First, Bluebirds will readily nest in man-made nest boxes, since much of their habitat has been lost to non-native birds, such as the European Starling and the House Sparrow, as well as loss of natural habitat due to land development. Second, Bluebirds are fun to attract. They are striking in appearance, sing a beautiful song, and, in general, make bird watching all the more rewarding. So, let’s get started making Bluebirds feel welcome in your yard with the most important step – providing a nesting box.
NEST BOX FEATURES:
- A bluebird box should be well ventilated, have drainage holes, and it should be easy to clean and easy to monitor. Having one side that opens for cleaning and one side that opens for viewing (with a plexiglass insert so the chicks won’t fall out while allowing you to see the birds up close) is a major benefit.
- A bluebird box should have an adequate roof overhang (2″ to 3″ minimum) as well.
- A bluebird box should not have a perch. While perches were once thought to make access to the house more convenient for the birds, predatory birds such as House Sparrows and House Wrens are attracted to perches, while bluebirds find them unnecessary for gaining entry. Often times the bluebirds will simply hop down from the roof overhang and swoop through the hole.
- Adding a predator guard with a metal ring around the hole will add an extra layer of protection from predators reaching into the nest box or being able to widen the hole for easy access. An elevated mesh floor to protect nestlings from blowflies makes an even better nest box.
- There should be at least 6″ from the bottom of the entrance hole to the inside floor. This depth helps to protect the birds and eggs from predators reaching in, and the added predator guard will make it even more difficult for a predator to reach the eggs or chicks.
- Wood nest boxes, such as cedar (which resists insect damage), are ideal, as are recycled plastics (easy to clean). If you decide to paint your wooden nest box, only paint the outside and use a light color.
- Do NOT use treated lumber to build your nest box, because of the chicks exposure to toxins in an enclosed space.
- Nesting boxes for Eastern Bluebirds should have entrance hole measurements as follows: round entrance hole should measure 1 1/2″ to 1 9/16″ in diameter such as this model; 1 3/8″ x 2 1/4″ if it is a vertical oval hole like this model; or a 1 1/8″ to 1 3/16″ if it is a horizontal slot entrance, as seen in this model. The entrance hole for Western and Mountain Bluebirds should be a 1 9/16″ round opening or 1 3/16″ slot entrance.
NEST BOX PLACEMENT:
- Mounting the nesting box on a metal pole helps reduce the predator and insect problems, more so than mounting the box on a tree or post.
- Mount the box so the entrance hole is at least 5′ above the ground and try to face the box away from the prevailing wind. If possible, turn the nest box so it faces a building overhang or perching place, such as a wire or tree limb, 20 to 100 feet away. Studies have shown that the male bluebird likes to perch where he can watch the entrance hole. It will also provide the fledglings with a safe place to fly when they leave the nest box.
- Avoid placing the nest box near bushes or woody areas. These areas tend to attract house wrens.
- Add a baffle to guard the pole from predators such as snakes or raccoons. There are several types, including the more popular stove-pipe and round sheet metal guards. One of the advantages of the round sheet metal guard is that most often they are designed so they can be added to an existing pole without taking off the bluebird house.
NEST BOX MONITORING:
- Monitor your Bluebird box a minimum of once a week during the nesting season, until the chicks are near to fledging.
- It is recommended you do not open the nest box once the chicks are 13 or 14 days old. Bluebirds will usually fledge in 18 to 21 days from the time they hatch. You do not want them to be startled into leaving the nest too soon. In some locales, bluebirds will nest two to three a times a season, and during the second or third cycles the chicks will fledge even earlier, 16 to 18 days.
- Bluebirds usually lay 4 to 6 light blue eggs (a small percentage, 4% to 5%, of bluebird nests will contain all white eggs).
- Incubation usually lasts 12 to 14 days. A rule of thumb for Eastern Bluebirds is that eggs will hatch 17 days after the first egg is laid.
- Remove the nests immediately after young have fledged. Brushing out the box and scraping off the feces is all that is necessary. Do not discard the old nest material directly below the house or you might attract predators.
- Keep records! You can obtain monitoring forms from the National Bluebird Society as well as Cornell Laboratory of Ornithology, which compiles data on bluebird populations in North America.
- Don’t become discouraged if your nest boxes are not occupied right away. If bluebirds are not common to your immediate area, it may take a few seasons before they find your nest box. Bluebirds generally return to the same area each year.
Follow these tips and before long, you can be enjoying bluebirds in your own yard!