Wildlife Shelters: Nest Boxes

Daniel Burden

Value Added Agriculture Program Coordinator
Iowa State University Extension and Outreach
djburden@iastate.edu

Summer is a great time to consider habitat upgrades and the many small outdoor projects that can be fun and easy to accomplish in a few hours. In particular, let’s consider shelters and nest boxes for birds, bats, insects and amphibians. When shelter boxes come to mind, we usually think about birdhouses. That said, there also are shelter and nest houses for every acreage-living critter from toads to falcons.

Birdhouses come in every size shape and style. The most effective ones use tried and true dimensions. Those are available in many books on the subject and plans are easy to find in print or on the internet. The best place to start is by constructing houses for bluebirds, wrens or tree swallows. Nest boxes for owls, kestrels (little falcons), woodpeckers, wood ducks and other larger birds involve quite a bit more material, work, and a well-chosen site for the final installation. If you are interested in these type of nest boxes, as with all wildlife projects, it is well worth the time to research the project and download plans appropriate to your species of interest.

The internet is full of interesting art-project-type birdhouses. These can be fun visual additions to your immediate outdoor living space, but when it comes to what is best for the birds, make sure that any nest box provides adequate ventilation, drainage and needed protection from heat, water, and predators; and perhaps a means for the little ones to leave the box. Perches look great on a birdhouse, but they have the potential to cause more harm than good. A perch gives a predatory jay, starling or house sparrow the perfect platform from which to pull a nestling from the box.

Wren, tree-swallow and similar small-bird houses should have a metal sparrow-excluder over the entrance hole. These are easily crafted from shop waste, or can be purchased at lawn and garden stores. For some desirable species, the robins, phoebes, purple and house finches, that love to nest in more open-platform-like boxes; it may be necessary to allow house sparrows to lay initial claim to the property, then forcibly evict them once they nest. By forcibly interrupting house-sparrow nesting, one gives the native species, especially in urban areas, a chance they would not have. A similar excluder plate is often attached to purple martin nest-gourds or houses to prevent owl predation on nesting adults and nestlings.

Squirrels will use nest or shelter boxes, especially for communal warmth during the coldest months if the house is so constructed. Flying squirrels are extremely secretive and reserved, but will inhabit nest boxes of the proper dimensions and if the box is in a place that suits their particular idiosyncrasies. Well-constructed squirrel boxes usually tend to be vertical affairs that incorporate ledges or some other internal structure. Most have the entrance hole on the side near the post or tree trunk and away from the prevailing wind. Like most shelter-type structures, placing the refuge in a protected place greatly increases its effectiveness.

Bats readily take to bat houses. Bat houses usually have internal baffles, oftentimes, a series of textured and properly spaced vertical dividers that make roosting easy for the bats. Bat houses have a lower entryway, often with an easy-to-grip ramp that angles up into the house. The bats land on the ramp, and then shinny up and squeeze between the dividers. I’ve built bat houses where I used hardware cloth as a gripping surface, but was careful that no exposed wire would create a hazard for the occupants. Wedged into a tight space the little flying fur balls stay warm, roosting together in cozy little groups in their communal bat condo.

Bat houses are a great way to impact local mosquito populations, but check with your local wildlife-extension professional regarding white-nose syndrome, an invasive fungus from Europe. The fungus is a serious threat to many bat populations and is spread by bat-to-bat contact. There was once some thought that bat houses promoted the disease, but the fungus is now recognized to thrive in damp caves and similar environs, not a nice dry bat house. If it is prevalent in your area, you may want to build a bat condo to help your local species. Videos on building bat houses, house plans and how to create bat-friendly gardens can be found by visiting the website of Dr. Merlin Tuttle’s wonderful International Organization for Bat Conservation.

A great application for any shelter-box project is to turn it into a do-it-yourself project for children. One simply builds a birdhouse, bat house or similar structure so that it is easily disassembled and reassembled. The screws cannot be overtightened and screw holes cannot be stripped, and the fastener’s head makes a nice external seal. Use a random-orbit sander on all wood surfaces to minimize the chance of picking up a wood sliver. One can spray on a coat of outdoor-rated sealer or paint make further finishing a breeze.

With the help of an adult or older sibling, the child assembling the structure lays out the parts and pretty much figures out what goes where. Assembly is easy since the screw holes are to dimension and tapped with threads. All the builder needs is a little patient work with a screwdriver. The result is a wonderful gift that gives people the joy of working together; expression that melds decorative visual art with practical habitat improvement. A child seeing a family of wrens or bluebirds grow and thrive thanks to the child’s attention and creative energy teaches a wonderful life lesson.

At the end of each season, nest boxes should be taken down and cleaned, and shelter boxes spruced up for the coming winter. Nest boxes take a beating in the winter, storing them indoors or in a sheltered space will ensure that they give you many seasons of service.

Shelter-box projects can be simple, to get the job done, or complex if more intense wildlife study is the focus. These days, there are various models of digital cameras and video recorders that are intended to be used for wildlife watching, or can easily be rigged to do so. Almost all of the units record to an SD card or similar storage device; some use Bluetooth technology to “talk” to a smart phone, tablet or similar computer. Some of the more advanced units are compatible with sensors or timers to trigger recording or develop a time-lapse series of images. For older children, constructing a shelter, developing a surveillance record and reporting on the knowledge gleaned from it, could be a great school or 4-H project.

Insects and amphibians, often overlooked for shelter needs, are very beneficial residents that can add a whimsical bit of fun in the garden, as well as contribute to pest-control. One can easily find plans for butterfly and bee houses, and these are a great way to make sure there is ample pollination for your fruit trees and vegetable garden. Old clay and especially ceramic planting vessels are perfect for the cool humid shelters needed by snakes and amphibians, especially if located in full shade near a water source. Small toads and tree frogs readily accept shelters made from scrap PVC water or drainpipe.

Predator excluder landscape features are an often-overlooked project that creates a much-needed bird-safe refuge for songbirds. Almost every evening in my neighborhood, a couple of the neighbor’s cats routinely patrol the shrubs in my yard for roosting songbirds. A solution is to plant arbor vitaes or junipers in a clump, within which is a ring of woven-wire fence that protects the inner sanctum of the wildlife cover. The wire fencing should have large enough holes for small birds to pass through, but small enough to exclude cats and similar domestic and wild predators. If smaller mesh is used, most birds will fly into the center of the ring. In winter, a few boughs over the top will provide additional environmental protection for the occupants. This type of shelter works well with larger predators an in urban yard situations where domestic cats are the primary concern. Weasels and mink are good climbers and this structure will slow them down, perhaps long enough to give the birds inside a chance to escape before they become an evening meal.