Purple Martins in Iowa
When purple martins are present in Iowa, when they nest, which native Iowa plants feed them, and how to host them in a USDA 4b–6a yard.
- Status in Iowa
- Summer breeder
- Nesting window
- May–July
- Broods
- 1 per season
- Hardiness zones
- USDA 4b–6a
- Nest box
- 1 3/4–2 1/8 in round, or starling-resistant crescent (3 × 1 3/16 in) hole, 6 × 6 in minimum (6 × 12 in preferred) floor, 10–20 ft on a telescoping pole, 40+ ft from trees
When to expect purple martins in Iowa
Purple Martins are summer residents in Iowa, arriving shortly before nesting begins in May and leaving after the young are independent. Through the season they feed on dragonflies, flies, beetles and moths; flying ants and wasps.
Humid continental prairie state, with loess hills in the west and the Driftless Area in the northeast.
Nesting in Iowa
Across Iowa, purple martins typically nest from May–July. Nest site: in the East, nests almost entirely in human-supplied martin houses and gourds. Females lay 3–6 eggs, incubate for 15–18 days, and young leave the nest after 26–32 days.
Hot, humid summers with thunderstorms.
- Have boxes cleaned and mounted before April — purple martins begin prospecting ahead of egg-laying.
- Use a 1 3/4–2 1/8 in round, or starling-resistant crescent (3 × 1 3/16 in) entrance on a 6 × 6 in minimum (6 × 12 in preferred) floor, mounted 10–20 ft on a telescoping pole, 40+ ft from trees.
- Fit a pole baffle or hole guard; ventilation gaps and drainage holes are essential.
- Clean out old nests after each brood and again after July.
Native Iowa plants that attract purple martins
Of the regional native plants we track for Iowa, these 8 provide food or cover purple martins use:
Early-summer berries arrive exactly when nestlings are being fed.
Acorns plus hundreds of caterpillar species for nestling food.
Drought-hardy prairie oak with large acorns and a heavy insect load.
Summer fruit and one of the top caterpillar host trees.
Late-summer berry clusters taken by over 40 bird species.
Lipid-rich red fruit fuels fall migrants.
Late nectar for insects and fall seed for sparrows.
Insect-rich in fall and seed in winter.
Feeding purple martins through the Iowa year
Purple Martins do not use feeders. Supporting them means supplying correctly built colony housing in the open and managing House Sparrows and starlings.
- Best foods: Crushed eggshells (calcium) offered on a tray near housing.
- Avoid: Seed and suet feeders — martins will not use them.
- In Iowa's summer: offer water and insect foods; natural food is abundant.
Frequently asked
Are purple martins in Iowa year-round?
No. Purple Martins are summer breeders in Iowa and leave for the winter.
When do purple martins nest in Iowa?
Nesting in Iowa typically runs May–July, with 1 per season. Clutches are 3–6 eggs, incubated for 15–18 days.
What native plants attract purple martins in Iowa?
Serviceberry, White oak, Bur oak, Black cherry, American elderberry, Spicebush, New England aster, Tall goldenrod are native plants in Iowa that provide food or cover for purple martins.
What size birdhouse hole do purple martins need?
1 3/4–2 1/8 in round, or starling-resistant crescent (3 × 1 3/16 in), with a floor of 6 × 6 in minimum (6 × 12 in preferred) mounted 10–20 ft on a telescoping pole, 40+ ft from trees.
Purple Martins in other regions
Other backyard birds in Iowa
Sources
- Purple Martin — All About Birds, Cornell Lab of Ornithology
- Purple Martin life history — Cornell Lab of Ornithology
- Purple Martin — Audubon Guide to North American Birds
- Purple Martin Conservation Association — housing guidelines
- eBird region overview and bar charts — Iowa
- USDA Plant Hardiness Zone Map (2023)
- Audubon Native Plants Database
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.