The
eastern bluebird (Sialia Sialis, 6.5") is a member of the thrush family, which also
includes the robin. They are blue on the head, wings, and back but are russet and white on
the chest. They like open fields where the majority of their diet of insects can be found.
The remainder of their diet consists of fruits and berries. They only migrate far enough
to stay where their food is available. They can be badly hurt if there is an ice storm in
the spring that covers the berries and reduces the available insects. They are secondary
cavity nesters. They build nests of grass and weeds in which they lay up to two broods of
blue or white eggs between March and July.
The bluebird population has been strongly affected by the actions of mankind and the
changes in land use. The bluebird population increased when Europeans cleared for farms in
the colonial and early American periods creating more habitats for them. However, later
events drastically reduced their numbers nearly to extinction in some areas. The house
sparrow (passer domesticus, 6.25") was introduced to North America in 1853 with the
intent that they would control insects. The starling (sturnus vulgaris, 8.5") was
introduced from Europe to the New York area in the 1880's. Both took a toll on the
bluebirds, as they are more aggressive, compete for the same nest sites, will kill adult
bluebirds and their young, and destroy their eggs. By 1900 the house sparrow was the most
common bird in the United States. However, its numbers began to drop when the oats used to
feed horses, on which the sparrows also feed, began to get harder to find as the
automobile replaced the horse. The house sparrow population is currently dropping at over
two percent per year but they are in no danger of becoming extinct. The bluebird
population also peaked around 1900, but began to decline rapidly, by up to ninety percent,
between 1938 and 1970. This was due to competition for nest sites, loss of habitat, the
use of DDT, and the bad winter of 1957/1958. However, people were not willing to lose the
bluebirds. In 1934 Thomas Musselman started the idea of building bluebird trails in
Illinois and William Duncan also started trails in Kentucky. Their efforts began to spread
nationwide in 1964. In 1976 Lawrence Zeleny wrote a book and a National Geographic article
that led to the formation of the North American Bluebird Society in 1978. All these
efforts led to a rebound in the bluebird population that still continues.
Kevins'
Bluebird Boxes. Kevin Stianchi and Troop 88 obtained materials, and built 27
bluebird boxes scattered along the trail. Many of them are in this area. Inside Bottom
Dimension 4” x 5½” Box is 11” high at back and 9” high at the front
with a 1.5” diameter hole.
The dimensions, location, and height of bluebird nest boxes are critical to make them a
success. As a secondary cavity nester, the bluebird must find rather than make a cavity in
which to build its nest.
Other cavity nesters are also trying to find holes and this leads to competition with the
house sparrow and starling mentioned above, and also native species such as chickadees,
titmice, nuthatches, woodpeckers, and wrens. Some of these birds are larger and can be
discouraged by using small openings on the boxes. For this reason the hole should not be
larger than 1 1/2 inches in diameter. House sparrows prefer nest boxes that are not set
low. Bluebird boxes should be set about four feet off the ground in areas where no grain
is available so they are not attractive to the sparrows. House wrens (troglodytes aedon,
5") are also major competitors for nest sites. Keeping the boxes at least 100 feet
from brush or trees will make the site less attractive to the wrens. Also, the wrens are
territorial and will prevent other wrens from using nest sites in a half-acre area. For
this reason, Kevin installed his boxes in pairs. Typical territories are: bluebirds (2 to
5 Ac.), chickadees (10 Ac.), nuthatches (25 Ac.), and titmice (2 to 5 Ac.).
A check in the spring of 1999 found four nested pair of bluebirds.
Kevin Stianchi and Troop 88 completed the boxes in January 1999.
A Flash of Blue
Scattered along the length of the trail are 27 prime real estate locations you may have
overlooked. Many of them are in this area. Who resides in hand crafted homes? It is none
other than the Eastern bluebird (Sialia sialis), a bright blue member of the thrush or
robin family.
Bluebirds are cavity nesters, seeking out existing tree holes to make their grass and moss
lined nests. These cavities have not yet formed in a young vigorous forest, and though
food items and other habitat requirements may be plentiful, a safe place to nest can be
the factor most limiting bluebird populations. Building bluebird boxes can encourage this
delightful birds return to old field areas, where plentiful food exists.
Precise hole size dimensions and box placement are needed to avoid nesting box use by
competing species such as chickadees, tree swallows, house sparrows.
Watch for bluebirds’ hunting ground dwelling insects, their main food items. During
the fall, they may also feed on sugar and fat-rich berries of fall fruiting shrubs. A
check in the spring of 1999 found four nesting pairs of bluebirds in this area.
