Spring's Journey North
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Weather and Songbird Migration
Primer by Ornithologist Dr. David Aborn
How to read the weather from a songbirds's point of view.
As I am sure you are aware, weather plays a very important role in bird migration. This spring, I will teach you
how to read a weather map to try to predict areas of the country that might see large numbers of migrants landing.
The Weather Channel
Let's start by looking at the general features of a weather map. The H's
and L's represent high and low pressure centers, areas of swirling air.
- The air around a high pressure center circulates clockwise
- Whereas the air moves counter-clockwise around a low pressure system.
The colored lines represent fronts, dividing lines between cold and warm air.
- Blue lines represent cold fronts, with warm air in front
(to the right of) the line and cold air behind (to the left) it. (Click for more information about cold
fronts by U. of Illinois or USA
- The red line is a warm front, with colder air in front of
it and warm air behind. (Click for more information about warm fronts by U.
of Illinois or USA Today.)
So what does this all mean for birds?
Watch the High Pressure Systems
Birds want to fly with a tailwind to help them travel farther. In the spring, this means winds moving south
to north. Headwinds, wind moving north to south (in spring), make it too difficult for birds to fly, so they are
forced to land. Bad weather, such as heavy rain, also forces birds to land.
Since highs follow cold fronts, birds will be force to land immediately following the
passage of a cold front. After the high has moved east, usually a day or two later, the birds have tailwinds and
Winds Associated With High Pressure
- On the right side of a high pressure system, the winds are coming from the north, so migrants
- On the left side, the winds are from the south, so birds take off to continue
The air around a high pressure center circulates clockwise.
Flags show direction wind is blowing from.
(Click on face of map to enlarge.)
Graphics Credit: Purdue University
So why don't birds use low pressure systems?
The reason is that low pressure systems often bring bad weather with them, so even though the winds may be right,
flying conditions are not good.
Is Today a Good Day for Migration?
Check out the Current Surface Map and test
your skills. Find the high pressure systems and look at the wind direction.
Until next week,
Dr. David A. Aborn
See USA Today's Amazing Weather Graphics!
These weather concepts can be very difficult to visualize. The following illustrations help to simplify a complicated