Episode 38Copyright © John Page Williams, Jr. all rights reserved.
This is John Page Williams with another reading from Chesapeake Almanac. The month is December and this chapter is entitled "Swan Time."
You can almost set your fall calendar by them. They're not quite as precise as ospreys in March, but they're close. Sometime shortly after November 15th, a cold front will sweep through the Bay country. That night, if you listen carefully, you'll hear them. Tundra swans, formerly known as whistling swans, flying in for the winter. They'll sound at first like geese, but the honks are higher pitched and more quavery, with the even higher pitched "wheeps" of the young birds--also called cygnets--mixed in.
Over the next few days, small groups will filter into the Bay, heading to the Blackwater National Wildlife Refuge on the Eastern Shore near Cambridge, or to the mouth of the Rappahanock River, Back Bay near Virginia Beach, or Lake Mattamuskeet in eastern North Carolina.
Some small groups will arrive, and then a week later, after another cold front, a day will come when the big birds pour into the Bay, a continuous stream of flocks ranging in size from 10 to 100 birds. They'll sleep a lot for a day or two and then settle into their winter routines.
The swans have a right to be tired; they've flown nearly non-stop some 1,500 miles from the North Dakota prairie pothole country. Even with tailwinds behind the fronts, it's a long haul. The swans typically spend the last half of October and the first half of November resting and feeding in North Dakota, where the pothole marshes make a good halfway point. The summer breeding grounds are on the tundra of the Canadian Arctic coast, the North Slope of Alaska, and the Bering Straits. Most of the birds from the Bering Straits (about 40,000) go down the Pacific flyway to the Sacramento River delta, but those from the other breeding grounds, another 30,000 or so, come to the Atlantic. It's an amazingly long migration by any measure, but it's especially remarkable that the signets make a trip at the age of five months.
If we could interview the adult birds, we'd find that most have returned to the same places they wintered last year. These migrations have been going on for thousands of years, so there must be some long family traditions involved. That's speculation, of course, but we know an amazing amount about what has been going on for the past 40 years because of remarkable research at the Johns Hopkins University. Dr. William J. L. Sladen and his associates have banded several thousand swans with colored, numbered, plastic neck collars. These are in addition to the U.S. Fish and Wildlife Service leg bands that all marked birds must carry. A few birds tagged by Dr. Sladen have also carried tiny radio transmitters.
Both the neck collars and the transmitters fall off in time (the former in several years, the latter within a couple of months), but in the meantime they yield large quantities of data. The great value of the collars is that they can be read with a 20x to 45x spotting scope. Thus the birds need not be recaptured and handled for researchers to gather data on their travels. It also means that lay people can help with the data collection, and a number of Bay region residents have gotten involved as amateur observers.
Sladen and his associates were able to work out many of the details of when swans migrate, under what conditions, and where. The original work in the early 1970s was supported in part by the U.S. Air Force, which is interested in bird/aircraft strike hazards. S 20-pound swan flying at 40 miles an hour can do as much damage to a plane as a cannonball. It will also, of course, damage the swan. Sladen's data helps pilots in the eastern United States avoid routes and altitudes frequented by the swans during migration times (from early November on into December and in late March).
The neck collar sightings carried out here on the Bay, at Lake Mattamuskeet, along the bird's migration routes in the Midwest, and on the Arctic tundra have provided details on where individuals go. These data give us a remarkable look into the private world of the tundra swan, demonstrating that they are, indeed, creatures of habit. in addition to using the same wintering grounds year after year, they breed in the same areas of the tundra each spring.
Why do swans make such a long trek back and forth across the continent? We can only speculate, but a large part of the answer may be that the wintertime Chesapeake is the closest coastal body of water that provides plenty of food and reasonably ice-free conditions. Birds from the Canadian Arctic and Alaska's North Slope come this way because they have a migration corridor that provides them with the waterways—prairie potholes in the Great Lakes, for example—that they need for feeding and safe roosting at night.
In the end, it is probably the Bay's creeks, coves, and shallow flats that bring the birds to us. The swan's traditional foods are small shellfish, especially the small, tiny, soft shell clam Macoma balthica, and the rootstocks, tubers, and seeds of submerged aquatic Bay grasses. Up through the 1960s, there was plenty of both to keep the swans well fed.
During a period in which Dr. Sladen was studying the swans, there have been shifts in their wintering patterns. The reasons are all too familiar. The acreage of Bay grass has declined drastically. Even though there have been recent rebounds in some areas, there's still less than it was 50 years ago. Without this staple food, the swans return to the traditional haunts, feed on clams for a short period, and then move on. They're big, warm-blooded creatures who need lots of food to keep up their body temperatures, even with their swansdown parkas. There simply aren't enough small clams in some of the rivers to hold them for any length of time. For a period between the late 1980s and the late 1990s, there simply weren't enough small clams, for example, in a river like the Severn near Annapolis, to hold swans for any length of time. There was no grass. It was gone. Back in the 60s and 70s, as many as 2,000 swans wintered there, feeding on huge grass beds. In 1994, the grasses started to come back, and after a 10-year hiatus, swans began to trickle in. The numbers on the Severn now are not as high as they were back in the 1960s, but the swans are back. There are swans reliably there because the grasses are back. Redhead pondweed, and especially sago pondweed, draw them in like magnets.
Fortunately, we haven't lost our swans to other regions yet. As creatures of habit, they keep coming to the Bay and are at least somewhat adaptable. During the time the grasses had disappeared, they began to move into farm fields to feed with the Canada geese. Early in the year, they'd forage for scrap grain, later they graze on cover crops. National wildlife refuges like Blackwater and Mattamuskeet, which have managed for waterfowl, also hold thousands.
A few flocks settle in around communities where people put out corn for them, like Hillsmere Shores on the South River below Annapolis. Feeding swans is a big responsibility. Anyone who begins must continue every day, and a flock of 30 birds can go through a half a ton of corn a month. Nevertheless, corn is addictive to swans, and swans in turn to people, so many residents feed flocks year after year. It should be no surprise that neck collar studies show these birds to be the same individuals each winter.
Thanks to the swan's adaptability, the Bay's winter swan population is still strong. We can only hope that if we reverse the decline in its water quality and if the grasses continue to come back, the birds will return to some of their old haunts on the rivers. The farmers wouldn't mind. Swans can cause significant crop depredation, and their big feet compact soil.
Tundra swans are spectacular citizens of winter on the Chesapeake. we have good opportunities to enjoy watching them, and we have a responsibility to them as well as to ourselves to make the Bay a place worth returning to each winter.
For more happenings around the Bay in December see our other Chesapeake Almanac podcasts and read our blog posts "Buffleheads and a Winter Miracle" and "Getting Outside in December."
