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Eastern Bluebirds

Scientific Name: Sialia sialis 

Thrushes Wildlife Note (PDF)


Bluebird Nesting Box Plan (PDF)
How to put together your bluebird box kit (10:28)
Woodcrafting for Wildlife
The North American Bluebird Society
The Bluebird Society of Pennsylvania (BSP)

Bluebird Basics

Eastern bluebirds have long been the displaced darlings of Pennsylvania's spring, as well as the poster bird for what can go wrong when people introduce non-native species to a new area.

Bluebirds suffered considerable - almost unrecoverable - losses in the twentieth century as a result of the injudicious introductions of house (English) sparrows and European starlings to New York City - and ultimately America - in the 1800s, and the toxic toll DDT exacted on many songbirds and raptors for decades beginning in the 1940s. Further complicating the bluebird's plight, particularly in Pennsylvania, has been the loss of open spaces to development or reforestation.

Pennsylvania's bluebird population was probably its strongest ever in the late 1800s and early 1900s, before starlings and house sparrows became too plentiful, and before the advent of DDT. It was the period just after large sections of the Commonwealth's forests had been logged off and a time when farms covered about two-thirds of the state. Pennsylvania's human population was half what it is today. Combined, that translated into lots of open space - preferred habitat, few environmental issues and limited competition with other cavity nesters. Bluebird paradise.

With time, though, America's bluebirds began to lose their grip. The European transplants began to dominate the nesting cavities bluebirds preferred. DDT and other harmful pesticides hampered reproduction until they were banned nationally in '70s. And Pennsylvania's open spaces slowly, but steadily, were reclaimed by trees, or worse, buildings. The bluebird's perfect world was slipping away, and it was helpless to reverse the troubling tailspin it found itself in.

Bluebirds needed help competing with the more aggressive European species, and American ornithologists soon recognized this problem. By the 1930s, a national movement had started to remedy the bluebird's "homeless" status. But whatever gains were made for bluebirds likely were offset by the increased usage of DDT - and a general disregard for many environmental concerns - during the war years of the '40s.

"Bluebirds were in deep trouble in the mid 1900s, just before America's environmental awaking in the '60s," explained Dan Brauning, Pennsylvania Game Commission Wildlife Diversity Section chief. "Just about everything seemed to be working against this handsome, and extremely popular songbird. But the situation started to improve for bluebirds in the 1960s and '70s as more and more Americans rallied to help by placing nest boxes in their backyards and creating bluebird nest box trails."

The Game Commission regularly campaigned for bluebirds by encouraging Pennsylvanians to consider getting involved in the fight to make the state a friendlier place for them. But then the bluebird has always had someone to champion its well-being in the Commonwealth, even before the creation of the Game Commission in 1895. In the state's second oldest songbird protection law, dated 1843, bluebirds were one of several species listed specifically for complete protection in Allegheny and Franklin counties. The $2 fine for breaking the law was equivalent to about a $50 fine today.

It's not hard to figure out why bluebirds were so popular in the 1800s, and probably well before that, given their striking blue and orange plumage and willingness to nest close to homes and in the fence-posts that once separated farms and agricultural fields. John J. Audubon referred to the bluebird as a "lovely bird ... full of innocent vivacity," and surely countless Americans had similar feelings toward it.

The Game Commission's Howard Nursery, near Milesburg, has been manufacturing bluebird nest boxes and box kits for more than a quarter century. Each year, about 9,000 kits are manufactured there and sold or provided to Pennsylvanians to help bluebirds. That annual influx of new nest boxes helps to ensure Pennsylvania remains a "keystone state" in bluebird conservation.

"That bluebirds currently nest in all of Pennsylvania's 67 counties is directly related to the interest Pennsylvanians have shown toward bluebird conservation and doing something more for wildlife in their yards over the past 50 years," explained Brauning. "But we should not consider the bluebird's comeback a done deal, because their existence seems destined to hinge on the continued involvement of people who care about the species. If people stop putting out nest boxes for bluebirds, there undoubtedly will be serious repercussions."

Bluebirds have the unique distinction of being the only member of the thrush family to nest in a cavity. But they get plenty of competition for nesting sites from other wildlife. In addition to house sparrows and starlings, native species such as the tree swallow, house wren, great-crested flycatcher, black-capped chickadee, and tufted titmouse also use cavities. It's also not uncommon to find flying squirrels, white-footed mice, deer mice, even yellow jackets and bumblebees using nest boxes.

Given the aforementioned list of possible tenants, it's not hard to understand why nest boxes are in such demand. Add to that the diminishing number of fence-posts found in rural America - caused by field consolidation, farm loss, and use of prefabricated plastic and metal posts - and the dwindling number of snags and mature trees with cavities in Penn's Woods, and it hits you like a runaway train why bluebirds are so dependent upon people and why their future will always be hazy.

Countless Pennsylvanians already are involved in bluebird conservation, because they enjoy seeing bluebirds, or simply would like to lend a helping hand to a songbird that could use all the help it can get. Most have bluebird nest boxes in their yard; others maintain bluebird nest box trails. Casual conservationists probably account for the biggest share of this ongoing outreach effort. They also are responsible for putting nest boxes in locations that simply won't do much for bluebirds.

"People frequently ask the Game Commission why bluebirds won't use a nest box they've placed in their yard," said Doug Gross, Game Commission ornithologist. "More often than not the reason is the box was placed in an undesirable location. People often mistakenly place nest boxes in places where they'd like to see them, rather than locations that satisfy bluebirds.

"A box is best placed on a post - not a tree trunk - four to six feet off the ground in direct sunlight. Preferred locations are open backyards, meadows, near fencerows or agricultural fields, and around cemeteries or athletic fields. Boxes placed too close to houses and other buildings, waterways and wetlands, or forested and brushy areas will attract nesting competitors and predators."

Of course, it should be pointed out that a bluebird nest box used by any species other than a house sparrow - starlings can't access the entrance of a properly-constructed bluebird nest box - is still a box that's serving wildlife and helping to fill a habitat deficiency. If helping bluebirds is your objective, then place or relocate your nest box to an area where there will be limited nesting competition and predator problems, and where bluebirds are more apt to find it. If you're reusing a box, remove old nesting materials from inside before hanging it. Otherwise, recognize its worth to other wildlife and place it where it'll do some good.

The best time to erect a bluebird box is right now. The earlier a nest box is placed afield or in a yard, the better its chances are of attracting bluebirds. Males - the more vibrantly-colored ones - start shopping for nest boxes in early to mid March. After attracting a female, they build a nest in the box. In late April - and often again in mid June - the female lays eggs.

"Although Pennsylvania's bluebird population appears to be stronger today than any time over the past 50 years, the species surely needs to remain in the public's eye to ensure its well-being and that it continues to prosper," emphasized Gross. "Probably nothing reinforces the need for bluebird nest boxes more than seeing bluebirds scrapping with house sparrows over a box. It's a sight that inspires people to get a nest box and help make a difference locally. So please do put out nest boxes, and put them where they can help. Please encourage your neighbors to do the same.

The Bluebird Society of Pennsylvania, as well as the North American Bluebird Society , have done much to promote bluebirds and the species' never-ending need for nest boxes. Their websites offer a variety of features that will familiarize interested landowners with ways to make their properties more attractive to bluebirds.

- By Joe Kosack, Wildlife Conservation Education Specialist

Eastern Blubird