Western Screech-Owl Nest Box (PNW / Cornell Spec)

Western Screech-Owl Nest Box (PNW / Cornell Spec)

A fully 3D-printable nest box designed to Cornell Lab / NestWatch specifications for Western Screech-Owls (Megascops kennicottii). Two-piece design — monolithic body and friction-fit roof — prints without supports on a large-format printer.

Species & Range

Western Screech-Owls are small, cavity-nesting raptors found throughout western North America. They're in decline across the Pacific Northwest due to habitat loss and competition for natural tree cavities. A properly built and placed nest box gives them a real alternative. They're also excellent pest control — their diet includes mice, insects, and other small invertebrates.

This box also works for Northern Saw-whet Owls, which share similar cavity requirements.

Design Features

• 8×8" (203×203mm) interior floor and 12" (305mm) interior height per Cornell/NestWatch cavity-nester specs
• 3" (76mm) entry hole — sized for screech-owls while excluding starlings and most squirrels
• Interior climbing grooves scored into the front wall below the entry hole so owlets can climb out to fledge
• Landing shelf with integrated 45° support ramp — prints without supports
• 5 drainage holes in the recessed floor for moisture management
• Ventilation slots near the top of both side walls
• 3 mounting holes in the back wall for lag screws into wood (wall or pole mount)
• Friction-fit roof with a locating lip that drops into the cavity — lifts straight off for annual cleanout, no tools needed
• 6mm floor recess keeps the cavity above any standing water

Print Settings

Body

• Printer: Requires 325×320×325mm build volume (e.g., Bambu Lab H2C)
• Dimensions: 211 × 218 × 315mm
• Orientation: Open top facing up, entry hole facing forward
• Material: PETG recommended for outdoor UV and weather resistance
• Layer height: 0.20mm
• Walls: 3–4 perimeters
• Infill: 15–20% gyroid (adds thermal insulation)
• Supports: Tree supports needed for the entry hole's top arc (~76mm bridging span)

Roof

• Printer: Requires 325×320mm bed (e.g., Bambu Lab H2C)
• Dimensions: 251 × 296 × 18mm
• Orientation: Pre-oriented — top face down on the build plate for a smooth exterior finish. Lip points upward.
• Material: PETG
• Layer height: 0.20mm
• Infill: 20% gyroid
• Supports: None needed

Installation

• Mount height: 10–15 feet above ground on a wall, post, or tree
• Facing: Entry hole facing east or south — screech-owls like to sit in the entrance and soak up morning sun
• Surface: Lag screws through the three back-wall holes into wood (chimney casing, shed wall, or a 4×4 post)
• Bedding: Add 2" of untreated wood shavings to the floor before mounting — screech-owls don't build nests, they lay eggs directly on whatever substrate is in the cavity
• Timing: Install by February to be ready for spring nesting season
• Cleanout: Lift the roof off once per year in late fall after fledging season. Remove old debris, replace wood shavings.

Fit & Tolerance

The roof lip has 0.2mm clearance per side for a snug friction fit. If your printer runs tight or loose, adjust the LIP_GAP parameter in the included Python source and re-export. The source script is fully parametric — all dimensions are defined at the top of the file.

Notes

• Painting the exterior with flat dark latex paint improves UV resistance and helps absorb solar heat for roosting warmth. Do not paint the interior.
• Do not add a perch pole below the entry hole on the exterior — external perches give predators and starlings a platform to harass nesting owls. The small landing shelf is sufficient.
• This box is sized for Western Screech-Owls and Northern Saw-whet Owls. It is not large enough for Barn Owls or Barred Owls.