For the Birds Radio Program: Wintering Brown Thrashers
This year there have been several wintering Brown Thrashers, including one on the Isabella Christmas Bird Count.
One of the most joyful moments of every April for me is when I hear a Brown Thrasher singing for the first time of the year. The first migrants are invariably hormonal males and their distinctive song carries a good distance, so most years I hear Brown Thrashers before I see them. Their song is long, with repeated imitations of a wide variety of sounds. Because of their close These long-tailed, rusty birds with a golden eye are closely related to mockingbirds, as one of their old names, the Ferruginous Mockingbird, attests.
This year, for some reason Brown Thrashers are turning up in north country long before spring. One was seen on the Duluth Christmas Bird Count, two different ones were found on the Two Harbors Christmas Bird Count, and one was even found on January 3 on the Isabella Christmas Bird Count. Brown Thrashers typically winter in the southeastern states west to central Oklahoma and Texas, but there are over 50 records of them found in winter in Minnesota, almost invariably at feeders. In Sam Robbins’s book, Wisconsin Birdlife, he notes that there was no record of them wintering in Wisconsin at any time during the 19th century. The first known Wisconsin winter record was on January 25, 1913. In the 1930s there were occasional records, and from 1940 on, there has been at least one overwintering Brown Thrasher somewhere in Wisconsin almost every year. Brown Thrashers have expanded their breeding range toward the north, south, and west during historical times, mostly due to the increased amount of brushy habitat as forests are cleared and as agricultural land is abandoned, and in Florida due to citrus plantations where they now feed and nest. Birds have been wintering since the early 1900s, when global warming wasn’t an issue—individuals that do overwinter are more likely to be detected, but also to survive and pass on their genes, thanks to feeders. But since so many of these overwintering birds probably don’t survive except during the mildest winters, both feeders and global warming probably contribute to this change in their wintering distribution.
Both Bob Janssen and Sam Robbins note that these winter birds are typically found at feeders, and that most of the individuals disappear by January. It’s possible they migrate late, but more likely that they succumb to predators or the cold. In their normal wintering range, they feed on a lot of berries, fruits and nuts in winter. They feed on the ground, and spend much of their time hiding in shrubbery and dense tangles, so unless you keep a brush pile or have the right habitat in or near your yard, you’re not likely to ever see a Brown Thrasher in your yard in winter. But if you do have the right conditions and do notice one, you can increase its chances for survival by setting out special treats for it. Raisins, chunks of apple, frozen blueberries, cherries, and other fruits set out on a low platform feeder or in a bowl set on the ground are all good choices for wintering fruit-eating birds. Also Brown Thrashers in balmier settings eat a lot of insects, so setting out mealworms for a wintering bird will help it a lot. One spring we opened a new box of cereal that was infested with bugs. Rather than throwing it in the garbage, I spread it under a feeder, and immediately a host of birds, including White-throated and Lincoln’s Sparrows and a Brown Thrasher, appeared and ate all the bugs. Once a thrasher discovers a special fruit and insect feeder, it’s likely to visit it regularly.
I hope by spring I’ll learn that one or more of these four visiting northern thrashers survived the winter and is off to raise a new family, a testament to the power and strength of a 2 ½ ounce bird getting by with a little help from its friends.