You Can Feed More Birds
The easiest way to nurture backyard birds is also the best.
Dear Avant Gardener, I love birds and I’d like to do my part to nurture them in my quarter acre suburban yard near Philadelphia. I don’t have a lot of time or energy to fill a bird feeder or bird bath. And I’ve heard bird feeders can spread avian flu, anyway. So, what’s the easiest thing I can do to nurture birds in my yard? — Lazy Bird-Lover
The easiest way to nurture birds on your small property is also one of the best: Simply plant a small native oak or a plum or cherry tree. Underplant it with a few native groundcovers and you’ll have a perpetual bird feeding machine. In addition to nurturing birds, you’ll create more shade on your property, a boon in an era of global warming.
Before you balk at the size of a mature oak or wild cherry tree, be assured there are smaller species native to most regions of the United States. In the Mid-Atlantic, native bear oak (Quercus ilicifolia) grows to just 15 to 20 feet and native chokecherry (Prunus virginiana) reaches 20 to 30. You can site these trees in most yards without damaging the home or creating too much shade.
The early bird gets the caterpillar.
Why are caterpillars necessary to nurturing birds? As entomologist Doug Tallamy writes,
Most of North America’s terrestrial bird species, some 96 percent in fact, rear their young on insects rather than seeds and berries (Peterson 1980), and we are learning that in most of those species, the majority of those insects are caterpillars or adult moths. Caterpillars are so important to breeding birds that many species may not be able to breed at all in habitats that do not contain enough caterpillars (Narango et al. 2018). – Nature’s Best Hope,
Quercus and Prunus trees are caterpillar mega-hosts.
Tallamy and his research assistant Kimberly Shropshire analyzed data on which plants have the ability to host caterpillars in every county in the U.S. What surprised them, writes Tallamy, was that
[W]herever we looked, about 5 percent of the local plant genera hosted 70 to 75 percent of the local Lepidoptera species!
These mega-hosts are keystone species. And in most counties, Quercus (oak) and Prunus (cherry or plum) are the No. 1 and No. 2 tree and shrub genera in terms of the number of caterpillar species they host. In the Main Line, oaks host more than 500 species of caterpillars, for example.
By the way, many local Lepidoptera — moths and butterflies — can’t breed on an English oak or Japanese flowering cherry. And no breeding moths and butterflies, no caterpillars, no birds. You may be surprised to find that almost all the trees at your local nurseries are such imported or “exotic” species. Pass these up.
Siting your oak
Site your Quercus or Prunus near another tree or shrub, if possible. In fact, Tallamy recommends planting trees in a grove approximately 10 feet apart on center. (Shrub-sized trees can be planted more closely.)
They may seem crowded at first, but they will interlock their roots and support one another in high winds.
This is counter to traditional horticulture, which aims to maximize individual plant size. It’s true oaks grow tallest and lushest in sun, but in the wild they grow in forests after pioneer trees like birches have grown up around them.
Tallamy recommends you “interview plants before you hire them.” Your tree may take years to become substantial and can take decades to reach mature height. If you spend less than a hundred dollars on a sapling and decide you aren’t crazy about the location, you can transplant it, if it’s too big, make it a snag.
Creating habitat under your tree
Before they mature to breed again and create more caterpillars to feed your birds,
[Nearly all caterpillars] fall to the ground where they either burrow into the soil to pupate underground or spin a cocoon in the leaf litter under the tree.
Underplanting your tree with native groundcovers — living mulch — will create a microhabitat for the pupae to survive and emerge as moths and butterflies.
Since you’re trying to maximize bird food, why not choose some low, sun-tolerant plants that are also host to caterpillars themselves? Groundcovers that host the most caterpillars in your area include wild strawberry (Fragraria virginiana), common blue violet (Viola sororia), and spotted geranium (Geranium maculatum).
Near-ish you, Go Native Trees offers hundreds of native tree species grown from local seed. They also sell groundcovers and can advise you about what’s best for your site.
— The Avant Gardener
P.S. What landscape challenge do YOU plan to tackle this year? Send your rambling questions to DearAvantGardener@gmail.com. (I edit questions for publication.) Paid subscribers receive priority.
Why, How, Wow!
For most bird species, caterpillars are the richest available source of carotenoids, which they need to raise healthy young. What’s astounding is just how many caterpillars it takes to feed a nest of baby birds: hundreds or even thousands a day, depending on the bird species. For example, biologist Richard Brewer found that over the course of a typical 16-day nesting period, Carolina chickadee parents delivered 6,000 to 9,000 caterpillars to bring one nest of tiny birds to fledging. And they continued to feed caterpillars to their young for another 21 days.
Various small Quercus and Prunus species are native to each region of the U.S. You can find them at large native plant nurseries. Many species are also available nationwide through the Audubon native tree program at Bower and Branch. Although planting in fall is optimal in many regions, availability tends to be greatest in spring.
Small native Quercus trees by region (from east to west)
Northeast and Mid-Atlantic: Bear oak (Quercus ilicifolia)
South and Florida: Sand live oak (Quercus geminata)
Middle: Chinkapin oak (Quercus muehlenbergii)
Texas and Southwest: Escarpment live oak (Quercus fuciformis)
California: Leather oak (Quercus durata)
Northwest: Oregon white oak (Quercus garryana)
Small native Prunus trees by region (from east to west)
East and Midwest, except Florida: American plum (Prunus Americana)
Everywhere except southeasternmost states: Chokecherry (Prunus virginiana)
Southern, through Texas: Chickasaw plum (Prunus angustifolia)
Southwest: Mexican plum (Prunus mexicana)
California: Holly-leafed cherry (Prunus ilicifolia)
Northwest: Oregon cherry (Prunus emarginata)
These images illustrate how small Quercus and Prunus species can enhance home landscapes around the country. Already have an oak, cherry, or plum? Plant more! On our small property in Rhode Island, I’m planting a hedge of 10 beach plums (Prunus maritima).
This East Hampton garden designed by New York-based Hollander Design includes beach plum.
Leather oak (Quercus durata) is native to dry slopes and ridges in chaparral and woodlands of the north and central coast of California. It’s a mounding shrub four to 10 feet tall and wide with attractive flowers.
Small trees can even be planted in containers, like these chokecherries (Prunus virginiana). They are native to the entire U.S. except the southeasternmost states.
Escarpment live oaks (Quercus fusiformis) form a glade at the Ladybird Johnson Wildflower Center in Austin, Texas.
Want to find top caterpillar hosts in your area? Type your zip code into National Wildlife Foundation’s Native Plant Finder.
Want to learn more about living mulch? Read this post from NOT! Your Granny’s Garden.
Considering cutting down a tree? Before you do, read 1,000+ Reasons to Love a Snag.
Note: This is an updated version of a column published before I launched the Dear Avant Gardener newsletter.