Spring Swallows, Sonoma County, California

April 4, 2007 on 10:36 pm | In Bird Alert |

Greetings Birders!
I am thrilled to put out this Bird Alert to announce that the Barn Swallows have arrived in the San Francisco Bay Area, as of my observation this week. This rainbow-colored fowl is only with us in the warm months of the year, and I thought this would be an ideal moment to feature him in a post on Birding Sonoma County.

The purpose of this article is to help you learn to identify both Barn Swallows, Hirundo rustica, and Tree Swallows, Tachycineta Bicolor, by learning the field marks that set these two splendid species apart. Let’s begin by looking at a detailed illustration:

With their diamond shape and fabulous colors, swallows are easy for even beginning birders to identify. But then, you need to be able to look closely to determine which swallow you’ve sighted. I am using the Barn and Tree Swallows because my observation has led me to conclude that these are our two commonest swallows here in Sonoma County.

As you can see from the above illustration, color and shape are going to be our two most important fieldmarks for distinguishing between these birds. The striking, bi-color blue and white of the Tree Swallow and the blue, red and orange of the Barn Swallow rival the hummingbird for sheer iridescence. They seem to flash and twinkle as they swoop through the sky like miniature kites. Note that I am also showing you the undersides of the birds, as this is how you will most commonly see them, flying overhead. So, there is a decided difference in coloration to help you here.

But what about when you’re staring up into a bright sky at a swallow-like bird and cannot see its color well because of the sun in your eyes? Studying shape is the answer! It is the tails of swallows that tell me who they are, even when they are very high. Both Barn and Tree Swallows have forked tails, but just take a gander at the scissor-like feathers on the tail of that Barn Swallow. No other North American swallow has a tail with such a pronounced fork to it, and such pointed end tips. By contrast, the tail of the Tree Swallow is more rounded and stubby. The wings of the Barn Swallow also appear more slender and pointed when compared to the broad wings of the Tree Swallow.

The average Tree Swallow measures about 5 3/4″, and the Barn Swallow is about one inch longer. Both birds twitter in flight, and the juveniles of both species are duller in color.

Unlike the spring/summer visitor, the Barn Swallow, Tree Swallows are apparently year-round residents in the Bay Area, but I want to share that I rarely see them until the spring begins to warm up. Once it does, go to just about any pond, marsh or other body of water in Sonoma County and you are almost sure to see these birds. Our first ever sighting of the amazing Barn Swallow was by the sea in Pt. Reyes. We were able to walk within a foot or two of one who was perched on a sign and his colors just astonished us.

Both species line their nests with feathers, but the Barn Swallow makes his nest of mud in the eaves of buildings, and the Tree Swallow builds his in a woodpecker hole or nesting box. Providing nesting boxes for Tree Swallows can truly assist this species in the difficulties it faces trying to find a vacant cavity for its family to live in. Competition for such sites can be fierce and if you would like to promote the local Tree Swallow population, why not offer a box for them? You’re sure to enjoy the observation opportunities this will afford you! Both species lay some 4-6 white eggs.

If you’d like to see some super swallows this week, I highly recommend a drive to the Napa-Sonoma Marsh which I’ve been blogging about with such excitement these past months. My husband and I sat beside the water yesterday and watched the swallows fill the sky with their unique opulence. They are one of those birds that gives me a sense of peace, calm and freedom from cares.

Whether you prefer the sapphire and diamond splendour of the Tree Swallow or the parrot-like plumes of the Barn Swallow, look for mixed flocks of these graceful little gems for the rest of the sunny season.