Birding Guidelines: Birdhouse Hole Size Chart - Birds and Blooms
How Big Should The Hole In My Nesting Box Be? - YouTube
Make a nest box | BTO - British Trust for Ornithology
NestWatch | Nest Box Placement - NestWatch
BBC - Breathing Places - Make a Nest Box
Bird box hole size guide (for all wild birds that use boxes) - Bird Barn
Sussex Wildlife Trust 🦔 on X: "Did you know you can attract different species of bird to nest in your garden by using different styles of bird box & hole size? #Birdbox