Recently, at a wild bird trade show in Missouri, a women approached me and thanked me for “a great idea.” She said she had read a story I had written about winter roosting boxes a few years ago. Candace Stuart, owner of a Wild Bird Center in Denver, began offering workshops for kids to build small roost boxes for chickadees.
I had singled chickadees out because they roost individually, while many cavity-nesters roost communally on cold winter nights. I’ve found reports of as many as 10 bluebirds, 46 winter wrens, 50-plus pygmy nuthatches, and 29 white-breasted nuthatches roosting together in a single cavity. They gather to conserve body heat on the coldest winter nights. On milder nights they perch amidst the protective cover of evergreen vegetation or persistent dead leaves clinging to an oak branch.
Roosting behavior gives backyard birders another opportunity to provide a critical resource for cavity-nesters. A typical roost box for social species is designed to conserve body heat and minimize heat loss.
Though cavity-nesters often roost in ordinary nest boxes, this may be simply because better roost sites are not available. Nest boxes are typically well ventilated, and the hole is positioned at the top of the cavity. These openings promote heat loss by allowing heat to rise and escape. During nesting, this promotes heat loss and keeps boxes from overheating.
A roost box
on the other hand, is designed to conserve heat. It measures approximately eight inches square and 20 inches high. There should be no air vents, and all upper joints can be sealed with a silicone bead to completely eliminate air flow.
The only opening is a 2.5-inch entrance hole cut into the bottom of the front panel. Inside, a series of shelves or quarter-inch dowels run from side to side. The dowels should be staggered to minimize the amount of droppings that fall from birds perched above to those perched below.
Finally, be sure one side or the bottom of the box is removable so it can be cleaned out occasionally. Hang the roost box five to eight feet above the ground in an open southerly exposure to take advantage of solar radiation, and if possible, place it so it is protected from the prevailing winds.
For detailed winter roosting box plans, visit Cornell’s Lab of Ornithology web site, www.birds.cornell.edu, and search “roost box.” If building a roosting box sounds too difficult, many wild bird stores and nature centers sell them.
Another option is to modify ordinary nest boxes for the winter. First, remove all old and soiled nesting material from used boxes and replace with a one-inch cushion of dry, insulating grass. Then plug all vent holes with a pliable, putty-like material that can be easily removed in the spring.
Unlike most cavity-nesters, chickadees roost singly in tiny cavities. Often the cavities are barely big enough to accommodate a single chickadee.
In the article I had written several years ago, I suggested building very small roost boxes for individual chickadees. This was what had caught Candace Stuart’s attention. She began offering a class in her store for children to build small roosting boxes for chickadees.
With no real plans to go on, she imagined a chickadee roost site and pre-cut pieces to form a small cavity with inside dimensions of about four inches wide, three inches deep, and three inches high. A 1.25-inch entrance hole sufficed.
I asked Stuart if chickadees actually used the boxes. She said she didn’t get much feedback until an older women came in one day to tell her story.
This woman built 10 of the little boxes and placed them on a row of trees in her backyard. And every night when temperatures got especially cold, she watched as individual chickadees entered each box.
Getting to work
I’m going to build a few of these boxes before winter sets in. I’ll place them under roof in several open sheds that will provide extra shelter from the elements.
Finally, I must add a word of warning. During periods of extreme cold, birds sometimes die while roosting. This is natural and unavoidable, though it can be shocking to find a box full of dead birds in the spring.