Perch Supply
Nest box specification

Purple Martin house dimensions

The Purple Martin nests in in the east, nests almost entirely in human-supplied martin houses and gourds A box built to its measurements — and no bigger — is what makes it choose yours.

Purple Martin in flight showing iridescent dark plumage
Photo: Rhododendrites / Wikimedia Commons

The specifications

Entrance hole
1 3/4–2 1/8 in round, or starling-resistant crescent (3 × 1 3/16 in)
Floor (inside)
6 × 6 in minimum (6 × 12 in preferred)
Mounting height
10–20 ft on a telescoping pole, 40+ ft from trees
Bird size
7.5–7.9 in, 1.6–2.1 oz
Clutch
3–6 eggs
Incubation
15–18 days
Time in nest
26–32 days
Broods
1 per season

Build and mounting checklist

  • Drill the entrance to exactly 1 3/4–2 1/8 in round, or starling-resistant crescent (3 × 1 3/16 in) — 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 Purple Martin box, by state

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

PlaceUp byNestingClean out
FloridaFebruaryMarch–JulyAugust
TexasFebruaryMarch–JulyAugust
AlabamaMarchApril–JulyAugust
ArizonaMarchApril–JulyAugust
CaliforniaMarchApril–JulyAugust
GeorgiaMarchApril–JulyAugust
LouisianaMarchApril–JulyAugust
MississippiMarchApril–JulyAugust
North CarolinaMarchApril–JulyAugust
South CarolinaMarchApril–JulyAugust
VirginiaMarchApril–JulyAugust
ArkansasAprilMay–JulyAugust
ConnecticutAprilMay–JulyAugust
DelawareAprilMay–JulyAugust
IllinoisAprilMay–JulyAugust
IndianaAprilMay–JulyAugust
IowaAprilMay–JulyAugust
KansasAprilMay–JulyAugust
KentuckyAprilMay–JulyAugust
MarylandAprilMay–JulyAugust
MassachusettsAprilMay–JulyAugust
MichiganAprilMay–JulyAugust
MinnesotaAprilMay–JulyAugust
MissouriAprilMay–JulyAugust
NebraskaAprilMay–JulyAugust
New JerseyAprilMay–JulyAugust
New YorkAprilMay–JulyAugust
OhioAprilMay–JulyAugust
OklahomaAprilMay–JulyAugust
OntarioAprilMay–JulyAugust
OregonAprilMay–JulyAugust
PennsylvaniaAprilMay–JulyAugust
Rhode IslandAprilMay–JulyAugust
South DakotaAprilMay–JulyAugust
TennesseeAprilMay–JulyAugust
WashingtonAprilMay–JulyAugust
West VirginiaAprilMay–JulyAugust
AlbertaMayJune–JulyAugust
MaineMayJune–JulyAugust
ManitobaMayJune–JulyAugust
New BrunswickMayJune–JulyAugust
New HampshireMayJune–JulyAugust
North DakotaMayJune–JulyAugust
Nova ScotiaMayJune–JulyAugust
SaskatchewanMayJune–JulyAugust
VermontMayJune–JulyAugust
WisconsinMayJune–JulyAugust

Full Purple Martin species guide →

Frequently asked

What size hole does a Purple Martin need?

1 3/4–2 1/8 in round, or starling-resistant crescent (3 × 1 3/16 in). A hole cut to this size admits the Purple Martin (7.5–7.9 in) while keeping out larger competitors.

How big should a Purple Martin house be inside?

A floor of 6 × 6 in minimum (6 × 12 in preferred). The Purple Martin lays 3–6 eggs, so the floor has to hold the full clutch plus growing nestlings.

How high should I mount a Purple Martin box?

10–20 ft on a telescoping pole, 40+ ft from trees. Mount on a pole with a predator baffle where possible rather than a tree or fence.

How long does a Purple Martin use the box?

Incubation takes 15–18 days and the young stay in the nest 26–32 days. Broods per year: 1 per season.

Sources

  1. Purple Martin — All About Birds, Cornell Lab of Ornithology
  2. Purple Martin life history — Cornell Lab of Ornithology
  3. Purple Martin — Audubon Guide to North American Birds
  4. Purple Martin Conservation Association — housing guidelines
  5. NestWatch nest box plans and species requirements — Cornell Lab

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.