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It's All in the i-Details - Magnificent Mergansers

Take a walk along London’ s Greenway Park this winter and you are likely to see one of our distinctive diving ducks. You won’t even need binoculars for one of the species, since the bright white body of a male Common Merganser shines like a beacon against the dark Thames River. The head is an intense blackish green, or rich green in full sunlight, the long bill is red and the upper body is all black. A bird spectacle! It’s partner, or hopeful partner, wears a completely different plumage with a rusty head, pale gray body and white breast. Females and males will likely be in close proximity as the ducks are looking for prospective mates, even this early in the year.

There are three merganser species found in the London area, but one is considered a rarer sighting here than the others. In order of decreasing size, the list includes Common Merganser, Red-breasted Merganser and Hooded Merganser. The Red-breasted is seen infrequently on our water bodies but usually gathers in great numbers along salty coastlines or in the Great Lakes. The smallest merganser or “Hoodie” can also be seen on the river at Greenway, but may be inconspicuously tucked into a corner on the far shore, if the males aren’t out displaying to the females.

Mergansers can all show a variable look to their head feathers. When they are actively feeding and diving, their crown looks sleek and flattened. If they are just paddling along, displaying or anticipating the approach of a raptor, such as an eagle, the head feathers can be raised. It looks like someone has rubbed gel into their “hair” and ruffled it about for a spikey look. A Common Merganser’s crest flares horizontally, at the back of the head, but the Red-breasted’s horizontal headress look much shaggier and shredded, often described as “wispy”. This is true for both males and females. Male Hoodies have been endowed with an impressive white head crest, bordered in black, but the all-brown females wear a fuzzy halo of fine feathers. Sometimes, it looks like their hair is standing on end in surprise.

A close-up of a merganser bill gives a good clue as to their main food prey. Both upper and lower mandibles have a finely serrated edge, perfect for keeping a tight grip on wiggly, slippery fish. It serves well for picking up crustaceans and water bugs too. They feed underwater and will sometimes swim along with just their face below the surface on the lookout for a meal. They are considered diving ducks not dabblers, like Mallards though. The scientific name of a Red-breasted Merganser is Mergus serrator which highlights their sawbill characteristic.

The main identification challenge amongst mergansers is between the Common and the Red-breasted, particularly females. Both have the chestnut head, gray body and deep flame-red bill, but on a Common, the rusty neck meets white breast in a sharp demarcation and there is a white patch under the chin. The female Red-breasted lacks the chin patch and the transition between throat and top of the breast is a gradual and pale merge of russet and gray. Add to that, a steeper forehead, thinner neck and general appearance of a smaller and more delicate looking bird and the field marks should add up to give you the rarer species here. Males can be quickly differentiated from the Common by the speckled brownish breast feathers, and white collar band, noticeable even in flight.

If you are willing to brave the cold and wind, I hope you can get out to look for mergansers in the city. It can be quite entertaining to watch them feed, sometimes nabbing a fish that seems way to big to swallow. Or if you would like to watch the entertaining courtship “antics” of a Hooded Merganser, from the comfort of your home, check out one of the You Tube videos such as this one

Although mergansers are very serious in their rituals, it will bring a smile to your face.

**photos from top - female Common Merganser, male and female Commons, male and female Hooded Mergansers, female type Red-breasted Merganser, male Red-breasted in flight, male Common Merganser with fish

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