to dry their feathers after being in the water, not to regulate body temperature. Double-crested Cormorants have "wettable" feathers, which means the outer feather layers are loose and absorb water to increase weight. They also trap less air in order to reduce buoyancy and improve diving efficiency. (Birds of North America online - Double-crested Cormorant).

 

On 9 October 2018, the temperature in Barrie hit a high of 27C plus high humidity. The "Brown or Ino" Double-crested Cormorant cooled itself by "fluttering the gular" area to move air into its mouth and esophagus.The normally-plumaged cormorant did the same. Please see video showing it "fluttering the gular"

 

Double-crested Cormorant with an aberrant plumage was very active swimming and feeding along the Barrie shoreline. 7 October 2018

 

It caught several fish. The gulls tried to take it away. 7 October 2018

 

Minnows are abundant in Lake Simcoe. 7 October 2018.