Fishy Friday: 10 Things about the Double-crested Cormorant
Day 11 of 100 days of Blogging
Today is Fishy Friday! Our new feature where we highlight a different fish-eating species of bird each week. Today’s feature is all about the Double-crested Cormorant, one of the most numerous and widely distributed species of the 6 North American cormorants.
Early Birder’s Fishy Friday Profile #1
Double-crested Cormorant (Phalacrocorax auritus)
Family: Phalacrocoracidae French: Cormoran à aigrettes
#1. Birds that breed in the interior of the continent and on the Atlantic Coast are strongly migratory, most winter on the coast from North Carolina to the western Gulf of Mexico. Cormorants (along with Pelicans) are the only regularly occurring sea-bird species not protected under the Migratory Birds Convention Act, 1994 (MBCA).
#2. Its primary diet consists of slow-moving or schooling fish but it may also infrequently eat other aquatic creatures such as insects, crustaceans, eels, and amphibians.
#3. The ‘double crest » from which its name is derived is only seen for a short period of time at the beginning of the breeding season. It describes small tufts of feathers over the eyes.
#4. The Double-crested Cormorant is an agile diver. It dives from the surface and propels itself with wings by its side and uses its powerful totipalmate (all 4 toes are connected by web) feet to propel itself stealthily underwater. Although not well documented, estimates place it to depth on average of 10-15 metres, although some have been recorded to over 25 metres.
#5. Unfortunately, the Cormorant’s ability to pursue its prey underwater also makes it susceptible to being unlikely prey itself, that is by ending up as « by-catch » in gillnets. While the Double-crested is not considered to be one of the more high-risk species in this regard, Birdlife International reports that over 400,000 sea birds world wide end up as unintended victims to these fishing practices. Read more about this issue as it relates to Canada’s policy here as well as here. (Something else to think about the next time you eat fish!).
#6. Swimming cormorants occasionally hold their heads underwater before diving, apparently looking for prey.
#7. It is able to seize its underwater prey by grasping fish using the hooklike nail at the tip of the upper half of its bill.Small prey may be swallowed underwater but it brings harder to handle prey to the surface where it then shakes it or hammers it on the water. It can also toss its meal into the air and catches it again and swallows it whole.
#8. Double-crested Cormorants Nest on the ground, cliffs or on trees. Both adults take part in nest building. Males brings most of the material and the female constructs the nest.. Both sexes incubate the eggs with the female doing more of the work during the first half of the incubation period. The pair takes turns sitting on the nest at 1-3 hour intervals
#9. This bird has a history of human “persecution” from fisherman who claim it eats so much fish that catch rate are significantly reduced. Evidence does not widely support this but nevertheless it has resulted in a variety of legislation and culling of colonies over time.
#10. A cormorant standing with its wings spread out into the prevailing wind is a common sight for anyone watching these birds. It is generally believed that the primary reason is to dry its wings and that it can’t fly well with wet wings.