Hirundo rustica Linnaeus, 1758

Barn swallow

A graceful swallow with a forked tail that nests in mud cups under eaves.

Order: Passeriformes
Family: Hirundinidae
Group: Birds
Ontario status: Established, nests in mud cups under eaves provincewide

Why it matters

A beloved insect-eater, a single family eats thousands of flies and mosquitoes a summer. The conflict is droppings under nests on porches and patios. And critically: barn swallows are Special Concern in Ontario (down-listed from Threatened by COSSARO in 2021), their active nests are protected federally under the Migratory Birds Convention Act and cannot be removed while occupied.

Origin

Native across the northern hemisphere, a bird that moved into human buildings centuries ago and never looked back. Ontario's swallows return from South America every spring.

Behavior

Hawks insects on the wing all day in graceful swooping flight. Builds neat mud cups on vertical walls under overhangs, often in loose colonies. Migrates to South America for winter, gone from Ontario roughly September to April.

Living conditions

Open country near structures: barns, sheds, bridges, and house eaves for mud-cup nests; open fields and wetlands for aerial insect hunting. Needs a mud source (puddles, pond edges) for nest building.

Signs of presence

Mud-cup nests stuck to walls under eaves, often in rows
Deeply forked tails flashing over fields on summer evenings
Mud-gathering at puddle edges in spring
Chattering, twittering calls around the nest site

Weaknesses

Completely dependent on human structures for nesting in Ontario, no barns or eaves, no swallows
Needs accessible mud; paved-over landscapes starve nest building
Aerial insectivore, insect declines hit it directly
Long migration (~10,000 km each way) with all its hazards

Myths and facts

Myth You can knock down swallow nests to stop the mess.
Reality Wrong legal basis, right instinct to hesitate: barn swallows were down-listed to Special Concern in Ontario in 2021, so the Ontario Endangered Species Act carries no nest-disturbance offence for them. But active nests are protected federally under the Migratory Birds Convention Act, nests with a live bird or viable eggs cannot be disturbed. Deterrence must happen before building starts, and even that has rules.

Research notes

Morphology

Length 150-190 mm including the deeply forked tail streamers, wingspan 290-320 mm, weight 17-22 g. Steel-blue back, rust-red throat and forehead, pale belly. Outer tail feathers elongated into streamers (longer in males).

Diagnostics

Confirm by: deeply forked tail + steel-blue back + rust throat. Tree swallows share the eaves but have a square-tipped tail and clean white belly; cliff swallows build enclosed gourd-shaped mud nests, not open cups.

Easily confused with

Tree swallow, Tachycineta bicolor Tree swallow has a notched-but-not-forked tail and nests in cavities and boxes, never in mud cups under eaves.
Cliff swallow, Petrochelidon pyrrhonota Cliff swallow builds enclosed jug-shaped mud nests in colonies; the barn swallow builds open cups.

Life cycle

Egg: Clutch 4-5 speckled eggs; incubation 13-17 days by the female
Nymph or larva: Chicks fledge at ~3 weeks; parents feed fledglings for another week
Adult: Lifespan 4-8 years typical; strong nest-site fidelity, returns to the same building yearly
Egg to adult: Hatch to fledging ~21 days
Generations per year: 1-2 broods per year

Development

Oviparous; altricial chicks in a mud-cup nest.

Reproduction

4-5 eggs per clutch × 1-2 broods/year.

Distribution

Native range: Holarctic, North America, Europe, Asia
Ontario: Breeds provincewide wherever open foraging meets nesting structures; declining
Global: The most widespread swallow species on Earth

Ecology

Obligate aerial insectivore, flies, beetles, wasps taken on the wing. Mud-cup nests on vertical surfaces under overhangs; often reuses and repairs the same nest across years. Long-distance migrant: winters in South America. Population declining across the northeast, Special Concern in Ontario (COSSARO down-listing from Threatened, 2021); still listed Threatened on federal SARA Schedule 1 (COSEWIC reassessed Special Concern in May 2021; Governor in Council decision pending).

Resistance

N/A, not a pesticide target species.

IPM implications

THE legal fact first: Special Concern on Ontario's Species at Risk in Ontario List (COSSARO 2021 down-listing from Threatened), Ontario ESA species/habitat offences do not apply, but occupied nests are federally protected under the Migratory Birds Convention Act, 1994: disturbing a nest with a live bird or viable eggs is an offence. Beneficial species regardless: each pair removes thousands of flying insects per season. Monitoring: spring nest-building surveys map the colony. The only lawful lever is pre-season deterrence (netting and ledges before mud pellets appear), and Ontario's recovery strategy favours providing alternative nesting structures over exclusion. Any plan starts with the MBCA, not the technique.

Chemical ecology

Minimal published work; colony and pair coordination is vocal and visual.

Genetics and DNA

Reference genome published: Formenti et al. 2019 (GigaScience), high-quality barn swallow reference genome; VGP bHirRus1 (2021, GCF_015227805.2).

Taxonomy

Passeriformes: Hirundinidae. Hirundo rustica Linnaeus, 1758, the most widespread swallow on Earth.

Open questions

Drivers of the Ontario decline: relative roles of insect loss, nesting-site loss, and conditions on South American wintering grounds.

References

COSEWIC assessment and Ontario recovery strategy, Barn Swallow (ontario.ca species at risk)
Brown & Brown, Barn Swallow (Hirundo rustica), Birds of the World, Cornell Lab of Ornithology
Barn Swallow, Species at risk in Ontario (ontario.ca/page/barn-swallow; status: Special Concern)