Canada Geese in the Atlantic Flyway

Canada Geese in the Atlantic Flyway
		by *Jay B. Hestbeck* National Biological Service

Fig. 1. Midwinter number of Canada geese in mid-Atlantic, Chesapeake, and South regions of the Atlantic Flyway, 1948-93 (Midwinter Survey, U.S. Fish and Wildlife Service, Office of Migratory Bird Management).

Large changes have occurred in the geographic wintering distribution and subspecies composition of the Atlantic Flyway population of Canada geese (Branta canadensis) over the last 40 years. The Atlantic Flyway can be thought of as being partitioned into four regions: South, Chesapeake, mid-Atlantic, and New England. Wintering numbers have declined in the southern states (North Carolina, South Carolina, Georgia, Florida), increased then decreased in the Chesapeake region (Delaware, Maryland, Virginia), and increased markedly in the mid-Atlantic region (New York, New Jersey, Pennsylvania, West Virginia) (Serie 1993; Fig. 1). In the New England region (Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut), wintering numbers increased from around 6,000 during 1948-50 to between 20,000 and 30,000 today (Serie 1993).

Overall, the total number of wintering geese reached a peak of 955,000 in 1981 and has since declined 40% to 569,000 in 1993. Compounding these distributional changes in wintering numbers, the subspecies composition has also changed. The Canada goose population is composed of migrant geese (primarily B.c. canadensis and B.c. interior) that breed in the subarctic regions of Canada and resident geese (primarily B.c. maxima and B.c. moffitti) that breed in southern Canada and the United States (Stotts 1983). The number of resident geese in Maine to Virginia has increased considerably from maybe 50,000 to 100,000 in 1981 (Conover and Chasko 1985) to an average of 560,000 in 1992-93 (H. Heusman, Massachusetts Division of Fisheries and Wildlife, personal communication). This rapid increase in resident geese suggests that the migrant population has declined more than the 40% decline observed in total wintering geese from 1981 to 1993.
Population Changes
Changes in population numbers result from changes in production, survival, and movement, acting singly or in combination. Consequently, understanding the reason for population changes involves detecting variation in survival, production, and movement over time and relating that variation to changes in wintering numbers. During the 1970's, the decrease of wintering geese in the South and increase in the Chesapeake region appeared to result from increased survival of geese in the Chesapeake and possibly from movement or short-stopping of geese from the South to the Chesapeake (Trost et al. 1986). Short-stopping occurs when migrant geese winter in a more northern location than their traditional, more southern, migration terminus.

Fig. 2. Harvest rate of Canada geese in the Atlantic Flyway, 1962-92 (Harvest and Midwinter Surveys, U.S. Fish and Wildlife Service, Office of Migratory Bird Management) and eastern Canada, 1968-92 (Harvest Survey, Canadian Wildlife Service, National Wildlife Research Centre).

During the 1980's, the decrease of wintering geese in the Chesapeake appeared to result from an 11% decrease in average survival from 1963-74 to 1984-88 (Hestbeck 1994a). This decrease in survival corresponded to a 36% increase in average harvest rate for the Atlantic Flyway from 1963-74 to 1984-88 (Fig. 2). Overall, the flyway harvest rate, as a 3-year average, increased from 19% in 1962-64 to 34% in 1982-84, and then slowly declined to 31% by 1990-92. The eastern Canada harvest rate has slowly increased from 4.2% in 1968-70 to 8.1% in 1990-92. The slight decline in the harvest rate in the flyway since 1982-84 has been partially offset by harvest rate increases in eastern Canada.

Fig. 3. Production ratio of Canada geese in Quebec and Atlantic regions of eastern Canada, 1975-93 (Waterfowl Parts Collection Survey, Canadian Wildlife Service, Atlantic Region, Sackville, N.B.).

The decrease in number of geese wintering in the Chesapeake region in the 1980's was not related to changes in production. Production for migrants, measured from the Canadian data, remained constant over the period of population decline in the Chesapeake (Fig. 3). Average production recently declined during 1991-92 for geese harvested in Quebec. I also used harvest age ratios for the mid-Atlantic and Chesapeake regions to test for differences in production between these regions (Hestbeck 1994b). If the changes in wintering number resulted from changes in production, the average annual change in the age ratios would be higher for the mid-Atlantic region than for the Chesapeake region. The average annual changes were not different between these regions, however, indicating that regional production differences were not present.

		Flying neck-banded goose (Branta canadensis). Courtesy R. Gehman
The decrease in number of geese wintering in the Chesapeake region in the 1980's was not caused by migrant geese short-stopping in the mid-Atlantic instead of returning to the Chesapeake. From neck-band data, the probability of returning or moving to the different regions was estimated and indicated that, although geese traditionally returned to the same wintering area, they also changed wintering areas from year to year (Hestbeck 1994b). In years with harsher winters, geese wintered farther south than during milder winters (Hestbeck et al. 1991). Overall, the probability of returning or moving to the Chesapeake region was higher than the probability of returning or moving to any other region. When population size, survival, and movement were combined to estimate net movement among regions, the estimated net movements among regions were small and did not correspond to the changes in numbers of wintering geese. Taken together, these results suggested that the increases in the number of wintering geese in the mid-Atlantic region did not result from short-stopping of geese.

The increase of wintering geese in the mid-Atlantic most likely resulted from expanding resident populations. Resident geese generally have larger body sizes, allowing them to winter farther north than smaller-bodied migrant geese (Lefebvre and Raveling 1967). Resident and migratory-resident geese may selectively remain in the mid-Atlantic region. In addition, the resident population may be increasing faster than the migrant population because survival and production appear higher for residents than for migrants. Residents survive better partly because they are familiar with areas of food and refuge and may avoid hunting areas (Johnson and Castelli 1994). Production may be higher for resident than migrant geese because the climate is less variable and milder with a longer growing season in southern Canada and the United States than in the subarctic. Resident geese may also reach reproductive age earlier than migrant geese because the southerly growing season is longer, providing greater food resources.
		For further information: Jay B. Hestbeck National Biological Service Massachusetts Cooperative Fish and Wildlife Research Unit University of Massachusetts Box 34220 Amherst, MA 01003

References
Conover, M.R., and G.G. Chasko. 1985. Nuisance Canada goose problems in the eastern United States. Wildlife Society Bull. 13:228-233. Hestbeck, J.B. 1994a. Survival of Canada geese banded in winter in the Atlantic Flyway. Journal of Wildlife Management 58(4): 748-756. Hestbeck, J.B. 1994b. Changing number of Canada geese wintering in different regions of the Atlantic Flyway. In D.H. Rusch, D.D. Humburg, M.D. Samuel, and B.D. Sullivan, eds. Proceedings of the 1991 International Canada Goose Symposium. Milwaukee, WI. In press. Hestbeck, J.B., J.D. Nichols, and R.A. Malecki. 1991. Estimates of movement and site fidelity using mark-resight data of wintering Canada geese. Ecology 72:523-533.	Johnson, F.A., and P.M. Castelli. 1994. Demographics of Canada geese breeding in southeastern Canada and the northeastern United States. In D.H. Rusch, D.D. Humburg, M.D. Samuel, and B.D. Sullivan, eds. Proceedings of the 1991 International Canada Goose Symposium. Milwaukee, WI. In press. Lefebvre, E.A., and D.G. Raveling. 1967. Distribution of Canada geese in winter as related to heat loss at varying environmental temperatures. Journal of Wildlife Management 31:538-546. Serie, J. 1993. Waterfowl harvest and population survey data. U.S. Fish and Wildlife Service, Office of Migratory Bird Management, Laurel, MD. 68 pp. Stotts, V.D. 1983. Canada goose management plan for the Atlantic Flyway, 1983-95. Part 2. History and current status. The Atlantic Flyway Waterfowl Council. mimeo. Trost, R.E., R.A. Malecki, L.J. Hindman, and D.C. Luszcz. 1986. Survival and recovery rates of Canada geese from Maryland and North Carolina 1963-1974. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 40:454-464.

References

Conover, M.R., and G.G. Chasko. 1985. Nuisance Canada goose problems in the eastern United States. Wildlife Society Bull. 13:228-233.

Hestbeck, J.B. 1994a. Survival of Canada geese banded in winter in the Atlantic Flyway. Journal of Wildlife Management 58(4): 748-756.

Hestbeck, J.B. 1994b. Changing number of Canada geese wintering in different regions of the Atlantic Flyway. In D.H. Rusch, D.D. Humburg, M.D. Samuel, and B.D. Sullivan, eds. Proceedings of the 1991 International Canada Goose Symposium. Milwaukee, WI. In press.

Hestbeck, J.B., J.D. Nichols, and R.A. Malecki. 1991. Estimates of movement and site fidelity using mark-resight data of wintering Canada geese. Ecology 72:523-533.

Johnson, F.A., and P.M. Castelli. 1994. Demographics of Canada geese breeding in southeastern Canada and the northeastern United States. In D.H. Rusch, D.D. Humburg, M.D. Samuel, and B.D. Sullivan, eds. Proceedings of the 1991 International Canada Goose Symposium. Milwaukee, WI. In press.

Lefebvre, E.A., and D.G. Raveling. 1967. Distribution of Canada geese in winter as related to heat loss at varying environmental temperatures. Journal of Wildlife Management 31:538-546.

Serie, J. 1993. Waterfowl harvest and population survey data. U.S. Fish and Wildlife Service, Office of Migratory Bird Management, Laurel, MD. 68 pp.

Stotts, V.D. 1983. Canada goose management plan for the Atlantic Flyway, 1983-95. Part 2. History and current status. The Atlantic Flyway Waterfowl Council. mimeo.

Trost, R.E., R.A. Malecki, L.J. Hindman, and D.C. Luszcz. 1986. Survival and recovery rates of Canada geese from Maryland and North Carolina 1963-1974. Proceedings of the Annual Conference of the Southeastern Association of Fish and Wildlife Agencies 40:454-464.

Canada Geese in the Atlantic Flyway

Population Changes