Common Merganser

Common Merganser - Our Largest Merganser

Common Merganser Male  [Lisa De Leon Photo]

The Common Merganser (Mergus merganser) is a common resident duck in New Brunswick.  It breeds here in summer and is present on most large open fresh waters during the winter.  I recently saw a raft of about 75 Common Mergansers sleeping on open water below the Mactaquac Dam.  They we huddled close together as they slept on the water, heads under their wings, all facing in the same direction.  Occasionally one would wake up and change its position only to soon tuck its head again.  It was a peaceful sight.  This is a common behaviour of this species in winter.

When one sees a flock of Common Mergansers on the water they show a lot of white, the white of the sides and breast of the males.  As seen in the photo above, the male has a white breast, sides, and wing feathers, a dark green head and back and a red bill.  The bill is long, narrow and serrated on the sides for catching fish.  The female has a rufous-brown head and neck, white chin and breast, gray body and red bill.  The white chin on the female is an identifying feature which distinguishes it from the female Hooded Merganser.  The female Red-breasted Merganser is similar  to the Common but has an all white chin, neck and breast.  

Common Merganser  Female [Lisa De Leon Photo]

The Common Merganser breeds as far north in Canada as there is open water.  Freeze-up in the fall pushes them south with some remaining on whatever open water is available. They nest in holes in trees or on the ground in wooded areas.  New Brunswick provides good nesting habitat for this species.  We have all seen female mergansers on our rivers, lakes and streams with a long line of ducklings behind them.  The females must make good mothers because you can sometimes see a female with 25 young ones, obviously there is some sharing of care of the young.  

Common Mergansers Sleeping

Common Mergansers feed on insects, fish and aquatic plants.  They feed either by diving and catching the prey underwater or by dabbling from the surface.  Sometimes while a flock is feeding gulls will hover around them waiting to steal the fish as they come to the surface.  

Common Mergansers are sometimes called 'sawbills' because of the serrated edge to their bills.  They share this name with other mergansers and smews, an European merganser.