It’s never too late to go nesting

“I’ve been wanting to put nesting boxes in my backyard. Would you say it’s too late to be doing that?”

Jennifer Greenleaf, Portland

A nesting box doers not need to be new, but it’s not a bad idea to clean it out before the early spring arrivals. Jack Milton/Staff Photographer

We have recently received multiple questions about when to put out nest boxes and bird houses, a sign that spring is on everyone’s mind despite our recent weather. The real estate market for a lot of our cavity nesting species may already be past its initial peak, but the answer is that it is never too late to put up a nesting box. Many of the species that are already using boxes, like Eastern bluebirds or black-capped chickadees, are likely to have multiple broods each year, so even if you missed their first attempt, you can be ready for the second.

For the uninitiated readers, it’s worth mentioning that there are a group of birds, called “secondary cavity nesters,” that rely on cavities either created naturally or made by another species (that includes us humans putting up bird boxes). Woodpeckers are an example of a “primary cavity nester,” as they excavate a new cavity for each nest. In the years that follow, that cavity can be used by several different species, and often mammals too. I’ve been keeping track of a cavity at Maine Audubon’s headquarters that was created by hairy woodpeckers in the spring of 2017. They successfully fledged one chick, and the following winter a southern flying squirrel used the cavity as a roost. It was vacant in 2018, but used by tufted titmice in 2019, who fledged at least two chicks. By putting up a birdhouse, you are helping these secondary cavity nesters by giving them a jump-start on having a place to nest.

Before everyone runs out to hang up birdhouses, we should pause and acknowledge the responsibility and maintenance that comes with providing housing. First, make sure you are not doing more harm than good: Check that the birdhouse has proper drainage (holes in the bottom corners should do) and adequate ventilation. Don’t put up a bird house if you know there are outdoor cats in the area. Cats are non-native surplus hunters that should not be let outdoors and we should not be attracting birds if only to lead them to their demise.

Speaking of non-native species, keep house sparrows out of boxes. These old-world sparrows are invasive and very aggressive, often killing native species like bluebirds on their nests, and then building their own nests on top of them. Lastly, it is helpful to clean out birdhouses annually. This helps remove parasites, like mites that might be surviving in old material, or remove pests like mice that use the box in the winter. I often do it in February or March, just as it is getting warmer but before most species have started claiming boxes. That said, don’t worry if you forget to clean them out. Birds are pretty smart and can do their own cleaning. Plus, it’s not like there is some mythical creature that walks around cleaning out tree cavities every March!

Putting up bat boxes? Go batty!

We received a very nice, double-sectioned bat house as a Christmas gift, but were waiting for warmer weather before putting it up. When is the best time and where is the best location for installing a bat house? We live in Portland, just off Back Cove.

Thanks in anticipation of your help,

Gretchen Stanton, Portland

What a perfect gift, and I hope everyone gives or receives a bat house this year. Bats are in serious trouble and providing a safe place to raise their young is one of the best things we can do to help. Rather than treating your yard with insecticides, put up a bat box and let bats keep pests under control, while not destroying biodiversity around your house. Bats will pick off mosquitoes at over 1,000 per hour.

The one obstacle with bat houses, in my opinion, is the rate of adoption. Bird houses can become occupied days after installation, while a bat house can take a few years to become occupied. So you need to be in this for the long haul.

I should give a shout-out to Bat Conservation International ( which has amazing information on bats and bat houses. I’ll mention a few key points for installing houses here but recommend everyone visit the BCI website for more information.

Location, location, location, right? This is especially important for placing bat houses in Maine’s temperate climate. Keeping them warm is key here, so mounting the house to be south facing will help maximize their exposure to the sun (six to eight hours of direct sunlight is the goal). Painting them a dark color can also help increase temperature; “too hot” is really not a concern in Maine. Next, get the house high, 20-30 feet up, and clear of vegetation. You want to make it easy for the bats to come and go. Lastly, mounting the houses on poles or the side of a building has much faster adoption rates than putting them in a tree.

We’ve lost over 90% of our non-migratory bats in Maine since white-nose syndrome (a fungus) was found on Maine bats in 2011. With low reproduction rates, every one that we can help will make a difference.

Do you have a nature question for Doug? Email questions to [email protected] and visit to learn more about virtual and backyard birding, online classes and other programs about wildlife and habitat.

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