Spring 2004

Table of Contents

Living with Washington's Wildlife: Swallows

(Editor's note: This newsletter regularly features excerpts from "Living With Wildlife in the Pacific Northwest," a book-in-progress by WDFW's Seattle-area wildlife biologist Russell Link that focuses on species most often encountered by people.)

Swallows are migratory songbirds that occur and breed in the Pacific Northwest from spring to fall. They are sparrow-sized birds with long, pointed wings and streamlined bodies developed for fast, acrobatic flight. They are seen swooping and flying over fields, orchards, lakes, and anywhere else that flying insects are abundant.

Seven members of the swallow family breed in the Pacific Northwest. Of these seven species, barn and cliff swallows regularly build mud nests attached to buildings, a process that sometimes brings them into conflict with humans.

The barn swallow (Hirundo rustica) is a distinctive bird with bold plumage and a long, slender, deeply forked tail. It has blue-black upper parts, a reddish throat and breast, and a rust or buff colored belly. Females are slightly duller and shorter-tailed than males. Although they are still common in Washington, Breeding Bird Census data indicate that barn swallows have decreased significantly in the state since 1980.

The cliff swallow (Petrochelidon pyrrhonota) looks somewhat like the barn swallow, but has relatively broad, round wings and a short, squared-off tail. The back, wings, and crown of the adult are a deep blue, and its belly is light colored.

Feeding
Swallows are insectivores, catching a variety of insects in midair with their wide-gaped bills and expert flight. Barn swallows eat some berries, seeds, and dead insects from the ground, particularly during bad weather.

Swallows will fly several miles from their nest site to forage. Long periods of continuous rainfall make it difficult for adult swallows to find food, occasionally causing young birds to die. Swallows drink mid-flight; as they fly over water they dip their bill to the surface to drink.

Nesting
Barn and cliff swallows construct nests formed from mud pellets that they collect in their beaks. Barn and cliff swallows travel up to a half-mile to gather mud from the edges of ponds, puddles, and ditches. Gathering mud and constructing nests are social activities for cliff swallows; even unmated swallows may build a nest that goes unused.

To find one of their mud sources, look for swallows landing on the ground, which they rarely do other than when nest building. The birds will remain on the ground for a minute or so and then fly off to a nest site. The collection site will be marked with numerous small holes made by the birds as they poke their beaks into the mud several times to get a good load. You may also see swallows flying with feathers or grass —materials used in the final stages of nest building.

Barn swallow nests are cup-shaped; cliff swallow nests are gourd-shaped. The interior of both these birds' nests contains an inner cup lined with grass, hair, and feathers.

Historic nesting sites of both barn and cliff swallows include cliffs, walls of canyons, and vertical banks protected from rain. Today, barn swallows almost always build nests on eaves, bridges, docks, or other man-made structures that have a ledge that can support the nest, a vertical wall to which it can be attached, and a roof. Cliff swallow nests are built on vertical walls, natural or man-made, frequently with some sort of sheltering overhang. Freeways, bridges, barns, and other large buildings are regularly used.

Barn swallows usually nest in single pairs; cliff swallows nest in colonies that may contain a dozen to over 500 nesting pairs. Barn and cliff swallow nests are prone to external parasite infestations. Colonies may not be reoccupied because of heavy infestations, and if parasite populations become too great, both species will prematurely desert their nests, abandoning their young.

Reproduction
Nest building is done by both sexes, and in mild years may begin as early as late March. Time from start of nest building to departure of young is 44 to 58 days.

Brood parasitism is common among cliff swallows. Females will lay eggs in other females' nests and will also carry eggs in their beaks from their own nests to the nests of others.

Both parents take turns incubating three to five eggs, which hatch after 12 to 17 days. Both sexes care for the young, which begin to fly at 20 to 25 days of age. After learning to fly, the young remain in the nest, or near it, to be fed by parents and to roost at night. They leave the nest after a few days and will remain in the area for several weeks.

Barn and cliff swallows can raise two clutches per year. Re-nesting will occur if nests or eggs are destroyed. For example, nests may fall because they were built too rapidly, or may crumble because of prolonged wet or humid weather.

Migration
Swallows are among the "neotropical migrants" that spend six or more months in southern climates, not to avoid cold temperatures so much as for the lack of insects to eat during winter in the north.

Barn and cliff swallows begin their return to northern climes in late winter and early spring. Depending on weather conditions, they are usually first spotted in Washington in late March or early April.

Swallows are usually first to begin the southern migration in mid-August to early September. They gather in large groups (sometimes as many as 2,000 birds) on telephone wires and other perches before departing. Swallows migrate during the day, catching flying insects along the way. They will normally not move into areas unless flying insects are available for food, which occurs after a few days of relatively warm weather —60 degrees or more.

Attracting Swallows
To best manage your property for swallows, protect nearby undisturbed wild areas, including wetland, lake, or grassy areas of any size used by swallows for drinking, mud collecting, and feeding.

Also, retain as many large snags —dead or dying trees— as possible for swallow perching and/or nesting. Avoid using insecticides, not just for swallows, but for the nearly 70 percent of Pacific Northwest breeding birds that eat insects.

Supplementing the supply of nest materials and installing nest boxes are other ways to enhance your property for swallows. Swallow species that use nest boxes are violet-green swallows, tree swallows, and purple martins; barn swallows will use nesting platforms.

Have nesting materials and boxes available for use by early March. Mud can be provided to barn swallows and cliff swallows by spraying a shaded area with water to create a mud puddle. A mudfilled, elevated birdbath may serve as a cat-safe mud-gathering site for swallows. Claylike soil with some humus is a good building material because plant fibers strengthen the nest. Swallows will also gather small downy feathers and 3-inch lengths of dry grass placed nearby.

Preventing Conflicts
It has been speculated that one reason swallows choose to nest on door stoops, light fixtures, and porch fronts is because the close proximity to humans keeps crows and other predators away. The birds will even risk cat predation and human vandalism and nest close to the ground if the location is in a place frequented by humans. The barn swallow's close association with humans in Europe goes back over 2,000 years. Thus, when you thwart a barn or cliff swallow's nesting effort, you may be denying the birds their only chance at successful reproduction.

Conflicts with swallows occur primarily because of the droppings and other debris they deposit in inconvenient places. (Swallow droppings are NOT a public health concern unless hundreds of nests are involved.)

When swallows first hatch, the parents eat their droppings, which keeps the nest clean and insect free. After a few days, the adults carry the droppings away from the nest to prevent detection by predators. After about the twelfth day, the young back up to the edge of the nest and defecate out over the rim.

Placing newspaper or some similar material where droppings accumulate can solve the problem. As necessary, the paper and droppings can be added to a compost pile, dug into the ground (droppings make wonderful fertilizer), or placed in the garbage. Similarly, a blanket or sheet can be used to cover a car or other structures and moved when needed.

Another solution is to install a board under the nest(s) to catch the droppings and debris. Because of its close proximity to the nest, the board should be cleaned as needed to prevent infestations of insects and mites that may live in the accumulated debris.

If for some reason swallows nesting on a building or other structure cannot be tolerated, a barrier can be installed. Barriers include any physical structure placed between the swallow and the structure. A permit is not required for this method if it is done before the birds arrive, during nest building when there are no eggs or young in the nest, or after the birds have left for the winter. If swallows have eggs or young in the nest, exclusion may not be used without a permit.

To prevent barn swallows from nesting on door jambs, window jambs, and other sites on the side of a building, cover the area with bird-netting or 1-inch mesh chicken wire. Drape the material from the outer edge of an eave down to the side of the building. Remove wrinkles and folds that could trap or entangle swallows or other birds.

Bird netting and chicken wire are available from nurseries, hardware stores, and farm supply centers. Some pestcontrol companies sell a heavy-duty netting material with a larger mesh than common black netting used to protect fruit from birds. The netting is not as likely to create problems for songbirds, which sometimes get caught in the smaller mesh netting.

Attach the barrier using staples, brass cup-hooks, adhesive-backed hook-andloop Velcro, trash-bag ties, or other fasteners. The barrier may also be first stapled to or wrapped once or twice around wood laths, which are then attached to the structure. This technique can also be modified to keep swallows from entering a breezeway or similar sites.

Another technique is to hang a curtain of bird netting or chicken wire from the eave. The curtain should be 3 to 4 inches from the wall and extend down from the eave 18 inches or more.

A solution for small areas is to install aluminum foil, aluminum flashing, or heavy plastic over the spot where swallows nests are unwanted. The smooth surface will prevent swallows from adhering mud to the wall. Painting the area with a glossy latex paint may also be effective. It may be possible to offer barn swallows an optional nesting site by constructing a nest platform.

Hawk, owl, and snake models, noisemakers, revolving lights, red-and silver flash tape, and hanging pie tins are unlikely to deter swallows.

According to federal law, nest removal is permissible only if it is not occupied by adult birds or no eggs have been laid. At the first sign of nest building, use a water hose or pole to knock down nest materials. Because swallows are persistent at rebuilding nests, you will need to continually remove the nest mud for several days until the birds stop.

Swallows are strongly attracted to old nests or to the remnants of deteriorated nests, so all traces of mud should be removed. Swallows are federally protected and any permit to lethally control them in extreme conflict cases is issued by the U.S. Fish and Wildlife Service. Some examples are concerns for aircraft safety from a nesting colony at an airport or potential food contamination from a colony over a loading area at a food-processing center. In most cases a permit for lethal control will not be issued for swallows nesting on a residence or other buildings and causing aesthetic damage.