Now that it is autumn, most Western Bluebird daughters have moved on to new territories. A few daughters stay behind with most of the sons and spend the winter with the parents. They love to eat mistletoe berries and will sleep together on cold nights all tucked into a nest box for warmth.
These lovely blue and rust colored birds only weigh about an ounce. Normally they need about 15 calories a day and 23 calories if raising young (equivalent of over 55,000 calories for a 150 pound person). During summer, they eat lots of insects but in winter, they eat mostly fruits and seeds and supplement with insects. They like tasty grasshoppers, caterpillars, beetles, ants, wasps, pillbugs, spiders and snails. For this reason they are a gardener’s friend.
The summer breeding range for these bluebirds extends north to the Pacific Northwest, British Columbia and Montana. Bluebirds are considered cooperative breeders which mean they breed as individual pairs but may have others help out at the nest. So in the spring when the parents have a new brood, the sons who have not found a mate will help out with feeding the young. Even sons who have found a mate may be feeding their own young and still help out mom and dad. What good kids they are! On average, nests with both parents and helpers have a higher success rate of fledges.
Bluebirds do not have a strong bill to excavate a cavity for a nest. They use cavities excavated by woodpeckers, or cavities in dead trees for their nests. Threats to bluebirds include loss of habitat from logging, development and grazing. Leave that dead tree on your property and check back in spring to see who has made it a home. Or put up bluebird nest boxes. Nest boxes have allowed a declining bluebird population in some parts of the country to make a comeback.