"Shifting Spring Weather Is Messing With Birds' Delicate Clocks"
"Timing is everything for migratory songbirds chirping away in North America's trees. If they arrive too late, they'll get only the scraps of spring's insect buffet. Plus, the best nesting spots and mates will be taken, leaving them with lackluster prospects for making baby birds. Arrive too early, and they'll face a hostile winter chill."