Sonoma County Nest Box Dimensions Chart
Note: 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 | 8x8 | 18 | 9-12 | 5-30 |
| *Wood Duck | 3x4 (oval) | 12x12 | 24 | 12-16 | 5-40 |
| *Downy Woodpecker | 1 | 4x4 | 12 | 6-8 | 5-20 |
| *Hairy Woodpecker | 1 | 6x6 | 14 | 6-8 | 6-20 |
| *Pileated Woodpecker | 4 | 12x12 | 24 | 12-16 | 15-25 |
| *Northern Flicker | 2 | 7x7 | 18 | 14-16 | 6-20 |
| *Chestnut-Backed Chicadee | 1 | 4x4 | 12 | 6-8 | 5-15 |
| *Oak Titmouse | 1 | 4x4 | 12 | 6-8 | 5-15 |
| *White-Breasted Nuthatch | 1 | 4x4 | 12 | 6-8 | 4-20 |
| *Red-Breasted Nuthatch | 1 | 4x4 | 12 | 6-8 | 4-20 |
| *Pigmy Nuthatch | 1 | 4x4 | 12 | 6-8 | 4-20 |
| *Bewick’s Wren | 1 | 4x4 | 12 | 6-8 | 6-10 |
| American Kestrel | 3 | 9x8 | 21 | 9-10 | 15-30 |
| Ash-Throated Flycatcher | 1 | 6x6 | 12 | 6-8 | 6-20 |
| Tree Swallow | 1 | 5x5 | 10 | 2-5 | 3-15 |
| Violet-Green Swallow | 1 | 5x5 | 10 | 2-5 | 3-15 |
| Purple Martin | 2 | 6x6 | 6 | 1 | 12-25 |
| House Wren | 1 | 4x4 | 12 | 2-6 | 6-10 |
| Western Bluebird | 1 9/16 | 5x5 | 12 | 6-7 | 5-10 |
