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 Owl616 x 207 x 71615-30
*Northern Sawwhet Owl27 x 7128-1010-20
*Screech Owl38 x 8189-125-30
*Wood Duck3×4 (oval)12x122412-165-40
*Downy Woodpecker14x4126-85-20
*Hairy Woodpecker16x6146-86-20
*Pileated Woodpecker412x122412-1615-25
*Northern Flicker27x71814-166-20
*Chestnut-Backed Chicadee14x4126-85-15
*Oak Titmouse14x4126-85-15
*White-Breasted Nuthatch14x4126-84-15
*Red-Breasted Nuthatch14x4126-84-20
*Pigmy Nuthatch14x4126-84-20
*Bewick’s Wren14x4126-86-10
American Kestrel39x8219-1015-30
Ash-Throated Flycatcher16x6126-86-20
Tree Swallow15x5102-53-15
Violet-Green Swallow15x5102-53-15
Purple Martin14x4122-66-10
House Wren14x4122-66-10
Western Bluebird19/165x5106-75-10
SOURCES FOR MORE INFORMATION ON
CAVITY NESTING BIRDS
  • A Guide to Installing and Managing Wood Duck Boxes. 1994 California Waterfowl Association
  • Bird Watching for Dummies. 1997. IDG Books Worldwide, Inc.
  • Cornell Nest Box Network, Research Kit. 1998. Cornell Laboratory of Ornithology, Ithaca, New York.
  • Field Guide to the Birds of North America. 1983. S.L. Scott, editor. National Geographic Society, Washington, D.C.
  • For the Birds. July 1977. U.S. Fish and Wildlife Service.
  • Sonoma County Breeding Bird Atlas. 1995. Madrone Audubon Society. Betty Burridge, editor.
  • The Birder’s Handbook; a Field Guide to the Natural History of North American Birds. 1988. P.R. Ehrlich, D.S. Dobkin, and D. Wheye. Simon and Schuster, New York.
  • The Complete Birdhouse Book: the Easy Guide to Attracting Nesting Birds. 1990. Donald and Lilian Stokes. Little, Brown and Company, Canada.