Most clutches contain five or six eggs. In Pennsylvania bobolinks nest most successfully in the northwest and northeast on farmland at high elevations where cool spring and early-summer temperatures retard hay growth and delay cutting until after broods have fledged. Most cross the Caribbean and winter in South America. Many ornithologists believe the red-winged blackbird is the most populous bird species in North America. Redwings breed across the continent and as far south as Costa Rica and the Caribbean Islands.
Adults are seven to nine inches long.
Redwings arrive on the breeding grounds in late February and early March, with males preceding females by a week or two. In summer, redwings eat dragonflies, mayflies, caddisflies, midges, mosquitoes, caterpillars, beetles, grasshoppers, cicadas and many other insects. In fall and winter they turn to seeds, which make up about three-quarters of the annual diet. They consume seeds of grasses and weeds, and grains dropped by farm machinery. Flocks of red-winged blackbirds may damage corn, wheat, oats, barley, rice and sunflower crops.