The Easy Way to Nurture Birds
Signed, Lazy Bird-Lover
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. And do it soon, in fall when the weather is warm and becoming rainier where you live. You’ll want to underplant it with a few native groundcovers, and that’s pretty much it. In addition to nurturing birds, you will create more shade on your property, a boon in an era of global warming.
Please don’t be intimidated by the length of this answer! I want to give you the whys, as well as the hows. All in all, you can probably research, shop, plant and tend your tree for around $100 in fewer than 10 hours using the tips and resources below. Then you’ll have a perpetual bird feeding machine.
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, where you live, native scrub oak (Quercus ilicifolia) grows to just 15-20 feet and native beach plum (Prunus maritima) reaches only 15 feet. You can easily site these trees where they won’t damage your home or create more shade than you want.
Read on for tips where to buy small oaks and cherries native to each U.S. region and how to site, plant and nurture your tree. But first, here’s the science behind why planting oak (Quercus genus) or plum or cherry (Prunus genus) trees is not just easy, but one of the best ways to sustain bird populations.
The early bird gets the caterpillar.
Entomologist Doug Tallamy and his research assistant study the relationships between plants and insects. The insect order Lepidopterae encompasses moths and butterflies, which are caterpillars in their larval stage. Why are caterpillars relevant to nurturing birds? As Tallamy writes in Nature’s Best Hope,
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).
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.
Quercus and Prunus trees are caterpillar megahosts.
So where do bird parents find caterpillars to feed their young? 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. They knew that some genera host hundreds of caterpillars, while others have no record of hosting any caterpillars. What surprised them, writes Tallamy, was that “wherever we looked, about 5 percent of the local plant genera hosted 70 to 75 percent of the local Lepidoptera species!”
And in most counties, oaks and cherries are #1 and #2 among trees and shrubs for the number of caterpillar species they host. To see the top caterpillar hosts in your are, type your zip code into National Wildlife Foundation’s Native Plant Finder, which uses Shropshire’s data. Oaks (Quercus) host 519 species of moth and butterfly caterpillars in one Philadelphia zip code, for example.
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.” You’ll want to create a micohabitat for their pupae to survive and emerge as moths and butterflies. I’ll tell you exactly how to do this below.
So, here are the steps to creating a habitat that will feed (and shelter) birds by providing what’s needed for hundreds of moths and butterflies to breed and complete their lifecycle, right in your yard.
Step by step instructions for lazy bird lovers
1. Consider a few possible locations.
Within your lot, you’ll want to site your tree somewhere that’s
sunny or mostly sunny,
at least half the tree’s expected mature height from your house,
at least 10 feet (or half the tree’s mature height, if less) from another tree,
where neither its branches nor its roots will interfere with power lines or underground utilities (imagine its mature height and a diameter around it of the same size both above and below ground), and
where you’d most like shade and/or screening from something tall nearby.
Some of these guidelines may be counter to what you’ll hear from nurseries, including those linked below. Nursery advice is generally based on traditional horticulture–tending plants for maximum individual size–rather than how these trees grow naturally. For example, oaks grow tallest and lushest in sun, but in the wild they grow in forests after pioneer trees have grown up around them.
Nurseries also specify big distances between trees, which again is not how oaks or plums grow naturally. Tallamy recommends planting several trees in a grove approximately 10 feet apart on center. “They may seem crowded at first, but they will interlock their roots and support one another in high winds.” If you’re not planting your tree close to another one, plant it a distance from the house at least the species’ mature height.
For example, your quarter acre suburban lot might have a 25 foot deep west-facing front yard and a 50 foot deep backyard. If you select an American plum (Prunus americana), which grows to 25 feet maximum, you could site any of these locations:
Along the front edge of your property to shade that side of the house on summer afternoons and lower your cooling bills
25 feet from the back of your house to provide shade in the backyard
Just inside your back lot line to minimize the eventual shade and screen the view of your neighbor’s house
Remember, your tree may take years to become substantial and can take decades to reach mature height. Tallamy recommends you “interview plants before you hire them.” If you spend less than a hundred dollars on a sapling and decide you aren’t crazy about the location, you can transplant it later or, if it’s too big, cut it down.
2. Find and order the right plant for the place.
This could be the most time-consuming step. (If you prefer to get a tree with minimum effort, skip to the list of regionally native trees available online.)
Most importantly, you want a tree that evolved naturally near your home–because the local moths and butterflies evolved along with it. Many of local Lepidoptera can’t breed on an English oak or Japanese flowering cherry, and no breeding moths and butterflies, no caterpillars, no birds. I will write more on this another time, but take my word for it now. And be vigilant. You may be surprised to find that almost all the trees at your local nurseries are imported or “exotic” species. Pass these up.
It’s also great if you can find plants bred from seeds from your local ecoregion and raised locally. These will be best adapted to the conditions where you live. But don’t sweat it too much. Frankly, although native plants are becoming more readily available, it’s still difficult to find local ecoregion plants.
Fortunately, another Tallamy resource can help you find and buy locally native species, both online and locally: Audubon’s Native Plant Finder. Just input your zip and a page with several tabs will appear, open to the Best Results tab. Filter for the keyword Quercus or Prunus. If results appear, you’ll see descriptions of locally native species. Click on Buy Now and a popup will let you choose Buy Local or an online source such as Audubon partner Bower & Branch.
If you click on Buy Local, you’ll be routed to the Resources tab. There you’ll find nearby Audubon centers (there are several in the Philadelphia area) that can help locate Quercus and Prunus saplings and native ground covers locally. Or scroll down the Resources page to the local nursery section and call around.
If you do not see species in the Best Results tab, go to the Full Results tab and repeat; the results will be a list of local species, without descriptions or links to purchase. Then you can either go to the Resources tab and follow the instructions above to try to find the species locally.
However, you admitted you’re lazy, and even with the Audubon tool, searching for native plants can be a bear. For example, Bower & Branch may not have the species you want or may only offer it in sizes larger than what’s affordable to you. Never fear.
For you and bird lovers elsewhere, here are lists of small, native Quercus and Prunus seedlings and saplings by region that can be sourced online for less than $100. Most are adapted to a range of soil types and moisture levels. Several of the sites have additional locally native species in the genus. Unfortunately, I do not have time to vet the sources other than a cursory review of their sites, so caveat emptor.
Small native Quercus available online for less than $100
Texas and Southwest: Texas live oak (Quercus fuciformis)
California: Interior live oak (Quercus wislizeni)
Small native Prunus available online for less than $100
Northern half: Chokecherry (Prunus virginiana)
Southern, through Texas: Chickasaw plum (Prunus angustifolia)
(Native ranges from The Sibley Guide to Trees).
3. Pick and buy a groundcover or two.
As I mentioned, you’ll want to replace any turf grass around your tree with native plants so your caterpillar pupae can survive there. Initially, when your tree is small, you’ll need plants that can handle sun. Since we’re trying to maximize bird food, why not choose some low, sun-tolerant plants that are also host to caterpillars themselves?
These low-growing plants appear among the top eight caterpillar hosts for a Philadelphia zip code at National Wildlife Foundation’s Native Plant Finder: wild strawberry (Fragraria virginiana), common blue violet (Viola sororia), and spotted geranium (Geranium maculatum). Readers from other areas can repeat the process for themselves.
You can probably find native groundcovers at a local nursery (see Audubon resources above). If the ones you pick aren’t available, the staff can recommend others. Make sure you let them know you will be planting the groundcover plants close together as “green mulch.” Perennials are also readily available online at major native nurseries like Prairie Moon, which sells three-packs of violets (Viola sororia) for $21. Spacing them 6 inches apart (about the middle of the range Prairie Moon recommends), six violets will probably be sufficient to put around your tree; they will spread over time.
4. Plant your tree and groundcovers.
Planting a small native tree is easy:
Soak the plants in their pots and the ground where you plan to plant them with water.
Plant the tree first. Start by digging a hole the depth of the pot and twice its diameter, setting the dirt and any sod aside.
Unpot it by tipping it upside down with your fingers spread over the dirt on either side of the stem or trunk. (If the sapling is big, turn it on its side and pull off the pot.) If necessary, squeeze the plastic and push or cut roots that emerge from the holes at the bottom.
Loosen the roots a bit with your hand. If they tightly circled, cut them on the outside so they can easily grow into the dirt around them.
Put the plant into the hole, making sure the place where the stem or trunk meets the roots is at ground level. If this “collar” is too low, place some dirt or chunks of removed sod upside down at the bottom of the hole. Once the collar is level with the ground, refill the sides of the hole with removed dirt and upside down sod until the tree stands straight. Press the dirt with your hands to eliminate any air between the nursery dirt and your topsoil.
Now you can plant the groundcover into the loose dirt around the edge of the hole you created. Repeat the steps above for each plant, placing them in a circle. Do not put additional dirt over the collars where the stem or trunk meets the roots.
Remove any excess soil or simply spread it around on the turf nearby. You want your groundcover to expand into the turf anyway.
Water again, deeply—at least 2 inches of water. If you’ve got some dead leaves or leaf mulch lying around, spread them around the dirt to help retain moisture. Voila!
(Again, my recommendations diverge from traditional horticulture. For example, I don’t recommend amending the soil or adding store-bought topsoil. There are reasons. Trust me for now.)
5. Let nature alone.
From here on out, nature takes over. (I told you it was easy, didn’t I?) One thing you should do is pay attention to how much it rains. For the first couple of months, add another two inches of water each time a week goes by without an inch of rain. Other than that, less is more. Leave the leaves where they fall. Let any stray twigs or branches stay on the ground. Laziness can be an asset when it comes to gardening for wildlife. Listen to the excellent audiobook of Tallamy’s Nature’s Best Hope, especially Chapter 8, to find out why.
Now, sit back and enjoy knowing you’ve done the best thing you can for the birds.
The Avant Gardener
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