This is a species of rather open shrublands, riparian cover, forest edges. Like most warblers, the Orange-crowned is mostly a foliage gleaner, feeding on insects (Let's hear 3 cheers for insects!), but the diet also includes a few seeds, small fruit and insect galls. Some birds even regularly visit sapsucker drillings for sap or sugar feeders set out for hummingbirds.
Orange-crowned Warblers are perhaps our most obscure regular warblers. They are dull greenish birds with a grayish supercilium, a rather thin bill, and greenish-yellow underparts marked with faint dusky longitudinal streaks. The undertail coverts are greenish-yellow, but there may be a small white dot around the vent. A small yellow patch under the tail helps identify this small warbler. The orange crown is usually hidden except during courtship when it can be seen flickering up and down. They have no wing bars.
The song is a weak, slurry trill, "brrrrrrrrr-r-r-r-" that either drops (usually) or rises in pitch at the end.
Below are other webpages with more info on this bird: