All About Backyard Nest Boxes

by Leda Beth Gray

The main design element to consider when selecting or building a house for chickadees and titmice is the entrance hole size. The rest of the nest box dimensions and construction details recommended in books on the subject are fairly standard. However, some books recommend 1-1/8 inch for chickadees and 1-1/4 inch for titmice, and at least one recommends 1-1/8 inch for both species. My friend Sue, who has had Oak Titmice nest in a box in her yard, noticed that the Oak Titmice were able to fit through the 1-1/8 inch opening and were building a nest in the box, but pecked at the hole, apparently trying to enlarge it. After Sue obligingly enlarged the entrance hole to 1-1/4 inch, she observed House Sparrows looking in the opening and investigating the nest box. This induced her to put a mask over the hole effectively reducing the size back to 1-1/8 inch, which precluded the sparrows. The titmice continued their nesting activity through these changes.

Christmas Bird Count Data show a decline of about four percent per year in the San Jose count circle over the last 30 years, but no detectable trends in the Mt. Hamilton and Palo Alto circles. In addition, Interior Department Breeding Bird Survey Data show a few percent per year decline of the Oak Titmouse in California over the same time period. So it is worthwhile to consider whether you will be able to offer the Oak Titmice a 1-1/4 inch entrance hole without competition from House Sparrows. Some books suggest that House Sparrows can be discouraged by repeatedly removing their nesting material. Other cavity nesters can also be attracted to this larger size opening including nuthatches and wrens.

Choosing a site for the nest box is extremely important. It was suggested on the directions that came with one of the boxes we purchased that it receive sun for roughly half the day. Our successful box is located in a spot where it receives late morning and noon sun and afternoon shade. I have seen other successful boxes that were in light shade all day. Not providing a perch either on the box itself or right next to it is also very important because this keeps predator birds such as the jays from being able to land in a convenient spot to stick their heads into nest box holes or otherwise disrupt nesting activities. Our chickadees could deal with some jay aggression, but we suspect that they would not stay with a nest box location that provided easy access for jay attacks.

It is important to place the box where it will be safe from four-legged predators. Our successful box is mounted on an exterior porch wall, where it would be difficult for any climbing animals such as cats, raccoons or rodents to reach it. A second box in our yard that was successfully used one time is hanging from a sturdy tree branch in a position that is sufficiently far away from other tree branches so as to be out of the reach of predators. Sue has her nest boxes mounted on poles, with baffles on the poles to keep animals from climbing up. She found out through an unfortunate experience of having a nest of titmice disappear overnight that it is important to keep branches trimmed well away from the nest box locations. A secondary but important consideration in locating nest boxes is visibility from your house. It is very rewarding and entertaining to be able to view nesting activities from windows, and this makes it more convenient to monitor the boxes, especially for elderly or disabled bird watchers.

It seems to be a good idea to put a layer of small non-aromatic wood chips or shavings in the bottom of the box for chickadees and titmice to remove. As mentioned in the above article, the birds seem to think they are excavating the cavity. As careful as they often are to dispose of the chips in various locations away from the nest, they usually still drop enough to be visible - a telltale sign that nesting activity has begun. Even though chickadees appear to be excellent housekeepers, it is important to remove the nesting material when the nestlings have fledged in order to get rid of mites that may have gotten a foothold in the nesting material and which could attack the next batch of nestlings. The box should be completely swept out and new wood shavings put in.

One thing that has very entertaining results, is to put out nesting materials for the birds. A suet basket is a handy way to do this, or just using the wire "twisty ties" to fasten the materials to branches around the yard. Cat hair is ideal, as is sphragnum peat moss. Other types of hair, plant down, and cotton stuffing out of chairs (natural materials are best) may also be accepted. Watching birds collecting these materials is very entertaining. Putting out suet toward the end of the nesting cycle gives chickadees and titmice a "fast food" option when feeding voracious youngsters that are just about to fledge. It is important not to let it spoil in warm weather. I keep blocks of suet in the freezer and only put out portions of blocks at a time to minimize spoilage.

One final note is that it is a good idea to keep records about the nesting activities in your yard. You will then be able to compare the timing of nesting activities in your yard from year to year. In addition SCVAS is interested in receiving data on the timing of nesting activities of cavity nesters in Santa Clara County. The very successful Bluebird Nest Box program started by SCVAS last year turned out to benefit many other cavity nesters including titmice and chickadees. SCVAS is keeping records on these nestings and we would like to include data from any other nest boxes in the county as well. Please send any such information to the SCVAS Chapter Office. Good luck and have fun!!