Blackbirds eat mainly insects in summer and seeds in winter. This is when an individual sticks its bill into a crevice or vegetation or beneath a rock or a stick, then suddenly opens its mandibles to push aside or pry away a screening object to expose an insect, spider, seed or some other edible item. Bobolinks feed on beetles, grasshoppers, caterpillars, ants and other insects, millipedes, spiders, seeds of weeds and grasses, and grain. They nest on the ground in moist meadows and fields of hay, clover, alfalfa or weeds. The adults land away from the hidden nest and walk to it.
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.