The common loon is perhaps the most iconic bird associated with the great Canadian outdoors, and especially with the picturesque lakeland of "cottage country". It famously summers across the breadth of Canada, while wintering mostly on salty coastal waters around the U.S.A. (and in small numbers on the Great Lakes). The breeding range extends from St. John's to the Yukon, and Vancouver Island to southeast Baffin Island. Each lake is said to support one breeding pair, though larger lakes will host more. The common loon is the best-known of four North American species, which are placed by taxonomic concerns at the very start of bird guides (e.g., Godfrey, 1979, pp.9-14). Loons, I think, are beloved by many Canadians. The British might agree, but disdain the name "loon", preferring their common name for the species, Great Northern Diver. In the British Isles, this is largely a coastal bird, especially in the north and west.
Somewhat awkward on land, the common loon is a very strong swimmer, catching and even devouring fish underwater. In June 2020 I saw one from the main road bridge in Campbellford: it was a "textbook" loon, except for a few white specks around the base of the dagger-like, otherwise black bill, and the lighting, which caused the black collar around the throat to shine with a deep green iridescence. The bird was busy fishing, diving with vigour, and later rising swiftly like a grey ghost, apparently at a shallow (circa 30-degree) angle to the surface. Two months later another sighting was made at Allan Mills on the Crowe River, a rural and surely more typical home for this large and impressive diving bird. The best evidence for local breeding, on a larger water body, is down by Wilson Island, by the east end of the Percy Reach, where a loon family was spotted near the Hogan family residence on 07 August 2020.
A lyrical account of the common loon (Forbush and May, 1939, pp.3-5) merits one quote, at the least:
"Often towards nightfall I have heard his wild storm-call far out to windward against the black pall of an approaching termpest like the howl of a lone wolf coming down the wind; and have seen his white breast rise on a wave against the black sky to vanish again like the arm of a swimmer lost in the stormy sea".
The limited number of observations (mostly 24 April to 04 August) reflect our more "terrestrial" beat, as opposed to spending time on lakefront and river (the Trent canal / river in Campbellford is a pleasant waterway, but though the grassy banks may be attractive to families of Canada goose with their fluffy young, it was not designed to attract nesting loons!). But see the August 2020 sighting of a family, above. The late observations of 29 October and 01 November 2021 on the Trent river in Campbellford are probably the same bird: a closer look on the earlier occasion affirmed the bird in winter plumage.
Absent time spent at possible nesting sites, we would expect to see the bird mainly on migration, except for unpaired individuals engaged in fishing along the rivers. Personal experience in the past two decades supports the published distribution: lakes and rivers from north of Thunder Bay to the Ottawa River valley. Loons have been seen at Presqu'ile park to the south (the Lighthouse and Beach 4 areas); Emily Park near Lindsay; Balsam Lake and Baptiste Lake near Bancroft; Tooey Lake near Denbigh, and elsewhere. From these regional observations, the bird may be seen in the region from at least late April to early November (see below for more definitive data).
The common loon breeds across the vast extent of the province (Cadman et al., 2007, pp.140-141), excepting only the farmland and cityscapes of southwest and southern Ontario. We could almost use a geological map to constrain its breeding distribution: it breeds on the Canadian shield, rather than the limestone platform that covers most of southern Ontario, west from Ottawa to Lake Simcoe to the southern shores of Lake Huron. The main exceptions, where the bird may be found in summer, include the north shore of Lake Ontario east from Toronto, and the Tobermory peninsula. It may breed locally in small numbers, as indicated in the Atlas, on and downstream from Rice Lake in the Trent watershed. The loon is territorial, and vocal day and night in announcing its presence. Loons remain near the nest site well into fall, until first adults and then the young migrate south.
In the recent past, especially in the COVID-19 pandemic, there has been an increase in the use of high-powered motorboats and personal watercraft. The noise, disturbance to water and silt, and damage to shoreline nests may all impair nesting and foraging activities and threaten the young (Bream, 2021). The immediate Campbellford section of the Trent, a simple waterway, is not much affected in this way: the loons were not nesting here. The main damage will be on larger, easily accessible lakes with a high volume of powerboat traffic.
The common loon is quite common as a migrant at Presqu'ile provincial park, roughly 40 km to the south, from early April to early December. Extreme early and late dates in the park are 29 March and 31 December, though average fall departure is in early December (LaForest, 1993, pp.26-27). Similar dates are noted in Peterborough county, to the northwest (Sadler, 1983, p.34). Two graves of the Woodland period, excavated at Serpent Mounds on the north shore of Rice Lake, apparently yielded loon beaks, indicative of some special significance for this familiar lakeland bird.
Across Lake Ontario, in New York state, the common loon breeds often in the
Adirondacks, seldom elsewhere. It is a common migrant on larger water bodies,
especially along Lake Ontario, and is most numerous in April
and November. It winters on the Atlantic ocean off the east coast of Long Island
(Levine, 1998, pp.96-97).
References
Bream,ML (2021) Where have all the loons gone? Toronto Star, E1,10, 21 August.
Cadman,MD, Sutherland,DA, Beck,GG, Lepage,D and Couturier,AR (editors) (2007) Atlas of the Breeding Birds of Ontario, 2001-2005. Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, Ontario Ministry of Natural Resources, and Ontario Nature, 706pp.
Forbush,EH and May,JB (1939) Common loon. In `Natural History of the Birds of Eastern and Central North America', Houghton Mifflin Company, Boston, MA, 554pp.
Godfrey,WE (1979) The Birds of Canada. National Museums of Canada, Ottawa, 428pp.
LaForest,SM (1993) Birds of Presqu'ile Provincial Park. Friends of Presqu'ile Park, Brighton, Ontario / Ontario Ministry of Natural Resources, 436pp.
Levine,E (editor) (1998) Bull's Birds of New York State. Comstock Publishing Associates, Cornell University Press, 622pp.
Sadler,D (1983) Our Heritage of Birds: Peterborough County in the Kawarthas. Peterborough Field Naturalists / Orchid Press, Peterborough, ON, 192pp.