Eastern Bluebird

Fun Facts about Mountain Bluebirds

APPEARANCE:

  • Mountain Bluebirds have no blue pigments in their feathers. Instead, each feather barb has a thin layer of cells that absorb all wavelengths of color except blue. Only the blue wavelength is reflected and scattered, resulting in their blue appearance to our eyes.
  • Adult males are small and stocky, with a round head and thin bill.  The coloration of the adult males is an iridescent sky-blue overall, darker on their backside than on their underside.
  • Bluebird females of all species have duller plumage than males; this may reduce their visibility to predators.
  • Females and immature Mountain Bluebirds are mostly gray-brown with tinges of pale blue on the wings and tail.  Their bellies are mostly are rusty grayish.
  • Length:  6.3-7.9 inches
  • Weight:  1.1 ounces
  • Wingspan:  11:0-14.2 inches

SONG:

  • The Mountain Bluebird has two song types.  At dawn they make a loud emphatic chirping sound, much like the Robin.
  • During the day, they perform a soft warbling sound that is repetitious and may last several minutes.
  • Mountain Bluebirds use a soft, nasal, non-musical "tew" or "peu" note, and a high pitched "tink" to communicate alarm.

HABITAT:

  • Mountain Bluebirds seek open areas in higher elevations with a variety of short grasses, shrubs, and trees during breeding season at elevations up to 12,500 feet above sea level.
  • They like prairie and tundra edges, meadows, sagebrush flats, alpine hillsides, pastures and recently burned or clear-cut areas.
  • During the winter, Mountain Bluebirds can be found at lower elevations, in meadows, hedgerows, prairies, and grasslands with few scattered trees and bushes, pinyon-juniper and oak-juniper woodlands, as well as agricultural areas.
  • Mountain Bluebirds are generally not found in the most arid desert habitats.

FOOD:

  • Bluebirds consume about 4 grams of food per day, or about 12% of their body weight. This is equivalent to a two hundred pound human eating 24 pounds of food each day.
  • During breeding season, Mountain Bluebird mostly eat insects.
  • Their favorite foods are beetles, grasshoppers, and caterpillars.
  • In the winter season, Mountain Bluebirds eat small fruit, seeds, and insects, as available.
  • Spiders are also an important part of the adult Mountain Bluebird's diet.
  • Plant items that are eaten include grapes, currents, elderberries, cedar berries, and the seeds of sumac, mistletoe and hackberry.
  • Unlike other Bluebirds, Mountain Bluebirds are able to hover above the ground while searching for insects. This enables them to live in areas with few trees or shrubs.
  • The young nestlings are fed mostly beetles and grasshoppers.

NESTING:

  • Nesting occurs from March through August.
  • Adult Bluebirds tend to return to the same breeding territory year after year, but only a small percentage (3-5%) of young birds return to where they hatched.
  • Mountain Bluebirds are generally monogamous, staying together throughout the breeding season, and may breed together for more than one season. However, some birds may switch mates during a breeding season to raise a second brood.
  • Mountain Bluebirds are cavity nesters, but will use artificial nest boxes as well. 
  • Males look for appropriate nest cavities, but the females do the choosing.
  • The male Mountain Bluebird will look for nesting boxes or nesting cavities along roadsides that face away from the road.
  • Males may carry nest material to the nest, but they do not participate in the actual building.
  • The males spend much of that time guarding their mates to prevent them from mating with other males.
  • Female Mountain Bluebirds fill the cavity floor with coarse, dry grass stems and other vegetation, hollowing out a cup just large enough to allow her to cover her eggs.  The interior diameter of the next is roughly 2", while the cup is generally deeper than 2".  The cup of the nest is placed as far as possible from the entry to the cavity.
  • The female lines the cup with finer plant material, such as fine grass stems, narrow strips of soft bark, and sometimes narrow strips of wool or feathers.
  • Nest building can take over a week.
  • Only the female incubates the 4-6 eggs which she maintains at a temperature of 98 to 100ºF.
  • Bluebirds may raise two and sometimes three broods per season.
  • Pairs may build their second nests on top of the first nest or they may nest in an entirely new site.
  • Both sexes defend territories; however, the males tend to defend territory edges while the females primarily defend the nest site.
  • The male continues to take care of the recently fledged young while the female begins to re-nest.
  • Young from the first brood will occasionally help raise their siblings in the second brood.
  • Clutch size:  4-8 eggs
  • Number of Broods: 1-2
  • Egg Length:  0.8-1.0 inches
  • Egg width:  0.6-0.7 inches
  • Nestling Period:  18-21 days
  • Egg Description:  Pale blue to bluish white, rarely pure white
  • Condition at Hatching:  Unfeathered, helpless

ATTRACTING MOUNTAIN BLUEBIRDS TO YOUR BACKYARD:

  • Mountain Bluebirds love mealworms and can be drawn in with a small dish filled with mealworms.
  • Consider putting up a nesting box well before nesting season, as Mountain Bluebirds will use nesting boxes, if they are available.
  • Nesting boxes should be put up away from buildings, and dense woods.
  • Ideally Mountain Bluebirds like open space, with scattered clumps o trees, or low shrubs.
  • Nesting boxes should be mounted in pairs, at least 100 yards apart, with 10-20 feet between boxes in a pair.
  • The entrance hole of the nesting box should face away from prevailing winds and should be about 1.75 inches in diameter, located about 6 inches above the floor of the box.
  • About 100 feet from the box there should be a place to perch, for when the fledglings leave the nest.
  • A guard should be attached to keep predators from raiding eggs and the young.

MORE FUN MOUNTAIN BLUEBIRD FACTS:

  • Mountain Bluebirds can fly at speeds up to 45 miles per hour if necessary.
  • A Mountain Bluebird can spot caterpillars and insects in tall grass at the remarkable distance of over 50 yards.
  • Eastern Bluebirds will occasionally breed with Mountain Bluebirds and successfully raise young.

Information gathered from WBU and All About Birds.  Photo taken by JT.