On Saturday while I was driving to work, I went past a small pond and noticed hundreds of some species of bird. I was actually surprised to see such a large flock right in Wausau but it is the time of year that they are headed south. I realized the conditions had been perfect for the birds to migrate! We had a very warm day Friday with highs in the 60's. Then a strong cold front moved through Friday night dropping the highs for Saturday back into the 30's. In addition we had a very tight pressure gradient (when a strong high and low are close to each other) which produced gusty winds out of the North. I had just experienced what I have been researching this past week for my next wonder piece.
I know duck hunting is a huge sport around the area and in this week's edition, I am going to talk about "How Does Weather Affect Ducks' Migration?"
After doing some research and speaking to a local teacher at SPASH, Duwayne Behnke, one of the main reasons a bird has to move locations is for food. If it can't eat, it has to go to a place where it is able to find nourishment. The main movement occurs in the fall when places north of us begin to get covered with snow or freeze over. This means the birds need to move their location to able to find a new field or lake with food.
Weather plays a huge role in the movement of birds especially fronts. It is also important to note that different birds come at different times. According to Dale Humburg, chief biologist for Ducks Unlimited: "In the Mississippi Flyway, you can expect cold fronts during the first half of September to be responsible for blue-winged teal movements, as well as the initial shoveler and pintail movements. Gadwalls and wigeon move sometime around mid-October, and during the last week in October to the first week in November, expect to see initial mallard movements and some diver movement. But the late migrations require a cold front that freezes things tight up north as well as snow cover. Those conditions will often put an end to the hunting in the northern Midwest, with snow cover being the exclamation point on the end of the season. If it's just cold but there is no snow, many waterfowl may delay their movement because they can still reach their food"
According to the same article they mention that the birds use the northerly winds after a cold front to migrate. At that time the winds are strong and out of the north and they help to move the bird a farther distance using less energy. Generally, most waterfowl will come behind the front to take advantage of the natural tailwind. Rain also plays a role in that the rain will put the birds on the ground since it is uses more energy for them to fly when it is raining.
So what is the perfect weather for migration? In general they say cool temps, clear skies and breezy conditions behind a cold front are perfect to get the birds heading south.
A few facts:
Most ducks migrate at speeds of 40-60 mph (if you factor in the tail wind behind a front they could be traveling up to 800 miles during an 8 hour flight. Some researchers say that it could take them 7-10 days to recover from that flight!)
They fly usually at 200 to 4000 feet but they can fly higher; there have been reports as high as 20,000 feet.
For a clip on how hunters track the cold weather please refer to "What Hunters Look For."
Meteorologist Kristen Connolly