Spring is on the way. Songs of cardinals and chickadees fill the morning air. Soon songbirds will be migrating through Iowa. And many will be nesting here.
Bluebirds, our cultural symbol of happiness, are among the first to start. Already, bluebirds perch near my bluebird house, declaring to any potential rivals that this place is taken.
If you are a baby bluebird, your main food is caterpillars. The parents also bring spiders, grasshoppers, other tiny creatures, and a few berries. But the favorite food of baby bluebirds is caterpillars.
Caterpillars are soft and squishy. Just the right texture for the parents to push down the delicate throats of their hatchlings. Caterpillars are perfect packages of fats and proteins, ideal building material to grow little wings, bodies, and feathers.
Nature in the Backyard
A few years ago, I woke up to just how important caterpillars are to birds. Here is the book that changed my life: Bringing Nature Home: How You Can Sustain Wildlife with Native Plants, by Douglas Tallamy, professor of entomology and wildlife ecology at the University of Delaware. The book is easily available everywhere.
Tallamy’s book showed me that insects, especially caterpillars, actually make life possible for birds. Nearly all of our nesting songbirds, from chickadees to wrens, raise their young mainly on caterpillars. I realized that if I want bluebirds in my backyard, I need caterpillars.
What do caterpillars need?
Before it gets its wings, every moth or butterfly goes through the caterpillar life stage, when it mostly eats leaves. Many caterpillars feed on specific native plants that have co-evolved with them over the eons. Monarch butterflies: milkweeds. Painted lady: thistles and mallows. Fritillary butterfly: wild violets. Skippers: big bluestem and other native grasses. Luna Moth: leaves of oak, hickory, and black walnuts.
Non-native flowers such as zinnias, petunia hybrids, and hostas are simply inedible to most local caterpillars. And if those are the only kinds of plants available in a yard, it is very hard for birds to raise young.
Doug Tallamy’s Chickadees
Tallamy did research on Carolina chickadees, which are closely related to our black-capped chickadees of Iowa. His team looked at chickadees in suburban yards around Washington, D.C. The chickadees typically have a breeding territory not much bigger than a residential lot, where they find nearly all the food for their young. The researchers studied how nesting success or failure correlated with the percentage of native plants in each yard.
Over 150 homeowners let researchers install chickadee birdhouses and study the plants in their yards. Researchers recorded the percentage of native vs. nonnative plants. The homeowners reported how many baby chickadees fledged from each birdhouse.
The study’s results showed that if the native plant biomass was at least 70 percent, chickadee populations sustained themselves. That is, enough young survived so that the population would hold steady or increase.
However, if the native plant biomass was less than 70 percent, the chickadees did not produce enough young to sustain themselves. They might fledge some young, but if it were up to those backyards, the chickadee population would fall each year. Only because birds moved in from other areas did those homeowners continue to see chickadees.
Wow! Now I really had to start planting more native wildflowers in my backyard.
Reforming My Backyard
When I began to replant my backyard for the sake of birds, I started adding native wildflowers. A huge variety is available, and they are just as beautiful as the non-native six-packs that dominate ordinary garden centers in spring. But there are specialty nurseries that offer native wildflowers as seeds or young plants. Every year, a garden of native plants increases in beauty, interest, and value to birds.
As part of my ongoing project, I also now remove non-native shrubs such as amur honeysuckle, which does not support the insects that birds need. Amur honeysuckle leafs out in woodlands earlier than native species and shades out spring ephemerals that are vital to birds at this season.
Helping Migrants, Too
Every spring, a flood of songbirds migrates northward through the Midwest, including warblers, vireos, and thrushes. Most do not nest here. They have an errand far to the north. They travel fast, flying all night, spending the days resting and feeding so that they can continue their journey.
They arrive in Iowa just as trees are unfurling their spring leaves. Those leaves are little bird feeders, a bonanza of tiny caterpillars, at the very moment that the birds arrive to harvest them.
Rewards of Planting Native
It gives me great pleasure to see a warbler in my backyard in spring and to know that what it finds here will help it survive and complete its mission. Besides making attractive landscaping in our yards, native flowers, grasses, and trees are growing food for the birds we love. And growing happiness in our souls.
Plants & Trees That Support Birds
Here are a few native wildflowers that support birds and are gorgeous in a garden:
- Black-eyed Susan
- New England Aster
- Stiff Goldenrod
- Wild Bergamot
- Butterfly Milkweed
- Purple Prairie Clover
- Prairie Blazing Star
In a space that allows for planting a new tree, one that is native to the area will support vastly more birds than a tree whose home is on a different continent. Here are a few great native trees for Iowa and the Midwest:
- White Oak
- Red Oak
- Black Willow
- Shagbark Hickory
- Downy Serviceberry
- Black Cherry
- Sugar Maple
- River Birch
- Hackberry
- Eastern Cottonwood
Nurseries with Native Midwest Plants
- Ion Exchange, Harpers Ferry, IA
- Prairie Moon Nursery, Winona, MN
- Prairie Nursery, Westfield, WI
- Midwest Native Nursery, Lincoln, NE
- Pleasant Prairie Nursery, Williamsfield, IL
Diane and Michael Porter operate Birdwatching.com, supplying binoculars and other birding necessities to birdwatchers. Diane’s free nature newsletter, My Gaia, is found online at MyGaia.Substack.com.