Watching swallows in Colorado is a mesmerizing experience as they dart gracefully across rivers, fields, and open skies. Their swift, acrobatic flight and shimmering feathers make every sighting unforgettable.
In spring and summer, these aerial hunters can be seen catching insects midair, resting on wires, or swooping low over water. Each species displays unique colors, calls, and behaviors, making identification exciting for bird enthusiasts.
Exploring mountain trails, wetlands, or suburban areas, you can enjoy observing swallows’ energy, skill, and beauty up close, gaining a true sense of Colorado’s vibrant birdlife.
Different Types of Swallows Found in Colorado
Barn Swallow (Hirundo rustica)
The Barn Swallow is one of the most recognizable swallow species in Colorado, easily identified by its deep blue back, rusty orange throat and forehead, and long, deeply forked tail. Adults measure about 6.7–7.9 inches (17–20 cm) in length with a wingspan of 11–13 inches (29–33 cm). Their slender, streamlined body and pointed wings make them exceptionally agile fliers, ideal for catching insects mid-air. Juveniles are duller in color, with shorter tails and less vibrant markings.
Barn Swallows are highly social and often form large flocks during migration. They are known for their graceful, acrobatic flight patterns, frequently gliding and swooping close to the ground or water surfaces. Their vocalizations include a series of chirps and twittering calls that help maintain contact within the flock. In Colorado, they are commonly seen from spring through early fall, particularly near open fields, farms, and water bodies where insects are abundant.
Feeding primarily on flying insects such as flies, beetles, and wasps, Barn Swallows capture their prey on the wing with remarkable precision. They often feed over meadows, rivers, ponds, and even roadsides. Their high metabolism and constant need for protein make them almost always on the move during daylight hours. Occasionally, they may also feed on small berries or seeds, though insects dominate their diet.
Breeding occurs from late spring through summer, and Barn Swallows construct cup-shaped nests out of mud, usually attached to buildings, bridges, barns, or cliffs. Both males and females participate in nest building, though females primarily line the nest with feathers. A typical clutch consists of 3–7 eggs, which hatch after about two weeks. Nestlings fledge in another 18–23 days, after which the young birds remain near the nest before joining the adults in migration.
Cliff Swallow (Petrochelidon pyrrhonota)
Cliff Swallows are medium-sized swallows with pale, buff-colored foreheads, brownish-orange cheeks, and glossy blue-black upperparts. Their distinctive gourd-shaped mud nests, often clustered together, make them highly visible in Colorado during breeding season. Adults are around 5.5–6.3 inches (14–16 cm) long with a wingspan of 11–12 inches (28–30 cm). Their short, squared tails differentiate them from the Barn Swallow’s deeply forked tail.
These birds are extremely social, often nesting in colonies that can include hundreds of individuals. Colonies are typically located under bridges, cliffs, or overhangs, where each pair builds a mud nest using saliva to cement the mud together. Cliff Swallows are noisy and active, often performing communal displays in flight and engaging in synchronized swoops and dives that create impressive aerial patterns.
Cliff Swallows feed almost exclusively on flying insects, including flies, beetles, and dragonflies. They forage in large flocks, often skimming over fields, wetlands, and open waters. Their highly maneuverable flight allows them to catch insects on the wing with great skill. They are also known to roost communally outside the breeding season, forming large groups that can number in the thousands.
Breeding in Colorado begins in late spring, and each pair maintains a small mud nest within the colony. The female lays 3–5 eggs, incubated for about two weeks. Both parents feed the young, which fledge in roughly 24 days. Because they nest in colonies, Cliff Swallows benefit from safety in numbers, though they can be vulnerable to parasitic insects and occasional nest predation.
Tree Swallow (Tachycineta bicolor)
Tree Swallows are medium-sized swallows with metallic blue-green upperparts, white underparts, and slightly notched tails. Adults measure about 5–6 inches (12–15 cm) in length, with a wingspan of 11–12 inches (28–31 cm). Their iridescent coloration makes them striking in flight, especially when sunlight highlights the blue and green tones. Juveniles appear duller, with grayish backs and muted white undersides, making them less conspicuous until after their first molt.
Tree Swallows are highly aerial birds, spending much of their time gliding and darting above lakes, ponds, and open fields in search of insects. They are often seen hovering briefly before making sharp turns to snatch prey mid-air. Colorado populations are migratory, arriving in spring and leaving by late fall. During migration, they often gather in large flocks, sometimes mixing with Violet-green Swallows and Barn Swallows.
These swallows feed mainly on flying insects, including mosquitoes, flies, and beetles, but they may also eat berries and seeds in late summer and fall. They hunt using their aerial agility, often flying just above water surfaces or open meadows. Tree Swallows are known for their quick, erratic flight patterns that make them efficient and difficult to follow visually.
Tree Swallows nest in tree cavities, old woodpecker holes, or artificial nest boxes. The female lines the cavity with feathers to keep eggs and chicks insulated. Clutch sizes typically range from 4–7 eggs, which hatch in about 14–15 days. Both parents feed the nestlings, which fledge in roughly 20 days. Nest sites are often near water, which provides both abundant insects and safety from some predators.
Northern Rough-winged Swallow (Stelgidopteryx serripennis)
The Northern Rough-winged Swallow is a small, modestly colored swallow with brown upperparts, pale underparts, and slightly notched tails. Adults are about 5–5.5 inches (12–14 cm) long, with a wingspan of 10–11 inches (25–28 cm). Their plain appearance distinguishes them from more colorful species like the Barn or Tree Swallow, though their rough-edged wing feathers, visible upon close inspection, give them their name.
These swallows are often solitary or found in small groups rather than large colonies. In Colorado, they favor nesting along riverbanks, cliffs, or stream edges, where they excavate burrows in sandy or earthen banks. Northern Rough-winged Swallows are strong fliers and often hunt close to water, using quick, low flights to catch insects. They are less acrobatic than other swallows but are highly persistent hunters.
Their diet consists almost entirely of flying insects, including flies, beetles, and ants. They forage low over water or open fields and sometimes glean insects from surfaces, though aerial hunting is most common. They are flexible in feeding, able to exploit small insect swarms and even congregate near other swallows when insects are abundant.
Breeding occurs in late spring and early summer. Females lay 4–7 eggs in burrows dug into soil or pre-existing cavities. Both parents feed the chicks, which fledge in about three weeks. Northern Rough-winged Swallows are migratory, leaving Colorado in late summer or early fall to spend the winter in the southern United States or Central America. Their preference for natural cliff and riverbank habitats makes them indicators of healthy riparian ecosystems.
Bank Swallow (Riparia riparia)
The Bank Swallow is a small swallow with brown upperparts, white underparts, and a distinctive dark band across the chest. Adults measure about 4.7–5.5 inches (12–14 cm) in length, with a wingspan of 10–11 inches (25–28 cm). Their short, square tails and slightly forked wings give them a compact appearance in flight. Juveniles have paler plumage and shorter tail feathers, making them less striking than adults.
Bank Swallows are highly social during the breeding season, often nesting in dense colonies along riverbanks, sand pits, and lakeshores in Colorado. Each pair excavates a vertical burrow in sandy or soft soil, where they lay their eggs. The species’ preference for bare, vertical banks makes them sensitive to habitat disturbance, though protected areas along rivers and reservoirs provide ideal nesting sites.
These birds are agile fliers and feed almost exclusively on flying insects, including flies, beetles, and small wasps. They hunt low over water or open ground, often swooping in tight, rapid maneuvers to catch prey. They are especially active in the morning and late afternoon, when insects are most abundant. During migration, they may form large flocks with other swallows, increasing foraging efficiency.
Breeding occurs in late spring, with females laying 4–6 eggs per clutch inside the burrow. Both parents feed the young, which fledge in about three weeks. After breeding, Bank Swallows congregate in communal roosts before migrating south to Central and South America for the winter. Their presence along riverbanks also makes them important indicators of healthy riparian ecosystems.
Violet-green Swallow (Tachycineta thalassina)
The Violet-green Swallow is a medium-sized swallow with iridescent green upperparts, bright white underparts, and distinctive white patches on the sides of the rump. Adults are about 5–6 inches (12–15 cm) long, with a wingspan of 11–12 inches (28–31 cm). Their glossy, metallic coloration is particularly striking in sunlight, and their small, notched tails help distinguish them from similar swallows. Juveniles are duller, with grayish backs and muted whites.
Violet-green Swallows are highly aerial and very active, frequently seen flying high above lakes, meadows, and forest edges in Colorado. They are agile and swift fliers, often performing acrobatic twists and dives while hunting. During migration, they form small flocks, though in summer they may defend nesting territories aggressively. These swallows are most visible during late spring through summer in Colorado.
They feed primarily on flying insects such as flies, beetles, and moths. Their foraging often occurs over water or open clearings, and they are capable of rapid aerial pursuits to catch fast-moving prey. Occasionally, they also consume small berries in late summer. Their flight behavior, with rapid wingbeats and glides, allows them to exploit insect swarms efficiently.
Breeding occurs in tree cavities, cliff crevices, or nest boxes. Females lay 4–7 eggs, which hatch in roughly 14 days. Both parents feed the chicks, and young fledge in about three weeks. Violet-green Swallows are often seen near water sources and open woodland edges, where insect availability and cavity nesting opportunities are abundant.
Purple Martin (Progne subis)
The Purple Martin is the largest swallow species in North America, with glossy dark purple-blue feathers covering most of the body. Adults measure 7–8 inches (18–20 cm) in length, with a wingspan of 13–16 inches (33–41 cm). Males are uniformly dark, while females have lighter underparts and slightly duller coloration. Their large size, square tail, and broad wings make them distinctive in flight. Juveniles are paler and mottled compared to adults.
Purple Martins are highly social birds that rely almost entirely on artificial housing in eastern Colorado, though western populations may use natural cavities. They form large colonies during breeding, with dozens to hundreds of individuals nesting together. Males defend nesting territories and perform aerial displays to attract females. Their loud, gurgling calls are characteristic of martin colonies.
These swallows feed exclusively on flying insects, catching beetles, dragonflies, and flies on the wing. They forage in open areas such as meadows, near lakes, or above suburban neighborhoods. Their large size allows them to cover more area and capture larger insects compared to smaller swallows. They are most active during early morning and late afternoon.
Breeding occurs in late spring, with females laying 4–5 eggs per clutch inside artificial houses or natural cavities. Both parents participate in feeding the young, which fledge after about 28–32 days. Purple Martins migrate south to Central and South America for the winter. Their dependence on human-provided housing has made them a favorite species for bird enthusiasts in Colorado.
Cave Swallow (Petrochelidon fulva)
The Cave Swallow is a medium-sized swallow with brownish-orange upperparts, paler underparts, and a slightly forked tail. Adults measure about 5.5–6 inches (14–16 cm) in length, with a wingspan of 11–12 inches (28–30 cm). Their pale forehead and rufous coloring on the throat and belly distinguish them from other swallows. Juveniles appear duller, with more grayish tones and shorter tails.
Cave Swallows are colonial nesters, often building gourd-shaped mud nests in caves, under cliffs, or beneath man-made structures like bridges. Colonies can range from a few dozen to hundreds of birds. In Colorado, they are relatively rare and typically found in the southern and western regions, where suitable nesting sites exist.
They feed mainly on flying insects such as flies, beetles, and wasps, capturing them on the wing with fast, agile flight. Cave Swallows are often seen foraging in mixed flocks with Cliff Swallows, especially near water or open fields. Their flight is strong and direct, punctuated with quick twists to catch prey efficiently.
Breeding occurs in spring and early summer, with females laying 3–5 eggs per clutch inside mud nests. Both parents feed the chicks, which fledge after roughly three weeks. Cave Swallows migrate to the southern United States or Central America for the winter. Their specialized nesting habits make them highly dependent on specific cliff or cavity habitats.
Best Time and Locations to Observe Swallows in Colorado
Swallows in Colorado are primarily migratory, arriving in spring and leaving by early fall. The peak viewing season is from April through September, with late spring (May–June) being the best time to see nesting activity. During this period, adults are busy building nests, feeding chicks, and performing their acrobatic aerial displays, making them easier to spot. Early morning and late afternoon are particularly ideal for observing swallows in flight, as insects are most active and the birds are foraging heavily.
Barn Swallows are extremely widespread and can be seen almost anywhere near open fields, farms, lakes, and towns. They often nest on barns, bridges, and other man-made structures. Cliff Swallows prefer colonies under bridge overhangs, highway structures, and cliffs, especially along rivers and reservoirs. They are highly social, so large groups are visible at once.
Tree Swallows are best observed near ponds, lakes, and wetlands, where they hunt for flying insects. Artificial nest boxes and tree cavities near water are hotspots for breeding activity. Northern Rough-winged Swallows favor riverbanks, sandbars, and stream edges, where they dig nesting burrows. Observers can often see them flying low over water or along forested edges.
Bank Swallows nest in vertical sandy banks along rivers and lakes, making riparian areas the prime locations for sightings. Violet-green Swallows are commonly seen near mountain meadows, open forests, and streams, often flying high above water or along ridgelines. Purple Martins, highly social, are best observed in artificial martin houses in suburban areas and near lakes where insect activity is abundant. Cave Swallows are rarer in Colorado but can be spotted in southern and western regions, nesting under cliffs, bridges, or in caves.
Overall, water sources, open fields, cliffs, and man-made structures are the key habitats to focus on. Observers who visit these areas in spring and summer mornings or late afternoons will have the best chance of seeing swallows performing their spectacular aerial foraging behaviors.
FAQs about Swallows in Colorado
What types of swallows can be found in Colorado?
Colorado is home to eight main swallow species: Barn Swallow, Cliff Swallow, Tree Swallow, Northern Rough-winged Swallow, Bank Swallow, Violet-green Swallow, Purple Martin, and Cave Swallow. Some are common and widespread, while others, like the Cave Swallow, are rare and mostly found in southern and western regions.
When is the best time to see swallows in Colorado?
The best time to observe swallows is during their breeding season, from April to September, with peak activity in May and June. Early morning and late afternoon are ideal for watching them in flight as they forage for insects.
Where should I go to watch swallows?
Different species prefer different habitats. Barn Swallows are common near farms and buildings, Cliff Swallows under bridges and cliffs, Tree Swallows near ponds and wetlands, Northern Rough-winged Swallows along rivers and streams, Bank Swallows on sandy banks, Violet-green Swallows in open forests and mountain meadows, Purple Martins in artificial martin houses and lakesides, and Cave Swallows under cliffs or bridges in southern Colorado.
What do swallows eat in Colorado?
All eight species are insectivores, feeding primarily on flying insects such as flies, beetles, wasps, and dragonflies. Some, like Tree and Violet-green Swallows, may also eat berries occasionally in late summer.
Are swallows migratory in Colorado?
Yes, all eight species are migratory. They arrive in Colorado in spring to breed and leave by early fall, traveling to southern United States, Central, or South America for the winter.
