The Wilson's Warbler is a fairly small warbler, with a long tail and a relatively short bill. The adult male has a black, shiny cap, a yellow forehead, eyering, and eyebrow. His cheeks are an olive green which matches his upper parts. The males under parts are entirely yellow. The female does not have the black cap, but might have some black on her head close to the forehead. the female has an olive crown and olive to yellow lores and forehead. I took this photo in 2010 of the first Wilson's I recall seeing in my yard in 14 years. One of my favorite warblers to watch. They are so funny darting here and there.