By Lauren Flesher
They’re stealthy. They’re quick. They have far too many legs. They’re spiders, and they’ve been vilified for centuries. They’re not all bad, though. Spiders perform a great many ecosystem services, from agricultural pest control to disease prevention. They’re especially beneficial to native birds. Here are some key reasons a true bird lover should leave that spider alone.
Spiders as Bird Food
Spiders are like an energy bar for birds—the bite-sized packs of protein are incredibly nutritious. This is especially important during migration, when birds are physically taxed and need much more food to keep going. Many species of smaller birds, particularly hummingbirds, will also take advantage of a sticky spider web and steal the captured insects from the silk. It’s the bird equivalent of a convenience meal!
Spiderwebs and Nests
Many species of birds use spider silk when constructing their nests. It has the advantage of being strong while also being flexible. As the nestlings grow, the nest can stretch with them, and the silk allows for easy repair in the case of damage.
Spiders as Nest Pest Control
House Wrens have discovered an ingenious way of keeping mite levels under control. While the nests of other birds are ridden with the parasites, the House Wren places spider egg sacs inside her nest. When the egg sacs hatch, the baby spiders will have an abundance of mites to eat, and the House Wren nestlings will be thankful. Talk about a win-win.
More About Spiders and Birds
Spiders aren’t always a bird’s best friend, though. The Goliath Birdeater Tarantula does not prey primarily on birds, but it won’t pass up the opportunity if a bird stumbles onto its path. Thankfully, it can only be found in the northern swamps of South America, but even in the United States, bird-eating spiders exist. Songbirds will occasionally become stuck in spiderwebs and die there, because their struggles to escape only further entangle them. Sometimes a spider will cut the bird free, then repair its web.
Because web repair is costly in time and in nutrients, spiders such as the garden orb weaver will weave a visible pattern into their webs, called a stabilimentum. Many arachnologists believe the stabilimentum serves as a warning to birds and other large animals that the web is there, thus saving the spider the trouble of repairing it when a large animal comes crashing through. It has been documented, however, in rare cases, that a golden orb weaver will take advantage of a snared bird, encase it in silk, and eat it. These predation methods are mostly opportunistic, and always involve smaller birds such as hummingbirds and kinglets.
When it comes to spiders, we may want to squash them on sight, but clearly the benefits of having them around outweigh the dangers. So take the time to hug your creepy-crawly neighbors today…or maybe not.