The below nestbox is designed for the Common Merganser. squirrels may use this box.
Suitable Nestbox Size: 33 inches tall. No perches at the entrance holes as they would aid predators.
Floor Dimensions: 10″ x 10″ with ventilation holes (suggested 5). Although some experts disagree with the notion that ventilation openings are needed at all. Please refer to this article for further information. This may also depend on location of nest box, exposure to direct sun as well as material used to build the nest box.
Entrance Hole: 5 x 5 inches, located about 30 above the floor
Roof: Hinged, secured with shutter hooks. Sloped down, overlapping on the sides and the front reduces exposure to rain and makes it more difficult for predators to get to the chicks or eggs.
Hardware: Best to use corrosion resistant, stainless steel and dichromate plated screws
Material to be used: Red Cedar (more durable than other wood material), rough cut boards or exterior-grade plywood at least 1/2″ thick. Unpainted.
Predator Guard: An inverted metal cone attached below the nextbox will provide some protection against predators
Mount about 4 to 10 feet up on a tree or a post
Within 1/4 mile of bodies of water (lakes or rivers) or marshes; best placed facing water or in standing water to reduce the risk of predation