With their deep blue backs and rusty-colored breasts, bluebirds are one of the prettiest songbirds in Pennsylvania. If a yard has an open or grassy space, bluebirds can be neighbors. It is easier than most people think.

Many local bird species build open-air nests in trees and bushes. Others are cavity-nesters—they need a fully enclosed space to lay eggs and raise their young. Natural cavities are usually found in dead or dying trees. Looking to be good neighbors, suburban homeowners usually cut them down. Because of this and increasing land development, natural nesting cavities are hard to find.

The Bluebird Society of Pennsylvania’s (BSP) mission is to protect primarily bluebirds, but also other native birds that need these enclosures. When a natural cavity is not available, certain species will use small nesting boxes. That’s why BSP encourages homeowners with suitable yards to build or buy a bluebird nesting box. Even if bluebirds are never seen in a neighborhood, over time they will find the box if it is erected in or near an open field. In our area, desirable cavity nesters who will use a box includes bluebirds, tree swallows, and chickadees.

There are plenty of open fields off Route 896, and in the housing developments that dot Oxford Road in New London. Sue and Paul Zuk have lived in one such development for the past 35 years. The houses in their neighborhood sit on one-acre parcels with large front and back lawns. This is ideal bluebird territory.

Five years ago, the Zuks purchased a nesting box and have been rewarded ever since with bluebirds.

“It’s amazing how they gravitate to that box,” Paul said. Even during the non-nesting season (October through early April), bluebirds seem to be more in the vicinity since they installed the box.

“We’ve had a lot of bluebird activity there. And last year we had a brood,” Sue said proudly.

Last year, Paul noticed that five babies were sitting on the garage roof and nearby trees. “Probably three or four days, they were around. And then they kind of went their own way after that,” he said.

“We’re still trying to be more observant about their lifestyle patterns and everything, but we actually saw the babies come to this feeder,” Sue said. The Zuks have multiple feeders very close to their house so they can admire the birds.

“I think those are baby bluebirds! So, we looked them up,” Sue said.

The Zuks are learning. Even though they saw babies last year for the first time, it is likely that they have been raising bluebirds since they installed the box five years ago. It’s also possible that bluebirds use the box to roost in the off-season.

The Zuks are new to the BSP.

“Last year we went to the Farm Show,” Sue said. “There was a table for the Pennsylvania Bluebird Society and we signed up because we love birds. We get their newsletter, and I love it.”

Many Chester County parks have a series of nesting boxes, called bluebird trails, that are maintained by BSP volunteers. During the “season,” which starts in April and runs through September, trail monitors check these boxes once a week to record nest-building progress, the number of eggs laid, and the number of babies who successfully leave (or fledge) the nests. They fix bent support poles, leaky roofs, and clean out spent nests so another pair can start the life cycle again. In October, trail monitors submit their reports to the BSP, which aids in tracking and research.

The BSP encourages individuals to have their own bluebird trail in suitable backyards, even if it’s just one nesting box. Simple building plans are on the BSP website. Boxes also can be purchased at many area stores. They should be installed in an open area, with the entry hole facing east to shield the cavity from wind and rain.

During the winter and especially in March, bluebirds scout out suitable nesting boxes. Once a pair decides on a home, females take four or five days to build a nest. They then lay one egg per day. After she lays all of her eggs (usually between four and six), she provides warmth by sitting on them and the 14-day incubation period begins. After hatching, babies stay in the box for 18 to 20 days. When it’s time for them to fledge, the parents stop feeding and one by one, like planes taking off at an airport, the birds come up to the entry hole and fly out of the box. They no longer need the nest, so it’s time to clean it out and hope for another round.

Just like trail monitors, homeowners should check boxes--which is really part of the fun. The Zuks were not aware of this, and have kept their distance when there was activity. “We were worried we’d disturb them and they would fly away,” Sue said. This is a common misconception. The birds will not abandon the nest, provided it’s only opened once per week for a short time to record progress.

Movie character Forest Gump famously compared life to a box of chocolates— “You never know what you are going to get.” Opening a nesting box is similarly filled with wonder—there could be a nest, eggs, or babies. Seeing the nest will help verify which bird species moved in. Bluebirds lay blue eggs and have neat nests of pine needles or sometimes straw. Chickadees have brown-speckled white eggs and use moss, with the egg cup lined with soft white fur. Tree swallows lay pure white eggs and use straw or pine needles with feathers on top to hide the eggs. House wrens, a cute but aggressive native, have eggs similar to chickadees, and disheveled twig nests.

English sparrows, also called house sparrows, are neither native nor desirable. They have eggs similar to chickadees but disorganized straw nests. “There were sparrows in there a couple of years ago, and we went and took out the whole nest,” Sue said. “We could tell it was a different type of a nest. We looked it up.”

They did the right thing. House sparrows were introduced from England to Brooklyn in the 1880s, and have become a real problem nationwide. They, as well as house wrens, have been known to take over bluebird nests, puncture eggs, and kill the inhabitants.

Birds typically lay eggs in the early morning, so it is best to check a box after that. Knocking on the side of the box first is a good idea, as an incubating bird will likely, but not always, fly out (do not stand in front of the entry hole!). Boxes should not be opened after the babies are around 12 days old, as it may cause them to fledge prematurely. After babies leave, they do not return to the nest. It’s time to remove it and hope for another family.

According to the BSP’s next box tracking report, Chester County volunteers reported that 1,263 bluebirds (up 17 percent from 2022), 3,696 tree swallows, and 413 chickadees fledged from monitored boxes in 2023. People checking boxes and reporting results help the BSP track trends and anticipate problems. Homeowners like the Zuks help keep native birds thriving.

“I’m excited to check this box every week,” Sue said.

The Pennsylvania Bluebird Society welcomes new members and volunteers. Bluebird nest box building plans and other information can be found on their website thebsp.org. They also have a Facebook page.