Certain bug eaters, like eastern bluebirds, can switch to berries and stay all year. But given the limited life of berries, most bug eaters head south, some way south.
Take tanagers, for instance. Scarlet and summer tanagers fly to South America for wintertime bugs, scarlets to western South America as far south as Bolivia and summers to Central and South America down to Peru.
So these two tanager species, along with other tropical migrants, fly roughly 3,800 miles to nest—and then return home. What makes this scenario truly quirky, however, is the 240 or so tanager species that don’t migrate. Of course, not every so-called “tanager” is closely related to scarlets and summers. And some birds with other names are, in fact, tanagers. So it’s not clear-cut.
About 60 percent of tanagers remain full time in South America. And about 30 percent of those gravitate to the Andes Mountains. Likely, they’ve chosen their respective habitats because that’s where they find the most bugs with the least competition from other bug lovers.
Come breeding season, though, even 3,800 miles away, reduced competition for food is the trade-off for the migration effort. “Our” tanagers can raise larger broods here than if they stayed "home" and struggled with only 12 hours of daylight for garnering food for themselves and their babies.
Thinking about the arduous 3,800-mile journey--facing storms, high-rise walls of glass, habitat destruction, wind turbines, absence of shelter and reliable food sources—makes me ache, wondering how birds survive the obstacle course we’ve set up for them. When I see them each spring, I’m awed by their persistence, their instinctual drive, their very existence.
Now, in early February, they're already beginning the 3,800-mile return journey north.