The birds divide their lives between Central America and the Pacific northwest of North America. Central America is full of insects; the birds feed on them by scraping their beaks along leaves and twigs. Their trilling calls serve to alert others of their species to their presence, ensuring that they spread themselves out away from each other, thus making sure each has enough territory to provide him or her with ample food. Come spring, they gorge themselves, building up their fat for the long journey northward.

Primarily in what are today Oregon and Washington, the birds mate and raise their young. The males display yellow hoods and sing songs that declare their territory and attract females.

The female does most of the work of building a nest and of sitting on the eggs until they hatch, but both female and male provide the hatchlings with food. According to...