Published: 03/17/2021

Dear Journey North Readers,

Spring migration is underway! There are lots of signs of springs here in Tennessee; wildflowers are in bloom, upland chorus frogs and spring peepers are calling, and robins and mockingbirds are nesting. The most exciting sign of spring for me, however, is the arrival of migratory birds! Swallows and martins, which both migrate early, arrived about 2 weeks ago. The first sightings of Blue-headed and Louisiana Waterthrush came in this week. Along the Gulf coast, Ruby-throated Hummingbirds have been seen, along with Northern Parulas and White-eyed Vireos. 

So how can you know when to expect migratory birds to arrive where you live? Just watch the weather, of course! Just like pilots look at the weather to avoid storms and find good tailwinds to help speed them along, birds do the same. In the spring, birds want winds coming from the south and clear skies. Watch the cold fronts (the blue lines on a weather map) and high pressure centers (the H’s on a weather map). On the right side of a high pressure system, the winds are from the north and cause migrating birds to land. On the left side, the winds are from the south and aid migration. Since high pressure systems follow cold fronts, birds are forced to land immediately following the passage of a cold front. After the high pressure system has moved east, usually a day or two later, birds have tailwinds and take off again. 

The Cornell Lab of Ornithology puts some of this information together for their “BirdCast” reports. These reports forecast the intensity of migration across the country based on weather conditions. For example, not much migration is happening in the Southeastern US as there is rain over much of the region. South of the rain, however, there is a moderate amount of migration occurring as skies are clear and winds are southerly. When those migrating birds encounter the rain, they will be forced to land. 

Start learning how to read a weather map, and then see if you can predict whether you will be seeing migrating birds in your area. I will be back next week to let you know what is happening. Spring migration is just getting underway – there is lots of excitement to come!

David Aborn