Nest box specification

Hooded Merganser house dimensions

The Hooded Merganser nests in tree cavity or nest box near water A box built to its measurements — and no bigger — is what makes it choose yours.

Ducks and geese (Anatidae)Hooded MerganserLophodytes cucullatus

The specifications

Entrance hole: 4 × 3 in oval
Floor (inside): 10 × 18 in
Mounting height: 6–20 ft
Bird size: 15.8–19.3 in, 16–31 oz
Clutch: 6–18 eggs
Incubation: 26–41 days
Time in nest: Ducklings leave within 24 hours
Broods: 1 per season

Build and mounting checklist

Drill the entrance to exactly 4 × 3 in oval — oversized holes let in European Starlings and larger predators.
No outside perch: cavity nesters don't need one, and it helps House Sparrows and predators.
Unpainted interior, 3/4-inch untreated wood (cedar or pine) or poly-lumber for insulation.
Drainage holes in the floor corners and ventilation gaps under the roof.
A side or front panel that opens so you can monitor and clean the box.
Rough or grooved inner front wall so nestlings can climb out.
Pole mount with a stovepipe or cone baffle to stop snakes, raccoons and cats.

When to put up a Hooded Merganser box, by state

Boxes should be up and clean a month before local nesting starts. Dates shift with latitude:

Place	Up by	Nesting	Clean out
Arkansas	January	February–May	June
Connecticut	January	February–May	June
Delaware	January	February–May	June
Illinois	January	February–May	June
Indiana	January	February–May	June
Iowa	January	February–May	June
Kentucky	January	February–May	June
Maryland	January	February–May	June
Massachusetts	January	February–May	June
Michigan	January	February–May	June
Missouri	January	February–May	June
New Jersey	January	February–May	June
New York	January	February–May	June
North Carolina	January	February–May	June
Ohio	January	February–May	June
Oregon	January	February–May	June
Pennsylvania	January	February–May	June
Rhode Island	January	February–May	June
Tennessee	January	February–May	June
Virginia	January	February–May	June
Washington	January	February–May	June
West Virginia	January	February–May	June
British Columbia	February	March–May	June
Maine	February	March–May	June
Manitoba	February	March–May	June
Minnesota	February	March–May	June
New Brunswick	February	March–May	June
New Hampshire	February	March–May	June
Ontario	February	March–May	June
Quebec	February	March–May	June
Saskatchewan	February	March–May	June
Vermont	February	March–May	June
Wisconsin	February	March–May	June
Alabama	December	January–May	June
California	December	January–May	June
Florida	December	January–May	June
Georgia	December	January–May	June
Louisiana	December	January–May	June
Mississippi	December	January–May	June
South Carolina	December	January–May	June

Full Hooded Merganser species guide →

Frequently asked

What size hole does a Hooded Merganser need?

4 × 3 in oval. A hole cut to this size admits the Hooded Merganser (15.8–19.3 in) while keeping out larger competitors.

How big should a Hooded Merganser house be inside?

A floor of 10 × 18 in. The Hooded Merganser lays 6–18 eggs, so the floor has to hold the full clutch plus growing nestlings.

How high should I mount a Hooded Merganser box?

6–20 ft. Mount on a pole with a predator baffle where possible rather than a tree or fence.

How long does a Hooded Merganser use the box?

Incubation takes 26–41 days and the young stay in the nest Ducklings leave within 24 hours. Broods per year: 1 per season.

Sources

Timing reflects typical patterns for the region as a whole; local dates vary with elevation and year. Check the linked eBird bar charts for your county.