Wednesday, June 26, 2013

Telling Swallows from Swifts

Tree Swallow
Tree Swallow, Beaverton, Oregon, 18 May 2011 by Greg Gillson.
Many beginning birders struggle to differentiate swallows from swifts. Even separating the different swallows from each other is one of the first identification challenges a beginning birder faces. No doubt part of it is that both swallows and swifts are most-frequently seen darting rapidly through the air, backlit against the sky. If you can't follow them or even find them in your binoculars, how are you to identify them and see those subtle field marks?

As Kenn Kaufman says, in his new Field Guide to Advanced Birding (2011), it's not so much that swallows are misidentified, but "simply left unidentified."

But, then, how do some birders identify them nearly instantly as they fly high overhead, not even using binoculars? They differ subtly in behavior, habitat and niche, seasonality, and voice. Structurally, the wing bones are different so that the flight styles are notably different. Specifically, swallows flap more slowly and swoop gracefully, while swifts have more direct flight with rapid wing beats and brief glides.

Swallows

Behavior
Swallows are often seen flying through the air darting after insects, or seen sitting on wires.

Habitat and niche
Most swallows are usually found over open country or water. They can feed low to the ground or quite high in the sky, sometimes over cities or forests. They frequently perch on telephone wires, bare tree branches, fence lines. Most are cavity nesters in trees, nest boxes, cliffs, or banks, some creating enclosed mud nests on cliffs, barns, or porches.

Flight style
Feeding flight consists of graceful glides, banking, and turns interspersed irregularly with snappy, irregular deep flapping on flexible, broad-based, pointed wings. Commuting flight is more direct, interspersing several flaps with short pauses or brief glides with wings partially open (or nearly folded so that the tips of the wing are back near the tail).

Shape
Swallows have very short necks and very short, broad bills. They have rather short tails--look at the photo of the flying swallow below and note that the white undertail coverts (body feathers) come nearly to the end of the tail. Swallows have pointed wings. Look how far the flight feathers extend past the rump in the photo above. But notice that it is only the the outer part of the wing that is long. The inner arm part of the wing is exceedingly short compared to the outer "hand" portion of the wing--look how close the wrist is to the body! The base of the wing is quite wide, creating rather triangular shaped wings in flight.

Seasonality
In the Pacific NW, swallows are present in good numbers primarily from late March to early October, with some species arriving earlier (late January), with stragglers occasionally seen through the winter west of the Cascades.

Voice
Swallows have various chirping and grating calls, strung together into "songs" that can't be considered very musical!


Tree Swallow
Tree Swallow, Forest Grove, Oregon, 6 July 2007 by Greg Gillson.

Swifts

Behavior
Swifts are almost only seen flying through the air darting after insects. They have weak feet and are not able to perch on wires or tree limbs.

Habitat and niche
Depending upon species, swifts are found over open country, towns,  forests, or cliffs. They usually fly quite high in the sky. They fly into and cling to the insides of chimneys, cracks in cliffs, or hollow trees. During migration thousands may converge at dusk to roost for the night in old stone chimneys at favored locations.

Flight style
Direct flight with rapid wing beats interspersed with occasional set-winged glides.

Vaux's Swift
Vaux's Swift, Forest Grove, Oregon, 22 September 2009 by Greg Gillson.

Shape
The arm bones of swifts are so short that only the outer hand is present--very much like the wing of a hummingbird. Flight is thus twinkling with rapid wing beats on stiff, narrow pointed wings. The tail on Vaux's swifts are short to nearly absent; others have forked tails.

Seasonality
In the Pacific NW, swifts are present from mid-April to early October.

Voice
Swifts have squeaky, chipping calls.

Vaux's Swift
Vaux's Swift, Hillsboro, Oregon, 3 August 2008 by Greg Gillson.
Range in the Pacific Northwest

The following are the locations where swifts and swallows are most often encountered in the Pacific Northwest.

Tree Swallows are abundant over ponds. They use nest boxes placed very near water.

Violet-green Swallows are found in town and over forested lands. They nest in holes under eaves or nest boxes in yards.

Barn Swallows are found in country and towns, nesting in open barns and sheds.

Cliff Swallows nest under barn eaves and cliffs.

Banks Swallows nest in colonies in river banks. They are rather rare west of the Cascades.

Northern Rough-winged Swallows nest in river banks.

Purple Martins are rather rare and local in the Pacific Northwest, along the coast, Columbia River, and mountains.

Vaux's Swifts are regular over towns and forests.

White-throated Swifts are local over cliffs and rimrock in the Great Basin.

Black Swifts are rare in mountains.


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