The clear, “bouncing-ball” trill of the Field Sparrow is a familiar summer sound in brushy fields and roadsides of the East and Midwest. The singer is a small, warm-toned sparrow with a rusty cap, neat white eyering, and pink bill. Though still common, Field Sparrows have declined sharply in the last half-century, partly because of the expansion of suburbs, where Field Sparrows will not nest. Populations in the prairies have remained strong thanks in part to measures like the Conservation Reserve Program.