BANGOR DAILY NEWS • September 28, 2023
A majority of American songbirds are neotropical migrants. That is, they nest in the northern latitudes but winter in the tropics. That raises an obvious question. If there’s enough food for them down there all winter, why do they bother to nest up here? Fundamentally, it’s a math problem. First, North America is larger than Central and South America combined. Up here in the north, they have room to spread out. Down there, they must cram together with the abundant birds that live in the tropics year-round. There is enough food to sustain everybody in winter, but not enough to start and feed a growing family. Too much competition. Second, neotropical migrants can simply make more babies up north, where there is seasonally more food and less competition. ~ Bob Duchesne