An iconic sign of a healthy wilderness—or not
by Bob Bancroft
This spring’s massive flooding on the Saint John River brought an unexpected visitor into the hardwood floodplain forest where I spend time in the summer. Upstream from the lake where it traditionally nests, a common loon (Gavia immer) was exploring the watery woodland. A symbol of the north, many consider loon calls the essence of wilderness.
This loon was biding his time, waiting for the water to subside and a mate to return. They would eventually construct a nest within a precarious metre (or yard) of the water’s edge in the lake downstream.
Their nest is a mound of vegetation gathered nearby. The chosen site may be an old muskrat house, a floating mat of grasses, a sandy beach, a half-floating log or an island shore affording some isolation from predators. The pair needs to slip quickly between water and nest as they take turns incubating eggs at 38°C (100°F). They seek out coves offering shelter from waves. With legs positioned far back on their bodies, loons are aquatically adept, but almost comically clumsy on land.
A survivor for 60 million years, the common loon is suited to nesting in eastern Canada’s wooded lakes. They arrive each spring after overwintering along our Atlantic coast. Drab grey winter plumage renders loons difficult to recognize on the ocean. Feeding upon small fish and crabs, they maintain body warmth in the frigid sea by applying oil from a gland at the base of their tail to the outer contour feathers. Built-in barbed filaments enable them to zip those feathers back together using their beaks. This creates an outer, waterproof seal around the birds, keeping inner, insulating down feathers dry. Oil slicks at sea can quickly upset this arrangement.
Migration from the Atlantic to inland lakes occurs after a spring moult into their handsome black and white breeding plumage. Unusual for birds, the males are slightly larger. Both genders are powerful fliers. Pumping at 260 wing beats per minute, they can cruise overland as high as 460 metres (1,500 feet) at speeds of up to 160 km per hour (100 mph) with the advantage of a tail wind.
Loons come well-equipped for submarine maneuvers with solid bones that render them less buoyant and more easily able to dive. They expel air from their lungs and flatten their feathers to eliminate air before a dive. Underwater, their heartbeat slows to conserve oxygen.
Loons are long-lived. One female in Michigan was leg-banded and identified 29 years and 10 months later.
Typically, two eggs are laid from mid-May to early July. The size of their territory depends upon factors like food availability, but most loon pairs require 10 to 75 hectares (25 to 185 acres) of lake area to raise their young. Yellow perch, bullheads and other small fish make up about 80 per cent of their diet. The remaining 20 per cent is composed of frogs, crayfish, snails, leeches and insects like dragonfly nymphs.
Positioned downwind from many of the continent’s major industrial polluters, the dry precipitation and acidic rainfalls in parts of Saltscapes country diminish fish populations and the food chains that support them. Water in increasingly acidic soils eventually drains into lakes, lowering the food resources for loons. Some lakes are abandoned. Other human-induced changes include the release of heavy metals like mercury when impoundments are created behind dams. Mercury can be taken into food chains and concentrated in loons.
Loon habitat is also cottage country, with its summer trash cans and garbage dumps attracting raccoons and skunks. In spring, before trash cans fill up, these animals scour shorelines for nests. Crows and herring gulls also search the shores, while mink and weasels mount regular patrols.
Then people arrive, often on the long weekend in May. The loons stay warily near the nest, as docks are repaired, and boats hit the water. The pair begins to exit and approach the nest underwater to keep its location secret. Unfortunately, the sheltered nest sites are also favourite landing spots for boats out for a picnic. The loons perform a strange dance when the boat arrives but are unable to lure or scare people away. People think they are being blessed with loon magic. As eggs grow cold, the adults eventually give up and swim away. The abandoned eggs lie hidden on the shore until a raccoon ambles upon them one evening. If it’s not too late in the season, the loon pair may even begin searching for another nest site.
When loon pairs attempt to nest on a reservoir, water level fluctuations associated with hydro power or water supply can drown eggs or place a nest too far from water. Concerned residents can help loons on impoundments by building a nesting raft for them and anchoring it in a quiet cove on their lake as soon as the ice leaves in the spring.
The loon’s digestive system includes a gizzard that mistakes lead sinkers for grit and retains them for grinding food. The birds also are attracted by coloured lead jigs lost underwater by anglers. These lures frequently have painted eyes and mimic prey. This can result in lead poisoning. Anglers can use non-toxic alternatives to lead fishing gear, such as the metals bismuth and antimony.
Youngsters are covered in brown-black down and soon leave the nest to swim. They climb on their parents for warmth and for protection from snapping turtles and larger fish like bass and pickerel. Parents feed them for the first two months, which involves dodging canoes, personal water craft and water skiers who sometimes try to run them over. Variations on this scenario unfold, with youngsters separated and vulnerable, until cottagers return to cities after Labour Day.
By mid-September the lake is quiet. Surviving juveniles are diving to catch their own meals. At 10 to 12 weeks of age, they make their first awkward flights. The adults leave for the sea as their youngsters’ flying prowess improves. Young loons are often the last water birds left on the lake as ice creeps in from the shores. They must take wing for the ocean, or risk being trapped with insufficient taxi distance for a takeoff.
Across North America, the population of loons has been estimated at 252,000 to 264,000 pairs. More than 94 per cent of the population resides in Canada, with 56 per cent in Ontario and Quebec. There has been long term population recovery over much of its range across North America—but breeding populations in Nova Scotia as well as New Hampshire, Vermont, Connecticut, New York, Michigan and Washington States are in decline. In western Nova Scotia, for example, breeding success has fallen below the level considered necessary to sustain the population.
If loons have disappeared from a lake where you fish or spend the summer, please consider volunteering that information to the Canadian Lakes Loon Survey.
Loons sure could use our help!