In April, the air at the refuge is filled with the sound of red-winged blackbirds -- what Roger Tory Peterson calls the "voice of the spring marsh." The song of males staking out their territories is especially prevalent, as is the sight of their signature red "shoulders." Redwing females are a dull-colored brown by comparison, and blend in with the reedy environment in which they build their nests.

Above: A male red-winged blackbird.