Bluebirds feed primarily on spiders and insects in the spring and summer, turning more to berries and seed in the fall and winter. If you wish to provide supplemental food and/or encourage backyard visits, offering mealworms is a good choice.
Mealworms are the larval form of the darkling beetle (Tenebrio molitor). They are clean, easy to raise and are a nutritious food supplement readily accepted by many bird species, including bluebirds. They do not carry human diseases.
Oh, so yummy!
Mealworms can be used to attract bluebirds to the area of a new nest box. They can be a valuable supplemental food source during nesting or periods of cold or rainy weather.
All three species of bluebirds find mealworms to be a real treat.
Mealworms can be purchased from several commercial suppliers or you can raise your own. The North American Bluebird Society has information on raising mealworms on their Web site.
If you do not already have bluebirds in or around your yard, just putting out mealworms probably will not result in "instant bluebirds," although other birds, especially in winter, will love having the mealworms available. Once bluebirds become accustomed to watching for their mealworms, they will show up almost immediately after the mealworms have been put in place or may even meet you when you arrive with their favorite treat. You may want to establish a set time each morning and evening to put out a supply of mealworms for your new best friends.
Mealworms can be placed in a cup or on a saucer. Commercial mealworm feeders are available but are not necessary. If larger species are consuming all of your mealworms try offering mealworms from inside a hopper type feeder modified to have 1 9/16" holes in both ends. Offer the mealworms only inside the feeder.
Bluebirds will also eat fruit. Check with a wild bird specialty store for fruit or fruit/seed mixes that will be popular with bluebirds.