The Baird's Sparrow is similar in shape to the Grasshopper Sparrow but has streaks across the breast. Juvenile Grasshopper Sparrows have streaked breasts and can be separated by their whitish, not yellow, crown stripe and lack of dark streaks on the side of the throat. Henslow's Sparrow has olive face and rusty wings. LeConte's Sparrow has different face pattern. Other sparrows likely to be found in field habitats have longer tails and smaller heads as well as different markings (Song, Vesper, Savannah, Field, for example).
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.