One day it’s drab outside, the next day there is a colorful bit of fluff and feathers in the front yard that has just accomplished an amazing feat of migration. Some of those birds, weighing just a few ounces, fly thousands of miles from the tropics to the northern forests.
Migrating birds navigate by using the sun and stars, the earth's magnetic field and probably mental maps. Although that means a warbler that successfully hatched and flew south last summer has to remember the route and fly it in reverse.
It’s not easy. And sometimes birds don’t make it.
Many migratory birds, such as orioles and yellow warblers, will reach their peak arrival here from mid- to late May.
The early birds, like the tiny yellow-rumped warbler, are here by late April or the beginning of May. They have found a niche in nature that allows them to arrive ahead of the feathered mob, find a spot for a nest, attract a mate and get on with the survival of their species.
The early bird can muscle in on some prime real estate for nesting, which means a better chance to hatch and raise young and have the young learn to fly. Then everyone travels south by late summer.
Birds arriving too late are pushed into marginal habitat and are less likely to successfully nest for a variety of reasons: less food, more predators and exposure to the elements.
So there’s the gamble: Arrive early and with warm weather, or even average temperatures, thrive and prosper. Arrive late, or get hit with a cold wet spring, and lose.
— Bruce Auchly, Fish Wildlife and Parks