Eastern Bluebird. Photo © John Terpstra

Eastern Bluebird Project

The Thunder Bay Bluebird Recovery Program (TBBRP) was established in 1988 with reports of 58 Eastern Bluebird (Sialia sialis) fledglings and 97 Tree Swallow (Tachycineta bicolor) fledglings for the first summer. The establishment of the program was the result of financial assistance of two Community Wildlife Involvement Program grants and the helping hands of the inmates and staff of the Provincial Correctional Farm who, over a two year period, constructed nearly 800 nest boxes. Since then, through annual community workshops and information sessions over the past decade, those nest boxes and hundreds of others, constructed by volunteer groups and individuals, have been mounted and monitored throughout the Thunder Bay District.

Annually, wildlife watchers and bird lovers are taught how to select the right habitat for bluebirds, how and where to mount the nest boxes, how and when to monitor the nesting process and keep accurate records.

Correct habitat, careful monitoring and record keeping are the most critical elements. With these considerations respected, raising cavity nesters can be a gratifying experience. Other constructive native cavity nesters, who benefit from this program and the addition of artificial cavities, are Tree Swallow, Black-capped Chickadee, Red-breasted Nuthatch and Great Crested Flycatcher. House Wren, also native, can create havoc by puncturing or removing eggs of other birds. Also disastrous to a nest box trail are House Sparrow (Passer domesticus), imported, who will kill anything in order to take over a nest box and European Starling (Sturnus vulgaris), another import, who will oust any occupant where the entrance hole is large enough to permit their entrance.

If you have any questions, or if you would like to become involved in the project, please contact us at easternbluebird@tbfn.net.

Click on the image to view the TBFN 2023 Eastern Bluebird Project Update2023 TBFN Eastern Bluebird Project Update
Eastern Bluebird nest building. Photo © John Terpstra
Eastern Bluebird on post. Photo © John Terpstra
Eastern Bluebird feeding chicks. Photo © John Terpstra

Welcoming the Eastern Bluebird – A Guide to Successful Bluebirding in the Thunder Bay Area (click to expand)

Eastern Bluebird Trail Monitor 
Essential information and guidelines

1. Eastern Bluebird Nestbox Design

The Peterson nextbox is the style of choice as supported by current research but other designs are in use which may be more readily constructed by those with limited skills and equipment. One inch rough lumber (cedar is best) or 3/4 inch rough indoor plywood (outdoor plywood contains dangerously high levels of formaldehyde) provides essential insulation from heat and cold.


  1. Avoid painting boxes dark colours: they will absorb too much heat. Use an exterior grade latex paint and give the top a second coat. A heavy grade of linseed oil stain works well, too.
  2. Adequate ventilation is critical: drill holes at top of sides under overhanging roof.
  3. Entrance holes should be 1 1/2 inches in diameter or, if oval, 1 3/8″ by 2 1/4″.
  4. Cat ‘N Coon guards at entrance holes are recommended where there is a threat of predation by either of these predators
  5. All boxes should have a side or front that swings open so boxes can be monitored regularly and cleaned out when necessary.

2. Placing Your Eastern Bluebird Nestbox

Eastern Bluebirds will feed in areas of short grass or sparse vegetation, locating their pray from elevated perches. Install your boxes in areas that provide open space with adequate perches such as open woodlots, pastures, orchards, hayfields, large rural lawns and roadsides.


  1. Place boxes 200 yards or more from farms, feedlots, buildings, or any other areas where there are house sparrows!
  2. Avoid areas where domestic or feral cats are common.
  3. Box pairs should be placed at least 100 yards from the next pair to avoid territorial disputes between bluebird pairs. Placing boxes in pairs (20-25 feet apart) may reduce competition between bluebirds and tree swallows by allowing one pair of each species to nest in close proximity.
  4. Install boxes 4 to 5 feet above ground.
  5. Face boxes toward trees or shrubs that are within 50 feet of box so that young birds can fly easily to a perch when they leave the nest. Trees & shrubs also provide roost sites for adults.
  6. To avoid ant problems, do not place nest boxes on wooden fence posts that are rotten or deteriorating.
  7. Obtain permission before installing next boxes on utility poles.
  8. Do not place nestboxes near brushy vegetation along forest edges where house wrens will likely occur.
  9. Avoid placing nest boxes where chemicals are sprayed frequently.
  10. Discourage climbing predators such as raccoons by placing an inverted metal cone below the box or using a metal or plastic pipe covered with carbona wax or axle grease.
  11. See bibliography for additional information sources.

3. Monitoring Your Eastern Bluebird Nestbox

Eastern Bluebirds raise one or two broods per year in Thunder Bay. They begin as early as mid May and second nestings have been observed. Nests have fledged as late as August 26th for second nestings. Monitor nest boxes with these dates in mind, daily if desired but at least every 7 days. By checking this often you will observe things at the nest not seen if the boxes are checked less frequently.

Monitoring Guidelines:

  1. Assign each box a number. Record information from a particular box on an INDIVIDUAL NEST RECORD FORM every time the box is checked. Use one form from each box.
  2. Check boxes and clean them in early spring; if mice have nested take care not to inhale dust when cleaning. Beware of Hanta Virus which can be fatal to humans. Do not allow mice in boxes.
  3. Carefully peek into a box to see if the female is incubating; if she is, leave the area quietly.
  4. When peeking into nestboxes be careful in case hornet or wasp nests are attached to the top of the box (if possible, remove such nests).
  5. If eastern bluebird nests are built too high (at or just below the entrance hole) then remove some nest material to lower the nest so raccoons or other predators cannot reach into the nest. Once again DO NOT disturb a female on the nest.
  6. Avoid opening a nest box when the nestlings are close to fledging (after 12 days old) or they may get excited, leave the box prematurely and perish.
  7. To check for blowfly larvae, lift the nest at each visit. If present, these parasites will generally be found in or near the bottom of the nest box or nest material. If larvae are found, tap the nesting material to dislodge the larvae. Remove them from the box. When heavy infestation occurs (fifty or more), you may need to remove the entire nest and make a new nest from dry grasses.
  8. Remove old nests as soon as the nestlings have left if it is early in the season and there is a possibility of a second nesting and there are no vacant nest boxes nearby. Save clean, abandoned nests to be used to replace blowfly infested or wet ones as required.
  9. Whenever a house sparrow nest is found, remove it immediately including the eggs and young. Destroy adult house sparrows when caught. House sparrows and starlings are not native to North America and are not protected by law. All other species are protected and their nests that contain eggs or young should not be disturbed. Move nest boxes from areas with house sparrows.
  10. Nest boxes may be left open during the winter to avoid use by mice.
  11. See bibliography for sources of further information.

4. Record Keeping

Put your observations from each visit to a particular box on the INDIVIDUAL NEST RECORD FORM, using one form for each box. Retain these for your own records or return them with the completed annual EASTERN BLUEBIRD NESTBOX SURVEY FORM (a summary of the data for all of the houses you monitored) at the end of the nesting season (August 31). Send to the Thunder Bay Bluebird Recovery Committee (address is listed on survey form). The committee members can help you fill this out.

5. Identifying Nest Failures

To maximize the effectiveness of eastern bluebird trails, it is important to identify causes of any nest failures that might occur. The following information should help. Please complete the section of the Individual Nest Record form on causes of lost eggs or nestlings or, if unable to positively identify the cause, list as unknown.

  1. Raccoon. A relatively new predator to Thunder Bay but one from whom we will be hearing much in the future! Raccoons will eat bird eggs, young and adults, can climb nearly anything and can reach into the nest cavity to grab eggs or birds from the nest. Look for a nest that is disturbed. Claw scratch marks may be found on the nest box. Raccoons eat their food outside the nest cavity… so look for coarsely broken eggshell fragments or feathers below the nest cavity entrance or near the nest box.
  2. House Wren. Most nest losses attributed to wrens occur in nests containing eggs. The eastern bluebird (or other species) eggs are punctured and left in the nest, or are removed after being punctured and either dropped beneath the cavity entrance or carried away. The puncture holes may be very small. Wrens may build their nest on top of these eggs, so check underneath wren nests which are built over active eastern bluebird nests.
  3. House Sparrow. They destroy eggs but frequently kill young and adult eastern bluebirds by pecking at their scalps. Look for eastern bluebirds with substantial damage to the scalp region. Feathers will be missing and blood will be found. House sparrows frequently build their nests over the corpses of their victims. Avoid placing nest boxes where these deadly predators exist such as near farmyards and in towns and cities.
  4. Red and Flying Squirrels. Squirrels will enter the nestbox and, unlike raccoons, squirrels eat the eggs inside the nest cavity where small fragments of eggshell may be found. They can be a problem near pine trees.
  5. Other. Other types of nest failure that are uncommon include humans, wasps and house cats. Unless you actually observe these types of predations, record nest failures as unknown. Vandalism can sometimes be a problem, too.
  6. Heat. During extended periods of hot weather, part or entire broods of both eastern bluebird and tree swallow young may die in nestboxes from overheating. This type of nesting failure can only be proven when individual nest boxes are checked every day. If you suspect that a brood may be suffering from heat, you may want to check that box more frequently.
  7. Cold. If the weather is cold, cover the side ventilation holes and the horizontal space above the door with duct tape to prevent heat loss. DO REMOVE IT if the temperature rises to the norm.
  8. Blowflies. Nesting birds are often parasitized by blowfly larvae (Apauline spp.). Adult blowflies lay their eggs in the bluebird’s nest. After hatching, the larvae feed on the blood and body fluids of the bluebird nestlings by attaching to their feet, legs, abdomen, bill, or wing and tail feather shafts. They feed mostly at night and drop from the nestlings during the day, returning to the bottom of the nest box. Up to 85% of eastern bluebird nests may be parasitized by these larvae. Artificial nest boxes appear to contain more larvae than natural cavities, with larvae more numerous during the late summer nesting period. A single nest may contain as many as 250 blowfly larvae. When heavy parasitism occurs, the nestlings are weakened and sometimes killed. To determine if there are larvae in the nestbox, gently lift the nest material at each visit and look for the larvae on the bottom of the nest and in the material. If larvae are found, estimate how many larvae are present and report this in the “comments” section of your INDIVIDUAL NEST RECORD FORM. Remove the larvae by scraping them from the bottom of the box. Dispose of them. Construct a new nest from dry grass if the blowfly count appears to number more than 50.

6. Bird Species Commonly Found Nesting in Eastern Bluebird Nest Boxes

  1. Eastern Bluebird: Found in farmlands, roadside fencelines and open woods. A loosely built cup is made of fine grasses, weed stems, and occasionally pine needles. Three to six, commonly 4 to 5, pale blue, bluish white, and occasionally pure white unmarked eggs are laid. Incubation is by female for 13 to 15 days. Eastern Bluebirds in Thunder Bay sometimes have a second brood. This was especially true in 1998 when the practice of second nestings was observed on many Bluebird trails in the Thunder Bay area.
  2. Tree Swallow: Found in marshes, wooded swamps, open woods, and fields. Nest is built in any suitable cavity. Nest material is an accumulation of dry grasses, usually lined with feathers; 4 to 6 smooth, oval eggs are laid. Eggs are pure white. Incubation is by female only, and it lasts for 13 to 16 days; they raise one brood.
  3. House Wren: Found in farmlands, open forests, suburban areas and parks. The male arrives first and sets up a territory, building dummy nests made of twigs in all available nest sites. The female chooses one of these nests, and she builds a cup of grasses, plant fibers, rootlets, feathers, hair and rubbish; 5 to 8 eggs are laid. Eggs are smooth and oval, white and thickly speckled with minute reddish or cinnamon brown dots. Inclubation is by the female for 12 to 15 days. Can raise 2 broods. Note: a House Wren may destroy the nest, eggs and young of other birds nesting within its territory. The wren will commonly poke holes in the eggs of other bird species.
  4. Black-capped Chickadee: Found in deciduous or coniferous forests and rural and suburban woodlots. The bottom of the cavity is filled with moss and a nest cup lined with wool, hair, fur, moss, feathers, insect cocoons or cottony fibers; 5 to 10, commonly 6 to 8, oval, smooth-shelled eggs are laid. The eggs are white, rather unevenly spotted and dotted with reddish brown. Incubation is by the female for 12 to 13 days.
  5. House or English Sparrow: Found in cities, farms and parks. Nest is a huge ball of grasses, weeds and trash with an opening on the side. The inside of the nest is lined with many feathers, hair and string; 3 to 7, commonly 5, oval, smooth-shelled eggs are laid. The eggs are white to greenish white and are spotted with grays and browns. Incubation is by the female for 12 to 13 days. Normally 2 broods are raised. Note: The House Sparrow is an exotic species that is very aggressive and competitive with native cavity-nesting birds for available nesting sites. Sparrows kill young and adult bluebirds by pecking at their heads. They sometimes build their nests over the dead bodies of their victims. For these reasons it is important that House Sparrows be prevented from nesting in Bluebird boxes. Remove any nests that can be positively identified as a House Sparrows’. Check the box often because they are persistent nesters. If you cannot deter the House Sparrows from using a particular box, stuff the entrance to the box with a rag or grass or cover with duct tape for several days to prevent it from nesting and leave the entrance blocked until you see or hear that the Bluebirds and Tree Swallows have returned, usually by May 18th or earlier if a warm spring. DO NOT ALLOW THE HOUSE SPARROWS ON YOUR TRAIL! Trapping the male (especially) may be the only way to get rid of these deadly predators; otherwise, remove your boxes. Do not put Eastern Bluebirds or other native birds at risk!

These plantings will attract and feed birds including Bluebirds:

Remember, the best trail, even if it is only one pair of nestboxes, is a closely monitored trail!

  • Serviceberry
  • Red Osier Dogwood
  • Cotoneaster
  • Hawthorn
  • Bush Honeysuckle
  • Russian Olive
  • Tartarian Honeysuckle
  • Flowering Crabapple
  • Sweet Gale
  • Virginia Creeper
  • Chokecherry
  • Pin Cherry
  • Sumac (smooth)
  • Poison Ivy
  • Raspberries
  • Alderberry (red)
  • American Mountain Ash
  • Showy Mountain Ash
  • Nanny berry
  • Downy Arrowwood
  • Highbush Cranberry
  • Common Buckthorn (alder leafed)

Recommended reading:

  • Brunell, Dr. Shirl 1988
  • I Hear Bluebirds
  • Vantage Press, Inc. 115 pp.
  • Grooms, Steve and Peterson, Dick 1991
  • Bluebirds!
  • NorthWord Press, Inc. 160 pp.
  • Scriven, Dorene H. 1999
  • Bluebird Trails: A Guide to Success 3rd Edition
  • Copyright 1999 by the Bluebird Recovery Committee of the Audubon Chapter of Minneapolis, National Audubon Society. Published by: Bluebird Recovery Program, Box 3801, Minneapolis, MN 55403 210 pp.
  • Toops, Connie 1994
  • Bluebirds Forever
  • Zeleny, L.W. 1976
  • The Bluebird: How you can help it’s fight for survival
  • Indiana Univ. Press, Bloomington. 170 pp.