Nest-Box Theater

Want to see wildlife? Here's the ticket.

By Dan Prusi

The snow was deep that day in March, but a thick crust made for excellent snowshoeing. I was making the rounds on my 77 acres where I had about 100 nest boxes in place for wood ducks, bluebirds, owls, and other birds. I walked up to a black ash tree with a box made from a hollow length of oak. I tapped it gently. After a few taps, a flying squirrel scampered out of the entrance hole and perched atop the box. Another tap and a second squirrel emerged. I kept tapping and eventually five flying squirrels had exited the box and clung to the tree trunk. This was just one of many pleasant surprises I?ve had during 20 years of working with nest boxes.

I hung my first nest box when I was 8 years old. I'd received a birdhouse kit as a gift. My dad helped me assemble and place the box, and I was thrilled to see tree swallows move in that same spring.

As an adult I vowed to improve my property for wildlife by hanging a variety of nest boxes. It's been hard work, but I've been rewarded with a front-row seat to some amazing wildlife theater.

Bluebird Bungalow

Woodworking for Wildlife, published by the Department of Natural Resources, provided answers to nearly all my questions on the "who, what, where, and why" of nest-box design in Minnesota.

I chose the eastern bluebird as my first priority because this species had suffered serious population declines. Tree swallows, English sparrows, and starlings often destroy bluebird eggs and sometimes kill the adult bluebirds. In recent years, concerted efforts to erect bluebird nest boxes and place them in suitable habitat have curtailed the competition and helped increase bluebird populations across the United States.

It took me several years to recruit my first bluebird tenants. Finally, I discovered the trick: Place two boxes about 30 feet apart on the edge of an open grassy area. Usually one box attracts a pair of tree swallows, which defend the neighborhood from other tree swallows but allow a bluebird pair to nest next door. With paired boxes, I often see as many as 75 swallow hatchlings and 20 young bluebirds in a single summer nesting season.

Wood-Duck Nursery

My property consists of a mix of woods, fields, and wetlands. It has plenty of small snags with cavities for most of the native wildlife that depend on such places for dens or nests. However, wood ducks and hooded mergansers need large trees with larger cavities near water, and these are in short supply.

While wood ducks and hooded mergansers will nest a mile or more from the wetland where they raise their young, cavities near water make the journey from nest cavity to brood-rearing areas much shorter and, therefore, less dangerous for ducklings. One season, the two-dozen wood-duck boxes along my ponds and sloughs had more than 80 young wood ducks and mergansers.

One woody hen in particular provided me with several years of fun. She was banded, so I was able to identify her. She nested in the same box for five consecutive years. During the first four years, she hatched about 50 eggs, including some hooded merganser eggs. (Both species will lay eggs in the other's nest.)

In her fifth nesting, she was sitting on 17 eggs. One evening I saw a mink enter and leave the box. The mink killed the hen. With the box located on an island, I was unable to intervene; but I am not sure I would have. While we humans might see the loss of this productive wood duck as tragic, it was an example of nature in action.

Lessons Learned

Helping wildlife is an important part of placing nest boxes. Using predator guards gives the nesters a better chance of success in raising their young. Including a side panel that swings open allows you to rid the nest of blowfly larva or other pests that might invade the box.

Nest boxes can also be valuable for enabling children to watch birds raise their young. You bring the animals to you, rather than having to go out to locate a nest. Youngsters are thrilled when they can peek into a box and see young birds, beaks open and begging to be fed. Quiet, careful inspection of the boxes "done in moderation" will not cause the birds anything more than a bit of anxiety.

Checking and maintaining the nest boxes is always an adventure. I have read that great crested flycatchers will sometimes decorate their nests with shed snakeskins. I have not seen this, but one flycatcher nest had several shiny stones tucked in among the eggs.

I have also learned to tap many times before opening a box. More than once, when I opened a hinged side panel, a squirrel or bird scrambled out just inches from my face. Once I discovered a hornets? nest inside a duck box and had to do a fast descent down the ladder and make my escape wading through a slough.

Over the years I have had at least four species of mammals and a dozen different kinds of birds make use of boxes and nest structures I've erected. The smallest were wrens; the largest, great horned owls. The young birds and animals that entered this world inside our nest boxes now number in the thousands. The expense was minimal, the effort enjoyable.

And the reward: countless hours of watching.

Dan Prusi is a freelance writer in Floodwood. He writes a nature and outdoors column, Tales from Cedar Valley, for several newspapers.