Baltimore County Public Schools

Office of Outdoor Science

Maryland Green Schools Project

By Thomas Melito

Maryland Green Schools

The Maryland Green School Program is a holistic, integrated approach of educating students, teachers, and the community about environmental best management practices and environmental stewardship through authentic learning. By adding Bluebird boxes to your schoolyard, your school would be partially meeting Objective Two of the Maryland Green School Program, in which they have to meet four of the seven criteria. Adding Bluebird boxes to the schoolyard allows you to satisfy the “Building Structures for Learning About the Environment” criteria.

Blue Bird Information

Background Information

Common throughout Maryland in the early to mid-1800s, the Eastern Bluebird (Siala sialis), is one of the most loved and beneficial birds in North America. During the late 1800s through the 1980s, Eastern Bluebird numbers started to decline rapidly for a number of reasons. One significant contributing factor was the loss of habitat due to human development. Bluebirds are cavity dwellers and with the spread of human development, came the loss of trees. With the loss of trees, came the lack of suitable nesting cavities needed by bluebirds to successfully raise young. Another explanation as to the bluebird decline is competition for nesting cavities from non-native species such as starlings and house sparrows. Pesticide use has also played a role in the decline of bluebird populations.

Habitat/Diet

Eastern Bluebirds prefer semi-open habitat such as forest edges near meadows and parklands. They will often perch in the open searching for their prey which during the warmer months, consists primarily of insects and spiders. During the colder months, their diet switches to wild fruits and berries. Typical winter foods include Virginia creeper, Sumac, Bayberry, Honeysuckle, Winterberry and many other berry producing vines and shrubbery.

Breeding

Bluebirds search for natural cavities or nest boxes along the edges of woods or pastures, orchards, meadows, and large gardens. Hollow limbs, holes in tree trunks, or deserted woodpecker holes are all used as nest sites. These cavities can range in height from as low as three feet off of the ground to as high as 30 feet off of the ground. Competition with starlings for these natural cavities often forces bluebirds to seek out nest boxes. The nest, built by the female, is generally composed of grass but may also include pine needles and fine rootlets. The three to seven eggs are oval and light blue in color. In Maryland, the eggs are usually laid from March to as late as August. Maryland Bluebirds often produce three broods annually. Incubation is done almost entirely by the female and normally takes 13 to 14 days, while both male and females feed the nestlings.

Installing and Monitoring a Nest Box

The following tips are useful for establishing and maintaining a successful bluebird nest box.

  • Site selection: Open areas near school fields with low or sparse ground cover and scattered trees is ideal. Poor habitat selection may result in houses with sparrows.
  • Avoid brushy and heavily wooded areas: These habitats are more suitable for house wrens which will often out compete Eastern Bluebirds for the nestboxes.
  • Face boxes towards open areas: Ideally, the entrance hole should face away from prevailing winds and have southern exposure. Bluebirds are very forgiving if you can’t meet every point. A tree or bush of suitable perch 40 to 100 feet from the box provides a place to rest for a fledgling out on its first flight.
  • Keep the boxes at least 100 yards apart: This will allow bluebirds to establish a territory around their nest box. An exception to this rule is if swallows are found in the area. If swallows inhabit the area, then place two boxes approximately 20 to 30 feet apart from one another. Swallows are territorial so if one swallow claims a bluebird box, then that still leaves the other box 20 feet away for bluebirds to inhabit. If you’re making a bluebird box trail with swallows in the area, then the next pair of boxes should be at least 100 yards away. This strategy encourages the successful nesting of both the bluebirds and the equally beneficial tree swallows.
  • Monitor the boxes: check them at least twice a week to record progress of the nesting and to control Starling and House Sparrow inhabitation.
  • Always remove House Sparrow nests (typically a nest with a hodgepodge of odds and ends such as grass, cloth, feathers, twigs and even possibly litter) immediately! After the bluebird fledglings have permanently left the box, remove the nest. This will encourage second and third broods.
  • Inspect boxes in fall and late winter: Clean and repair the box by tightening screws, adding caulking to cracks, removing nests, etc.
  • Protect the boxes from predators: Predation is a very real threat to bluebirds, even on pole-mounted boxes. The baffles prevent predators such as raccoons, snakes and cats from climbing up the pole and reaching/crawling into the box. As a result, it is recommended that a predator baffle be included on each box. Be sure to add a predator baffle below the bluebird box. A predator baffle can come in many shapes and sizes but most are metallic and circular and are attached to the pole. Below are examples of how a baffle can be made and what they generally look like. They are widely available in birding stores and online.

Predator Baffles:

  • Keep a bluebird journal: record the date, species using the box, description of nest, number of eggs, number of nestlings, number of young fledged and any other pertinent observations.
  • Share your results: send your data to one of numerous online bluebird conservancy groups.

Sample Chronology

Late January/early February: The box should be mounted and cleaned

February to mid-March: The Bluebirds are scouting out nesting sites.

Mid-March – July: Nest building, usually takes 2 – 6 days.

Mid-March – August: Egg laying generally takes 5 – 7 days with usually one egg per day

being laid for a total of 4 – 7 eggs.

Mid-March – August: Incubation takes about 12 – 14 days. While they may sit on their

eggs during the egg laying period, full time incubation doesn’t begin until

all eggs are laid.

April – August: Hatching may occur over a 24 – 48 hour period.

April – August: Fledging generally takes 17 – 18 days. When the babies are 28 days, they

can fly quite well.

April – August: The fledglings are feeding themselves by day 30.

April – August: Most Bluebirds have one to four broods per year. The further north one

goes in North America, the less the number of broods occur per year. After

each brood fledges, the nest from each nest box should be removed.

October: Clean out the nest box of any previous nests. Bluebirds are less likely to nest in

a box if it has an old nest in it. Tighten screws.

November – February: Bluebirds and other birds will often roost in the boxes in order to

stay warm.

Bluebird Box Plans and Instructions

The Bluebird Box illustrations on page five through six were a compilation of many designs available on the internet. It was created with simplicity in mind whereby the boards needed are widely available and a single box can be created out of only two different boards. It is easily constructed with either hand tools or power tools and a minimum of materials. The box should be not only durable, but easy to clean, repair, and observe the developing chicks.

Ideally nest boxes should be rough cut, and made out of cedar or cypress to last longer, but pine will suffice. Do not use pressure-treated lumber or exterior plywood as both are chemically treated and can be harmful to the Bluebirds. If rough cut wood isn’t used, groove the interior surface of the box to aid the nestlings in climbing out of the box. Be sure to use galvanized screws so it will be more successful in inclement weather.

It is possible to paint the next box exterior but under no circumstances should the interior be painted. If the exterior is to be painted, at all costs avoid using dark colors and painting the entrance hole.

Bluebird boxes should be mounted five to six feet above ground level on aneight foot section of galvanized pipe. If possible, the pole should be cemented into the ground to prevent vandalism to the entire structure. B.C.P.S. grounds crew will handle this if you contact them ahead of time. Boxes should NOT be attached to trees or poles. Attach the box at the top and bottom of the pole using carriage bolts, washers, and nuts.

Eastern Bluebird Nestbox Plans

MATERIALS LIST

  • Standard board 1" x 6" x 4' long
  • Standard board 1" x 10" x 10 1/2" long (for roof)
  • 1-5/8" galvanized screws -- approx. 20
  • 1-3/4" galvanized nail for pivot point -- 2

For Kits:

  • Drill pilot holes for screws, put in screws, disassemble (this should make it easy for elementary age students to assemble since holes will be enlarged).
  • Place approx. 20 screws and bent screw in a Zip-lock baggie.
  • Tape together the materials using packing tape.

Eastern Bluebird Nestbox Plans, Part Two

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