"Lincoln's sparrow has a distinctive buffy wash across the breast and is finely streaked on the breast and sides. The reddish brown crown bears a central gray stripe, and there is a broad gray eyebrow stripe as well ... It is a smaller slimmer bird than the song sparrow, with a grayer face and more finely streaked breast. Lincoln's sparrow also lacks that bird's prominent central breast spot."

The "buffy eyering" & "slender bill" (The Sibley Guide to Birds, p. 499) contrasts this with the Vesper Sparrow.

"... often raising its slight crest when disturbed (Alsop, 494)."

Compare this to the closely similar Savannah Sparrow.