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 Lincoln's Sparrows are very similar to juvenile Swamp and Song Sparrows. Savannah Sparrow is similar but has a yellowish supercilium and lacks a buffy breast. Swamp Sparrow has a rusty crown, rusty wings and much less streaking on the breast.
Length and wingspan from: Robbins, C.S., Bruun, B., Zim, H.S., (1966). Birds of North America. New York: Western Publishing Company, Inc.