The Song Sparrow can be told from the Lincoln's Sparrow by its larger bill, heavier streaking on the breast and flanks, lack of buffy color on the breast and face, brown back, larger size and longer tail. Juvenile Song Sparrows are very similar to juvenile Swamp and Lincoln's Sparrows. Savannah Sparrow is similar but smaller-billed and shorter-tailed with a yellowish supercilium. Fox Sparrow is much larger.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.