Beneficials

Cavity Nesting Birds

Healthy populations of cavity nesting birds provide significant benefits to farms and ranches. Understanding the roles played by the various species of birds, and their relationships to the habitat, is important for landowners who seek a better understanding of the ecological functioning of their land.

Pest control is one of the biggest benefits that cavity-nesting birds bring to farms and ranches. Sonoma County Winegrape Commission encourages growers to use integrated pest management practices so that pesticides are only applied when pests pose economic risk, and to choose materials that are effective, yet have low environmental impacts. (Sonoma County Grape Grower’s Values Statement) Birds help provide biological control as a component in an integrated pest management farming system.

By encouraging specific species of cavity nesting birds on their property, landowners can promote alternative means of pest control. For example, some cavity nesters such as the barn owl consume rodents as a large portion of their diet. A breeding pair of owls can consume at least two rodents every night, and when their young have hatched this number can increase significantly. Not surprisingly, this type of consumption can result in a decrease in rodent activity and control costs and an increase in farm productivity.

Some species of cavity nesting birds, such as the kestrel, provide indirect pest control benefits simply through their presence in an area. The kestrel preys on a variety of smaller birds, who may be considered pests by some landowners because of the damage they do to crops. These pest species will avoid areas frequented by kestrels and thus provide the landowner with a low cost method of pest control. The benefits of kestrel presence are increased when considering that the remainder of its diet consists of rodents and insects.

See also: The Hungry Owl Project and Sonoma County Wildlife Rescue Barn Owl Maintenance Program

General Guidelines for Nest Box Projects

Starting a bird box program on your property or in your neighborhood is as easy as building a suitable nest box for the desired species and installing it in the proper location. It is really quite simple! However, there are a few guidelines to follow to increase the likelihood of a successful occupation.

  • Nest boxes must be built to the proper dimensions for the birds you wish to attract. The entrance hole is of particular importance because it must be large enough to let the target species in, yet small enough to exclude any possible competitors.
  • All boxes need some form of protection from predators. A predator guard on the box or metal siding collar on the nest pole is mandatory. (See nest plans for details)
  • Always use galvanized nails. They hold up better and last longer.
  • Boxes need proper ventilation during times of hot weather. This can be accomplished by drilling several 1/4” holes into the upper portion of the sides of the box. (See nest plans for details)
  • Don’t paint or lacquer the insides of the boxes or use pressure treated lumber – the toxic fumes may harm the birds.
  • Boxes should be cleaned out after the chicks have fledged or at the end of the season. This encourages birds to nest again and removes any parasites or fungal growth, which can be harmful to the birds.
  • Boxes should be placed with entrances facing away from the prevailing direction of winds and storms.
  • Boxes should be placed within 15-100 feet of perching sites, such as trees, shrubs, or fences.
  • If you wish to paint the outside of your boxes, use light colors that will reflect the sun’s rays. The boxes may overheat with dark colors.
  • Nest boxes need to be installed securely. Birds will avoid boxes that swing or sway in the wind.
  • Most boxes do not need a perch, which may actually attract pest species such as starlings and house sparrows.
  • Beveling the ends on the top and front pieces of wood makes for a tighter fit.

Sonoma County Nest Box Dimensions Chart

Each species has its own unique nesting criteria, and many factors determine whether or not a bird will use a box. However, it is important to construct the boxes according to the chart dimensions. The entrance hole diameter is critical to a successful nest box.

* Denotes species that reside year-round in Sonoma County.

Native Bird Species Entrance Hole Diameter (in.) Floor Size (in.) Box Height (in.) Entrance Above Floor (in.) Height Above Ground (ft.)
*Barn Owl
6
16 x 20
16
4
15-30
*Northern Sawwhet Owl
2
7 x 7
12
8-10
10-20
*Screech Owl
3
8×8
18
9-12
5-30
*Wood Duck
3×4 (oval)
12×12
24
12-16
5-40
*Downy
Woodpecker
1
4×4
12
6-8
5-20
*Hairy
Woodpecker
1
6×6
14
6-8
6-20
*Pileated
Woodpecker
4
12×12
24
12-16
15-25
*Northern
Flicker
2
7×7
18
14-16
6-20
*Chestnut-Backed Chicadee
1
4×4
12
6-8
5-15
*Oak Titmouse
1
4×4
12
6-8
5-15
*White-Breasted
Nuthatch
1
4×4
12
6-8
4-20
*Red-Breasted Nuthatch
1
4×4
12
6-8
4-20
*Pigmy Nuthatch
1
4×4
12
6-8
4-20
*Bewick’s Wren
1
4×4
12
6-8
6-10
American Kestrel
3
9×8
21
9-10
15-30
Ash-Throated Flycatcher
1
6×6
12
6-8
6-20
Tree Swallow
1
5×5
10
2-5
3-15
Violet-Green Swallow
1
5×5
10
2-5
3-15
Purple Martin
2
6×6
6
1
12-25
House Wren
1
4×4
12
2-6
6-10
Western Bluebird
1 9/16
5×5
12
6-7
5-10v

Sources for More Information on Cavity Nesting Birds

Acknowledgements

  • Established in 1976, Circuit Rider Productions, Inc. (CRP) is a private non-profit service agency dedicated to the enhancement of environmental and human resources.
  • Principal Author: John D. Crandall, Biologist
  • Rocky Thompson, CRP Restoration Planner, was instrumental during all phases of this project. Creative design and layout were made possible by Glenda Doughty. Special thanks are also due to the following people for technical review and comment, Karen Gaffney (CRP), Katherine Gledhill (CRP), Lisa Shanks, (NRCS), Charlette Sanders (NRCS), and Joan Dranginis (Madrone Audobon).
  • Breeding notes and other specific information was obtained from The Birder’s Handbook: a Field Guide to the Natural History of North American Birds by P.R. Ehrlich, D.S. Dobkin and D. Wheye. 1988. Simon and Schuster, New York, NY.
  • Breeding dates were obtained from the Sonoma County Breeding Bird Atlas. 1995. Madrone Audobon Society. Betty Burridge, editor.
  • Box plans courtesy of the Natural Resources Conservation Service.
  • Major funding provided through a grant from the USDA Natural Resources Conservation Service’s Environmental Quality Incentives Program.
  • Special thanks to: Cal Crandall, Robert Carrol Woodworking, Jason Miller, Anna Eyler, Pamela Middleton and Diane Serlin.