Thursday, August 4, 2016

Common Tern

Unusual Breeding Bird in Fredericton Area

Common Tern

The Fredericton area did not have breeding terns until the creation of the Mactaquac Headpond.  The former Mactaquac River emptied into the St. John River above the location where the Mactaquac Dam was being built.  The flooded Mactaquac River basin became the Mactaquac Arm or Mactaquac Lake.  As it filled up in 1968 a new ecosystem was created. This resulted in ample aquatic, marsh, and riparian habitat which was available for new and existing species.  One of those species was the Common Tern.  Birds of New Brunswick:  An Annotated List states that the Common Tern nests sparingly along the St. John River.  The largest colony in the province is at Kouchibouguac Park with 4000 to 8000 nesting pairs.  A small colony has been struggling in recent years to continue to nest on Machias Seal Island where lack of food for offspring is limiting nesting success.

The Common Tern is about the size of a small gull, 29-32 cm (12 in) long.  Its shape and wing beat are distinctive.  It arrives here in May and departs in August or September.  It is interesting to watch it dive for small fish to feed its very vocal young.  The adult makes a keeeyurr sound.

The Common Tern might be mistaken for the Arctic Tern which also nests off New Brunswick's east coast.  However, the Common Tern has a black tip to its bill and longer legs than the Arctic Tern.  There is a slight difference in the wing pattern, the Common showing a dark wedge in the outer primaries and the Arctic showing just dark wing tips.

The Common Tern is a long-distance migrant.  It breeds along the eastern US coast, through the Maritime Provinces, Labrador and across Canada to Alberta.  It winters along the coast from Middle America to South America.  It is thought that the colony at Kouchibouguac may be the largest known breeding colony.  Another one of our natural wonders!

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