Virginia Bluebird Society

Bluebird Trail Monitoring Information
Clickable Links Bluebird Nesting Characteristics Equipment for Monitoring Predators and Pests Winterizing Bluebird Nest Boxes Other Cavity Nesters That Use Bluebird Boxes	Tips on Monitoring Nest Boxes: Opening the Box After the Bluebirds Have Fledged If You Find a Baby Bird
Bluebird Nesting Characteristics
Make neat, cup-shaped nests of dry grass or pine needles (may have a few feathers mixed in).
Bluebird eggs are pale blue or white (never spotted)
Nest building takes 4 to 5 days but may be built in as few as 2 days.
Early in the season, nest building may take weeks to occur, so do not clean out early nest attempts if you do not see activity for a while.
Bluebirds lay 4 to 5 eggs- one each day. The female begins incubation only after all eggs are laid so that they hatch at once [more under "Tips" below].
Average incubation time: 12 to 18 days.
Young grow and develop and are ready to fledge after 18-21 days depending on the weather and availability of food.
Bluebirds in warmer climates will make two to three nest attempts in a season.
The Bluebird Book by Donald and Lillian Stokes (p. 83) is a good reference on estimating the age of nestling bluebirds.
We have developed a Bluebird Nesting Guide sheet (click to download this PDF document) which may be of use when monitoring to keep track of what to expect each time you open an active nest box. It incorporates most of the information show above. Return to Top of Page
Tips on Monitoring Nest Boxes
Take note of adult birds seen in the area of the box.
Keep accurate records in order to keep other trail monitors on your trail well informed.
Try to know the date the last egg was laid so you can more accurately estimate when incubation begins and/or the age of the nestlings. (average hatch date is two weeks after last egg is laid).
If nestlings are 12 days or older, do not open the box. (Opening box may cause 12+ day old fledglings to fledge prematurely. When in doubt, don’t open the box.).
Monitor only during calm, mild or dry weather to prevent chicks from being chilled. Return to Top of Page
Opening the Box:
Stand away from front entrance of box.
Do not tap on the box, but make noise as you approach the box to warn the bluebirds that you are coming.
Open the box carefully in case the female is still inside, and note: number of eggs or nestlings, and approx. age of nestlings.
Also note things like partial or complete nests, nest material used, predation that may have occurred, infestations (ants, blowflies...), any work or repairs needed for box.
Record this information for bluebirds and other native cavity nesters using the box.
Make sure the box is closed securely when you leave. Return to Top of Page
After the Bluebirds Have Fledged:
After you are sure the young have fledged and the box is empty, open the box and check for any unhatched eggs and note this in your records.
Check for dead babies. Try to account for all eggs that were in the nest to get an accurate fledgling count.
Remove the old nest. If you find blowflies or their larvae, spray the box with a weak solution of pyretherin (1%) and leave the box open for 24 to 48 hrs. Return to Top of Page
Predators and Pests
Wasps - Scrape out nest, rub bar of soap on inside of roof and/or sides of box to discourage them. Keep boxes away from pine trees. The following website provides additional information on the European Paper Wasp http://bluebird.htmlplanet.com/paperwasp.htm.
Snakes - Eggs of young disappear but the nest remains intact. Predator guards eliminate most snakes but they can drop off trees. Position boxes away from trees or overhanging branches.
Squirrels, raccoons, opossums - Nest is destroyed and eggs and/or young are gone. Use Noel guard over the hole to discourage these predators.
Cats – Can jump as high as six feet straight up and kill the adult birds as they are feeding the young, or they can perch on box and pull babies out of the nest. Use wire guard over the hole to protect adults and babies.
Wrens - Can be pests on a bluebird trail. They may build "dummy" nest in many boxes and may pierce the eggs of bluebirds to reduce competition for resources. If wrens are a problem, move boxes at least 50 yards from brush or trees. By law, active wren nests cannot be removed. Wrens are native species.
Ants - Put a small amount of Vaseline around the pole way up underneath the snake guard. Be careful to keep the Vaseline away from the possibility of getting onto the feathers of the birds. If nest is infested, build a new nest out of dry grass, transfer eggs and/or young to new nest and discard old nest into a plastic bag.
House Sparrows - Adult and/or young found dead in box with head pecked in. Sparrow may start new nest on top of dead birds. Remove any house sparrow nests and eggs from box. Place nest and eggs in a plastic grocery bag and carry away from nest so predators are not attracted to the area and sparrows cannot conveniently reuse the materials for their next nest. House sparrows will re-build every week all summer long, so be persistent- they are hard to discourage. Traps are an effective way to reduce or eliminate sparrow problems. Trapped sparrows must be dispatched. Wildlife rehabilitators often accept sparrows to feed birds of prey. House Sparrows are not native species and are not protected by law. They are killing our songbirds at an alarming rate and displacing them in their nesting cavities.
Blowflies - Adult flies lay eggs in box, larvae that suck the blood of nestlings at night. During day larvae can be found on the floor of the nest box. Check under nest and check nest material for signs of larvae. Young in infected boxes may also have visible scars. Brush larvae out of box. If number of larvae is large 50+, make a new nest and carefully put young in your "handmade" nest and discard old nest into a bag. The following website provides additional information on the blowfly www.birdblowfly.com. Return to Top of Page
Other Cavity Nesters That Use Bluebird Boxes
House Sparrow - nests are sloppy and made of grass, trash, and other fibers haphazardly woven together. Nest typically fills most of the box. House Sparrow eggs are white with brown spots. (See above)
Chickadee and Tufted-Titmouse - nests are made of moss, fine plant material, animal hair and/or feathers. Eggs are white and oval-shaped.
Tree Swallows - build nests of grass that they line with feathers. Feathers can arch over top of nest box. Eggs are oval and white.
House Wren - nests are made of sticks, often nest fills the box. Eggs are white with heavy brown spots. Return to Top of Page
Winterizing Bluebird Nest Boxes
Bluebirds and other cavity nesters often use nest boxes in the winter for nightly roosting. A small group of birds may cluster together for warmth, all in the same box. Our boxes are designed with lots of ventilation so that bluebirds don't "cook" inside the boxes in the summer heat. But this ventilation can be a disadvantage to birds trying to retain the heat during the winter. On a nice fall day, inspect all of your boxes. Make necessary repairs, and make sure the inside of the box is clean and free of pests. For winterizing, we have been using the foam insulation that is used around window air conditioning units. It is easy to break into small cubes to stuff into the large vent holes between the roof of the bird box and the side wall. Flexible weather stripping that comes in a putty-like cord can be pushed or formed into the cracks along the sides of the box. Do not plug the bottom drainage holes or the box entrance. Though not necessary, it is a nice touch to gather dry grasses or use dry straw to fashion a "nest" for the bottom of the box. Just before the nesting season next spring, clean out the box again and remove the foam insulation and weather stripping from the cracks. You can save the pieces of foam in a zip lock bag for next season. In a cool, wet spring, it might actually benefit the birds to leave the insulation in the cracks to help keep the warmth in for the nestlings. Since you will be monitoring your boxes weekly, you can remove the insulation when the temperatures begin to rise. by Julie Kutruff Return to Top of Page
Equipment for Monitoring
For trails monitored by a team, we recommend assembling the following equipment in a 5 gallon bucket and keeping it in a central location where team members can pick it up prior to monitoring.
Bucket... to carry supplies. You can also turn upside down and stand on it to get a better view inside a nest box, but be careful.
Field Notebook... to keep an account of what is happening on your trail.
Pencil or Pen... to make notes in the field notebook.
Mirror... to aid in viewing inside nest boxes if it is difficult to see inside.
Gloves... oil on your hands may attract predators.
Screwdriver... for opening the box.
Alcohol Hand Sanitizer... to use on your hands frequently while monitoring to help prevent the spread of harmful bacteria.
Plastic Bags... to carry away any sparrow or old bluebird nests. Don’t drop nesting material on the ground near the box - this attracts predators. Encourage team members to bring new supplies.
Paintbrush... to clean out box. Many of us also include a toothbrush for rough spots and corners.
Small Bar of Mild Soap... used to rub on interior of next box to discourage nesting by wasps.
Note: You may also want to bring a small flashlight, camera and a pair of binoculars for your own use. Return to Top of Page

Virginia Bluebird Society

Bluebird Trail Monitoring Information

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