Weather and Songbird Migration Primer by Ornithologist Dr. David Aborn How to read the weather from a songbirds's point of view Dear Students: 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. The air around a low pressure system moves counter-clockwise . 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 of) it. (Click for more information about cold fronts by U. of Illinois or USA Today.) 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. (What winds would be favorable for fall migration?) Headwinds (in springtime, wind moving north to south; in fall, wind moving south to north) 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 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. Winds Associated With High Pressure On the right side of a high pressure system, the winds are coming from the north, so migrants land. On the left side, the winds are from the south, so birds take off to continue High Pressure 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: Unisys Weather 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. Dr. David A. Aborn David-Aborn@utc.edu See USA Today's Amazing Weather Graphics! These weather concepts can be very difficult to visualize. The following illustrations help to simplify a complicated topic: High Pressure System Low Pressure System Warm Front Cold Front Copyright 2001 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form