Barn Swallow Tails - Flash or Substance
Nature in Santa Clarita, it’s not what you look at but what you see.
I get dizzy watching barn swallow at work. Because they move so fast and change directions so rapidly, it’s difficult to get a close look at them. A few weeks ago Lilian and I were fortunate to find three barn swallows taking a brief rest.
We’ve known for a long time that female barn swallows prefer males with longer tails, and all adult tails are embellished with long, thin, “streamers”. Take a look at the photos and you’ll see for yourself. The two adults have tails of different lengths with tail streamers. The juvenile, seen in the other photo, is lighter in color and is too young to have tail streamers.
Is there a reason for the long tails? Sure. Barn swallows feed on flying insects like mosquitoes, which they catch and eat while they are flying. The forked tail gives the barn swallow increased maneuverability and the ability to fly at low speeds without stalling.
But is there a reason for the tail streamers? We used to think they were simply ornamental. In the 19th century, Charles Darwin cited tail streamers as an example of sexual selection, which occurs when a physical trait becomes ornamental rather than practical. The trait is exaggerated in order to help an individual acquire a mate. Natural selection, on the other hand, occurs when a trait serves a practical purpose; it helps individuals adapt to their environment and survive. To put it in simple terms, think of it as flash versus substance.
We know more now about the science of flight than we did in the 19th century. So researchers decided to take another look at barn swallows and see if that earlier theory could now be tested. It’s not surprising that they found a range of optimal tail lengths. But what about those long streamers? Are they flash or substance? According to recent research, streamer length does not extend beyond what is aerodynamically useful. (For more details, go to http://www.huliq.com/17650/new-theory-on-the-function-of-barn-swallow-ta....)
So it turns out that streamers are not an example of sexual selection after all and those female barn swallows are more practical than we first thought. It’s not about how flashy you look. It’s really about how adept you are at catching mosquitoes.
Our next Wildflower Hike is scheduled at Towsley Canyon on Saturday, April 28, from 8-10 AM. Towsley Canyon is located on the Old Road, west of I-5 and about 1/4 mile south of the Calgrove exit.
We also have a full moon hike scheduled for Tuesday, May 1, from 7-9 PM.
You can listen to stories like this every Friday morning at 7:10 a.m. on "The Hike Report", brought to you by your hometown radio station KHTS (AM1220) and by the Mountains Recreation and Conservation Authority.
For our complete hike and activity schedule and for trail maps, go to www.LAMountains.com.
To see what's playing on radio station KHTS, go to www.hometownstation.com/or tune in to AM 1220.