Few birds are held in higher esteem than the bluebird. In poetry and
prose, the bluebird is always a symbol of love, happiness, and renewed
hope. Three species of bluebird are found in North America: the mountain
Bluebird Sialia currucoides, the
Eastern Bluebird Sialia sialis,
and the Western Bluebird Sialia
Bluebirds belong to the thrush family, whose
members are found throughout much of the world. Another of North America's
well-loved birds, the American Robin, is also a thrush.
The mountainBluebird is a little larger than a House Sparrow but
smaller than an American Robin. The back, wings, and tail of the male are
a bright azure-blue, and the throat and breast are a lighter blue, which
fades to white on the abdomen.
On the female, the flight feathers
and tail are pale blue and the head and back are a mixed wash of blue and
gray. The throat is brownish-ash, blending to white on the lower breast.
Immature birds resemble females, except for the mottled breast
characteristic of all juvenile members of the thrush family.
The mountainBluebird inhabits western North America. Its breeding
range extends from the Yukon Territory, south through British Columbia
east of the Coast Range. It breeds as far east as eastern Manitoba.
The mountainBluebird is the most migratory bluebird species,
although many individuals simply move locally to southern elevations.
Like other thrushes, mountainBluebirds are ground-feeders and eat
mostly insects. Where elevated perches are not readily available,
particularly near nest sites, the mountainBluebird will obtain most of
its food by hovering in the air a metre or more above the ground in a
hawk-like manner, as it searches the earth below for food. Other members
of the thrush family do not use this hovering technique.
winter, mountainBluebirds travel in flocks, often with Western Bluebirds
and Sparrows, and feed on insects and small fruit, such as mistletoe,
hackberry, and currants. They typically begin to move north in March, but
often arrive in northern latitudes when snow still blankets much of the
ground and temperatures still dip below minus 20°C. These hardy birds can
usually withstand short spells of cold and stormy weather; however, during
prolonged severe conditions they may freeze or starve to death.
mountainBluebirds sometimes migrate alone but more often travel
in flocks of up to 50 birds (rarely up to 200). They travel during the day
at a leisurely pace, stopping frequently to feed. They can sometimes be
seen strung like brilliant blue jewels along a barbed wire fence, scanning
bare patches of ground for weed seeds and dead insects. Highly aggressive
birds, they usually sit at least a metre apart. There is a continual
flashing of blue, as first one and then another leaves its perch
momentarily to pick up a tasty morsel. After working the fence line for
some time, they disappear over the next ridge or clump of trees, leaving
behind a soft warbling song. (A louder song is heard most often in
pre-dawn hours of the breeding season.)
Before the tail end of the migration has passed through, resident
mountainBluebirds have fanned out over areas with suitable nesting
habitat. Sparsely treed grasslands, wooded ravines and valleys, badlands,
and mountains all meet the nesting requirements of mountainBluebirds, but
treeless plains are avoided.
The males often arrive first, and
waste little time in searching out suitable nesting sites: woodpecker
excavations and decayed cavities in trees are used where available. In the
treeless badlands, bluebirds nest in cracks and crevices of steep eroding
hillsides. In built-up areas, they move into machinery, nooks and crannies
in buildings, fence-posts, and utility poles. Recently, the birdhouse has
become an important nesting site.
Once the male has found cavities
to his liking, he entices a prospective mate to inspect them. The male
goes in and out of each cavity, fluttering excitedly about the female and
calling continually, all in an effort to have her accept the site. This
exuberant display may last, off and on, for hours or even days, until a
female finally condescends to try out the cavity for size. She decides
whether to accept or reject the site.
After a nest site is agreed
upon, both birds defend the immediate area. The female builds the nest of
dry grass stems and finer plant material, including thin strips of soft
bark, while the male oversees her activities and guards against intruders:
this may take anywhere from two days to more than a week.
after completing the nest, the female lays one egg each day until the
clutch, usually with five or six eggs, is complete. Occasionally there are
up to eight eggs in a clutch.
Incubation starts after the final
egg is laid and lasts for approximately 13 days. Only the female performs
this task. She sits on the eggs all night and most of the day, leaving the
nest briefly to feed. Occasionally, the male brings food to his mate.
After the eggs hatch, the blind, naked, and helpless fledglings
must be fed. The female spends much of her time the first week brooding
the young and feeding them with food delivered by the male. On a diet of
insects, including beetles, cutworms, and grasshoppers, the fledglings
grow rapidly, doubling their body weight two or three times during the
first week of life. The young birds' droppings come encased in a sac which
can be carried away by the adults, so the nest remains clean for the first
week or two. At 14 days of age the tiny bodies are nearly completely
feathered, and the young leave the nest at about 18–21 days, although the
timing of fledging is quite variable. Bluebirds are able to fly about 100
m on their first rather haphazard flight.
The young are wholly
dependent for about 3 days, and may not be fully independent until 2
months later. Approximately half of adult pairs prepare a nest for a
second brood. This is usually built in the same cavity. The second clutch
of eggs is about one egg smaller than the first. If the eggs or young of
any brood are destroyed by predators, the bluebirds will avoid the nesting
site for the rest of the season and may move as much as 200 km to a new
Groups of one or more families and other individuals
remain in the area throughout the summer and autumn until cold weather
drives them south for another winter.
Eastern Bluebird and Western Bluebird
The Eastern Bluebird, with its deep sky-blue back and crown and
chestnut-red throat and breast, is found from southern Saskatchewan to
Nova Scotia, along the east coast to Florida, and around the Gulf of
Mexico to western Texas.
The Western Bluebird, which is
characterized by a blue throat and rusty upper back and breast, shares
some of the mountainBluebird's range in southwestern Canada. It occupies
southern British Columbia through southern California into central Mexico
and northward up through New Mexico to western Montana. It is scarcer than
the mountainBluebird, except west of the coast ranges.
All bluebird species
probably were never common, as they were limited by their nesting
requirements. Their preferred habitat is sparsely treed grasslands, and
they require cavities for nesting. However, in the 1800s as colonists
spread out across North America and cleared heavily wooded areas, bluebird
habitat increased. The settlers also controlled prairie fires, which
allowed more trees to mature and develop nesting cavities.
early 1900s, the bluebird's future looked promising. But this era of good
fortune was short-lived: more settlers arrived, land became more valuable,
and many thousands of hectares of bluebird habitat were completely denuded
of trees annually for farming. Also, Europeans brought with them intruders
— starlings and House Sparrows — which had little difficulty in evicting
the bluebirds from the few remaining nest sites.
continued to decline until some naturalists felt the bluebird was doomed
to extinction. Fortunately, bird lovers across North America began in the
1920s to build bluebird nest boxes in an attempt to reverse the decline.
This conservation effort really became popular during the 1950s and 1960s.
The results have been encouraging.
Competitors, predators, and parasites
Today humans still compete for habitat with bluebirds. Forestry
practices that remove dead trees and snags reduce the available nesting
cavities for bluebirds. Some people have helped to offset this loss by
creating trails of bluebird nest boxes. Unfortunately, sometimes other
people vandalize nest boxes and destroy their contents.
bluebirds tend to arrive early enough in spring to get first choice of the
available nest boxes, they must sometimes compete for them with Tree
Swallows, House Wrens, chickadees, House Sparrows, and European Starlings.
Starlings can be excluded from the competition by an entrance hole no
larger than 3.8 cm in diameter. In addition, each of the three bluebird
species competes with the others for boxes, where ranges overlap.
Once installed, bluebirds are well able to defend boxes that are
properly designed and placed to their liking. However, where House
Sparrows are abundant they may enter a bluebird box and go so far as to
kill young and adult bluebirds. Although it is too large to enter their
nest boxes, the main avian predator of the bluebird is the American
Kestrel, a small hawk.
Domestic cats and raccoons are formidable
predators of young and incubating female bluebirds. Deer mice and
chipmunks can also be problems. Smooth metal posts will often prevent
animals from climbing up to nest boxes.
A parasitic blowfly Apaulina stalia takes its toll of
bluebirds in some areas, although it is not thought to reduce population
size. The fly lays its eggs in the bird's nest, and the larvae attach
themselves to the young birds and may kill them by sucking their blood.
This parasite can be controlled by dusting nest boxes with diatomaceous
As a result of bluebird banding programs, we now know that some
bluebirds nest when they are one year old. The age record for a mountain
Bluebird is 4 years and 10 months, and an Eastern Bluebird lived 8 years.
Banding has also shown that successful breeders often return to the same
area or nest site each year.
Contrary to popular belief, very few
young bluebirds return to nest in the area in which they were raised. In
one study area, less than 1 per cent of the young fledged were found
nesting in that area in subsequent years. Probably, many do not survive to
breed, and survivors disperse to new areas.
The erection of
thousands of birdhouses by concerned individuals and organizations has
been responsible for preventing further depletion of bluebird numbers and
in many areas has increased populations. Bluebird nest boxes need not be
fancy; wood is the best material to use.
An ideal nest box for
bluebirds would have a floor 20 cm square, walls 25 cm high, with a 3.8 cm
diameter entrance hole located 18 cm above the floor.
The top of
the birdhouse should be easily opened for cleaning. It should overhang the
entrance hole to provide protection from rain.
Two 6-mm holes
should be drilled near the top of each side for ventilation and two 6 mm
holes should be made in the floor for drainage.
Perches should not
be placed on the birdhouse, as they only encourage House Sparrows to take
If an exterior finish is desired to preserve the
wood, a woodstain is adequate. If houses are painted, a light green,
brown, or gray should be used. White is too conspicuous, and a white nest
box is often shunned by bluebirds. Dark colors absorb heat, which may
become too intense for the eggs or young in the nest box. Do not paint or
varnish the inside of the box. The interior walls should have a rough
surface to aid the bird in climbing up to the entrance hole.
location of a bluebird house is important. Houses should be placed in
semi-open areas such as pastures, fields, and rural roadsides. A fence
post in a clearing with scattered trees about 20 m away is probably a good
location. Bird houses in urban areas or near farm buildings are usually
occupied by house sparrows.
The nest box should be placed on a
post 1 m or more above the ground. It does not matter which direction the
front of the house faces.
A "bluebird trail" consists of several nest boxes
spaced 200 m or more apart and in a manner convenient for inspection on
foot or by car, to record nesting success, band young birds, and clean out
boxes in the fall. Regular inspections also allow the nest caretaker to
remove nests of House Sparrows and other intruders. Some trails may be
only a kilometre long, while the longest runs several hundred kilometres
from Winnipeg, Manitoba, to North Battleford, Saskatchewan, with hundreds
of kilometres of branch lines leading off from the main trail.
- Bent, A. C. 1964. Life histories of North American thrushes,
kinglets, and their allies. Dover Publications Inc. New York.
- Godfrey, W. E. 1986. The birds of Canada. Revised edition. National
Museums of Canada. Ottawa.
- Peterson, R.T. 1961. A field guide to western birds. Second edition.
Houghton Mifflin Inc. Boston.
- Power, H.W., and M.P. Lombardo. 1996. mountainBluebird, Sialia currucoides. Birds of North
America, No. 222 (A. Poole and F. Gill, editors). Academy of Natural
Sciences, Phildelphia, and American Ornithological Union, Washington,
- Terres, John K., editor. 1980. The Audubon Society Encyclopedia of
North American Birds. Alfred A. Knopf, New York.
Issued under the authority of the Minister of the
Minister of Supply and Services Canada, 1979, 1996
Text: Lorne Scott
revised by Judith Kennedy and Erica Dunn in 1996
Photo: Robert McCaw