When junipers have heavy berry crops, western bluebirds (Sialia mexicanus) may gather in the hundreds to feed on the berries. Late last month Leonard and I came across a juniper tree teeming with western bluebirds while checking fence on our ranch near Lookout CA (Modoc County). Immature western bluebirds, including this pictured bird, were gorging on the abundant juniper berries along with the adults.
Bluebirds nest in cavities, such as natural holes in trees, old woodpecker holes or birdhouses. The nest is loose cup of twigs and weeds lined with fine grass. The female incubates 2 to 8 pale blue (occasionally white) unmarked eggs for 12 to 17 days. Both parents bring food to the nestlings. After 18 to 25 days the young birds fledge.
This immature western bluebird, strongly spotted dark on underparts and dull upper parts, may mature into a male with a rich blue head, wings and tail and orange chest or a duller female.