Perhaps the Bushtit family tree originated in Asia where the Chinese start building a house at the roof, for that is the way the birds commence home building. Speaking of this peculiarity Finley says: This pair began weaving a roof, then a round doorway, and next started interlacing the walls of moss fibers and lichens. From the doorway a sort of hall extended down to the main living room, which was warmly lined with feathers and required considerable hunting to complete. This soft bed was not finished until after the eggs were laid. Whenever one of the birds chanced on a feather, it was picked up and carried home. Like many people they found delight in furnishing their home gradually, picking up pieces here and there as opportunity offered.
In some parts of Oregon where moss hangs in long bunches from limbs, Bushtits use this natural beginning as a starter for the nest. I saw one build by getting inside a bunch of this moss and weave it into shape. Until I watched a pair feeding their youngsters, I had no idea what a tremendous amount of insects these little Nimrods destroyed. The parents were busy from dawn till dark, at about seven-minute intervals, each bringing a dainty in the form of caterpillar, moth, daddylonglegs or some other kind of insect. Without help from feathered assistant gardeners the woods would disappear and fruit and vegetables follow suit.
Transition and Upper Sonoran zones of arid interior from eastern Oregon and western Wyoming south to southeastern California and western Texas and from western Nevada to central Colorado.