Iowa · Summer breeder

Tree Swallows in Iowa

When tree swallows are present in Iowa, when they nest, which native Iowa plants feed them, and how to host them in a USDA 4b–6a yard.

Swallows (Hirundinidae)Tree SwallowTachycineta bicolor

Status in Iowa: Summer breeder
Nesting window: May–June
Broods: 1 per season
Hardiness zones: USDA 4b–6a
Nest box: 1 1/2 in hole, 5 × 5 in floor, 5–10 ft

When to expect tree swallows in Iowa

Tree Swallows 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 flies, mayflies and dragonflies.

Humid continental prairie state, with loess hills in the west and the Driftless Area in the northeast.

Nesting in Iowa

Across Iowa, tree swallows typically nest from May–June. Nest site: nest box or tree cavity lined with feathers. Females lay 4–7 eggs, incubate for 11–20 days, and young leave the nest after 15–25 days.

Hot, humid summers with thunderstorms.

Have boxes cleaned and mounted before April — tree swallows begin prospecting ahead of egg-laying.
Use a 1 1/2 in entrance on a 5 × 5 in floor, mounted 5–10 ft.
Fit a pole baffle or hole guard; ventilation gaps and drainage holes are essential.
Clean out old nests after each brood and again after June.

Native Iowa plants that attract tree swallows

Of the regional native plants we track for Iowa, these 8 provide food or cover tree swallows use:

Serviceberry

Amelanchier arborea · Tree

Early-summer berries arrive exactly when nestlings are being fed.

White oak

Quercus alba · Tree

Acorns plus hundreds of caterpillar species for nestling food.

Bur oak

Quercus macrocarpa · Tree

Drought-hardy prairie oak with large acorns and a heavy insect load.

Black cherry

Prunus serotina · Tree

Summer fruit and one of the top caterpillar host trees.

American elderberry

Sambucus canadensis · Shrub

Late-summer berry clusters taken by over 40 bird species.

Spicebush

Lindera benzoin · Shrub

Lipid-rich red fruit fuels fall migrants.

New England aster

Symphyotrichum novae-angliae · Perennial

Late nectar for insects and fall seed for sparrows.

Tall goldenrod

Solidago altissima · Perennial

Insect-rich in fall and seed in winter.

Feeding tree swallows through the Iowa year

Tree swallows readily take bluebird-style nest boxes; mount boxes in pairs 15–25 ft apart to share with bluebirds.

Best foods: Crushed eggshells in spring.
In Iowa's summer: offer water and insect foods; natural food is abundant.

Full diet breakdown for tree swallows · Best feeder for tree swallows

Frequently asked

Are tree swallows in Iowa year-round?

No. Tree Swallows are summer breeders in Iowa and leave for the winter.

When do tree swallows nest in Iowa?

Nesting in Iowa typically runs May–June, with 1 per season. Clutches are 4–7 eggs, incubated for 11–20 days.

What native plants attract tree swallows 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 tree swallows.

What size birdhouse hole do tree swallows need?

1 1/2 in, with a floor of 5 × 5 in mounted 5–10 ft.

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.