During breeding season, the birds are found in wet places such as wetlands, marshes, sedge meadows, and fallow fields. You may even occasionally find them in wooded areas along waterways. During the fall and winter, blackbirds are found in large colonies in agricultural fields, pastures, and grasslands. The birds are known to eat insects, seeds including grains, weedy seeds, and native sunflowers.
References
For more information, please see:
Cornell Lab of Ornithology- Red-winged Blackbird
http://www.allaboutbirds.org/guide/red-winged_blackbird/lifehistory
Wikipedia- Red-winged Blackbird
http://en.wikipedia.org/wiki/Red-winged_Blackbird
Video of Red-winged Blackbird
http://www.youtube.com/watch?v=q3QicOAiBXk
National Geographic
http://animals.nationalgeographic.com/animals/birding/red-winged-blackbird/