Great Cormorant

Great Cormorant Nesting Site 

Great Cormorants

Recently I visited a nesting colony of Great Cormorants (Phalacrocorax carbo) off Twillingate, NL.  They had taken over a large rocky 'island' off the mouth of Twillingate's large harbour.  The island was about 300 metres long and 50 metres wide, was completely rocky and had steep sides.  All birds had to land on the island at their particular claimed site with very little chance of walking around.  The roughness of the craggy rocks made multiple nesting areas.  There were about 80 to 100 cormorants on the island and many more were in the air around it.

The island was mainly taken over by the Great Cormorants.  No Double-crested Cormorants, no murres, no gannets were seen.  The only other species present were a few Herring Gulls and perhaps one Great black-backed Gull.  

Great Cormorants

Some cormorants were sitting on their nests.  Many were standing around possibly socializing or protecting their mates.  The photo above shows a Herring Gull also present.  The nests were made of sticks and a depression in the rocks was brought up to level and made safe with the sticks.  The nests are lined with seaweed or other refuse (garbage, like plastic).  It looked like these birds are careful nest builders.  They lay 3 to 5 pale blue or green eggs and both the male and female incubate them for 28 to 31 days.

Great Cormorants

The Great Cormorant is our largest cormorant, being 94 cm (36 in) long compared to our other cormorant species, the Double-crested Cormorant, which is 81 cm (32 in) long.  It is black with a white throat patch, yellow skin around its beak and a white flank patch.  The Double-crested does not have these white patches and has orange skin around its beak.  The young Great Cormorant is brownish with a white belly and the young Double-crested is brownish all over with no white belly.  It takes the Great Cormorant three years to get its adult plumage.  The Great Cormorant is mostly silent but deep groans can be heard around the nesting colonies.  

Great Cormorants

The Great Cormorant breeds only in maritime habitats in eastern Canada and Maine.  Nesting colonies are found around the Gulf of St. Lawrence, Newfoundland and south to Maine, on rocky islands and cliffs.  They move south in winter along bays and seacoasts to North and South Carolina.  

The Great Cormorant pursues its main diet of fish underwater, using its powerful feet to propel itself. It also eats crustaceans.  These birds are very sociable and are sometimes found in huge colonies.  This is one of the species trained by Japanese fishermen to help them fish.  An interesting fact about Great Cormorants is that they sometimes swallow pebbles to add weight to their bodies so they can dive deeper after food.  An interesting and obviously trainable species.