SWALLOWS and Conservation Biology Cooperative Extension University of California Davis, California 95616

Home , Cave swallow, Cliff swallow, Hirundo, Progne, Riparia, Stelgidopteryx

W. Paul Gorenzel Staff Research Associate Department of Wildlife, Fisheries, SWALLOWS and Conservation Biology Cooperative Extension University of California Davis, California 95616

Terrell P. Salmon Wildlife Extension Specialist Department of Wildlife, Fisheries, and Conservation Biology University of California Davis, California 95616

Fig. 1. Cliff swallow (Hirundo pyrrhonota) with nests on a building.

Identification Damage Prevention and Repellents Control Methods Not effective. Eight members of the swallow family Hirundinidae breed in North America: Toxicants Exclusion the tree swallow (Tachycineta bicolor), None are registered. violet-green swallow (Tachycineta Netting or wire mesh. thalassina), purple martin (Progne Trapping Strip doors. subis), bank swallow (Riparia riparia), Not allowed. northern rough-winged swallow Habitat Modification (Stelgidopteryx serripennis), barn swal- Shooting Substrate modification: slick low (Hirundo rustica), cave swallow surfaces discourage nesting. Not allowed. (Hirundo fulva), and the cliff swallow (Hirundo pyrrhonota). Of the eight spe- Nest Removal Architectural design: some cies, barn and cliff swallows regularly designs discourage nesting. Avoid Wash nests down with a water hose or build mud nests attached to buildings overhanging eaves. knock down with a pole. and other structures, a habit that Frightening sometimes puts them into conflict with humans. This is particularly true of the Not effective for barn or cliff swallows. cliff swallow, which nests in large colonies of up to several hundred pairs. Barn swallows tend to nest as single pairs or occasionally in loose colonies

PREVENTION AND CONTROL OF WILDLIFE DAMAGE — 1994 Cooperative Extension Division Institute of Agriculture and Natural Resources University of Nebraska - Lincoln United States Department of Agriculture Animal and Plant Health Inspection Service Animal Damage Control E-121 Great Plains Agricultural Council Wildlife Committee of a few pairs. Some homeowners con- sider barn swallows to be at most a minor nuisance. Many homeowners tolerate nesting barn swallows as pleasant and interesting summer companions around the home. This chapter will focus on cliff and barn swallows because of their close association with humans. The cliff swallow, 5 to 6 inches (13 to 15 cm) in length, is the only square- tailed swallow in most of North America (Fig. 1). It is recognized by a pale, orange-brown rump, white forehead, dark, rust-colored throat, and steel-blue crown and back. The cave swallow is similar in appearance, but has a rust-colored forehead and pale throat; it is restricted to southeast New Mexico and central, south, and west Texas. The barn swallow, 5 3/4 to 7 3/4 Fig. 2. Barn swallow with open, cup-shaped nest inches (15 to 20 cm) in length, is the lined with feathers. only swallow in the United States with a long, deeply forked tail (Fig. 2). Barn swallows have steel-blue plumage on Habitat from human activities. Their nests, the crown, wings, back, and tail. The originally built on cliffs or in caves and forehead, throat, breast, and abdomen Four basic conditions are found near crevices, are now built on beams or are rust colored. Females are usually most cliff and barn swallow nest sites: walls of buildings or other structures. duller colored than the males. (1) an open habitat for foraging, (2) a The presence of livestock and power suitable surface for nest attachment be- lines for perching are features com- Range neath an overhang or ledge, (3) a sup- monly associated with barn swallow ply of mud of the proper consistency nest sites. Cliff and barn swallows are found for nest building, and (4) a body of throughout most of North America. fresh water for drinking. Food Habits Breeding occurs northward to Alaska The original nesting sites of cliff swal- and the Yukon, across Canada, All swallows are insectivores, catching lows were cliffs and walls of canyons throughout the western United States, a variety of insects. Stomachs of 375 and vertical banks, usually along per- and south into Mexico. Barn swallows cliff swallows and 467 barn swallows manent streams. Human structures are common nesters in most of the collected in different areas of the coun- (for example, buildings, bridges) and southern United States, except Florida. try contained prey from the following agricultural-related activities (irriga- Until recently, cliff swallows did not orders: Hymenoptera (bees, wasps, tion, canals, reservoirs) have increased breed in the southern United States and ants) 29%, 23%; Coleoptera the number and distribution of suit- east of central Texas and south of (beetles) 27%, 16%; Hemiptera (true able nesting sites, and cliff swallow west-central Tennessee or western bugs) 26%, 15%; and Diptera (flies) populations have increased accord- Kentucky. Reports of new colonies in 13%, 40% for cliff and barn swallows, ingly. Historically, cliff swallows were eastern Tennessee, Louisiana, Ala- respectively. presumed to be most common in the bama, Arkansas, Mississippi, and western mountains. They spread east- Cliff swallows may forage over areas Florida suggest a range expansion into ward following human settlement and up to 4 miles (6.4 km) away from the the southern Atlantic seaboard and development of eastern North nest. They forage as a loose unit, and Gulf Coast states. Barn swallows are America. adults may be away from the colony also found in Europe, North Africa, for hours prior to the hatching of and Asia. The preferred habitat of barn swallows young. After the young hatch, a more includes open forests, farmlands, sub- or less steady stream of adults return urbs, and rural areas with buildings to the colony with food for the that provide nest sites. Like cliff swal- nestlings. lows, barn swallows have benefited

E-122 Barn swallows will fly several miles vive in unoccupied nests for up to 3 with many swallows using the same from the nest site to suitable foraging years without feeding and await mud source. A typical cliff swallow areas. Long periods of continuous returning swallows in spring. In select- nest contains 900 to 1400 pellets, each rainfall make it difficult for adult barn ing a nest site, cliff and barn swallows representing one trip to and from the and cliff swallows to find food, occa- apparently assess which nests are nest. sionally causing nestling mortality. heavily infested with parasites and Among cliff swallows, mud gathering avoid them. Cliff swallow colonies and nest construction are social activi- often are not reoccupied after 1 or 2 General Biology, ties; even unmated swallows will start years of use because of heavy infesta- nests. Mated swallows may build Reproduction, and tions. Cliff swallows will even prema- more than one nest per season, even turely desert their nests en masse, Behavior though not all will be used. A count of leaving their young to starve, when nests under construction will not give Migration swallow bug populations become too an accurate estimate of the number of great. Cliff and barn swallows winter in breeding cliff swallows. South America. They begin a north- Nest Construction ward migration in late winter and Egg Laying early spring overland through Central Cliff swallow nests are gourd-shaped, Cliff swallows usually begin laying America and Mexico. Swallows enclosed structures with an entrance eggs before the entrance tunnel is com- migrate during the day and catch fly- tunnel that opens downward (Fig. 1). pleted. Each day 1 egg is laid until the ing insects along the way. They will The tunnel may be absent from some clutch, usually 3 or 4 eggs, is com- not penetrate regions unless flying nests. The mud pellets used to build pleted. In Texas, egg laying may begin insects are available for food, which the nest consist of sand and smaller as early as late March to early April, occurs after a few days of relatively amounts of silt and clay. The nest while in North Dakota nesting may warm weather, 60 to 70oF (16 to 21oC) chamber is lined sparingly with not start until early to mid-June. or more. Arrival dates can vary greatly grasses, hair, and feathers. The nest is Within a large colony, the date of egg with weather conditions. In general, cemented with mud under the eave or laying varies due to the staggered cliff and barn swallows enter the overhang of a building, bridge, or arrival dates of the swallows. For small southern United States in mid-March other vertical surface. The first cliff colonies, laying may be more synchro- to mid-April and reach the northern swallow nests on structures are usu- nous. portions of their range by early June. ally located at the highest point possible, with subsequent nests attached Barn swallows typically lay 4 or 5 Site Selection below it, forming a dense cluster. eggs, but laying may be delayed for some time after nest building is com- Swallows have a homing tendency Barn swallow nests are cup-shaped pleted. The breeding season begins in toward previous nesting sites. Under rather than gourd-shaped, and the early April in the south to mid-June in suitable conditions, a nest is quite mud pellets contain coarse organic the northern portions of the range. durable and may be used in successive matter such as grass stems, horse Barn swallows are double-brooded, years. Most cliff swallows arrive at a hairs, and feathers (Fig. 2). The nest resulting in a prolonged nesting particular colony within a 24-hour cup is profusely lined with grasses and season. period. At large colonies, swallows feathers, especially white feathers. may arrive in successive waves. Resi- Barn swallow nests are also typically Nest Failures dent adults are the first to return, fol- built under eaves or similarly pro- lowed by adults who bred at other tected sites but not necessarily at the Renesting will occur if nests or eggs colonies, and by young swallows who highest point possible. Barn swallows are destroyed. Nests may fall because have not yet bred. The younger swal- often use a beam or the protruding they were built too rapidly or crumble lows include individuals not born at edge of a door or window jamb as the because of prolonged humid weather the selected colony. base for the nest, or attach the nest at or rain. House sparrows (Passer domesticus) sometimes usurp empty Swallow nests are inhabited by hema- the juncture of the two walls of an swallow nests and may also drive off tophagous (bloodsucking) insects and interior corner. swallows from new nests. A cliff mites. Swallow bugs (Oeciacus Both male and female cliff and barn swallow nest taken over by house vicarius), most common in cliff swal- swallows construct the nest, proceed- sparrows is identified by the abundant low nests, can spread rapidly by ing slowly to allow the mud to dry and nest lining (grasses, weeds, feathers, crawling from nest to nest in a new harden. Depending on mud supply and litter) protruding out of the colony or by clinging to the feathers of and weather, nest construction may entrance tunnel. Cats associated with adults. Infestations of swallow bugs take 1 to 2 weeks. Mud is collected at farm and other buildings are common and mites reduce nestling growth rates ponds, puddles, ditches, and other predators of barn swallows. and cause up to half of all nestling sites up to 1/2 mile (0.8 km) away, deaths. Swallow bugs are able to sur-

E-123 Hatching they can become a major nuisance, pri- if very compelling reasons exist. An marily because of the droppings they example might be the safety hazard of Both sexes incubate the eggs. Incuba- deposit. In such instances they may a nesting colony located at an airport tion begins before the last egg is laid create aesthetic problems, foul machin- where aircraft safety is in question and and ranges from 12 to 16 days for cliff ery, and cause health hazards by con- where other methods of control are not swallows and 13 to 17 days for barn taminating foodstuffs. Their mud nests applicable. In most cases (for example, swallows. Most studies report incuba- eventually fall to the ground and can swallows nesting on a residence or tion of 14 or 15 days. Whitewash on cause similar problems. Parasites other building), a permit allowing the ground below the nest or on the found in swallow nests, including lethal control will not be issued. rim of the nest entrance is a sign of swallow bugs, fleas, ticks, and mites, newly hatched nestlings inside the For permit requirements in your area, may bite humans and domestic ani- nest. This marking occurs when adults contact the closest US Fish and Wild- mals, although these are not the usual remove fecal sacs from the nest and life regional office or USDA-APHIS- hosts. In addition, cliff swallow nests later when nestlings defecate from the ADC district office. At the first sign of are often used by house sparrows, in- nest. nest building, contact the appropriate troducing another avian pest and its authorities, since swallows can build attendant damage problems and po- Fledging and Postnesting Period their nests and lay eggs in a short time. tential health hazards. Cliff swallow nestlings fledge 20 to 25 Timing is critical in those regions that days after hatching; barn swallows Barn swallows nesting singly or in require a permit. If a swallow problem fledge in 17 to 24 days. The juvenile small groups on a structure can cause has been experienced in the past at a swallows appear similar to adults but similar problems but of a lesser magni- site and is expected to reoccur, then are dull colored and have less sharply- tude due to the smaller numbers apply for a permit in advance of the defined color patterns. The fledglings present. birds’ return. A fee is charged for a return to the nest each day for 2 to permit. several days to be fed before leaving it Legal Status permanently. Within a week, juveniles Damage Prevention and will join flocks and leave the area. In the United States, all swallows are Control Methods classified as migratory insectivorous At least some cliff swallows raise 2 birds under the Migratory Bird Treaty Exclusion broods in a breeding season. Second Act of 1918. Swallows are also pro- broods are documented from Virginia tected by state regulations. It is illegal Exclusion refers to any control method and West Virginia but are uncommon for any person to take, possess, trans- that denies a bird physical access to a in central California. Late nests may port, sell, or purchase swallows or nest site. Exclusion represents a rela- result from renesting attempts after a their parts, such as feathers, nests, or tively permanent, long-term solution first failure, or from late nesters. The eggs, without a permit. As a result, to the problem. A permit is not re- time from start of nest building to de- certain activities affecting swallows are quired for this method except when parture is 44 to 64 days: 7 to 14 days subject to legal restrictions. eggs or young are in the nest. nest building, 3 to 6 days egg laying, Plastic net or poultry wire can provide 12 to 16 days incubation, 20 to 25 days Permit Requirements to fledging, and 2 or 3 days to leave a physical barrier between swallows the nest. Reports of colony occupancy A depredation permit issued by the and a nest site. Mesh size should be ranging from 110 to 132 days indicate US Fish and Wildlife Service may be about 3/4 inch (1.9 cm); however, 1- ample time for 2 broods. required to remove swallow nests. inch (2.5-cm) mesh has been used suc- Three of seven administrative regions cessfully. If plastic net is used, it After leaving the nest, swallows may of the US Fish and Wildlife Service in should be taut to reduce flapping in remain in the general area for several the continental United States require a the wind, which looks unsightly and weeks. By late summer there is a gen- permit regardless of the time of year. results in tangles or breakage at eral southward movement, and by the This includes nests under construction, mounting points. Do not use mist net end of September few swallows re- completed but empty nests, nests with or any other thin, flexible net with main in the nest site. Fall migration of eggs or young, or nests abandoned af- loose pockets or wrinkles that could swallows is not well documented. ter the breeding season. Four of the trap or entangle swallows. For best re- seven regions do not require a permit sults, install net or poultry wire before Damage if eggs or young birds are not present the swallows arrive. It may be left up in the nest. permanently or removed after the Cliff swallows nest in colonies and of- nesting season. If eggs or nestlings are present, a per- ten live in close association with hu- mit authorizing nest removal or the Attachment methods may vary ac- mans. Many swallow colonies on use of exclusion techniques is required cording to site requirements and the buildings and other structures are in- in every region and will be issued only degree of permanence desired. Net can nocuous. In some situations, however,

E-124 be attached using tape, staples, velcro, ing the entrance or blocking it with net net hung as a curtain to block an trash bag ties, or plastic fasteners such or wire is practical and effective. At entrance is recommended only where as zip ties or polyclips. Polyclips are a one site, cliff swallows abandoned there is no possibility of its being useful aid for installing netting. They nests inside barn lofts when entrance caught and ripped by equipment. snap together through the netting ways were partially closed. At ware- Weighting the bottom of the net will strands and allow the use of nails, houses and other buildings with fre- help keep it reasonably taut and in screws, or wire for attachment. A quent pedestrian or equipment position during windy weather. more elaborate method uses hooks, passage, opening and closing an en- Barn swallows have been repelled such as brass cup hooks, mounted on trance way may be bothersome and from nesting by clear monofilament wooden eaves and the sides of build- impractical. In these situations strip line attached under eaves. The lines ings. An advantage of hooks or velcro doors of vinyl plastic may be installed were spaced 12 inches (30 cm) apart is that the net can be taken down easily (Fig. 5). Strip doors consists of 6- to 16- and were in a parallel or zigzag pat- during the nonbreeding period or for inch (15- to 41-cm) wide strips of vinyl tern. painting or maintenance of light fix- hung like a curtain and are primarily tures. If hooks or staples are used, they used to control temperature in refrig- Habitat Modification should be rust-resistant to avoid un- erated areas. Strips overlap about 2 Substrate Modification. Modifica- sightly rust stains. For net, a support- inches (5 cm). Strip doors do not tion of the nest substrate has proven ing framework of wooden dowels require opening and closing like con- effective. Swallows prefer surfaces that along the edges can ease attachment to ventional doors and are not damaged provide a good foothold and nest the hooks and create a more equal ten- by passage of equipment. The use of sion on the net (Fig. 3). Net may also be stapled to or wrapped once or twice around wood laths, which are then nailed directly to the structure. On a concrete or cement structure, a power- activated tool, sometimes called a stud gun, can be used to nail the wood lath. The net or wire should extend from the outer edge of the eave down to the sides of the building so the eaves no longer provide swallows with protec- tion from the elements (Figs. 3 and 4). No openings should remain where swallows might enter. Hanging a curtain of netting from eaves is reported effective (Fig. 4). The curtain should be 3 to 4 inches (8 to 10 cm) from the wall and extend down from the eave 18 Fig. 3. Netting mounted on building from the inches (46 cm) or more. For barn outside edge of the eave down to the side of the building. Insert shows a method of attachment swallows the net or wire should be using hooks and dowels. extended down further than for cliff swallows to cover door and window jambs and to block off interior corners. Usually, swallows will not fly into a net or other obstruction, but will stop and hover in front of it. If only that sec- tion of a building where swallows have nested is netted, the swallows will often choose alternative sites on the same structure. Therefore, any part of a building suitable for nesting must be netted. Barn swallows frequently and cliff swallows occasionally enter buildings through doors or other open entryways and nest inside among the Fig. 4. Four methods which may deter swallow nesting. From left to right: Netting attached from the outer edge of the eave down to the side of the building; a curtain of netting; metal projections along rafters. In some instances simply clos- the junction of the wall and eave; fiberglass panel mounted to form a smooth, concave surface.

E-125 documented, architectural design does Toxicants, Trapping, and influence colony site suitability. Build- Shooting ings with overhanging eaves at acute There are no chemical toxicants cur- to right angles with the wall are poten- rently registered by EPA for swallow tial nest sites. Conversely, sites where control, and shooting, trapping, or the overhang and wall meet at an harming swallows is not permitted. obtuse angle or are rounded and concave are rarely used. The width of the Nest Removal overhang may be important to site suitability, although the point at which Nest removal should be initiated at the this becomes critical is unknown. Few first sign of nest building because of colonies are observed with an over- the difficulty in obtaining a permit to hang of less than 6 to 8 inches (15 to 20 remove nests with eggs or young. Usu- cm). ally nests can be washed down with a water hose or knocked down with a Substrate texture is a factor; wood, pole. Removing nests by these meth- Fig. 5. Strip doors of vinyl plastic allow passage stucco, masonry, and concrete surfaces of equipment and exclude swallows and other ods is a messy and time-consuming birds. are favorable substrates for nest at- process and may cause dispersal of tachment. Metal is rarely used as a nest parasites and water damage to the nest substrate. Nests on metal surfaces attachment. Removal of the rough sur- building. are usually located at a crotch or joint face of a wall and/or overhang makes where the swallow can gain a foot- As builders of mud nests, swallows a site less attractive. This may be hold. In situations where construction have evolved to persist despite nest accomplished in various ways. Fiber- is planned and swallows are present failures from rain or moisture. Wash- glass panels make nest attachment dif- on nearby structures, consideration to ing down nests is nothing more than ficult if installed between the eave and materials and design may eliminate fu- an artificial rainstorm. Because swal- wall to form a smooth, concave surface ture problems. Swallows may move to lows will persistently rebuild nests, (Fig. 4). A smooth surface is also cre- nearby structures if control is applied removal will be required for several ated by a curtain of aluminum foil or at an existing colony. days during nest building. Persistence plastic tarp draped from a wire strung is undoubtedly affected by the physi- along the junction of the wall and roof Frightening ological condition of the swallows, overhang. Other smooth-surfaced ma- Hawk, owl, or snake models; noise- past nesting history at the site, and the terials such as glass, plexigass, or sheet makers; and revolving lights have availability of alternate sites. The swal- metal can be used. shown little, if any, success or are lows may return the following year, A fresh coat of paint that dries to a unproven against swallows. As evi- and unless additional control mea- slick surface is sometimes effective. On denced by nests in and on buildings, sures are implemented, the whole pro- rough surfaces, painting is of doubtful barn and cliff swallows are relatively cess may need to be repeated. value because it does not alter the ba- tolerant of human activity and other Leaving swallow nests intact may be sic rough texture of the surface. Paint- disturbances. appropriate in some instances. For ing may be effective on smoother Repellents example, if swallows have established surfaces, but this technique has not a colony, raised their young, and left, been thoroughly tested. Chemical roost repellents (poly- nest removal would also remove nest butenes, sticky pastes, sprays) have parasites, thus improving the site for Metal projections such as Nixalite® not been proven effective. Unless a and Cat Claws® are sharp, needle-like the swallows returning the next suitable nesting site is almost entirely spring. Swallow bugs will overwinter wire devices generally installed on covered with repellent, swallows will building ledges and window sills to in the nests, and if the parasite load is still be able to land, gain a foothold, high in the spring, the swallows might discourage pigeons and starlings from and begin nest construction. A sticky roosting. Although adaptable to abandon the colony. If not, they would repellent may actually be counter- probably reoccupy the nests. At the mounting and use under eaves, metal productive by improving nest adher- spines have not been widely used for first signs of reoccupancy, such as ence. Cliff swallow nests built over a repair of old nests or building of new swallow control (Fig. 4). In one in- sticky repellent have been observed. stance, cliff swallows learned to land nests, nest removal (with a permit in Since state pesticide registrations vary, some locations) should be started and on the metal spines and eventually check with your local Cooperative built nests attached to them. continued until the nesting attempts Extension office for information on end. possible repellents. Architectural Design. Although all the factors that constitute a suitable colony site are not yet understood or

E-126 Economics of Damage Acknowledgments Erskine, A. J. 1979. Man’s influence on potential nesting sites and populations of swallows in and Control Canada. Can. Field Nat. 93:371-377. Figures 1 through 5 by Arlene Chin, Senior Art- ist, Visual Media, University of California, Johnsgard, P. A. 1979. Birds of the Great Plains: Costs of damage are difficult to quan- Davis. breeding species and their distribution. tify and vary with the particular site Univ. Nebraska Press, Lincoln. 539 pp. and the method of control employed. Mayhew, W. W. 1958. The biology of the cliff The cost of actual or potential damage For Additional swallow in California. Condor 60:7-37. can range from the cleanup of drop- Information Moller, A. P. 1990. Effects of parasitism by a pings on and around a structure, to haematophagous mite on reproduction in thousands of dollars from swallows Anon. 1981. Bird control problem solved with the barn swallow. Ecol. 71:2345-2357. netting. Pest Control 49:28-29. contaminating foodstuffs at a process- Pochop, P. A., R. J. Johnson, D. A. Aguero, and ing center or posing a danger to air- Barclay, R. M. R. 1988. Variation in the costs, K. M. Eskridge. 1990. The status of lines in craft at an airport. Similarly, control benefits, and frequency of nest reuse by barn bird damage control—a review. Proc. Vertebr. Pest. Conf. 14:317-324. costs vary greatly. When hosing is swallows (Hirundo rustica). Auk 105:53-60. used, costs are primarily labor-related. Beal, F. E. L. 1918. Food habits of the swallows, a Samuel, D. E. 1971. The breeding biology of barn Net is relatively inexpensive (from family of valuable native birds. US Dep. and cliff swallows in West Virginia. Wilson Bull. 83:284-301. about $9 to $33 per 1,000 square feet Agric. Bull. No. 619. 28pp. depending on quantity purchased, Brown, C. R., and M. B. Brown. 1986. Speich, S. M., H. L. Jones, and E. M. Benedict. 1986. Review of the natural nesting of the 1992 prices) and is reported to be effec- Ectoparasitism as a cost of coloniality in cliff swallows (Hirundo pyrrhonota). Ecol. 67:1206- barn swallow in North America. Am. Midl. tive for 4 to 5 years before replacement 1218. Nat. 115:248-254. is necessary. Labor and other equip- Emlen, J. T., Jr. 1952. Social behavior in nesting ment costs to install netting, however, cliff swallows. Condor 54:177-199. can be quite high. For example, mounting net on a concrete versus a wooden Emlen, J. T., Jr. 1954. Territory, nest building, Editors and pair formation in the cliff swallow. Auk structure, or 100 feet (30 m) versus 10 71:16-35. Scott E. Hygnstrom feet (3 m) above the ground can drasti- Robert M. Timm Emlen, J. T. 1986. Responses of breeding cliff Gary E. Larson cally increase costs. Costs for each site swallows to nidicolous parasite infestations. must be judged on an individual basis. Condor 88:110-111.

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