 
With Doug Collicutt
As seen in the Winnipeg Free Press, Sunday
Magazine, Nov. 12, 2000.
Snowbirds go further south than our geese.
OK, hands up, who knows where our Canada geese
go for the winter? And by our geese, I mean just the ones that come to
Manitoba in summer to breed. Now, hands down, all of you who were going
to say "south" or anything else as vague, like "the States" or "Central
America".
Don't know? Well, neither did I until last week.
Like so many of you, I took it for granted that Canada geese flew south
for the winter, and I didn't think about it any further. They're most
obvious to us in southern Manitoba during their spring and fall migrations,
when large flocks rest and feed along the way north or south. But once
they're out of sight, they're out of mind.
I didn't know where the geese went, but I knew
who would, so I called up Murray Gillespie and Garth Ball, waterfowl specialists
at the Wildlife Branch, Manitoba Conservation and asked them. Here's what
they told me.
Each spring, nearly half a million Canada geese
arrive in Manitoba to breed. By autumn there may be one and a half million
birds, parents and their young, ready to head south. (Natural and hunting
mortality will trim the numbers back by the time they return again.) But
they don't all go to the same place. There are many different populations
of Canada geese in North America. Each population has its own breeding
and wintering grounds, and the birds are pretty faithful to these. Geese
mate for life, and have a strong urge to return to where they were born
to raise their own young. Young birds learn the migration routes and the
location of the wintering and breeding grounds from their parents and
other adult birds. And it's on the wintering grounds that young birds
find their mates from within their own population. So, the populations
don't mix much.
Five different populations of Canada geese have
all or part of their summer breeding grounds in Manitoba. The furthest
south that any of these goes in winter is southern Illinois. The Eastern
Prairie population, that breeds as far north as Churchill, can travel
as much as 2400 km to winter in the region around Swan Lake Refuge in
Northern Missouri. The Mississippi Valley population, that breeds around
York Factory, also travels up to 2400 km, concentrating for the winter
near the Horseshoe Lake Refuge in southern Illinois. The Western Prairie
Population, which breeds in western Manitoba, travels about 1600 km to
southeastern South Dakota and northeastern Nebraska. The Rock Prairie
population spends summer in southeastern Manitoba; the geese at the Alf
Hole Sanctuary in Rennie belong to this group. They fly only about 1000
km to the Rock Prairie Refuge in southern Wisconsin. And finally, the
Interlake-Rochester population breeds in the Interlake and winters near
Rochester in southeastern Minnesota, traveling only about 1000 km as well.
The geese usually wait for the weather here to
turn bad - heavy snow and marsh-freezing cold - before leaving. They also
take advantage of favourable winds to make their actual migration flights.
If they can couple their 60 km/h air speed with a 40 km/h tail wind, that's
100 km/h ground speed. There are records of the Interlake Population making
the trip to Rochester overnight!
Why only that far south; why not all the way to
the Gulf of Mexico? Well, why go any further than you have to? Geese aren't
like human snowbirds, looking for warm weather get-aways. Migration is
expensive for them. It is a heavy tax on their annual energy budget. The
geese only travel as far as they have to, to reach open water and available
food. Open water affords protection and the waste grain in farm fields
provides ample food.
Once on the wintering grounds, the geese focus
on loafing around, conserving energy. Feeding sorties are interspersed
with lots of inactivity and plenty of sleep through the long winter nights.
Some populations of Canada geese used to winter
much farther south than they do now, and human activities may be the reason
this has changed. Modern farming practices, which result in lots of waste
grain; industrial activities, like power plants that keep water bodies
open; and hunting pressure, a serious disincentive to going further than
necessary; have shifted the wintering grounds of some populations further
north.
Have human activities altered more than just where
the geese overwinter? What about their numbers and the impacts that millions
of geese are having on their and our environments? More next week.
So how would you like a million and a half geese
descending on your locality for the winter? A little more on goose numbers
and their impact next week. |