In the last column, I provided tips on how to predict when migrating birds are likely to be seen in your local patch. Experiencing a fallout of migrants is exhilarating. In today’s column we will explore ways that you can experience migrating birds while they are in flight.

Some birds migrate during the day. We have all thrilled to Canada geese or double-crested cormorants winging their way in V-formation to more favorable areas. Hawks, eagles and falcons are diurnal migrants as well. They are adept at taking advantage of the vertical winds, called thermals, that form during the day because of uneven heating of the earth’s surface.

A rocky outcrop will warm more rapidly than an adjacent forest. The rocks warm the air, and the air rises and is replaced by cooler air from the adjacent forest. That cool air warms and rises. Hawks are masters at soaring from thermal to thermal, scarcely beating a wing.

A sunny day with winds in the right direction produces spectacular numbers of soaring migrants. Mount Agamenticus in York and Cadillac Mountain in Acadia National Park have several thousand raptors migrating over them each fall. Bradbury Mountain in Pownal can be great for spring hawk migrants.

Hawk watching is a boom-or-bust activity. Make sure the weather is right and you may be rewarded with more hawks than you can follow.

Shorebirds and most of our songbirds are nocturnal migrants. The risk of predation from raptors is low. The air is cooler; migrating birds raise their metabolic rate so high they must constantly dump heat or they will overheat. The cooler air helps them balance their heat budget. Finally, the air is less turbulent at night, making powered flight more efficient.

Migrating songbirds mostly migrate at 2,000 to 4,000 feet. Shorebirds may fly a bit higher.

How can you see these birds at night? Get your binoculars or better yet, a spotting scope and train it on the moon. If there’s migration, you will see the silhouettes of birds passing in front. Don’t expect to see birds flying at their normal migrating height, but as birds take off or descend, they are easily seen against the moon. The technique works well for birds that are no more than several hundred feet above the earth.

You can also appreciate migrating birds at night from radar. In the early 1940s, mysterious blips were detected on radar screens. The echoes were called angels. Now we know they were small flocks of birds.

The Doppler radar used now for weather forecasting is perfect for detecting bird migration. Here’s the URL for a great tutorial on how to use the freely available Nexrad radar images to monitor migration:

Yet one more way to appreciate nocturnal migration is to use your ears. Nocturnal migrants are noisy, regularly emitting short flight notes. In some cases the flight notes are similar to the calls the birds give while on the ground. But in many cases the flight notes are only given during a night flight.

Bill Evans has been a pioneer in the study of nocturnal flight calls. Visit his website at He has sonograms for a number of warblers and sparrows.

On a night that’s not too windy, you can hear the flight notes. But a microphone will capture many more. Evans provides directions on how to build a microphone system using cheap materials like a plastic flowerpot, saran wrap, a dinner plate and an inexpensive microphone.

Herb Wilson teaches ornithology and other biology courses at Colby College. He welcomes reader comments and questions at

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