Mealworms are the larval stage of the darkling beetle, Tenebrio molitor, and are a highly sought-after, protein-rich food source for backyard birds. Their nutritional composition offers a valuable supplement to a wild bird’s natural diet, especially during periods of high energy demand. Birds are particularly eager for this food during the spring and summer nesting season, when parents need concentrated protein to feed their rapidly growing young. Offering mealworms can significantly increase the variety of species visiting a feeding station.
Defining Mealworms and Preparation Types
Mealworms are technically not worms but the larvae of the darkling beetle, a common grain pest commercially cultivated as a pet and wildlife food. These small, golden-brown grubs are a concentrated source of energy. Live mealworms contain approximately 20% crude protein and 13% crude fat by weight, and their high moisture content provides hydration for birds.
Dried mealworms offer a more convenient and shelf-stable alternative. The drying process concentrates their nutrients, resulting in a protein content that can exceed 50%. To make dried mealworms more appealing and easier to digest, they should be soaked in warm water for about 30 minutes to fully rehydrate. Live mealworms must be kept cool, typically refrigerated around 40°F, to keep them dormant and prevent them from pupating into beetles.
Specific Bird Species Attracted to Mealworms
Mealworms attract nearly all insectivorous and omnivorous bird species, substituting for the wild insects that form the bulk of their natural diet. Eastern and Western Bluebirds are the most famous consumers of mealworms, readily visiting specialized feeders for this protein source. Live mealworms are especially effective in attracting bluebirds, as the larvae’s wiggling movement mimics natural prey and stimulates hunting instincts.
American Robins, which are primarily ground feeders, will quickly take to mealworms offered on low, open tray feeders or directly on the ground. The protein content is beneficial when Robins are raising multiple broods of chicks throughout the summer. Smaller, acrobatic species like Chickadees, Tufted Titmice, and Nuthatches are frequent visitors, often snatching a single mealworm before carrying it off to consume elsewhere.
Carolina Wrens, known for their insect-heavy diet, are strongly drawn to mealworms and will visit feeders multiple times a day. Even larger, seed-eating omnivores like the Northern Cardinal will readily consume mealworms, especially during the breeding season.
Best Practices for Offering Mealworms
Mealworms should be offered as a supplemental treat rather than a complete diet. They are naturally low in calcium, which can lead to bone deformities in nestlings. To counteract this deficiency, it is recommended to “dust” the mealworms with a fine powder of calcium carbonate or calcium citrate before feeding. This is achieved by placing the mealworms and powder in a plastic bag and gently shaking them until they are lightly coated.
Feeder choice is important, especially for live mealworms, which require a smooth-sided dish with walls at least two inches high to prevent the larvae from crawling out. Specialized bluebird feeders often use a cage design with entry holes sized to exclude larger species like European Starlings. Offering only small, limited quantities—such as a handful once or twice a day—ensures the food is consumed quickly and does not spoil.
Feeder hygiene is necessary to prevent the spread of disease, especially with high-moisture foods like rehydrated or live mealworms. Feeders should be thoroughly cleaned every two weeks, or more frequently in wet weather, using a solution of one part bleach to nine parts water, followed by a thorough rinse and air-drying. Placing the feeder away from heavy cover can deter squirrels. Limiting the daily offering helps prevent unwanted visitors like House Sparrows or Starlings from monopolizing the food source.