Bird Lore: Vaux’s Swift

There are over 90 species in the swift family on six continents. There are two species that summer and breed in Washington, Black Swift and Vaux’s Swift. The latter is a small dark aerialist, often overlooked in and above western forests. It can be seen in Edmonds during migration and usually on cloudy summer days. One or two can sometimes be seen among the swallows that feed over the Edmonds marsh. Look closely for a dark bird with a streamlined body and long narrow wings. Its stiff, rapid wingbeats are distinctive.

As the Vaux’s Swift migrates north to its breeding areas, industrial-sized brick chimneys have offered critical night roosting sites. Along the West Coast, many of these sites are monitored by Audubon Society chapters. This species often feeds low over water, favoring open sky over lakes, rivers, and woodlands. It nests in coniferous or mixed forest, as long as it is mainly old growth.

A wide variety of mostly flying insects makes of the diet of the Vaux’s Swift. They include flies, winged ants, bees, moths, mayflies, beetles, aphids and true bugs. This swift forages on the wing, capturing insects in its wide bill. Spiders and other sedentary insects that are carried high on air currents can also end up as swift food.

The Vaux’s Swift nests in solitary pairs or in colonies. Aerial chasing forms most of the courtship, including glides with the wings up in a sharp V. The nest is usually in a hollow tree, accessed by a woodpecker hole or a broken-off top. The nest is a half cup, shallow and attached to the inside wall of the tree. Both adults gather nest materials by breaking off small twigs from trees while they are flying. Sticky saliva cements the nest into place.

Both adults incubate the six eggs for about 18-19 days. The hatchlings may be brooded for the first week. Adults return to the nest with food about every 12-18 minutes and probably less often as the young birds grow. It has been observed that each adult returns to the nest with a ball of about 115 insects. The young can fly about a month after hatching. They may return to roost at the nest site for several days after they fledge.

The Vaux’s Swift is the smallest of the North American swifts. It roosts communally by the hundreds or thousands, dramatically spiraling down into the roost tree or chimney at dusk. This swift is named in honor of William S. Vaux, who was a member of the Academic of Natural Sciences and who pronounced his name vawks. The oldest Vaux’s Swift of record was five years and one month of age when recaptured during a Venezuela banding operation. Populations can be found year round in southern Mexico and Central America. There is a wintering population in Venezuela. Collective nouns for a group of any swifts include box, flock, screaming frenzy, and swoop.

Although there has been a cumulative population decline of 58% since 1968, Vaux’s Swift is a species of low conservation concern. The global breeding population is estimated to be 870,000. Logging old growth forests has had an impact on this species because it needs such forests for nesting. All species of aerial insectivores are undergoing severe declines. It was once said this was for reasons poorly understood. In light of recent news on the loss of insect populations, possibly due to insecticide use, the decline in aerial insectivore species seems to be an inevitable consequence.

You can watch Vaux’s Swifts swarm the chimney at Monroe’s former Frank Wagner Elementary School here: www.youtube.com/watch?v=9sxikh2aF3E. The Washington Legislature made funds available to make the chimney earthquake proof in lieu of taking it down. It was an amazing recognition of the critical role these brick chimneys play as roosting sites for this small swift. An evening visit to Monroe in August and September will allow you to see the spectacle at the former elementary school. You can listen to vocalizations here: www.xeno-canto.org/264029

— By Carol Riddell

Carol Riddell manages the bird education displays, on behalf of Pilchuck Audubon Society and Edmonds Parks & Recreation, at the Olympic Beach Visitor Station.

 

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