- 5.1 in
- 11–11.8 in
- 0.7–1.2 oz
- Smaller than a Purple Martin; slightly larger than a Bank Swallow.
- Hirondelle à front blanc (French)
- When a Cliff Swallow has had a hard time finding food, it will watch its neighbors in the nesting colony and follow one to food when it leaves. Although sharing of information about food at the colony seems unintentional, when a swallow finds food away from the colony during poor weather conditions it may give a specific call that alerts other Cliff Swallows that food is available. By alerting other swallows to a large insect swarm an individual may ensure that the swarm is tracked and that it can follow the swarm effectively.
- Although the Cliff Swallow can nest solitarily, it usually nests in colonies. Colonies tend to be small in the East, but further west they can number up to 3,700 nests in one spot.
- Within a Cliff Swallow colony some swallows lay eggs in another swallow's nest. Sometimes the swallow may lay eggs in its own nest and then carry one of its eggs in its bill and put it in another female's nest.
- When young Cliff Swallows leave their nests they congregate in large groups called creches. A pair of swallows can find its own young in the creche primarily by voice. Cliff Swallows have one of the most variable juvenal plumages, and the distinctive facial markings may help the parents recognize their chicks by sight too.
Formerly restricted to canyons, foothills, and river valleys with natural cliff faces and overhangs, Cliff Swallows have spread into a wide variety of habitats by nesting on buildings, bridges, and other human-made structures. They now live in grasslands, towns, broken forest, and river edges, but avoid heavy forest and deserts. In the south-central and northeastern states they are rare and localized breeders. Most colony sites are close to a water source, open fields or pastures for foraging, and a source of mud for nest building. Cliff Swallows spend the winter in grasslands, farmland, marshes, and the outskirts of towns in southern South America.
Cliff Swallows eat flying insects all year round, foraging during the day in groups of 2 to more than 1,000 birds. They feed on the wing above grassy pastures, plowed fields, and other open areas, but also over floodplain forests, canyons, and towns—often taking advantage of thermal air currents that bring together dense swarms of insects. In cool or rainy weather when insects are scarcer and thermals weaker, they may also feed over lakes, ponds, and rivers. Cliff Swallow colonies serve as foraging information centers as parents make trips back and forth to feed nestlings: unsuccessful foragers follow their successful neighbors to food sources. Their diet consists of many types of flying insects (particularly swarming species), including bugs, flies, bees, wasp, ants, beetles, lacewings, mayflies, butterflies, moths, grasshoppers, crickets, dragonflies, and damselflies.
- Clutch Size
- 1–6 eggs
- Number of Broods
- 1-2 broods
- Egg Length
- 0.7–0.9 in
- Egg Width
- 0.5–0.6 in
- Incubation Period
- 10–19 days
- Nestling Period
- 20–26 days
- Egg Description
- White, creamy, or pinkish, with brown speckles or blotches.
- Condition at Hatching
- Helpless, with bare pink skin, weighing less than a tenth of an ounce each.
Both sexes help build the nest, though the male may begin building before he attracts a mate. They gather mud in their bills along streambanks, lakesides, or puddles, usually near the colony but sometimes up to a few miles distant. They bring mud pellets back in their bills and mold them into place with a shaking motion. The finished nest is gourd shaped and contains 900–1,200 individual mud pellets. It measures about 8 inches long, 6 inches wide and 4.5 inches high, with walls 0.2–0.7 inches thick. The entrance, which is sometimes elongated into a tube, is about 1.7 inches high and 2 inches wide. The pair lines their nest with dried grass and continues patching it up with mud throughout the breeding season.
Each Cliff Swallow pair first chooses a colony, then takes over an existing nest or selects a space on the colony to build a new nest. Colonies may be located on cliffsides, caves, building eaves, bridges, highway culverts, dams, or large trees, and each nest is built at the juncture between a vertical wall and a horizontal overhang. The female spends more time than the male scoping out colony sites before they settle on one. An unmated male may choose a site on his own and later attract a mate.
Cliff Swallows are the most colonial swallow in the world, regularly forming colonies of 200-1,000 nests, with a maximum of 3,700 nests in one Nebraska site. They preen, feed, drink, and bathe in groups, and they continue sticking together in large flocks during migration and on their wintering grounds. Cliff Swallows sleep in trees for most of the year, but a breeding bird will start sleeping in the nest as soon as the structure is partially finished. They fight for nest sites by grappling in half-built nests or on the bare wall. Fighting birds sometimes fall into the water and manage to row with their wings to reach the shore. Nest owners defend their completed nests by sitting in the entrances, puffing up their head and neck feathers to look larger, and lunging at intruders. Each bird has one mate with whom it raises young, but the pair does not associate away from the nest, and both members frequently mate outside the pair bond. Cliff Swallow predators include Sharp-shinned Hawks, American Kestrels, Prairie Falcons, Peregrine Falcons, Barn Owls, Great Horned Owls, Mississippi Kites, Black-billed Magpies, Loggerhead Shrikes, Common Grackles, Acorn Woodpeckers, Red-headed Woodpeckers, bull snakes, rat snakes, coachwhip snakes, rattlesnakes, fire ants, mink, and domestic cats.
Cliff Swallows are numerous and their populations have been fairly stable in the last half-century, according to the North American Breeding Bird Survey. Partners in Flight estimates the global breeding population is about 40 million, with 79 percent breeding in the U.S., 12 percent in Canada, and 9 percent in Mexico. They are not on the 2012 Watch List. Cliff Swallow numbers probably increased dramatically beginning in the nineteenth century as they expanded into new breeding habitats such as bridges, buildings, and culverts. At the same time, their breeding has been impeded by the spread of invasive House Sparrows, which often take over their nests. In the northeastern United States, those conflicting influences caused Cliff Swallow numbers to drop during the 1900s. The northeastern population is currently low. Other regions that have seen declines include the Pacific Northwest, coastal California, and the Great Lakes, although these have been balanced by increases in other parts of the continent. Management officials have successfully increased local Cliff Swallow populations by trapping House Sparrows at colony sites. The species has expanded in the southeastern United States in recent decades.
Long-distance migrant. Cliff Swallows spend several months migrating at a leisurely pace through Mexico, Central America, and eastern South America to reach their wintering grounds. They migrate during daytime in groups of up to several hundred, foraging as they move.
Find This Bird
One easy way to find Cliff Swallows is to look for their gourd-shaped mud nests clustered under horizontal overhangs—many a highway overpass is swarming with Cliff Swallows in summer. To find these birds while they’re out foraging, head to a lake, river, or wetland and seek out foraging flocks of swallows. Scan the swallows carefully, focusing on finding a square-tailed bird with a pale, pumpkin-colored rump and dark upperparts. Scan the upper levels of a foraging flock, as Cliff Swallows often forage higher than other species.