Ruby-crowned Kinglet, Jackson Bottom Wetlands, Hillsboro, Oregon on 25 November 2006 by Greg Gillson.
This tiny little bird has quite an amazing song! It is a sweet, high-pitched chanting whistle: tee-tee-tee-tee, teer-teer-teer, teeter-teeter-teeter-teet! It sings this song in the lowlands during migration starting as early as February. However, the bird itself breeds high in the mountains in June and July. In fact, the breeding habitat seems to be Douglas-fir, Larch, Grand Fir, Engelmann Spruce forests of at least 5000 feet elevation.
So why "In the backyard..."? Because from September to May these drab greenish birds can be found in the lowlands including backyards and ornamental gardens, especially with some conifers, or even blackberry tangles.
Drab? Yes, that fiery red crest is only present on males, and only when they are displaying. Most of the time the red on the crown is barely visible, even on the males. Even the call is drab, a quiet, husky did-djit. But, oh, that song!
In your field guides you may be tempted to confuse this bird with the Orange-crowned Warbler, as it also is greenish with a red crown. The warbler has no eyering or wingbars, however, spends more time in the tree-top foliage (rather than bark and branches), and behaves in a more wary manner.
The Ruby-crowned Kinglet does look much like the Hutton's Vireo, with similar white spectacles and wingbars. The vireo has a thicker, hook-tipped bill and thicker blue-gray legs. The legs on kinglets are very thin, blackish with bright yellow toes.
Kinglets glean insects from bark and branches, migrating south and downslope after the breeding season. They often appear with chickadees and other small birds in winter in a mixed foraging flock. You may find them attracted to your suet feeder.
They respond quickly and boldly to pishes and pygmy-owl imitations. During this time of agitation they display the red crest as in the photo above.