In winter this tiny species is found in a wide variety of forested habitat types. It is usually part of large mixed species foraging flocks made up of chickadees, titmice, nuthatches, and creepers. In the summer, the Ruby-crowned Kinglet moves to higher elevations and latitudes to nest in dense coniferous forests. The nest is a small sack-like affair that hangs from a high limb. It has an entrance at the top and is made of moss, lichens, and plant down. When foraging for insects, this species often flitters up and hovers for a second near a leaf to snatch an insect sitting there.
The four-digit banding code is RCKI.