A male and female eastern bluebird perch on a nestbox. © JanetandPhil / Flickr

Backyard bird enthusiasts appreciate all native species. But there’s something extra special about bluebirds. The rush of joy when a bluebird visits our yard is often followed by research and the discovery that these beautiful cavity-nesting birds will use nest boxes.

It might seem simple enough: just buy or build a box, put it on a post, and wait for the bluebirds to move in.

But it’s important for would-be nest box hosts to understand that nest box management comes with much more responsibility, and some challenges that some might not be ready to take on.

The proper size and shape of the box, the size of the entrance hole, the height of the box, and baffles to prevent predators are all part of responsible nest-box management. (This applies to all nest boxes, not just those designed for bluebirds.)

A nest box’s size, location, and materials matter when it comes to keeping birds safe from predators. This box in Michigan is home to house martin chicks. © Kevin Kluczek

I had an exchange with someone recently about the idea of trying to educate people on the risks and responsibilities associated with putting up nest boxes on their property. Some folks interpret attempts to educate people on the responsibilities associated with nest boxes as negative and/or rude. I thought my response to that might be helpful to others seeking to help people understand the importance of being a responsible nest box host.

There are any number of threats to nesting bluebirds, including snakes, ants, wasps, and parasitic blowflies. One of the most difficult challenges for a nest box host is what to do about house sparrows. These nonnative birds are fierce competitors for nesting cavities, including nest boxes. The harsh reality is that house sparrows often kill adult bluebirds and their nestlings in the box, and build their messy nests on top of the carnage below.

Young eastern bluebirds are vulnerable to predators, including house sparrows. House sparrows are a non-native species that often kill native bluebirds when they take over a nest box. © Putneypics / Flickr

I monitored nearly 60 eastern bluebird boxes in a wildlife area for many years. As an animal lover, I was reluctant to do anything about the house sparrows nesting in the boxes. However, after seeing dozens of adult bluebirds and their nestlings killed by those non-native sparrows, in a very gruesome way, my feelings on the issue changed.

This is not about weighing the merit of house sparrows. This is about deciding whether or not you’re okay with killing bluebirds, and I don’t think anyone would feel good about facilitating that. Unless one is willing to manage house sparrows, European starlings, and other threats, they shouldn’t install nest boxes.
Decorative birdhouses can do more harm than good. The author recommends blocking the hole to prevent birds from nesting in an unsafe location. © Stephen Downes / Flickr

I also wanted to share a word of caution about decorative nest boxes. Adding a pretty bird house to your yard is fine, as long as you block the entrance hole. These boxes are rarely built with the safety of birds in mind, so preventing birds from using them is important.

Being a nest box host and helping native cavity nesters can be an intensely rewarding endeavor, but only if you’re a responsible host. Knowing and understanding the risks – and sharing that information with others – is important. It should not be viewed as discouraging or rude.

If you want to learn more about best practices for nest boxes, here’s a great resource that includes practical tips on nest box building, location, house sparrow management and much more.