I had called to ask for some fine points of bird identification, only to learn that my biologist friend had been watching the same flock of swans that I was. These spectacular birds, the largest of North American waterfowl, had made a migration stopover on a lake not far from my home.
They were there to rest, and load up on a banquet of underwater vegetation, which - based on what I saw through my binoculars - they seemed to be finding in abundance in the shallows just beyond the narrow band of ice rimming the lake. The autumn passage of both trumpeter and whistling swans usually signals the last stages of waterfowl migration through Minnesota. As the smaller waters freeze, swans move southward, congregating in bigger flocks on larger lakes.
Most of my swan sightings have been pairs, or small family groups, usually seen while duck hunting. What a discovery to find a gathering of nearly four dozen swans within a drive of a few minutes, rather than hours!
When your sense of size and scale is programmed for ducks and geese, you're ill prepared for the enormity of a swan. A trumpeter can measure 5 feet from bill to tail, twice the length of a greater snow goose, and weigh over 30 pounds, about four times the snow goose's weight. An average adult mallard weighs less than three pounds.
Perhaps because swans are an uncommon sight in the Midwest, even for hunters, their known stopover areas are often marked with signs warning of their presence, their protected status, and showing the telltale differences between swans and snow geese. Hunters who are lucky enough to observe swans close up, and in flight, are better prepared to identify them in the heat of the hunting moment, and avoid an unfortunate - and expensive - mistake.
Contrary to what I expected, Mike, my biologist friend, said this flock was made up of almost equal numbers of trumpeter and whistling swans. Though they may not be migrating to the same destination, trumpeter and whistling swans are very similar in their needs and habits. So it should have been no surprise that they would be found resting and feeding together.
It takes an experienced eye to tell these two swans apart. Both species, and both sexes, are almost entirely white. They are also similar in the proportions between their body, their long, slender neck, and their broad wingspan. In contrast, the young of both species - called cygnets - are a mousey gray, and look as though they might have fallen down a soot-filled chimney.
For some, the politically correct name for the whistling swan is tundra swan. There is some logic to this more contemporary name, inasmuch as this species nests farther to the north than the trumpeter, commonly on the tundra of the arctic and subarctic regions.
Mike said that the giveaway that there were both trumpeter and whistling swans was seeing a cluster of birds standing on the ice rim extending out from shore. "Some birds stood a good six inches taller than the others," he said. Those, he was certain, were trumpeters.
Size alone is not always the perfect identifier, because the smallest trumpeter and largest whistling swans may be similar in size. If you're close enough to see it, especially when aided by binoculars, a yellow spot at the base of the black bill is the mark of an adult whistling swan.
A foolproof identifier, though only found post-mortem, is the structure believed responsible for the trumpeter swan's "voice." The windpipe of the trumpeter makes an extra loop over a bony hump in the bird's sternum, or chest. This is believed to create the deep sound that some compare to a French horn. This is quite different from the whistling swan's higher-pitched, quavering tone, which some describe as "who who who." Ê
Almost a century ago, some of America's most eminent ornithologists believed that the trumpeter was on the brink of extinction. ÊFor generations swans were hunted for their feathers and meat. ÊThe Hudson's Bay Company, which most of us know as a fur trading firm, also dealt in valuable bird skins. Their records have been used as a kind of market-based barometer of the pioneer period population of trumpeter swans. From earlier abundance, trumpeter skins virtually disappeared from the ledgers of the Hudson's Bay Company after the 1870s.
Under the pressure of hunting and habitat change, a number of factors may have contributed to the population collapse of the trumpeter. One may be low nest density. Trumpeters are highly territorial, and generally will not tolerate another breeding pair nearby. Some territories have been estimated to be as large as 70 to 150 acres.
Compared to ducks, swans have small broods, often three or less, with survival sometimes averaging less than two cygnets per adult pair. Young are not able to fly for three to four months; a mallard can typically fly in two months, or less. Swans are quite intolerant of disturbance, particularly by humans, and may abandon their nests when this occurs.
If modern ornithologists are right about the trumpeter's original distribution, it was noticeably to the south of the whistling swan's range. Much of the whistler population breeds in the sparsely settled arctic and subarctic regions. The trumpeter, on the other hand, bred as far north as Alaska and Canada's Northwest Territories, but also south as far as Missouri, Illinois and Indiana. Contact with humans, including market hunting spring and fall, as well as habitat destruction and general disturbance, were more likely to affect the trumpeter than the whistling swan.
The whistling swan winters primarily on the East and West Coasts. The majority winter on Chesapeake Bay, and similar coastal areas from Maryland to Virginia to North Carolina. A substantial number also winter in California coastal marshes. The trumpeter once wintered in similar East and West Coast areas, as well as the lower Mississippi River Valley. In our region, a limited number winter in Minnesota and Wisconsin.
The continental population of trumpeter swans is estimated at roughly 16,000, about three-fourths of which is comprised of Alaskan birds. As a total population, trumpeters are not considered endangered, though their interior population - which includes birds in Minnesota and Wisconsin - is very limited. Whistling swans are far more abundant, their continental population estimated at about 140,000 birds.
Consider, however, that many duck and goose species number in the millions, and it becomes clear that these uniquely beautiful symbols of wildness are a rarity, their sighting a true high point for the bird lover.
