Immigration in a Small Population of Snow Geese

Johnson, Stephen

The Lesser Snow Goose (Chen caerulescens caerulescens) colony on Howe Island, near Prudhoe Bay, Alaska, is the only established nesting colony of this species in the United States. A study was initiated to follow the dynamics of this small population in 1980 when it became clear that oil development would proceed near the nesting colony and in nearby brood-rearing areas. Virtually all brood-rearing Snow Geese in the study area were banded in late July of 1980 through 1993 to determine return rates of banded birds and to determine whether immigration contributed significantly to the maintenance and growth of the population. This was a critical question if, in the future, a local catastrophe (e.g. foul cholera, oil spill) were to affect most or all of the birds in this small population. During this 15-year study, the Snow Goose population expanded from 39 to 412 nesting pairs. Based on markrecapture data from the banding programs, the immigration rates for females and males are estimated to be 12.8 ? SD of 4.39% and 60.7 ? 12.85%, respectively. Exceptionally high immigration rates for males were recorded in 1990 and 1993, when large numbers of twoand three-year-old females (banded as goslings) returned with unbanded mates from other populations. Many females apparently immigrated when they were juveniles. The origins of immigrants is still unclear because of limited banding at neighboring colonies. Resightings of neck-banded Howe Island geese indicate emigration of primarily males to Wrangel Island, Russia, and Banks Island and the Anderson River Delta, Northwest Territories, Canada. Received 1 June 1994, accepted 18 January 1995.

Immigration in a Small Population of Snow Geese

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