The Magic of Fasteners: Spider Silk and Nature's Velcro

Casey McFarland

Many bird nests are wonderfully built, and for anyone who’s ever found an old nest and tried to ease it from its resting spot for a better look knows that they can be surprisingly well-fixed into place.

Birds employ a variety of tactics and materials to construct, fasten, strengthen, and decorate their nests—they create complex knots, stitches and rivets (yes, rivets!), they sculpt and mold with mud, and weave and mat with grasses, feathers, fur and roots.

Spider silk is commonly used, as are plant fibers chosen specifically for their microscopic, snaggly texture. When combined, they form a wonderfully handy and versatile velcro of sorts. Bushtits—the small, charming and gregarious characters found across the west—create a nest fabric from lichens, mosses, grasses, spider webs and small flowers. Their nest—one of North America’s most easily recognized—is a deep, tubular “bag” hung from its upper end. Not only is this nest durable and flexible, but should it sag under the weight of eggs or nestlings, or stretch and list in heavy winds, the bushtit simply “unhooks” parts of the nest that fasten to twigs and branches, pulls them taut, and reattaches them.

Fastening materials—sticky, stretchy, grippy—whatever the quality may be, remind us that birds don’t just gather materials and squish them together. They skillfully stitch, pull, thread, form and attach each item they collect, and each is suited for a particular purpose. Fasteners offer insight into how a bird sees the world and its tactile relationship to it. Next time you have the opportunity to peer into a nest, consider why each item in it was selected and the role it served.