While some bluebirds overwinter in Wisconsin, most migrate south in the fall. Bluebirds arrive as soon as early March in Wisconsin, depending on the weather and remaining snow cover. By late March most bluebirds have returned, and nesting begins in early April.

Bluebird nests are made of fine grasses or soft white pine needles woven into a neat nesting cup just 3 or 4 inches wide and up to 3" deep, made by the female taking 1 to 7 days.

Bluebirds lay normally 4 to 6 light blue eggs, smaller and lighter color than their cousin, the Robin.

They lay one egg per day, then begin incubating so that they all hatch together, usually in 13 or 14 days.

The young hatchlings grow and remain in the nest for 17 to 20 days, depending on the food supply and brood size, till they leave the nest as fledglings. Thus, the entire process of raising a bluebird brood takes about 6 weeks; then a week or two later the hen may nest again in the same box, especially if the old nest is removed.

Bluebirds live mostly on insects during the warm months when insects are common and active, including caterpillars, crickets, grasshoppers and spiders.

They hunt for these ground insects by perching on tree branches, posts and wires and then flying down to capture them.

In early spring and fall when insects are scarce, they switch to eating the fruits and berries of many plants, including wild grapes, Virginia creeper, bittersweet, viburnum, hawthorn, crab apples and sumac.

Asking any known Bluebirder, contacting BRAW, and seeking the help from a Wisconsin County Contact (CC) is the first place to start.

Most CCs can provide advice for locating boxes, assist in building or providing boxes, and show how to monitor boxes.

They might also be able to help with the cost of setting up a trail. There are trails available for a new monitor to take over from a retiring veteran.

The most recommended nest box is the NABS-style, which has an oval-hole preferred and a nesting cavity not larger than 4" by 5", with the hole 4" to 6" from the floor, and a side-opening door that swings downward.

Other boxes that have most of these features and have been proven to be highly effective in producing bluebirds are the Peterson box, the Simple box, and the Troyer Slot Box.

Peterson Box

The Peterson nest box is a classic and highly successful design. It features a slanted front, which sets the angle for the birdhouse. The entrance hole is crucial for attracting bluebirds: 1-1/2" diameter for eastern bluebirds and 1-9/16" diameter for western bluebirds. These dimensions prevent larger and more aggressive species like starlings or sparrows from taking over the nest1.

Here are some key features of the Peterson nest box:

• Insulated Design: The 2x4 inner roof, back, and floor help insulate the box.

• Effective Placement: Placing bluebird houses by late winter ensures that bluebirds can nest in early spring.

• Easy Assembly: The Peterson box is straightforward to build from cedar, redwood, or pine.

• Regular Maintenance: Periodic cleaning is essential for maintaining a healthy nesting environment.

Simple Nest Box

A simple nest box that is suitable for small cavity nesting birds such as Eastern Bluebirds, House Wrens, Black-capped Chickadee, etc.

Some key features to consider when building a simple wood nest box for these small birds:

1. Entry Hole Size: The entry hole should be approximately 1.5 inches in diameter. This size allows bluebirds to enter while keeping out larger, unwanted species.

2. Dimensions: The nest box should have dimensions of at least 9 x 4.5 x 4.5 inches (though larger is better). A spacious interior provides a comfortable nesting space.

3. Good Drainage: Ensure that the box has proper drainage to prevent water accumulation inside.

4. Good Ventilation: Adequate ventilation helps regulate temperature and humidity within the nest box.

5. Monitoring Features: Consider adding features that allow easy monitoring, such as a hinged roof or a side panel that opens.

6. Protection: Protect the nest box from predators by placing it away from easy access points for squirrels, raccoons, and other animals.

Troyer Slot Box

The Troyer Slot Box is designed to be sparrow-resistant and is approved by the North American Bluebird Society. Some of its features include:

• A slanted front design.

• A smaller “cupped” nesting cavity.

• A horizontal-slot entrance.

• It opens easily for monitoring and cleaning.

• Research indicates that it is rarely used by house.

Unlike traditional round holes, this design deters sparrows from entering. The slot allows sunlight to filter in, which sparrows dislike, as they prefer dark cavities.

To see building plan for the Troyer Slot Nest Box, open this document. --> Troyer Slot Box.pdf (nabluebirdsociety.org)

Three designed plans for birdhouse plans for Eastern Bluebirds available HERE.

Skylight Nest Boxes

Boxes with plastic skylight roof openings have proven to somewhat discourage House Sparrows. However, they have not been proven to reliably attract nesting bluebirds, although Tree Swallows do readily accept them.

The open hole should face east, south or southeast to allow as much early morning sunlight to warm up the box, and limit the cold, wet north and west winds in early spring.

Absolutely!

Either a Noel wire guard or the Lucey Improved Predator guard with landing strip will keep racoons, opossums, cats, hawks, and owls away from eggs and chicks.

Nost box with Noel guard attached.

10. What is a good location for a nest box? Boxes should be set up in open, short grass areas within 20’ to 50' from a tree, post, or fence wire so the nesting couple can perch to look out for predators before entering the box, hunt for insects, and so the young have a place to land safely when they fledge. Keep away from houses, feedlots, farmyards or other places with House Sparrows, starlings, and wrens present.Locating Nest Boxes

What is a good location for a nest bBoxes should be set up in open, short grass areas within 20’ to 50' from a tree, post, or fence wire so the nesting couple can perch to look out for predators before entering the box, hunt for insects, and so the young have a place to land safely when they fledge. Keep away from houses, feedlots, farmyards or other places with House Sparrows, starlings, and wrens present.

Bluebirds need as much as 1 or 2 acres of short, sparse grass habitat to have enough territory to find the food necessary to raise a brood of 4 to 6 chicks.

If the neighboring property and yours are too wooded, brushy, or located close to farms and folks feeding cheap bird seed, they may sense that your yard has too many predators and competitors nearby.

Boxes should be checked (monitored) at least once in 7 to 10 days to see what is happening inside and to catch and correct any problem arising.

Things to do when checking the nest box:

• Record if a nest is present and what degree of it is completed.

• Count the eggs and determine what species is using the box.

Later on...

• Estimate when the last egg was laid, when they may hatch and when the young will fledge or have fledged.

Will bluebirds attempt a second or third nestingYes, that is why it important to clean out nest boxes as soon as the first hatch fledglings have left the nest.

Likewise, remove abandoned first nests that have infertile eggs or dead chicks in them.

How can I report nesting resultsGo to www.braw.org under “forms” to obtain a printable form for keeping track of nesting events during the season (Field Activity Collection Forms).

Submit results by September 30th, do this using one of our Nest Box Data Report Form.

Both forms are found under forms. T

Two nest box data report forms are available:

1) print -to-mail formm adn 2) an online form form options

ANTS:

If a nest of young is infested badly with ants, it may be necessary to move the chicks into a new nest you make from dried grass or needles, or into an unused nest you've saved.

Remove any ants that remain in the nest or box, then sprinkle a tablespoon of cinnamon on the floor of the box, and some more around the pole at the ground to deter them from crawling up the post.

Replace new nest and nestlings. One Bluebirder used this technique successfully 5 times in the last 3 years, saving every chick that had survived the initial ant infestation.

Diatomaceous earth is another good ant deterrent.

BLOWFLY:

The larvae of the blowfly are small, 3/8-inch long, gray maggots that feed on the underbelly of a chick drawing blood, then hide on the bottom of the nest.

When there are many of them present, they can kill the young birds. To check for them, when the young are from 7 to 12 days old, place a paint scraper under the nest and lift it gently to look for them, and then scrape them out of the box.

BLACKFLIES:

Permethrin spray used on human clothing (not on skin) kills ticks, but also works well for blackflies bothering bluebirds.

Spray the outside of the nest box and pole. Cover chicks with a jar or plastic container if nest is occupied.

How do you deal with wrens in nest boxes?House wrens can be limited by locating boxes away from wooded and brushy areas.

If they destroy eggs in a bluebird nest, there is little that can be done about it as they are protected as a native songbird. However, recent research has shown wren guards can protect bluebird eggs but must be employed as soon as the first egg is laid.

Check out www.braw.org for more information about wren guards.

To prevent wrens from nesting in a box after the first brood of bluebirds has left, the box and door can be left open for a week or two so that the wren avoids it, and then closed later so that the hen bluebird can nest again.

When you find a few sticks in the box, it may be a male's dummy nest made to protect his territory, or the beginning of a nest. Leave them in the first week and if there is no additional nesting or a nest cup, remove it in the second week. After that you must let nature take its course as it is unlawful to destroy the nest, eggs, or young of any native songbird.

Traps do not kill birds; they merely contain the bird in the box so it can be captured in a clear plastic bag by placing it over the box and then opening the door.

When a native songbird is mistakenly caught, it should be immediately released.

Van Ert traps should be checked within an hour of installing one.

Once in the bag, the bird can be killed as House Sparrows are an invasive, nuisance species and thus not protected by federal law.

For those who choose not to destroy sparrows, the use of a Skylight box should be considered. This box has a 3" hole in the roof covered with plexiglass. The extra daylight in the nesting cavity has been shown to prevent sparrows from using them by 90%.

A raccoon attack is the most common form of predation of a bluebird nest box.

If all or most eggs are missing or nesting material is disturbed or pulled out the hole, look for scratches on all sides of the box or muddy claw prints on the pole.

When eggs are broken, or chicks are found dead in the box that is most likely the work of House Sparrows.

When eggs have been pecked open and are lying on the ground that is likely the work of wrens, although wren and sparrow damage can be confused.

Tree swallows can do similar damage to other eggs. Often waiting to find what bird is nesting in the box next week is the only way to determine which likely did the damage the week before.

When there is no sign or clue as to what happened when eggs have disappeared, that may be the result of snakes or vandals raiding the nest.

Every nest box should be installed on a smooth metal pole, such as ¾-inch metal conduit, to limit raccoons, cats and snakes from climbing the pole and raiding the nest.

A second level of protection should include a wire-cage Noel Guard or Lucey Improved Predator Guard mounted on the face of the box, or a stovepipe or PVC baffle mounted on the pole, 6" beneath the box.

Removing boxes for the winter or leaving the box open are the best ways to limit damage to the hole as that is when woodpeckers are enlarging it trying to enter a roosting cavity.

Placing a metal guard around the hole can prevent woodpecker and squirrel damage. Plus, using one can repair the damage and re-size the hole to prevent starlings and cowbirds from entering the box.

The Bluebird Restoration Association of Wisconsin, founded in 1986, is an affiliate of the North American Bluebird Society (NABS) founded by Dr. Lawrence Zeleny in 1978.

Our mission is to increase the population of the Eastern Bluebird and other native cavity nesting songbirds through a coordinated, statewide nest box siting, installation, and monitoring program.

This is done with active persons serving as County Contacts and others who give workshops and presentations answering any questions, plus offering help providing nest boxes and assistance in establishing bluebird trails for anyone showing interest in monitoring one.

BRAW has an Information Packet with lots of helpful items that is provided free to new members Also, check its website: www.braw.org.

The North American Bluebird Society (www.nabluebird.org) lists every one of 60 state affiliates and offers fact sheets about many bluebird issues, and www.bluebirdconservation.com which has excellent videos on predator and sparrow control.

Other good sources are www.birds.cornell.edu and www.Sialis.org which have many useful materials.