Pictured are Red-Breasted Mergansers in north side East Bay.

It is November in the Bras d’Or Lake Biosphere and in the Mi’kmaw calendar that is “rivers starting to freeze time” (Keptekiwiku’s).

Although we attempt to track Mi’kmaw months as our common months based on the Julian calendar, they are not really equivalent. There are actually 13 moon cycles in the traditional Mi’kmaw calendar every year. Each cycle starts with the new moon and is named after a significant environmental occurrence at that time. So, Keptekewiku’s actually starts with the new moon around October 22 this year in the Bras d’Or Lake Biosphere.

“Rivers starting to freeze time” is the time that thin shell ice often starts to form overnight in quiet freshwater bodies, disappearing when the sun’s rays warm it later in the afternoon. This is a signal to some of the biosphere residents that it is time to find a spot to hibernate, although some have already picked their spots and made themselves comfortable.

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There are some brave Bras d’Or residents who stay and tough-out the winter conditions. Making themselves quite visible around the estuary shores in November are gatherings of merganser diving ducks. They choose more secluded spots during the breeding season. However, at this time of year, they gather in multi-species groups with other diving ducks, united by the common drive to fill up with a meal of fresh fish. Their noisy less-than-graceful hunting antics draw attention to the gatherings. Later in the winter these large aggregations make it easy for young birds to meet mates. Their frantic dances take on a more romantic flavour, incorporating courting displays with the fishing and feasting antics.

There are three types of mergansers observed around the Bras d’Or estuary. All three species are sexually dimorphic, meaning that the males and females look quite different. This makes field identification quite difficult. The most common Bras d’Or merganser is the red-breasted variety, a skinny-beaked beauty with a crest on the back of the head reminiscent of a punk-style hairdo. This species loves the conditions in the Bras d’Or estuary. Much of the estuary offers safe, shallow, salty water which is their preferred habitat according to the “Bird Bible”(Sibley’s Guide to Birds, National Audubon Society).

The Maritimes are near the southeastern limit of the species’ North American breeding range, extending throughout the Boreal Forest. This diving duck may look like our common cormorant or shag from a distance. However, it is smaller, with an adult length of about 58 centimetres (cm) compared to our common cormorant at about 84 cm. At this time of year, the adult male Red-Breasted Merganser has a rusty brown head with a long and ragged double crest, a pale chin, grey back, wings and tail, and a white belly. Their bills are a beautiful scarlet-orange. The white patch in their wing is visible in flight. The name “red-breasted” refers to the colour sported by the adult males when in their breeding plumage, not necessarily at this time of year.

The Common Merganser is not actually as common as the red-breasted variety in the Bras d’Or estuary. It is slightly larger than its red-breasted cousin (64 cm long) with a shorter, reddish bill and a white chin. It may be difficult to obtain a positive ID unless you see the two species together. Their bills are noticeable shorter and fatter than those of their red-breasted cousins. In other areas of their range, the Common Merganser lives mainly on freshwater rivers and lakes. However, the salty Bras d’Or estuary is a protected winter habitat so many do overwinter here in open water areas.

The third merganser that may occasionally be seen in the Bras d’Or Lake Biosphere is the Hooded Merganser. It is a smaller duck, with an adult length of about 46 cm and is quite rare in the Bras d’Or estuary. It does have a crest but it looks more like a lump at the back of its head rather than a punk crest. In the breeding male, this lump forms an attractive fan.

The autumn aggregations of mergansers around the Bras d’Or estuary follow schools of fish. They also eat other animals such as crabs, as well as some plant material. They are very cooperative and will sometimes work together to trap fish. The mergansers’ eyes are adapted for underwater viewing and they typically swim along the water’s surface, repeatedly submerging their heads to scan for food. The flocks of hunting birds often look quite frantic, diving to depths of up to five metres and catching prey after an underwater pursuit. The long, slender bill can come in handy as a probe to extract dinner from underwater crevices.

Their cooperative nature is the reason that early spring families of mergansers may feature one or two adults and an unbelievable parade of ducklings. Mergansers offer babysitting services to other families while the parents leave for fishing trips. I once counted an adult Red-Breasted Merganser with a temporary brood of 19 youngsters.

Enjoy your walks along the shore at this time of year and keep your eyes open for the performing mergansers as they prepare for their communal winter on the Bras d’Or estuary.

Dr. Annamarie Hatcher

Dr. Annamarie Hatcher is a consulting ecologist and a board member of the Bras d’Or Lake Biosphere Reserve Association. For more information about the Bras d’Or Lake Biosphere Reserve Association, please visit http://blbra.ca/.