By Will Brantley
Knowing how to read a weather map may be as crucial to your hunting success as decoys and calls
Few things in waterfowling build more anticipation than an approaching cold front. These weather events greatly influence the movements of ducks and geese in the fall and winter, but because of variations in timing and intensity, cold fronts can affect waterfowl in different ways.
Other weather patterns may also stimulate significant duck and goose movements during hunting season. Heavy rain can create backwater opportunities that puddle ducks will quickly exploit, and deep snow can cover grainfields where geese have been feeding, forcing them to travel elsewhere to find food.
Because of the many excellent weather resources available on the Internet today, observing weather trends and their effect on waterfowl has never been easier. "In this day and age, there is no reason for waterfowl hunters to be surprised by the weather," says Dale Humburg, chief biologist for Ducks Unlimited. "You can instantly check the forecast for wind direction and speed, cloud cover, temperature, and precipitation. If the dew point and temperature are the same, you know there will likely be fog. All this information is available online on weather websites. There's no reason to hunt with the wind in your face, or not have a rain coat if you need it."
Weather and Hunting
Sidney Gauthreaux is a professor emeritus at Clemson University. His area of expertise is radar ornithology, or the study of bird movements with radar. "At a Doppler radar station, you can easily gauge the speed of the target on the radar," he says. "Because waterfowl are such fast fliers, they're readily distinguishable on radar." Gauthreaux's studies have shown him many weather scenarios in which waterfowl are likely to move.
Some waterfowl species such as blue-winged teal are "hard-wired" for migration. In general, these species migrate to their wintering areas around the same time each year and stay there until spring. But other species, such as mallards and Canada geese, are more likely to be in flux near the freeze line throughout the season.
"In midwinter, you see big waterfowl migrations if you have a long period of cold weather," Gauthreaux says. "But what's interesting is that as soon as the conditions stabilize and thaw, birds that flew south may travel back north. And as you enter late winter, especially in the South, we often see big waterfowl movements to the north after long periods of warm weather."
A cold front is the edge of a cold air mass that is replacing a warmer air mass. Southerly winds and a falling barometer are usually the precursors, often with clouds and precipitation. As the front passes, the winds generally shift to the southwest and then to the north. Once the front has passed, expect to see high pressure with clear skies, cooler air, and northerly winds—good hunting conditions. But not all cold fronts are the same.
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"It doesn't take much to move early- season migrants," Humburg says. "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."
Gauthreaux agrees. "Whether or not numbers of late-season birds move with a cold front all depends on whether or not they will be debilitated in getting access to food," he says.