The Mountain Bluebird (Sialia currucoides) in the video clips below is busily building her nest. New video clips have been created showing her bringing in grasses and digging out the bowl for the eggs.

Videos: Mountain Bluebird

Western Bluebirds are a great canidate for nestboxes.
The photograph on the right is a male Mountain Bluebird (Sialia currucoides). Both the male and the female will forage and protect the nestbox. In the late fall every year we clean, sanitize and check the status of the birdbox camera inside the upper compartment of the box. The usual clutch size for Mountain Bluebirds is 5-6 eggs, but she may lay as many as 8.

She lays at a rate of one egg per day and doesn’t start truly incubating them until the last egg is laid; although she does sit on them occasionally to keep them alive. By waiting to incubate and then occasionally rotating the eggs beneath her the female bluebird is able to slow the growth rate of the eggs laid first and synchronize the hatching process. The nest was built be the female only, with the male bluebird mimicking her and carrying nesting material, but dropping it along the way. She is also the only one to incubate the eggs, although the male may feed her while she is on the nest. The male bluebird is usually engaged in protecting the nest and foraging for both himself and the female.

They may lay as many as three clutches in a single season, but most often only lay two. They will never lay three successful clutches in a single season and only attempt the third clutch if one or both of the first two clutches were unsuccessful. Mountain Bluebirds will sometimes reuse the same nest for each clutch and may even use this nest for next year’s young. Once fledged, the young will stay with the parents for anywhere from 10 days to 2 months and may greatly impact how many clutches the parents have that season.

Once hatched, she will brood for an additional week. When the nestlings are 18-20 days old, they will fledge the nest. After hatching, both parents forage for food and bring insects back to the nest for the young. If the female is in the nestboxshe will not allow the male to feed the young and controls all the food that enters the nest, eating most of it herself. The male can only feed the young directly if the female is away from the nest.  How long the fledglings stay with their parents, will determine if and when the birds return to lay a second clutch.

One of the predators that bluebirds  defend their nest from is the  Columbian Ground Squirrel (Spermophilus columbianus). The majority of this squirrel’s diet consists of grasses and plant parts, but it will occasionally eat birds, insects and other small animals.