Trumpeter Swans Relearn Migration

Abstract

F or 57 winters, swan conservation success at Red Rock Lakes National Wildlife Refuge in Montana has been measured by the increased numbers of trumpeter swans seeking handouts of winter wheat at the crowded man-made ponds. sign of success this year will be frozen ponds, no handouts, and no swans. Half a century of coddling has been so successful that the Rocky Mountain population of trumpeter swans (Cygnus buccinator) has grown from fewer than 200 individuals in 1935 when the refuge was founded to 2200 today. Because of behavioral peculiarities associated with migration, numbers are now the greatest liability of these snowy aristocrats with French horn voices. Approximately 1700 of the birds migrate to western Canada in summer to nest, but almost all return to the high Yellowstone country around the refuge to winter. other 500 swans have given up migrating entirely; they nest and winter in this harsh region where Montana, Idaho, and Wyoming meet. Unlike other birds, these swans seem to lack both the temperament and the knowledge to disperse voluntarily to better and less-crowded winter quarters. During winter, we have all our eggs in one basket, says Ruth Shea, a swan expert with the US Fish and Wildlife Service (USFWS). The swans are very vulnerable. A blizzard or disease could wipe out a large proportion of the population. Three years ago, the agencies and biologists involved in the Pacific Flyway Council shifted tactics in their half-century effort to pull the Rocky