One of the best-known birds of American farmlands, the Eastern Meadowlark usually delivers its bright song from a conspicuous perch. The Eastern and Western meadowlarks are so similar that at a distance only their songs and calls distinguish them. Moreover, the two may even learn each other's song where their ranges overlap. Meadowlarks are often polygamous; more than one female may be found nesting in the territory of a single male. Because the birds often breed in hay fields, their nests may be destroyed by mowing; unless the season is well advanced, they normally nest again. During migration and winter Eastern Meadowlarks band together in groups of up to a dozen birds and can be found in almost any open grassy area. In flight they keep their wings stiff, typically fluttering them a few times and then sailing.