I am sure you are aware, weather plays a very important role in
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
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.
air around a high pressure center circulates clockwise.
air around a low pressure system moves counter-clockwise
colored lines represent fronts: dividing lines between
cold and warm air.
lines represent cold fronts, with
warm air in front (to the right of) the line and cold air
behind (to the left of) it. (Click
for more information about cold fronts by USA
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 USA
what does this all mean for birds?
the High Pressure Systems
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.
highs follow cold fronts, birds will be forced 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
take off again.
Associated With High Pressure
the right side of a high pressure system, the
winds are coming from the north, so migrants
the left side, the winds are from the south,
so birds take off to continue
The air around a high pressure center circulates clockwise.
show direction wind is blowing from.
Graphics Credit: Unisys
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.
Today a Good Day for Migration?
Check out these weather
maps and test your skills. Find the high pressure systems
and look at the wind direction.
David A. Aborn
USA Today's Amazing Weather Graphics!
These weather concepts can be very difficult to visualize.
The following illustrations help to simplify a complicated topic: