Purple martins are social birds with a close relationship to people. Historically, they nested in dead trees hollowed by woodpeckers, and Native Americans began providing gourds as housing for them. Settlers later built martin houses on top of buildings. The introduction of house sparrows and European starlings, combined with logging, eliminated natural cavities for purple martins, and today east of the Rockies they are entirely dependent on man-made housing for nesting habitat. Adult males are overall iridescent dark purple and take two years to acquire this plumage. Females are gray-brown with small patches of iridescent purple on the head or back, and they appear very similar to juvenile males, though young males have some purple feathers on the chest, bellies, or undertail. In Ohio, purple martin populations have been in steep decline for decades, and because they nest there exclusively in man-made housing, which is in short supply, open habitat near water is especially suitable for adding a purple martin house. They need open habitat with ample room to swoop and catch flying insects, and a house can be placed near water or in an open area, but it must be near a human house and away from nearby large trees. Purple martins are agile insect hunters that eat large amounts of flying winged insects, especially dragonflies and damselflies. They build flat nests with straw, twigs, dried pine needles, or mud, then add a layer of fresh green leaves just before the female lays eggs. They typically lay between 4 and 6 pure white eggs. Before migration, they join other colonies to create large flocks and then travel over 4,000 miles to winter in South America. European starlings can be excluded by oval-shaped holes, and weekly nest checks are important to remove house sparrow nests.