Rough-winged swallows are small, agile birds that feed primarily on insects caught during flight. They forage over open areas like fields, marshes, ponds, and rivers, swooping down to grab bugs out of the air. Their diet consists mainly of flies, beetles, wasps, bees, butterflies, moths, mayflies, and dragonflies. Rough-winged swallows are adept at catching insects on the wing and can snatch tiny prey from the air with precision.
Typical prey
Some of the common insects and other arthropods eaten by rough-winged swallows include:
- Flies – House flies, deer flies, horse flies, stable flies
- Bees and wasps – Honeybees, bumblebees, paper wasps, mud dauber wasps
- Butterflies and moths – Many species
- Beetles – Ladybugs, june bugs, Japanese beetles, cucumber beetles
- Grasshoppers, crickets, and katydids
- Ants, termites, and other flying ants
- Mayflies
- Dragonflies and damselflies
- Spiders
- Aquatic insects – Midges, mosquitoes, caddisflies
Rough-winged swallows are aerial insectivores, meaning they catch all their prey while flying. They pluck insects out of the air using their wide mouths and grab them with their small, pointed bills. These agile flyers snap up bugs in mid-flight, sometimes even turning upside down to snatch insects from below. Their flying skills and quick reflexes make them well-adapted for catching insects on the wing.
Hunting strategies
Rough-winged swallows use several hunting strategies and techniques to catch insects:
- Hawklike flight – They cruise through the air and dive erratically to grab bugs.
- Low-flying over water – Skim the surface snapping up emerging aquatic insects.
- Perch hunting – Perch on branches, wires, or other elevated sites and fly out to catch passing insects.
- Swarm chasing – Follow swarms and concentrations of flying insects.
- Group foraging – Forage in loose flocks to maximize prey captures.
Their aerobatic flight and swift movements allow them to scoop up insects that most other birds would miss. Rough-winged swallows are well-designed for fast, acrobatic flight, with pointed wings, short bills, and compact bodies. These features give them great aerial agility and maneuverability for catching insects on the wing.
Diet composition
Numerous studies have analyzed the diets of rough-winged swallows across their range. The relative composition of their diet can vary based on habitat, location, season, and insect availability. But flies, beetles, bees/wasps, and mayflies typically dominate.
One analysis from New York found the following breakdown:
- Flies – 35%
- Beetles – 33%
- Bees and wasps – 12%
- Butterflies/moths – 5%
- Mayflies – 5%
- Other insects – 10%
Another study from Ontario, Canada found:
- Flies – 30%
- Beetles – 28%
- Bees and wasps – 15%
- Mayflies – 10%
- Ants/termites – 5%
- Other insects – 12%
In Oklahoma, one analysis reported:
- Flies – 22%
- Bees and wasps – 21%
- Beetles – 18%
- Butterflies/moths – 11%
- Grasshoppers – 9%
- Mayflies – 6%
- Other insects – 13%
So while the proportions vary, flies, bees/wasps, beetles, and mayflies make up the bulk of their diet across different regions.
Food consumption
Rough-winged swallows are voracious predators. They need to eat substantial amounts of insects each day to meet their high energy needs for flight. Exact food intake can depend on factors like body size, nesting stage, and weather conditions. But some estimates indicate:
- 700-1000 insects per day during the breeding season
- Up to 1400 insects per day when feeding nestlings
- An average of 275 insects per hour when actively foraging
Their high metabolism and demanding aerial lifestyle require a large quantity of insect prey. Rough-winged swallows can spend 5-8 hours foraging each day, consuming hundreds or thousands of bugs in that time.
Drinking and feeding
Rough-winged swallows sometimes skim the surface of water bodies to drink while flying. They scoop up a beakful of water without landing. But they do not feed while perched on the water’s surface, since they catch all prey on the wing.
These swallows will also occasionally pick insect fragments off the ground, but this makes up a very small portion of their overall diet. They mainly hawk insects from the air, not while perched.
Adaptations for aerial feeding
Rough-winged swallows have several key adaptations that allow them to catch insects on the wing:
- Wide gape – Their large mouth openings allow them to easily catch prey mid-flight.
- Short, pointed beaks – Well-suited for plucking insects from the air.
- Small bodies – Compact size provides agility and aerobatic ability.
- Pointed wings – Built for speed and rapid turns in pursuit of prey.
- Swift flight – Capable of swift horizontal and vertical flight to grab passing insects.
- Big eyes – Enhanced vision to spot tiny insects while flying.
These traits enable rough-winged swallows to deftly hawk insects and make split-second maneuvers to catch bugs on the wing. Their flying skills and aerial adaptations allow them to hunt successfully.
Nestlings
Adult rough-winged swallows provide their nestlings with the same insect diet they eat themselves. But the adults first catch the insects, then carry them back to the nest to feed the young. Nestlings can’t forage for themselves until they fledge and leave the nest.
Parent birds bring back mouthfuls of insects to provision the chicks throughout the day. They capture bugs near the nesting area and frequently return with food for the hungry nestlings. Parent swallows are diligent foragers, working from dawn to dusk to deliver enough insects to sustain the growing chicks.
Fledglings
Once young rough-winged swallows fledge and leave the nest, parents continue to feed and care for them. Fledglings follow the adults around begging loudly for food. Though clumsy at first, the young birds gradually improve at catching insects themselves.
Parent swallows bring insects to fledglings in mid-air until they become adept at self-feeding. This family foraging continues for several days after fledging. Eventually the young can hawk flying insects completely independently, learning the aerial feeding skills vital for their survival.
Seasonal and regional variations
Rough-winged swallow diets can shift throughout the year as insect populations change. The types of insects available also varies across different regions they inhabit. But they are able to adapt and target whatever flying insects are abundant at a given time and place.
In spring, newly emerged aquatic insects become important prey. In summer, terrestrial insects like beetles, flies, ants, and grasshoppers may dominate their diet. Variable fall populations of dragonflies, wasps, and others supplement winter flies.
Northern populations may consume more mayflies and midges compared to southern birds that eat higher proportions of wasps, butterflies, and beetles based on availability. But rough-winged swallows can deftly switch prey when insect communities change.
Spring
Common spring prey include mayflies, caddisflies, stoneflies, midges, craneflies, mosquitoes, and emerging aquatic insects.
Summer
Abundant summer insects like flies, bees, moths, butterflies, ants, beetles, dragonflies, and grasshoppers.
Fall
Late season wasps, flying ants, termites, and swarms of various species stock up fat reserves for migration.
Winter
Overwintering flies and other insects active on warm winter days help sustain wintering swallows.
Foraging habitat
Rough-winged swallows hawk for insects above open country, fields, marshes, streams, ponds, and lakes. They avoid dense forests, but may forage along forest edges. Prime feeding areas include:
- Grasslands
- Pastures
- Meadows
- Prairies
- Farmland
- Marshes and wetlands
- Ponds, lakes, rivers
- Open woodlands
- Suburbs and parks
Any habitat with abundant flying insects and space to maneuvere is ideal. Rough-winged swallows especially favor water bodies that attract aquatic insects to feast on.
Time spent feeding
Rough-winged swallows are daytime feeders. They spend much of their active day hunting on the wing when insects are most available. They may forage in spurts throughout the daylight hours, alternating periods of feeding with resting.
In one study, they were observed foraging about 5-8 hours total per day. They often have 2-3 major feeding periods, one in early morning, one late afternoon, and sometimes another midday.
These swallows feed most intensively early and late when insect activity peaks. But they may snack on insects opportunistically all day long during the breeding season when energy demands are high.
Weather and feeding
As aerial insectivores, rough-winged swallows rely on flying insects that are most active and abundant in warm, calm weather. Rainy, windy, or cold conditions can make feeding difficult.
During harsh weather, fewer insects fly so rough-winged swallows may not get enough to eat. Prolonged storms or low temperatures can starve swallows that can’t find food. So they need stretches of favorable weather to replenish energy reserves.
These birds will forage in light rain if enough insects are flying. But steady precipitation forces them to retreat to shelter until conditions improve. Wind also impedes flight and insect activity. So rough-winged swallows are fair-weather feeders adapted to temperate climates.
Migration and diet
Rough-winged swallows migrate long distances between their breeding and wintering grounds. While traveling, they feed on whatever insects are available en route, including:
- Midges
- Flies
- Termites
- Ants
- Wasps
- Bees
- Moths
- Butterflies
- Grasshoppers
- Dragonflies
Migrating swallows opportunistically hawk any insects they find along the way. Their stamina allows them to fly up to 500 miles nonstop if needed between food sources during migration.
They must replenish energy whenever possible on migration. So wetlands, fields, woodlands, and any habitat with insect concentrations provide important stopover feeding sites.
Diet in wintering range
In their tropical winter range, rough-winged swallows continue feeding on aerial insects. Abundant prey includes:
- Flies
- Mosquitoes
- Midges
- Termites
- Ants
- Butterflies
- Beetles
- Grasshoppers
- Bees
- Wasps
The warm climate of their winter range provides insects to feed on year-round. Rough-winged swallows spend winters hunting bugs over open wetlands, fields, savannas, and open woodlands.
Conclusion
Rough-winged swallows are supreme aerial insectivores with a diverse diet dominated by flies, bees, beetles, wasps, and mayflies. They exhibit great skill at snatching insects from the air using their small bills and agile flight. Rough-winged swallows need to consume hundreds to thousands of bugs daily to power their high-energy lifestyle. Their aerial feeding adaptations allow them to thrive across temperate North America.
