Birds definitely eat spiders, and these arachnids are a regular component of the diet for many avian species across the globe. Most insectivorous birds opportunistically prey on spiders, adding a valuable food source to their foraging repertoire. This feeding behavior is widespread among both migratory and resident birds. The presence of spiders in a bird’s diet often depends on the season, the bird’s specific feeding habits, and the local abundance of spiders.
The Nutritional Incentive
Spiders are a desirable prey item because they offer a concentrated source of specific nutrients required by birds. They are rich in protein and lipids, providing a dense caloric packet important during periods of high energy expenditure. This high-fat, high-protein content is beneficial for adult birds during the breeding season or before long migrations.
Spiders also contain relatively large amounts of the amino sulfonic acid taurine. Taurine is important for the development of young passerine birds, such as Blue Tits and Great Tits. Studies suggest that nestlings fed taurine-rich diets grow up to be bolder and more adept at spatial learning tasks. This specialized nutritional benefit explains why parent birds often selectively bring spiders back to their chicks.
Bird Species That Rely on Spiders
Many insectivorous birds actively hunt and consume spiders, utilizing various strategies across different habitats. Small, agile birds like wrens are enthusiastic consumers, often seeking them out in tight spaces like tree bark crevices and under leaves. Flycatchers, such as the Eastern Phoebe, catch spiders mid-air or pluck them directly from their webs.
Gleaning birds forage by picking insects and spiders from foliage and branches, including many types of warblers and chickadees. These species rely on spiders as a high-energy food, especially during migratory periods when they need to replenish fat reserves. American Robins hunt spiders in the leaf litter, while nuthatches specialize in working their way down tree trunks to find arachnids hiding in the bark. For some species, like the Great Tit, spiders can constitute up to 75% of the food delivered to their nestlings.
Size and Toxicity: Dietary Limits
While most spiders are safe prey, two main factors limit a bird’s consumption: the spider’s size and its defensive mechanisms. Very large spiders, such as certain tarantulas, are too big to be tackled by most common avian predators. They are often avoided due to the physical danger they pose, as the bird’s size dictates the upper limit of the prey it can safely subdue and swallow.
Spiders are venomous, meaning they inject toxins, rather than poisonous, which means they are toxic when consumed. Birds can safely eat virtually all venomous spiders because the venom must be injected into the bloodstream to cause harm, and it is harmlessly digested in the bird’s stomach. Birds typically kill the spider quickly with their hard beaks before ingestion, preventing any defensive bite. For the vast majority of common garden and forest spiders, a bird’s digestive system provides complete protection.