What a winter it has been!

Finally, Spring has sprung, and our feathered friends know it. With each day, our neighborhoods are more abuzz with bird song and the drumming of territorial woodpeckers. Feisty and defensive cardinals are attacking their own reflections in our windows. Goldfinches are already beginning to molt back to their brilliant breeding plumage. Gradually, a steady procession of long-absent species will be returning to our yards: first, the ubiquitous Chipping Sparrows, House Wrens, towhees and catbirds that toughed it out in the southeastern states for the past six months; soon after, a wave of thrushes, vireos, warblers, and orioles--all returning from a longer journey, having departed neotropical wintering grounds several weeks prior.

All this means that nesting season is right around the corner. Birds waste very little time; the process of choosing a mate and a suitable nest site commences as soon as enough invertebrate “baby food” (primarily caterpillars) has hatched out on trees and bushes to feed hungry nestlings. For most songbirds, this means that females are incubating eggs already by the end of May. The process starts even earlier for species that don’t leave our area during the winter months. Nesting gets well underway in April for many backyard feeder visitors, like chickadees, titmice, cardinals, and House Finches.

Springtime, then, is the ideal time to put up a nest box, in hopes of attracting one of our handful of cavity-nesting species to choose your yard in which to raise their family. For many decades, the target birds of most “bird houses” were Wrens (both House and Carolina), adorable and highly vocal songsters which adapt well to human proximity and are not at all picky about nest sites. Since the 1980’s, however, nest boxes for attracting the gorgeous and sweet-singing Eastern Bluebird have seemed to surpass wren boxes in popularity.

Indeed, it was the nest box that saved bluebirds from possible extinction. Long a farmland favorite, the docile and unassuming species experienced a precipitous decline throughout the first half of the twentieth century, due to habitat loss, changes in farming practices, and competition from non-native House Sparrows and European Starlings. These two aggressive species were introduced from Europe in the late 1800’s and immediately went to work evicting (or even killing) bluebirds over potential nest cavities in old trees and wooden fenceposts. By the 1970’s, bluebird populations in the eastern U.S. were just 15% of what they had been a half-century earlier. Fortunately, starting with the formation of the North American Bluebird Society in 1978, a groundswell of concern resulted in a proliferation of ‘bluebird trails,’ in which hundreds of nest boxes were erected in rural areas. Not long after, thousands of homeowners started offering mealworms, dried fruit, and other soft foods that fine-billed bluebirds need to survive the seasons when insects are scarce. The resulting recovery has been remarkable, with bluebird populations increasing at a rate of 2 to 3% annually for the past few decades. They’re not out of the woods yet, but bluebird numbers are now secure and nearing historical highs.

A major reason that bluebird boxes have been so successful is that, unlike irregular tree cavities, they are designed to have a specific 1.5-inch entry hole; this prohibits the larger starling from entering. However, House Sparrows are almost identical in size to bluebirds and can—and will—take over bluebird boxes if allowed to. This is where you come in.

Bluebirds are such delightful birds; who wouldn’t want them nesting nearby? Indeed, every spring, bluebird boxes are one of our most frequently purchased items at Wild Birds Unlimited. However, we would be remiss if we didn’t engage our customers in the conversation about the responsible ownership of a bluebird box. Competition from bullying House Sparrows is still the leading danger faced by bluebirds. Nest box owners need to ensure that they are creating favorable conditions for the intended species to raise their young and NOT unintentionally making the situation worse by providing opportunities for the invasive sparrow population to continue to grow, at the expense of bluebirds.

What, exactly, can you do to become a good bluebird steward?

1. Accept that not every yard provides good bluebird habitat. Unlike many bird species, bluebirds like plenty of wide-open space; in addition to farms, they thrive on schoolyards, cemeteries, and golf courses. If you live in a densely populated neighborhood—or too deep in the woods—you likely will not be able to attract them. If a bluebird box is placed in too urban a neighborhood, it will only draw House Sparrows. Rather than help their numbers soar, consider getting a smaller nest box, with an opening that only House Wrens or Carolina Chickadees can access.

2. Regularly MONITOR your nest box. Watch carefully which birds are going in and out of the box. Open it and quickly check on the nest, as it’s being built. (No, this will not scare the birds away.) House Sparrows make an incredibly sloppy nest, even using bits of trash in its construction; a bluebird nest, by contrast, is tidy, neatly woven, and almost exclusively made of grass. As they are an invasive species and considered pests (like Spotted Lanternflies, Stink Bugs or Norway Rats), House Sparrows are not protected in the U.S. It is perfectly legal to remove their nests and eggs and dispose of them. As they are determined breeders, you’ll probably need to remove multiple nests before they give up. Not everyone feels comfortable doing so, but it is perfectly legal to kill House Sparrows—and also Starlings and Pigeons. All other North American birds are protected.

3. Consider one of the newer “sparrow-resistant” nest box designs. Sadly, there is no foolproof box that will permit bluebirds to nest while excluding sparrows altogether; however, some boxes work better than others. Among them are boxes with a tapered bottom (doesn’t permit for sparrows’ large messy nests), boxes with oversized entry holes and/or extra ventilation (sparrows prefer a box that is dark inside), boxes made from a ‘slippery and smooth’ material like PVC pipe, and boxes with deterrents (nails, fishing line, streamers, etc.) on the roof which prevent the male House Sparrow from sitting on his favorite lookout perch.

4. Don’t encourage House Sparrows to congregate in your yard. While they’ll eat almost anything (ever see them scrounging for scraps underfoot at an outdoor café?!), House Sparrows are particularly fond of cracked corn and millet. Limiting the availability of these foods at your bird feeders can help keep sparrow numbers down.

If you are willing to be proactive in these ways, you may very well attract bluebirds to your yard and be able to enjoy them for years to come. However, if you’re the type who will mount a nest box somewhere in the yard and never monitor it, you may unknowingly be harming the local bluebird population by enabling their number one enemy to thrive. Please, for the sake of these beautiful but vulnerable birds, when you purchase a bluebird nest box, keep in mind that your investment as a responsible landlord needs to be one of time and attention, not just money spent upfront.