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Museum of Wildlife and Fish Biology / Outreach

   Education and Conservation through Preservation
tree swallow leaving nestbox

A banded adult Tree Swallow leaving a nestbox to gather food for small nestlings.

Songbird Nestboxes

The Museum of Wildlife and Fish Biology manages the Putah Creek Nestbox Highway.

To learn more about what is happening in nestboxes this season, visit our Songbird Nestbox Project Blog.

Nestbox Information


North America contains some 85 species of cavity nesting birds. Many of these play an important role in the control of insect pests. Unfortunately, the natural cavities or holes in which they nest are often in short supply due to cutting and felling of large dead or deteriorating trees. Those cavities that remain are often taken up by nonnative species, such as the European House Sparrow or the European Starling.

Artificial nest boxes (aka bird houses) mimic natural cavities and are readily used by cavity nesting birds. Nest boxes have been instrumental in increasing local populations of many cavity nesting species. Nest boxes are easily constructed and can be maintained to encourage target species and to discourage intruders.

Species Benefitted
Nest boxes benefit many different species. In California, the species most likely to nest in boxes include:


house wren eggs

Clutch of five House Wren Eggs.

Tree Swallow (Tachycineta bicolor)
Western Bluebird (Sialia mexicana)
Mountain Bluebird (Sialia currucoides)
Ash-throated Flycatcher (Myiarchus cinerascens)
House Wren (Troglodytes aedon)
Bewick’s Wren (Thryomanes bewickii)
Chestnut-backed Chickadee (Poecile rufescens)
Oak Titmouse (Baeolophus inornatus)
White-breasted Nuthatch (Sitta carolinensis)
Red-breasted Nuthatch (Sitta canadensis)
Pygmy Nuthatch (Sitta pygmaea)
Purple Martin (Progne subis)
Wood Duck (Aix sponsa)
Barn Owl (Tyto alba)
Northern Saw-whet Owl (Aegolius acadicus)
Western Screech Owl (Otus kennicottii)

For more information on these birds you may visit The Cornell Lab of Ornithology's All About Birds Bird Guide website or for full information, visit The Birds of North America Online.


Nestbox Building Plans
Box plans are widely-available on the web. While each species generally prefers a box of a specific dimension and hole size, in many cases one size box will fit many. (Our generic North American Bluebird Society style bluebird boxes have hosted up to seven different species—though not at the same time!) Often, it is more the specific habitat and placement of boxes that determines which species nest in them.

Nest box plans and other useful information:nestbox diagram

Tips for Nestbox Success
You can enjoy the beauty and fascination of birds—while providing much-needed breeding habitat for them—by following a few basic steps:

western bluebird eggs

Western Bluebird eggs in a nestbox.

  1. Figure out which species nest in your area and which habitats they prefer. Field guides and ornithological websites offer a wealth of information on birds and their natural history.  A little advance homework in this area will go a long way in determining the success of your nest boxes.


  1. Purchase or construct some boxes and place them in suitable habitats. Wherever possible, boxes should have an easterly or northerly exposure, and should receive afternoon shade, especially in hot climates. Boxes can be mounted on buildings, poles, or tree trunks, or can be hung by wires from tree limbs or eaves. Different types of boxes can be placed together to accommodate a suite of species, or a single type of box can be placed at intervals to accommodate individuals of the same species. In this case, it’s important to maintain a sufficient distance between boxes to avoid conflicts over territory (50 meters, about 165 feet, is generally sufficient, though some species with small home ranges, such as wrens, will tolerate smaller distances between boxes.
  1. Monitor your boxes regularly to insure their success and the safety of their occupants. Keep your distance early in the season when birds are making decisions about where to nest, as they are easily put-off at this time. After birds have constructed their nest, and especially after they have eggs and/or chicks (watch for food being brought to the nest box), box contents should be checked every 7-10 days. Any dead chicks should be removed, as should left-over material from failed nesting attempts. At the end of the breeding season (late summer or fall), old nesting material should be removed. Boxes can be left up over the winter to provide roosting habitat for wintering birds. It’s a good idea to check these boxes at the beginning of the breeding season (late winter or early spring) to make sure they’re clean and in good repair for the next occupants. The below links contain more detailed information on maintenance and monitoring of nest boxes.
tree swallow leaving box

A banded adult Tree Swallow leaving a nestbox to gather food for small nestlings.

Citizen Science
Many nest box monitors participate in citizen science projects, such as the Cornell Laboratory of Ornithology’s Nest Watch program or the California Bluebird Recovery Program. In these programs, you report your observations and the information you have gathered (species of bird, number of eggs, number of nestlings, time of nesting, etc.). This data gets compiled with everyone else’s data in a region-wide effort to better understand changes in bird populations.

Final Thoughts
Nest box projects can be as simple as a single box in your backyard, or as elaborate as a network of hundreds of nest boxes along a nest box “trail.” Click here for information on the MWFB's Putah Creek Nestbox Highway.What matters is that boxes are constructed with an eye towards the needs of their target species and are maintained lovingly and diligently by the people who care about them. Nest box projects are particularly well-suited for scouting organizations, senior centers, and school groups. Boxes can also be constructed to accommodate native squirrels, bats, and beneficial insects, and specialized “roost boxes” can be constructed for birds to use in winter. The important thing is to have fun and to enjoy helping an important and valuable wildlife group.

Additional Links for More Information on Nestbox Programs
California Bluebird Recovery Program:
Cornell Lab of Ornithology Nest Watch:
North American Bluebird Society:
Purple Martin Conservation Association:

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