Spiders, Birds, & Stabilimenta

Spiders may have found a way to prevent birds from crashing through their webs. We can take a lesson from the spider to keep birds away from windows.

What do spiders and humans have in common? Not a lot, you might think. Well, spiders and humans both construct invisible structures that birds blunder into, or through. With humans, it's windows (see my last blog entry Birds Attacking My Windows, and my article When Birds Attack Windows). With spiders, it's webs.

How do you stop a bird from flying through your web? It doesn't surprise me that the spiders may have solved the problem while humans are still grappling with it. It seems logical that birds, like humans, don't particularly enjoy being covered with clingy spider webbing, and spiders would see no advantage in having the web swept away by a big clumsy bird - especially if the spider happened to be sitting in the middle of the web at the time. So the answer lies in letting birds know where your web is located.

Some spiders, particularly the ones that like to sit in the middle of the web, build what's called a stabilimentum (one stabilimentum, two stabilimenta). It's a rather heavy zigzag pattern of silk at the center of the web, sometimes in an X shape, a T shape, or possibly just an I or a distinct patch. The theory is that at least one of the uses of this structure is to make the web visible to birds so that they don't fly through it. You can read a discussion of some of the other possible functions of the stabilimentum here

You can buy window decals that feature a spider's web with a bold stabilimentum in the center. Stuck on the inside or the outside of house windows, they are supposed to deter birds from crashing into, or attacking, the window. See my article When Birds Attack Windows for a photograph of one of these decals.

In the meantime, if you are out walking, keep your head up and watch out for the stabilimenta.

Related articles: Orb Weaving Spiders

Birds Glossary