orange-crowned warbler

spotted this in my back yard.
•The Orange-crowned Warbler is divided into four subspecies that differ in plumage color, size, and molt patterns. The one named celata is found in Alaska and across Canada, and it is the dullest and grayest. The Pacific Coast form, lutescens, is the brightest yellow. Found throughout the Rocky Mountains and Great Basin, orestera is intermediate in appearance. The form sordida is the darkest green and is found only on the Channel Islands and locally along the coast of southern California and northern Baja California.
•The boreal-nesting form of the Orange-crowned Warbler has one of the latest fall migrations of any warbler, not leaving its Canadian breeding grounds until late September or October.
•It is likely that most, if not all of the early fall (August and early September) reports of Orange-crowned Warblers from the eastern United States and southeastern Canada are actually dull Tennessee Warblers.
Flits through vegetation gleaning at tips of boughs, leaves, and tree blossoms; moves rapidly from perch to perch, probing with bill into clusters of leaves and moss; sometimes hawks for arboreal or flying insects.
Calls:
Song a fast trill, changing in pitch at end. Call a sharp "chip."