Mayne Island’s surrounding waters are a good place to look for diving ducks.
This group of ducks are also known as sea ducks and on Mayne Island we have records for nine different species, some quite rare. They are the Bufflehead, the Harlequin Duck, the Barrow’s and Common goldeneye, the Surf, White-winged and Black Scoter, the Long-tailed Duck, and the King Eider. The last two are considered very rare and vagrant. In the 2017 Christmas Bird Count the diver group of birds represented 13% of the total birds counted that day.
The diving duck group is distinguished from the other duck groups – dabbling and bay ducks – by several factors. One is that they generally are found in deeper open marine waters, high-energy wave environments or rocky shorelines. Their diet is mostly animal based: crustaceans, small fish, mollusks and sometimes fish eggs. The diet of dabblers and bay ducks is more plant and aquatic insect based with some marine animals.
The divers have their large feet set to the rear of their body, an adaptation to allow them to swim underwater. As in most duck species, the diver males have brightly coloured plumage while the female plumage is subtler. Sea ducks generally live long lives and can survive up to 18 years in the wild.
Of the species of diving ducks observed for Mayne Island, four of the most distinguishable are as follows:
The Bufflehead is the smallest diving duck in North America. It is a cavity-nesting duck that almost exclusively uses Northern Flicker holes for nesting, rather than the larger nest holes excavated by the Pileated Woodpecker which are used by other cavity nesting ducks. During the winter, look for these tiny ducks—particularly the striking black and white males—in sheltered bays along the Mayne Island coast. The small brown and black females with the diffuse white blotch on their heads are not as easily seen first off. Village Bay and Dinner Bay are particularly good sites for viewing these diving ducks. While they are foraging, they will spend half their time underwater, so have patience!
Buffleheads swim buoyantly, dive easily, and take flight by running a short distance on the surface. To dive, Buffleheads must compress their plumage to squeeze out air which allows for more efficient movement underwater. They hold their wings tight to their bodies underwater and use only their feet to propel themselves. In marine waters, Buffleheads eat shrimp, crabs, amphipods, isopods, snails, mussels, herring eggs, sculpins, and ratfish. While feeding in groups one ‘sentry’ usually stays on the surface to warn against predators.
Village Bay is usually the first place that you will see overwintering Buffleheads, sometime in mid to late October each year. Studies at Roberts Bay near Sidney support the belief that the same birds come back to the same sites each year. This is called site fidelity. In the Roberts Bay study a single banded Bufflehead appeared consistently on October 15th each year for over ten years. October 15th has now been proclaimed as National All Bufflehead’s Day as a celebration of this amazing event.
The Harlequin Duck should be recognizable to all because of the striking plumage of the male. It is interesting to note that “Harlequin” is the name for the masks worn in classical Italian comedies. This species favours fast-flowing mountain streams for breeding, and wave-washed rocky-cobble seashores during the rest of the year. It is estimated that BC supports 12,000-15,000 wintering Harlequins that breed within the province and in bordering provinces and states.
On Mayne Island, Harlequin Ducks are not abundant, but can be seen regularly throughout the winter as pairs or small groups. The best sites for viewing are from Georgina Point to Reef Bay where the predominately rock shoreline offers many opportunities for foraging Harlequins at all tide and wave conditions. Their diet consists of crustaceans, mollusks and some fish. When they dive, both their wings and feet are used for propulsion. At certain times of the year only males can be seen along our shores. This has to do with two factors: the males leave the females behind at the nesting area at the time of incubation and fly to the coast to molt. This happens usually in mid-May to early June. Meanwhile, brooding females remain at the nesting area until the chicks are ready to make the flights to the marine wintering sites in mid to late July. As with other sea ducks, Harlequin do not reach maturity for at least two years, so there are nonbreeding juveniles – both male and female – who may go to the breeding areas but leave earlier for their wintering sites to molt.
British Columbia supports about 60% of the world population of breeding and wintering Barrow’s Goldeneye. The majority of the population winters in nearshore coastal waters, with the Salish Sea being particularly important. The Barrow’s Goldeneye male is quite striking with its metallic green head, white swoosh and contrasting black body with white patches. The female is brownish with a diffuse swoosh on the head. There is evidence that Barrow’s Goldeneye return to the same wintering area.
The goldeneyes form large aggregations at their preferred sites—these gatherings have a cyclical pattern. The Strait of Georgia coastline of Mayne Island and the inner shores of Curlew Island are consistent and seemingly preferred places for feeding congregations. Fall and early winter numbers at these sites can be up to 1500 birds in some years. Fluctuation in these aggregations has been attributed to the goldeneye’s preference for edible blue mussels and to a lesser extent, barnacles, which are found at these sites in high densities. The goldeneye swallows these whole because its larger gizzard is able to crush and pass both the shell and the food through its system. Because of this site preference the goldeneye is vulnerable to loss of feeding opportunities should these sites be contaminated or lost to intertidal or near sub-tidal development. Blue mussels have been used as indicators of marine water quality because of their filtering behaviour and propensity to concentrate toxic substances like mercury, lead, or cadmium.
The Surf Scoter is a familiar sight in winter when over half a million birds congregate along the British Columbia coast, but only a handful of these remain to breed in the province. Adult male surf scoters are black, with noticeable white patches on their foreheads and at the back of their necks, distinguishing multicolored bills, white eyes, and orange legs and feet. Females are uniformly brown, sometimes exhibiting white patches on their cheeks or below their eyes.
For most of the year surf scoters frequent shallow marine waters and are most abundant over sand-mud, cobble, and rocky substrates. Population declines in most parts of the species range have been reported for several decades, especially among birds that winter on the Pacific coast. The causes for these declines are not clear.
Surf Scoters feed predominantly on bivalves – mainly mussels and sometimes clams. They also use their wings and feet for dive propulsion. In one study in Howe Sound, the majority of surf scoter flocks observed were over rocky substrates at a depth of 0-10 m near or on reefs with about three quarters of those observed in mussel habitat.
Like the goldeneyes, the Surf Scoter shows a pattern of large aggregations in some years and fewer in others. For Mayne this appears to be up to a three-year cycle, similar to the Barrow’s Goldeneye. Flocks of over 1500 birds have been observed in some years and almost totally absent in subsequent years. The prevailing theory is that dense aggregations of scoters can deplete the food source to the point that the birds abandon the site and move elsewhere. The ability to cause this sort of depletion is attributed to the scoters’ aggregate feeding strategy. What this means is that the scoters start feeding with a few individuals of the flock diving and pulling mussels off the substrate below. This then creates an opening in an otherwise continuous bed of mussels. Once the opening is established the whole flock begins to dive on the mussel bed enlarging the opening as the inside anchoring threads of mussels are weaker. In this way scoters can expend less energy procuring their food and are able to more quickly meet their food requirements.
The merganser group is classed in the same order as sea ducks, but is decidedly unlike them in appearance. These are large (other than the Hooded Merganser), long-bodied ducks with thin, pointed wings. Their bills are straight and narrow with serrated edges like teeth to grasp and hold fish prey. This is very unlike the flat bill of a “typical” duck. Females have shaggy crests on the backs of their heads.
Because of their diet, mergansers are also known as “Fish Ducks” or because of their bill structure “Sawtooth Ducks”. There are three types of these birds in North America and all three can be seen on Mayne Island at certain times of the year. The Common Merganser, as the name indicates, is the most abundant on the continental scale, but much less so on Mayne Island. The Red-breasted Merganser nests in the northern regions, but is more likely to spend its winter on the coast, living in saltwater. It is also the most numerous seen around Mayne Island.
The smallest of the group is the Hooded Merganser and can be found across the southern regions of Canada, throughout the US central plains to the eastern shorelines. We often see this species on its own or in pairs on ponds and in the sheltered bays of Mayne Island.
The Red-breasted Merganser is a medium-sized, fish-eating duck with a long, shaggy crest that is often found on the British Columbia coast in winter. Males have a dark green shaggy head, a red bill and eyes, and a rusty chest. Females lack the male’s bright colours and are mostly brown and white but also don the same shaggy head. They can be seen in very large flocks foraging for fish in Active Pass during tidal exchanges and loafing in Navy Channel on slack tides.
It is also frequently reported feeding along the Strait of Georgia side of Mayne Island. As with other sea ducks, its body weight compared to its wing area is large, which means it requires a long take off run to lift out of the water. Red-breasted mergansers are known to fish cooperatively whereby they dip their head and bill underwater to drive fish to shallower water for more easy capture. In terms of food requirements, it is estimated that these birds need to eat between 15 and 20 fish per day to meet their daily energy requirements. That represents about 4 to 5 hours of foraging per day, which for our marine waters would be over perhaps two tidal cycles.
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