by Ellen Honeycutt, Georgia Native Plant Society
The Eastern Bluebird is a native, year-round bird in Georgia, and I know it’s one that encourages a lot of us to learn more about the birds in our landscape. I am thrilled each spring to see a pair build a nest in one of my boxes. During the winter, I put out suet for them and a few mealworms, especially on very cold days, but during the spring and summer I let my plants provide for them.
Insectivores like the Eastern Bluebird eat insects primarily as adults and exclusively when still in the nest. A diet of insects includes flies, spiders, bees, beetles, wasps, and caterpillars. A recent study of breeding Carolina Chickadees found that the adults provided as many as 9,500 insects to a nest of four chicks over a two-week period. I certainly never realized that I had 9,500 insects in my garden, but the birds manage to find that many for their babies as well as more for themselves.
Growing insects for your resident (and visiting) insectivores is not hard to do when you use native plants as the backbone of your garden. Native insects evolved with native plants, and they flourish when those are available, creating lots of offspring for the birds to eat. Entomologist Doug Tallamy helped us to appreciate the closeness of this relationship with his book Bringing Nature Home. The book included a list of the native plant groups that support the largest number of insect herbivores (those that eat plants as part of their life cycle), such as butterflies and moths.
Fortunately, the number one plant group is the mighty oak (the scientific genus Quercus). It supports more than 550 different species of insects. Most of us have oaks in our landscapes already, and these native giants are in parks and along roadsides, attracting female insects to lay eggs and feeding insectivorous birds in the process. We didn’t even know, did we? The trees aren’t defoliated by these insects because the birds keep the insect populations in check.
Oaks can’t do it alone because many insects use something else, so let’s see what else is on Dr. Tallamy’s list. Number two is the family that includes native cherries and plums (the scientific genus Prunus). The black cherry that dropped tiny fruits on the driveway supports more than 450 insects, so it’s worth keeping. Additional trees and shrubs that support high numbers of insects are willow (Salix), birch (Betula), crabapple (Malus), blueberry (Vaccinium), maple (Acer), elm (Ulmus), pine (Pinus), hickory (Carya), and hawthorn (Crataegus).
Perennial plants are hosts for insect herbivores too. We all remember the relationship that monarch butterflies have with milkweed, right? At the top of the list for perennials is goldenrod (Solidago), a group of plants that has many well-behaved members that bring beauty to our fall gardens; it supports more than 115 types of insect herbivores. Other plants in the list include aster (Symphyotrichum), sunflower (Helianthus), Joe Pye weed and boneset (Eupatorium), violet (Viola), geranium (Geranium), Black-eyed Susan (Rudbeckia), and iris (Iris).
Most of these plants also have beautiful flowers that bring in the other insects that birds eat, such as bees, beetles, and butterflies as well as the predatory (and just as tasty to birds) arthropods like spiders. Using native plants in your garden brings a veritable smorgasbord of insect meals for your bluebirds, warblers, and many others. Spring is a great time to add native plants to your garden. Some of the best native plant sales happen in late March through April. Make your list of insect-growing plants now and rest easy all summer long while your garden feeds the birds for you.