SWALLOWS. Swallows, of the family Hirundinidae, are among the most conspicuous, well known, and beneficial of birds; they feed in flight on numerous insects detrimental to man. Seven of the eight species occurring in Texas are colonial to some extent, and all are migratory. Most have developed close associations with man and his works, constructing their nests on bridges and buildings or within highway culverts and birdhouses. They are streamlined in form, with relatively long, pointed wings and small feet, and, with the exceptions noted below, average between five and six inches in length. Snakes, hawks, and owls appear to be their major natural predators. All swallows are protected by federal and state law. Descriptions that follow are for adult birds.
The purple martin (Progne subis), the state's largest (about eight inches long) swallow, is probably the species best known to most city and suburban dwellers. This is the only United States swallow whose sexes differ markedly in appearance; males are shiny blue-black both top and bottom, and females and immatures have light breasts and bellies. Early northward migrants arrive in Texas in late January or February. They lay three to five white eggs in loosely built nests constructed of sticks and twigs within nestboxes or other available cavities and rear only one brood a year. The tree swallow (Iridoprocne bicolor) does not breed in Texas but is a common spring and fall migrant throughout the state. It is frequently seen near bodies of water and is a relatively slender and graceful flyer that intersperses curving glides with bouts of wingbeats. Its back is an iridescent greenish or bluish-black and its underparts are immaculate white. The violet-green swallow (Tachycineta thalassina) nests in forests and canyons of mountainous areas in western Texas. It is similar to the tree swallow but can be distinguished from it by the white markings that extend from its underparts around the base of its tail and almost meet at midline. It builds nests within tree cavities and holes in stream banks, as well as in bird boxes. It lays four to six white eggs and rears one, or possibly two, broods per season. Rough-winged swallows (Stelgidopteryx ruficollis) are agile and rapid fliers with slender shapes, brown backs, and lighter underparts. In Texas, they tend to be only loosely colonial and nest throughout the state in cliff crevices and holes in dirt banks or concrete embankments. Eggs are white and number three to seven; in Texas, one brood usually is reared. The bank swallow (Riparia riparia) is a small, relatively stocky, highly colonial swallow with light, fluttering flight, brown upper parts, and a dark breastband across its light underparts. Its breeding sites are widely separated and scarce in Texas, and their use is frequently irregular. The bank swallow lays three to six white eggs in grass nests constructed at the ends of burrows dug in dirt, sand, or gravel banks, and apparently rears only one brood per year in this state.
Barn swallows (Hirundo rustica) are common residents of country and suburban areas. They display shiny blue-black backs, rusty underparts, and a band of white spots across deeply forked tail feathers. Although average for swallows in body size, they have long tail feathers that increase the length of adults to about seven inches. Their flight is aggressive; they forage usually within thirty feet of ground level. They deposit three to six speckled eggs in an open cup nest of mud, grass, and hair, built on a barn rafter or culvert wall and usually lined with feathers. The barn swallow rears two to three broods during spring and summer. In south central Texas, at the northern margin of their distribution, cave swallows (Petrochelidon fulva) recently have begun to extend their range by utilizing highway culverts as substitutes for their traditional cavern and sinkhole breeding sites. Their upper parts are medium brown, and they have prominent buffy or light-orange rumps. The tail is short and unforked, and the underparts are light in color. The throat usually is buffy. A conspicuous forehead patch is chestnut brown in color. On the walls or ceilings of caves and culverts they build nests with flaring rims, composed primarily of mud or bat guano; they use less grass in nest walls than barn swallows. Cave swallows lay three to five speckled eggs and rear two or three broods. Along highways in South Texas, this species is frequently seen with the barn swallow; the two species occasionally hybridize. The cliff swallow (Petrochelidon pyrrhonota) is similar in size and color to the cave swallow, but its throat is usually much darker than that of the cave swallow, and Texas populations of cliff swallows may have either cream-colored forehead patches (in the northern portion of the state), cinnamon or fawn-colored forehead patches (southern portion), or chestnut forehead patches (the Big Bend). Cave swallow forehead patches are always chestnut brown. Major behavioral differences also separate these species. Cave swallows rear two to three broods and leave their breeding sites relatively late in the season (early September), while cliff swallows usually rear only one brood (three to five young) per season and leave their breeding sites early. The mud nests of cliff swallows are built in conspicuous locations beneath elevated rocky ledges and bridges or on buildings; they can be identified by their globular shape and tubular entrances. Urban populations of this species have been reduced in number by disturbance from the house sparrow and people; this problem continues in suburban and rural areas.
American Ornithologists' Union, Check-List of North American Birds, 5th ed. (Ithaca, New York, 1957). Roger Tory Peterson, A Field Guide to the Birds of Texas (Boston: Houghton Mifflin, 1960).