Closing Up Camp and Heading Home

By James Reddoch 

Now migration is at its peak. BirdCast estimated over 12 million birds passed over Oxford County this past week, including more than 5 million in a single night.

This morning at sunrise the forest was quiet. The drone of insects was punctuated only occasionally by a chickadee or a nuthatch. In the distance, a crow cawed. These are among the birds that will spend the winter here. But where are the migrants whose songs filled the woods just three months ago?

Only one hummingbird has visited my feeder all week. Hiking Long Mountain Trail on Saturday, I encountered only a few migrants. A yellow-bellied sapsucker hammered on the top of an ash snag. A red-eyed vireo—once heard singing incessantly across any forest—gave only a faint contact call. A little farther up the trail came the half-hearted whine of an eastern wood-pewee. It feels as if all the birds have closed up camp and gone home. In some respects, that’s exactly what has happened.

The chaotic days of establishing territories and finding mates—the reason for all that spring singing—are over. Eggs have hatched. Chicks have fledged and begun lives of their own. Now migration is at its peak. BirdCast estimated over 12 million birds passed over Oxford County this past week, including more than 5 million in a single night. All the energy these songbirds recently devoted to singing, breeding, and raising young is now focused on flying to their wintering grounds—most of it while we sleep.

Our understanding of migration is not as old as you might think. A little over 200 years ago, some believed that birds hibernated during the winter. Some even thought birds flew to the moon based on sightings of flocks passing across the face of a full moon. Bird banding, which began in the 1800s, was the first reliable tool for studying migration, but it required bands to be recovered. Gathering enough data to form an evidence-based theory of migration took time and no small measure of chance. Bird banding remains a key method today, but new technologies are rapidly transforming our understanding of when birds move and where they go.

 The MOTUS tower at Valentine Farm records the date and time when birds pass within range, but it also traces their journeys as they are detected by other towers. For example, one Swainson’s thrush recorded at Valentine Farm was tracked as it moved from New Brunswick, Canada, across the United States, over the Gulf of Mexico and Central America, and into Colombia, South America—a one-way trip of more than 4,000 miles.

Ground-based weather radar can track the mass movement of birds, and this data is now publicly available through Birdcast. The site offers migration forecasts, county-level estimates of numbers and species, and animated maps showing how migration is unfolding across the country. It is well worth visiting at this time of year for anyone interested in understanding more about the birds of our area. 

Even more detailed information comes from tiny radio tags light enough to attach to the smallest birds. A network of special towers called MOTUS Towers has been installed across

the Americas, providing unprecedented snapshots of the movements of different species, even individuals, over an entire season. The Mahoosuc Land Trust hosts a MOTUS Tower at Valentine Farm Conservation Center, and Western Foothills Land Trust hosts one at Roberts Farm. Data from these towers is available to scientists and the public. It not only records the date and time when birds pass within range but also traces their journeys as they are detected by other towers. For example, one Swainson’s thrush recorded at Valentine Farm was tracked as it moved from New Brunswick, Canada, past the farm, across the United States, over the Gulf of Mexico and Central America, and into Colombia, South America—a one-way trip of more than 4,000 miles.

So as you close up camp this year, or put away your summer clothes and stack firewood for winter, think about spring visitors we’ve enjoyed and wish them well on their travels. With a little luck, we’ll see some of them again in just a few short months.    

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