The Effect of Mild versus Extreme Weather Conditions on the Population Size of Geese and Their Distribution throughout Vilas Park during the Fall Migratory Season
Danielle Acker, Allison Dyer, Rosanne Santilli, and Bonnie Williams
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Overpopulations of the Giant Canada Goose (Branta canadensis maximus) have created conflicts with humans in urban areas, especially as a result of the large quantities of feces left by geese in parks. As early as 40 years ago, these geese were thought to be nearly extinct due to unrestricted hunting, harvesting of eggs and draining of their wetland habitat, but due to successful breeding efforts the population significantly increased over several years and now they are commonly found in urban areas .
The Lake Wingra and Vilas Park areas create near optimal habitat due to reduced number of predators (fewer hunters), plentiful food, and immediate access to water. Goose feces contributesto eutrophication (increased amount of nutrients) and bacterial contamination of Lake Wingra.
The purpose of our study was to determine how the goose population and distribution changes in response to weather throughout various areas of Vilas Park, Madison, Wisconsin. We hypothesized that under “extreme” weather conditions, there would be fewer geese present in the park and they would be concentrated in a smaller area; and there would be more geese that are more widely distributed under “mild” weather conditions.
We took waterfowl counts during the fall migratory season, selecting 20 days that fit specific criteria for “mild” (10 days) and “extreme” (10 days) weather conditions. We recorded the time, date, temperature, and other additional weather conditions that were present. (Appendix 2)
We defined “extreme” conditions as less than 35 degrees Fahrenheit in general or less than 40 degrees Fahrenheit if another condition such as snow, rain, wind, or clouds is occurring. If the wind is greater than 15mph sustained or gusts over 20mph then it will be considered extreme. We considered “mild” conditions as days with sun or mostly sun and anything that is not considered extreme and above 35 degrees Fahrenheit
We examined relationships between these weather conditions and goose distribution and population throughout the different zones of Vilas Park (Figure 1). We reviewed ten more waterfowl counts with the same criteria from 2001 to 2007 to help support out research
Results generally supported our hypothesis: there was an average of 247.8 geese present on “mild” days and 65.0 geese present on “extreme” days. (Figures 2 and 4)
We also found that on “extreme” days the geese were confined to only a few zones and tended to be huddled together within the zones, while on “mild” days the geese were more significantly distributed throughout the park and occupied all nine zones. (Figure 4)
The research from 2001-2007 also supported our findings with an average of 424.8 geese present on “mild” days and 26.5 geese present on “extreme” days (Figure 3)
Discussion
We consider implications of our results for management of geese and make recommendations for future studies.
One implication of our results could be global climate change because most geese leave when the lake or lagoon in the park has frozen over but with global climate change it can cause one day to be very "mild" while the next to be "extreme."
Another issue we faced while doing this study was the ability to count the geese. Sometimes it is difficult to get a perfect count of geese because on some days they were huddled together or there were large populations within the park.
Another important factor is the seasonal time change. In the beginning of the fall migratory season through the months of September and October we found more "mild" days than "extreme" days. As the fall migratory season progressed we found more "extreme" days because winter was approaching and temperatures were decreasing.
There are many possible ways to help manage the growing population of the Giant Canadian Geese: education community members, landscape modification, scare devices including dogs or noisemakers, sterilization, and coating the eggs with mineral oil.
After completing the study we were also able to consider any recommendations for further studies: count the geese during an exact time of day, further specification of weather conditions, conducting study over a longer duration, and to test and retest.
Appendix 2
|
Observation Number |
Date |
Temperature in Fahrenheit |
Weather Conditions |
Mild or Extreme |
Total Population |
|
1 |
9-9 |
73 degrees |
Sunny |
Mild |
93 |
|
2 |
9-16 |
67 degrees |
Sunny |
Mild |
119 |
|
3 |
9-22 |
63 degrees |
Foggy and cloudy |
Mild |
203 |
|
4 |
9-23 |
75 degrees |
Sunny |
Mild |
247 |
|
5 |
9-39 |
63 degrees |
Mostly Sunny, Windy |
Mild |
258 |
|
6 |
10-7 |
58 degrees |
Mostly Cloudy |
Mild |
184 |
|
7 |
10-20 |
58 degrees |
Sunny |
Mild |
361 |
|
8 |
10-28 |
46 degrees |
Mostly Sunny |
Mild |
700 |
|
9 |
11-3 |
52 degrees |
Mostly Sunny |
Mild |
124 |
|
10 |
11-3 |
60 degrees |
Mostly Sunny |
Mild |
189 |
|
11 |
11-7 |
41 degrees |
Rain/Snow Mix |
Extreme |
106 |
|
12 |
11-11 |
28 degrees |
Thin Ice on Lake |
Extreme |
9 |
|
13 |
11-17 |
32 degrees |
Very Cold and Windy |
Extreme |
382 |
|
14 |
11-19 |
31 degrees |
Sunny and Windy |
Extreme |
34 |
|
15 |
11-20 |
32 degrees |
Mostly Cloudy, Windy |
Extreme |
0 |
|
16 |
11-21 |
25 degrees |
Windy and Very Cold |
Extreme |
92 |
|
17 |
11-25 |
35 degrees |
Sunny |
Extreme |
0 |
|
18 |
12-2 |
27 degrees |
Cold and Windy |
Extreme |
27 |
|
19 |
12-12 |
18 degrees |
Light Breeze |
Extreme |
0 |
|
20 |
12-16 |
2 degrees |
Mostly Sunny |
Extreme |
0 |
This table is a list of all the waterfowl counts we used for our research. All this data was found during the 2008 fall migratory season.
