Thursday, March 15, 2012

Whistlers on the Wing

Banded Tundra Swan pair near Kalispell, MT (c) John Ashley
Paired (female on left) Tundra Swans at Church Slough near Kalispell, MT, on their way to northwestern AK.

Thousands of wild and free swans are winging their way north across Montana right now.

Many of Montana's birder lovers are flocking right now, too, risking spring blizzards for a chance to see migrating Tundra Swans and their slightly larger and rarer cousins, the Trumpeter Swans. Reports filtering in this morning include 3,500 swans at Freezeout Lake, building towards a late-March peak of 10,000 or more. Over here on the west side of the mountains, in the Flathead Valley, we currently have reports of more than 120 swans.

We know that Tundra Swans (formerly called "Whistling Swans") in the western population generally nest along the north and west coasts of Alaska, and winter between southern British Columbia and central California. But sometimes we also get small glimpses into the lives of specific individuals during the migration spectacle.

Marked swans seen in previous years at Freezout Lake include birds that were banded on nesting areas in northwestern Alaska (Yukon Delta, Kotzebue Sound), and on wintering areas in Utah and Nevada (Stillwater National Wildlife Refuge).

Closer to home, last March a pair of banded Tundra Swans (pictured above) rested up for several days at our local hotspot, Church Slough, along the Flathead River just south of Kalispell. These two birds were paired but their band numbers were not consecutive, so I was especially curious to learn their histories from the North American Bird Banding Lab.

It turns out that both of these swans were banded at the Noatak National Preserve, in northwest Alaska as 2+ year olds. But they were banded 1 year and 50 miles apart. Female U700 (the "pen") is probably a year older than her more southerly mate, male U976 (the "cob"), and both are at least five years old now. From their stopover point here in Montana, this pair had roughly 2,100 more miles to go (map below) before reaching their summer nesting grounds! So far, all we know about their wintering area is that it's somewhere farther south.

Tundra Swans mate for life and stay together year-round. They usually pair up as two-year-olds but don't begin nesting until they are 3-5 years old. The female lays an average of four eggs, and both adults take turns incubating for 31-35 days. During incubation, the male defends their nesting territory while also moulting his flight feathers, which leaves him flightless for about a month. The female delays her moult until after her eggs hatch and the family leaves the nest.

It takes about three months before the young swans ("cygnets") are old enough to fly. They will migrate together as a family in October, sometimes forming small flocks of several families and several nonbreeders. And in the spring they will fly through Montana again as pairs, much to our delight.

In the spring of 2003, a pair of the rarer and larger Trumpeter Swans chose a small lake in Montana's Blackfoot Valley for their nest site. That decision by one pair of birds set in motion what would become the Blackfoot Trumpeter Swan Restoration Project. That project is still going strong today, and you can follow their blog and track some of their swans here.

Meanwhile, if you're in the neighborhood of Montana, make plans to visit Freezeout Lake by the end of March. And if you're in the Flathead Valley, visit Church Slough soon - when the ice goes out in a week or so, the fishing boats will move in and the migrating swans, geese and ducks will disappear. A few scattered pairs will stay to nest in Montana, but we'll have to wait until fall to enjoy this migration spectacle again.

Map showing breeding area and migration stopover point for one pair of banded Tundra Swans (c) John Ashley
Tundra Swans U700 and U976 migrate through western Montana between their nesting grounds in northwestern Alaska and their wintering area somewhere between northwestern Montana and central California.