February 27, 2008
Dr. David Aborn

Dear Students:

Here in southeast Tennessee we got a dusting of snow last night, but signs of spring are around. In January, bluebirds were checking out some of the next boxes I have in my yard. Last week, I heard the first cardinals singing. The most exciting sign of spring, however, is that migration is underway!

Bird Migration Depends on Right Weather
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. Just like airplane pilots (and passengers, for that matter!), birds like clear skies for finding their way, and tail winds to help push them along. Therefore, when they have southerly winds, birds can fly a lot farther. When the winds come from the north, or when bad weather comes up, birds will be forced to land. Since north winds follow cold fronts, birds will be forced to land immediately following the passage of a cold front. After the high pressure area bringing those winds has moved east, usually a day or two later, the birds have tailwinds and take off again.

First: How to Read a Weather Map
You can get a clear understanding of the words I used above with this lesson on how to read a weather map. The reward is that you'll learn how you can use that information to forecast bird migration!

Early Migrants Starting to Arrive!
Prior to the front that moved through yesterday, the temperatures had been very mild (50's-60's), thanks to southerly winds. That allowed some of the very early migrants to make their way from the tropics to North America. Birders in Florida reported their first Purple Martins, Georgia reported Yellow-throated Warblers along the coast, and someone along the Alabama coast saw the first Parula Warbler of the year.

With the change in winds, migration has been stopped in its tracks ... much to the benefit of those of us in Tennessee! We have our first martins, as well as some Tree Swallows. This is just a small sample of what will be coming over the next several weeks.

What to Expect This Week
So what about this week? Take a look at today's weather map for clues. No fronts are on the horizon, so once this high pressure area moves east, winds will shift around to the south (tail winds), allowing birds that are hear to continue north, and a new influx of birds from the tropics to arrive:

It is too early to see a large number of birds arriving, but I expect there will be an increase in the number of swallows, martins, and some of the early warblers. Dust off your binoculars and start practicing!

Take Care.

David Aborn
North Chickamauga Creek Conservancy
Chattanooga, TN