DATA Series

Summary
Explore trends in Canada goose populations using data from the National Audubon Society’s Christmas Bird Count.

Objectives

• Explain the differences between migratory and resident Canada goose populations.
• Assess Canada goose population numbers by graphing historical count data.
• Predict Canada goose population trends and explore trends in your area.

Introduction
With fall upon us, you may expect to start seeing flocks of Canada geese heading south for the winter. Though Canada geese seem to be abundant they may not be migrating, they may be content just to stay where they are.

Easily recognizable by its sleek black neck and head and its white cheek patches, the Canada goose (Branta canadensis) is a familiar waterfowl to many throughout the U.S. and Canada. They thrive in parks, on golf courses, and near agricultural lands, so much so that they are often considered a nuisance. With populations of Canada geese booming, why are regulatory agencies concerned with bringing population numbers up? The fact is that there are two separate populations, migratory geese whose numbers are seriously low and resident geese whose numbers are soaring, creating a complex management situation.

Both the migratory geese and resident geese are the same species. They look alike (though resident geese are often larger), graze on short grasses and generally mate for life. They nest in a variety of habitats near water beginning at age three, and produce around six eggs per clutch. The major difference between the two groups is that migratory geese summer in Canada and the northern U.S. and winter in the southerly latitudes, whereas resident geese do not migrate. They stay in the same location year-round ranging from southern Canada to the middle U.S.

Migratory populations were high in the mid-eighties, but then began rapidly declining due to hunting pressure and low gosling survival. By 1995, migratory populations had dropped by 40% causing both U.S. and Canadian regulatory agencies to put a ban on hunting Canada geese. As the migratory population was dropping the resident population began to rise. The success of the residents may be due to a number of factors:

• Larger body size enables them to better survive winters
• By remaining in more southerly latitudes year-round they have a longer and less variable growing season
• By staying in the same place they are more familiar with the area and can more easily find food and habitat

As wildlife managers try to bring migratory population numbers back up, they are also trying to control resident populations. Besides being competition for migratory populations, resident geese destroy crops and may pose a health hazard. Concerns are that the waste from large numbers of geese, which may carry harmful bacteria such as E. coli may pollute the water and soil of our recreational areas, though this has not yet been proven.

Data Activity
For this month’s data activity, we will use the National Audubon Society’s Christmas Bird Count to examine Canada goose populations since 1950 in the four North American migration flyways. The Christmas Bird Count (CBC) conducted Dec. 14 – Jan. 5 is the world’s largest volunteer bird count and has been conducted for the past 101 years.

The four sample sites we will look at are Southern Nassau County, NY (Atlantic Flyway), Lakewood, OH (Mississippi Flyway), Wichita, KS (Central Flyway) and Seattle, WA (Pacific Flyway). You can choose to look at one or all of these locations.

To access the data, go to the CBC Database. For Step One, find a CBC Count Circle by Option C: Count Code, enter one of the following 4 letter abbreviations:

• NYSN = Southern Nassua County, NY
• OHLK = Lakewood, OH
• KSWI = Wichita, KS
• WASE = Seattle, WA

Click on Find Count.

For Step Two highlight or select the code and click on the “Add” button to add your count code to your query

For Step Three select your date range:

• County Year Start: 50 (=1950)
• Count Year End: 65 (=1965)

for Step Four hit the Make a Table button. Record the data for Canada goose, and repeat three more times changing the starting counts to 65, 80 and 95 to get the data for 1965-2006. Graph the number of geese observed over time. (Tip for Microsoft Excel users: Simply select and copy the data for Canada goose and paste in an Excel spread sheet then use the chart wizard to create an XY scatter graph).

Discussion Questions:

• What trends do you see in the numbers of Canada geese observed over the years?
• How do you think this ties in with the migratory vs. resident populations?
• What do you expect the numbers to do in the future?

To see what the goose population is doing near you, find a CBC Count Circle in your area. Go to the CBC database and select your state or province under Step One and click on the “Find Count” button. For Step Two select or highlight the area closest to you and click on the “Add” button to add your area to your query form. For Step Three select a date range for your location. For Step Four click on the “Make a Table” button to see the Canada goose data for the area closest to you.