FRIENDS OF EDGEWOOD NATURAL PRESERVE

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Swallows are the most conspicuous, well known, and beneficial of birds; they feed in flight on numerous insects detrimental to man. They’re instantly recognizable by their slender, streamlined bodies. They are “familiar” birds throughout the world (100 species in all), often nesting in close association with people, even inside their homes. They are known to many as harbingers of spring and as symbols of good luck. It’s difficult to think of an animal with more innate grace and beauty than swallows.

The swallow that “returns to San Juan Capistrano Mission” each March is the Cliff Swallow. Watching them gather mud to build their globular homes in colonies under bridges, or in the eaves of buildings is a sight to behold. They stuff as much mud as possible into their tiny beaks and carry it substantial distances.

The Cliff Swallow is one of 8 species found in California, all of which are migratory. The remaining seven are the Purple Martin (largest), Cave Swallow, Tree Swallow, Barn Swallow, Bank Swallow, Violet-Green Swallow, and the Northern Rough-Winged Swallow. Three of these species, the Cliff, Bank, and Barn are colonizing species that breed in colonies and build their nests close together. In this way, there is no territory for the individual bird to defend, except for its own nest.

Northern Rough-Winged Swallow Reprinted without permission from http://www.pma.edmonton.ab.ca/ vexhibit/eggs/vexeggs/passer/nrws.htm

Spring and early summer visitors to the Park passing under Hwy. 280 will no doubt be aware of one of the two California swallow species that nest at Edgewood. The conspicuous Northern Rough-Winged Swallow will be nesting in holes on the underside of the highway. Unlike the Cliff, Bank, and Barn, these swallows are not colonial. They prefer to nest in isolated pairs. This brown-backed, dusky-throated little swallow (5-6”) prefers the vast open grasslands near Hwy. 280 for low altitude aerial foraging. John James Audubon (1838) discovered the Northern Rough-Winged Swallow in 1819, virtually by accident when he collected a few of what he thought were Bank Swallows (also brown-backed) in Louisiana. Only with later, closer observations did he determine that he had actually collected representatives of a distinct species.

The most distinguishing characteristic of this swallow is its “rough” primary wing feather, from which its common name has been derived. This characteristic produces a “file-like” roughness when one’s finger is drawn along the edge of the quill from the base toward the tip of the feather. The function of these small serrations is unknown. Some ornithologists have suggested that they function to produce sounds that are a part of courtship flights.

The Rough-Winged Swallow arrives here from Mexico and Central America over well-defined routes in April, and departs in August. Unlike many small land birds, they migrate during daylight hours, with periodic interludes of foraging. Spring migration is prolonged and not pronounced, sometimes described as leisurely. They readily associate with other species, especially Bank Swallows. Immediately after arrival the swallows begin to show spasmodic interest in nesting sites. Individuals of both sexes hover close in front of available cavities, call, perch occasionally at the entrances, at times actually enter for a brief period, and sit watchfully close by. Occupancy rate of artificial cavities is high. However to date, they have avoided nest boxes in the Park. One has to wonder why they choose these cavities, which expose their nests to the hazards of spring rains and cold nights.

The other swallow that breeds in the Park is the Violet-Green Swallow, and they do use the nest boxes. The Violet-Green with its snow-white underparts and face, and shiny, rich, yellowish-green upperparts, is very similar in appearance to the Tree Swallow. It associates with other swallows while migrating and foraging over open country. They generally arrive in this area in May, after other cavity nesting species (bluebirds, chickadees, wrens, etc.) have begun their nesting. They readily accept a wide variety of cavity types, including abandoned woodpecker holes in trees and tree stumps, natural tree cavities, crevices and cracks in cliffs and buildings, and of course nest boxes.

Violet-Green Swallow Reprinted without permission from http://www.icehouse.net/ erickw/nestcam/swallowfacts.html

Several Violet-Green pairs have been documented helping Western Bluebirds to rear nestlings and subsequently breeding in the Western Bluebirds’ nests after their young have fledged. Occasionally a Violet-Green pair, which exhibit more aggressive behavior than the Western Bluebirds, will evict a bluebird pair from their nest cavity before their eggs hatch.

As with other swallow species, the Violet-Green feeds exclusively on flying insects which are swallowed in flight. They will feed at various heights, skimming low over fields or water, or circling high above ground, often at greater altitudes than other swallows. At whatever height we might find them, they're sure to appear extremely graceful and maneuverable.

The Birds of North America No 234, 1996: Dejong, M. J.

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