Double-crested cormorant (Phalacrocorax auritus ) - local seasonal appearance

Based on 109 observations in Seymour township, Northumberland county, southeast Ontario, June 1998- October 2020. Each day's observation involved anything from 1 to 9 individual birds. 91% (99/109) of the sighting-days were in the main fall migration, August-October. Extreme dates are 10 April (in 2020) to 05 November (in 2019), 29 and 28 October (2020 and 2017, respectvely).

There are roughly 30 species of cormorant, distributed around the globe: from the Bering Sea to California, southern Chile and the Antarctic peninsula; BC to the Gulf of St. Lawrence; around the British Isles; along the Arabian Gulf and the coast of East Africa; Namibia; Gambia; to China and New Zealand... Fishermen in southern China are noted for using captive cormorants to catch fish (e.g., Hoh and Leachman, 1998; Johnson and Yamashita, 2013; and an online photo essay by Andy Beales on the Guardian web site, 2016, with beautiful images of the ancient practice on the Li river near Guilin). The two British variants are the great cormorant (Phalacrocorax carbo) and the smaller shag (Phalacrocorax aristotelis). The shag is a distinct species, but in times past "shag" was a generic American folk term for cormorants (e.g., Pearson, 1936, pp.95-100). These birds are gregarious, and are found on freshwater lakes and along sea coasts, rather than in the open ocean. They are expert swimmers and divers, in pursuit of their principal food: fish (see, e.g., Scott, 1974).

Our double-crested cormorant is a striking, relatively large waterbird, all-black at any distance, often recognizable for its typical fast, close-to-the-water flight. At a distance the bird's profile recalls the common loon, but the head is typically tilted up slightly, so the silhouette is distinctive. Away from the Atlantic coast, it is the only cormorant likely to be seen inland in eastern Canada (Godfrey, 1979, pp.32-33). In our township the PLACE to look is any large body of water, including the Trent and Crowe rivers. The TIME to look is especially in peak fall migration, mid-August to mid-October. The birds are heading south, to stay with open water and a nice climate (e.g., we have seen this species along the north coast of Cuba in January; and McKeating (1989) notes that banded cormorants from western Lake Erie have been shown to winter on the Gulf Coast).

Less often, it may be seen in spring migration, circa (?) 10th April to 22 June. It must be said that the cormorant is much easier to find along the shores of Lake Ontario, whether in Toronto or due south of us, at Presqu'ile and Sandbanks provincial parks. The year 2004 was unique, boasting two spring sightings plus nine more sightings in the fall. It may be coincidence, but the bird was made to feel unwelcome at Presqu'ile that spring: in order to reduce the large local breeding population, birds were shot starting on 6th May as part of a cull, and eggs were oiled prior to the start of hatching in mid-June. Cormorants, like herons, will nest in trees, and their acidic droppings kill the host vegetation. More of this below.

2004's cull was followed by 13 years with low numbers around Campbellford, no more than 4 sightings per year, no more than 6 birds per day (and generally just 1-2 individuals). 2018-2020 have seen unprecedented numbers of sightings, with 77 sighting days to 29 October 2020. Some colder nights in a generally mild fall season (2020) may have encouraged the cormorants to keep moving south at the end of October! Record numbers were seen in the past two years (9 on 04 Oct. 2020, 8 on 07 Sept. 2019 and on 01 Oct. 2020, and 7 on 12 and 13 Sept. 2020), generally birds resting on the piers of the old railway bridge near Tim Horton's. The birds are clearly starting their migration, and often extend their wings to dry in the sun, while perched erect on the safety of the mid-river towers. These numbers are nothing compared to those encountered around roosts, as at Presqu'ile (qv).

At Presqu'ile park the cormorant is indeed an abundant migrant and breeding summer resident, present from early April to early November. Numbers of nests rose sharply during the 1980s, but the history of this species in our area has shown sharp fluctuations (LaForest, 1993, pp.36-39). In the Kawarthas, to the north and west, the bird is (or was) but an irregular visitor, with extreme dates of 27 April to 20 November (Sadler, 1983, p.36). Breeding bird surveys across the province can illuminate and update these observations. Cormorant numbers around the Great Lakes have risen rapidly since 1973. For nesting, in southeastern Ontario, the bird was virtually confined to the north shore of Lake Ontario (Cadman et al., 1987, pp.44-45). However, the birds favour the security of islands, as at Presqu'ile, including islands on some smaller inland lakes, as well as along the shorelines of Lake Ontario and Georgian Bay (Cadman et al., 2007, pp.152-153).

View the complete (or nearly so) 23-year (1998-2020) monthly data summary (738-kb pdf file).


An old controversy: fish thief or feathered scapegoat (?)

The cormorant has been observed extensively, for a long time (for an old review, see Bent, 1922). Cormorant populations fluctuate, the birds being subject to disease, climatic variations, food supply and human activities, amongst other factors. In the Great Lakes, the bird is a relative newcomer, thought to have spread from the west, reaching Lake Superior in 1913, and to lakes Erie and Ontario in the late 1930s (Levine, 1998, pp.118-120). In North America and Europe, for starters, the purported losses to fish stocks and the self-evident destruction of roost trees raise a periodic debate that is rising once again, in 2020. The past three decades illustrate what is obviously a much older issue (see, e.g., Power, 1992; Wynde and Hume, 1997; McRae, 2004; King, 2009; Cava, 2019). Being neither an ornithologist nor a fisherman, I can but observe the migration from Trent Hills, see the larger flocks at Presqu'ile, and read and listen to the debate. As of 0600 hrs EST, on Tuesday 15 September 2020, another round of the episodic but controversial cormorant hunt began in Ontario. Until the end of the year, hunters can shoot cormorants to a bag limit of 15 birds per day. To me, that seems like a lot, though perhaps modest compared to the current seasonal limit of 8 woodcock (qv) per day, the woodcock being a bird I have noted here only once every five years or so. Eight birds would be a 40-year birding "career" for me, to be shot (for what? - well, at least woodcock are reputed to be very tasty) in a single day. I can appreciate hunting for food, for subsistence, especially good, meat-rich game such as deer, moose or turkey, but ..... in the past some have made a meal of juvenile cormorants, though I don't imagine they are a popular dish today!

The 2020 hunt made the cut of topics on CBC Radio 1 the morning after the opening date. Clearly not all residents of "cormorant cove", as we might call some of the lakes where they breed and roost in season, are in favour. The debate is widespread, in, e.g., the British Isles (Wynde and Hume, 1997) and across North America and the Caribbean (King, 2009). As Power (1992, Toronto) noted, the problem returns over time, like mice to your pantry in the fall. Cava (2019) opined that a return to hunting of the double-crested cormorant may be ill-advised.

In 2004, at the time of that last above-mentioned cull, former Presqu'ile park naturalist Doug McRae noted that the drive to reduce cormorant populations was faulty wildlife management, based on a poor understanding of interlinked factors, including numbers of fish, birds and those invasive (but generally hard to see, and harder to shoot) invasive zebra mussels. As we know from Lake Erie, the mussel filter out the food from the water, clarity increases wonderfully, but the fishery crashes for want of supply near the base of the food chain. The invasive mussel, and declines in phosphorus levels due to controls on agriculture-related pollution of waterbodies, may be the main reason for fish stock declines, and possibly it is the cormorant that is but a dark, feathered scapegoat (?). Maybe the hunt is more about rural-urban political strategy, at the end of the day, than conservation science (?).

Again, I can't tell from my own data, though those cormorant sightings have risen strongly in each of the last three autumn migrations. A major cull will have the effect that many fishermen seem to desire, and some self-defined "conservationists" just love to shoot stuff. I'll quote Arthur Cleveland Bent, an indomitable doyen of ornithology on this continent. Bent (1922) describes the occurrence and habits of no less than 10 North American cormorants, all species or subspecies of the genus Phalacocorax. He provides observations (a century or more old, but I suspect bird habits and tastes vary but slowly) of roosting double-crested cormorants along the waterfronts of Quebec, Labrador and Maine, and of the biggest roosts he found, which were in Lake Winnipegosis, Manitoba. Islands in lakes are favoured nest sites for many water birds. The cormorants may nest in the same trees as great blue herons and American egrets. The food of the bird is also described in Bent's dense account of the species (ibid., pp.243-251), and for the most part sounds none too delicious to me. Examples (salt and freshwater habitats) include a lot of eels, parrot-fish, drum, and some crabs, but no salmonoids. Also capelin, flounder, herring, tom cod, sculpin and capelin *. So, this debate is not new. In describing a field visit to a roost in North Carolina, that highlighted eels as a preferred food of the double-crested cormorant, Pearson (1936, p.97) says "Market fishermen everywhere complain of the inroads these birds make on the food fishes of the sea, but a recent investigation by the Canadian Government proved beyond doubt that the destruction wrought by cormorants in the Gulf of St. Lawrence has been overrated greatly". Godfrey (1979, pp.32-33) noted that "extensive studies of the food of this species made by H.F. Lewis in eastern Canada revealed that it usually does little economic harm" . Those with a serious interest in the topic should scan a more recent, on-line review by Trapp et al. (1998) on the cormorant's impact on sport fish. This impact seems overall to be small, though localized harm may indeed occur, usually where there are fish hatchery efforts to support an intensive sport fishery. Many of these points were raised in a call-in debate on the 2020 Ontario cormorant hunt, on CBC Radio 1, 1200-1300 hrs EST, on Tuesday 22 September 2020. Again, I am no expert on anything fishy, but a critical reading of a slice of relevant literature leaves room to doubt a simple, black-and-white views of the bird's role in harming a typical fisherman's catch, away from specific sites of concentrated aquaculture. Some relevant factors: food chain, invasive species, phosphorus levels, fish-hatchery practice, and the fishy diet of the accused "culprit". We'll see. At present, while the offensive aspects of the bird's roosts are beyond doubt, a simplistic "fish thief" story is looking dodgy, and humans have a poor history of playing God...

View the complete (or nearly so) 23-year (1998-2020) monthly data summary (738-kb pdf file).

* Cadman et al. (2007, pp.152-153) update Bent from an Ontario perspective. Direct persecution by humans and the reproductive failures due to pesticides (until the banning of DDT) caused periodic crashes of provincial cormorant populations, as have diseases such as Newcastle Disease and Type E Botulism. Colonies tend to kill the nest trees within 7-10 years, but the cormorant will nest on the ground if need be. Adults will fly 16-24 km or more to feed. It has been said (Line and Russell, 1976, p.75) that "Often a hunting cormorant can fill its belly in only thirty minutes of hunting a day. This is perhaps the reason cormorants are so visible during the day, drying and sunning their wings, preening, displaying and playing". It may be that, rather than leaving control to hunters, the American experience in eastern Lake Ontario offers another solution. Prevention of cormorants from initiating colonies (or disruption of those colonies, as at Presqu'ile in the past), may offer at least a partial reduction in harm (Levine, 1998, pp.118-120).

So, there you have it! I'll update this page in due course, as and when I hear the next chapter in the cormorant saga.


References

Bent,AC (1922) Life Histories of North American Petrels and Pelicans and their Allies. Dover Publications Inc., 1964 reprint of Smithsonian Institution Bull. 121, 335pp. plus 69 plates.

Cadman,MD, Eagles,PFJ and Helleiner,FM (1987) Atlas of the Breeding Birds of Ontario. Federation of Ontario Naturalists and Long Point Bird Observatory, published by University of Waterloo Press, 617pp.

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.

Cava,S (2019) Cormorants in the crosshairs. ON Nature 59 no.2, 8-9, summer.

Godfrey,WE (1979) The Birds of Canada. National Museums of Canada, Ottawa, 428pp.

Hoh,E and Leachman,J (1998) Flying fishes of Wucheng. Natural History 107 no.8, 66-71, October.

Johnson,I and Yamashita,M (2013) China's ancient lifeline. National Geographic 223 no.5, 126-141, May.

King,RJ (2009) To kill a cormorant. Natural History 118 no.2, 24-29, March.

LaForest,SM (1993) Birds of Presqu'ile Provincial Park. Friends of Presqu'ile Park / Ontario Ministry of Natural Resources, 436pp.

Levine,E (editor) (1998) Bull's Birds of New York State. Comstock Publishing Associates, Cornell University Press, revised version, 622pp.

Line,L and Russell,F (1976) The Audubon Society Book of Wild Birds. Harry N. Abrams, Inc., Publishers, New York, 292pp.

McKeating,G (1989) Wild islands of western Lake Erie. In "Legacy: The Natural History of Ontario" (Theberge,JB editor), McClelland & Stewart, Toronto, 397pp., 263-266.

McRae,D (2004) By culling cormorants, we're shooting the messenger. Brighton Independent 32 no.20, 6-7, 19 May.

Pearson,TG (editor-in-chief) (1936) Birds of America. Garden City Books, Garden City, New York, in 3 parts, xliv+272, 271 and 289pp., 1917 and 1936.

Power,J (1992) Cormorant problem won't just go away. Toronto Star, B6, 21 November.

Sadler,D (1983) Our Heritage of Birds: Peterborough County in the Kawarthas. Peterborough Field Naturalists / Orchid Press, Peterborough, ON, 192pp.

Scott,Sir P (editor) (1974) The World Atlas of Birds. Mitchell Beazley Publishers Limited, London, reprinted in 1989 by Crescent Books, New York, 272pp.

Trapp,JL, Lewis,SJ and Pence,DM (1998) Double-crested cormorant impacts on sport fish: literature review, agency survey, and strategies. U.S. Fish and Wildlife Service report, 14pp.

Wynde,R and Hume,R (1997) Cormorants: black plague or black beauty? Birds 16 no.7, 33-35, winter.

Graham Wilson, posted 10 September 2014, major expansion on 16-18 Sept. 2020,
with wee edits and and update of the histogram of observations to 10 November 2020.


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