While the dimensions shown are considered optimum, they can vary from 8 x 8 inches to 10 x 10 inches inside dimensions. The hole can be from 9 to 12 inches above the floor. You can put an inch or two of sawdust, woodchips, dried grass clippings or fine chat in the bottom of the box. Sparrow hawks don’t build a nest, as such.
Place your box 15 to 30 feet high on the sides of barns or silos, on metal or wooden poles, in dead trees or, as a last resort, in isolated live trees. Live trees are least desirable because raccoon and snake predation on nests seems to be worse there. Use only aluminum nails in live trees. Locate the box in open or partially open land or at the edge of wooded draws or fencerows which are adjacent to pastures, hay meadows and roadsides. Try to locate the box within 15 to 30 yards of a tree with dead limbs, a snag or a power pole. These serve as a plucking perch where the male birds dismember their prey and pass the food to the female, who feeds the young. These perches also are used for preening, courting and as perches by the young when they learn to fly. If you want to use this nest box for screech owls, erect it 15 to 30 feet high in trees in the woods, along woodland edges or yards which have large trees. (Nesting screech owls are very protective and have been known to attack people and pets near their nests. These attacks are more frightening than injurious.)
This box may occasionally be used by squirrels, flying squirrels, bluebirds, starlings, other birds and even honey bees. All of these are a part of our wildlife scene.
Biology – Sparrow Hawks
Sparrow hawks (also called kestrels) are our smallest and most colorful hawks. They feed on mice, voles, insects, small birds and, rarely, on small snakes. However, they will kill some songbirds. While this is a natural and not necessarily disastrous event, you should know that it can happen. The beneficial role that sparrow hawks play in controlling rodents and nuisance birds far outweighs any harm they may do to your other birds. Sparrow hawks usually lay four or five eggs and incubate them for 29 to 30 days. First flight for the young takes place 30 to 31 days after hatching. Sparrow hawks usually have one brood per year.
Biology – Screech Owls
Screech owls are our smallest common owl and are year-round residents in Missouri. There are two color phases, gray and brown. Screech owls feed on almost any form of animal life from insects to mice, and they may also kill and eat small birds. They lay four or five eggs which they incubate for about 26 days. The young make their first flight at the age of 28 to 30 days. Nesting occurs from mid-March to mid-May, and they usually have one brood per year.