Cliff swallows are small, graceful birds that get their name from their habit of building gourd-shaped mud nests on vertical cliffs. Measuring just 5-6 inches in length, these sparrow-sized birds have a distinctive appearance that makes them easy to identify.
Size and Shape
Cliff swallows have a compact, chunky body shape. Their wings are pointed and slender, well-suited for fast, agile flight. When perched, they often hold their wings tucked close against their body. The tail is short and slightly forked.
As mentioned, they measure around 5-6 inches from the tip of the bill to the tip of the tail. They have a wingspan of approximately 12 inches. Overall, cliff swallows are very petite birds. They weigh just 0.7-0.9 ounces, which is similar in weight to a couple of nickels.
Plumage
The plumage of cliff swallows is elegant and distinct. Adults have glossy blue-black feathers on the crown, back, wings and tail. Their forehead, sides of the head and throat are a warm cinnamon-rufous color. The breast and belly are coated in buff-colored feathers.
There is a sharp delineation between the black back plumage and the lighter underside. When in flight, this contrast makes the light-colored chest and forehead very noticeable.
Male and females have identical plumage. The colors are more muted in juveniles, but still distinctive enough to identify the species.
Bill and Eyes
Cliff swallows have a very short, triangular bill that tapers to a point. The bill is black. Their eyes are also black.
They have a wide gape that opens extra wide when catching insects in mid-air. Small, stiff rictal bristles line the base of the bill, helping catch and trap insect prey.
Legs and Feet
Their legs are very short, with the tarsus measuring just 0.4 inches. The feet have four toes, three pointing forward and one pointing back. The toes are flattened laterally.
The legs and feet are covered in black feathers down to the toes. The claws are small and black. Overall, the legs and feet of cliff swallows are tiny and delicate.
Flight and Behavior
Cliff swallows are incredible fliers. They have long, pointed wings and are very agile in the air. They fly swiftly and dart about erratically when chasing down flying insect prey.
In level flight, they have quick, stiff wingbeats interspersed with short glides. Their flight path is usually straight and direct.
Around nesting sites, cliff swallows are highly social. They chatter constantly and gather in large flocks. But when migrating and foraging, they typically spread out over a wide area.
Similar Species
The combination of blue-black and rufous-cinnamon plumage is distinctive to cliff swallows. However, they do resemble two other species:
- Barn swallows – Barn swallows have deeply forked, longer tails, light colored underneath. The forehead and throat are a more vibrant cinnamon color.
- Cave swallows – Found in west Texas; small with uniform brown plumage. Lack the contrasting colors of cliff swallows.
Their small mud nests clinging to cliffs are also a reliable identification clue for these birds.
Nesting
The mud nests built by cliff swallows are engineering marvels. Shaped like retort-shaped gourds, the nests have a tubular entrance that opens downward and expands into a roomy chamber inside.
The nests adhere to vertical walls underneath overhangs on cliffs, bridges, buildings, and other structures. Swallows build them by collecting thousands of small mud pellets in their beaks and slowly constructing the nest shape.
Both males and females participate in nest building. Mud pellets are passed between the mates as they work. Nests are often reused year after year.
Migration
Cliff swallows spend their winters in southern South America. In spring, they migrate north into North America to breed. These birds are capable of traveling huge distances during migration.
They winter as far south as northern Argentina and Chile. Then every spring they fly thousands of miles north to their breeding grounds, which span from western Alaska clear across most of North America.
Migrating flocks form massive feeding swarms that can number in the tens of thousands of birds. They migrate during the day and stop to roost at night. It takes around 6 weeks to complete the full journey each way.
Diet
Feasting on flying insects is what cliff swallows do best. They catch insects in mid-air, swooping, diving and turning adeptly during pursuit. Occasionally they may glean stationary insects off of surfaces as well.
Their diet is composed mostly of flies, bees, wasps, flying ants, beetles, moths and mayflies. They eat hundreds of insects daily. They continue foraging on the wing even into dusk.
Cliff swallows need a constant supply of insects nearby their nesting colonies. They forage up to a mile away from their nests, but prefer to stay closer if possible.
Range and Habitat
During the breeding season, cliff swallows can be found across most of western and central North America. Their range stretches from Alaska down into Mexico, and east to the Great Lakes and Gulf Coast regions.
They are always associated with open areas that provide vast foraging habitat near ample vertical nesting surfaces. Typical habitats include river valleys, prairies, coastal areas, agricultural lands and areas with bridges/buildings.
They avoid dense forests and high mountain elevations. But anywhere with open flying room, cliffs and a bounty of insects will attract cliff swallows.
Conservation Status
Cliff swallows are still common and widespread across their breeding range. However, there are some concerning declines in parts of their range. Their overall numbers have dropped around 25% in the last 50 years.
The main threats seem to be pesticides reducing insect prey populations, and destruction of nesting habitat. Cliff swallows are protected under the Migratory Bird Treaty Act.
Interesting Facts
- Cliff swallow nests may be home to up to 15 different species of birds and insects that cohabitate with the swallows.
- Nests are often re-used for many generations, becoming layered with new mud each year. Old nests can reach 3 feet long!
- The Anasazi people of the Southwest considered cliff swallow nests good luck and build their homes near nesting sites.
- Cliff swallows arrive in San Juan Capistrano, California each year on March 19th, a date celebrated by the city’s annual swallow festival and parade.
Summary
With their distinct plumage, tiny size, and epic migrations, cliff swallows have captivated people for centuries. Watching them dart through the skies snatching up insects in midair is a sight to behold.
These little acrobats of the bird world build their mud-bottle nests across the vertical faces of cliffs, bluffs, and under bridges. Their stamina and aerial agility are admirable qualities, carried out by cliff swallows across North America every summer.