How Your Tree Helps Wildlife in Winter

By Joanna Brichetto
Tennessee Naturalist
SidewalkNature.com

Wondering how trees help birds and wildlife survive a Nashville winter?

Is your tree an evergreen? Dense needles and thick leaves offer shelter and “escape cover” for countless animals. Winter songbirds huddle in mixed flocks on Hemlock, Pine and Eastern Arborvitae to survive cold nights. Red berries on American Holly and the little blue “cones” on Eastern Red-Cedar pack good nutrition for many creatures, and are favorites of Robins and Cedar waxwings.

Is your tree a nut tree, like an Oak, Hickory, Walnut, Pecan or Beech? If so, those acorns and nuts were a boon when animals built body mass in fall, and will be a boon later when cached stores are found and eaten. 

Is your tree a Hackberry? In winter, Hackberry fruits (drupes) are literal life-savers for creatures great and small, but especially for birds like Robins, who do not eat the seeds we offer in feeders. Chipmunks crack and eat the soft kernel inside the pit, but most animals swallow the fruit whole. Even the weird (and harmless) galls on hackberry trees are food: squirrels eat the plant lice sheltering inside.

Is your tree a butterfly host plant? On Black Cherry, Hawthorn, Plum, Willow and other native host trees, some caterpillars overwinter in leaves that stay on the tree. In spring, the larvae wake and resume their life cycle. One beautiful butterfly example is the Red-spotted Purple.

Is your tree missing a big branch? A cavity can host Great Horned Owls (who select territory in winter), or be a hibernaculum for Eastern red bats (who eat your mosquitos in summer).

On any native tree, there will be tiny insects and other arthropods doing their thing on and in the bark. To birds and small mammals, these are healthy meals. Lichens and fungi are also on the menu.

Sap is another winter tree food. If you see a neat grid of holes in a trunk, it’s the work of our winter visitor, the Yellow-bellied Sapsucker. These woodpeckers drill “wells” in Sugar Maple, Birch, Tulip Poplar and other trees. They lick sap, nibble bark and eat insects that eat the sap. (The holes don’t hurt the tree.) Other animals use the wells, too. On a warm, winter afternoon, you might see a Mourning Cloak butterfly sipping a sapsucker well.

Leave the Leaves

Here’s a winter tree food people may not know about, but birds do: leaves! Those leaves that fell from your tree in autumn are teeming with bird food. Why? Because most butterflies and moths overwinter in our yards—as either eggs, caterpillars, pupae or adults—and they do so in leaf litter. When we shred, blow or bag leaves, we destroy a major source of food for birds, as well as a major part of next summer’s butterfly count. 

To “leave the leaves” helps your tree, too: leaves are free mulch and fertilizer for the plant that grew them. Even turf lawns benefit from a light layer, but extras can be raked into edged beds or compost, or donated to neighbors with gardens.

Native Matters

These are only highlights of how native trees can support winter wildlife. Why does “native” matter? Plants and animals have evolved together in place, and with specialized relationships. Trees from other continents cannot sustain our local foodweb.

Given the shocking reality that one-third of all plant and animal species are at risk of extinction in the next 50 years, we don’t have time to plant merely for decoration: we must plant for life. Native trees can give us the prettiness we want, while giving fellow creatures a chance to survive.

Resources:

For why and how to Leave the Leaves, see this article from the Xerces Society.

Read more about butterfly host trees in the Going Native column, “What to Know About Native Trees and Butterflies.”

To learn which trees are native to your zip code and how many butterfly and moth species they support, check the National Wildlife Federation’s online Native Plant Finder.

The 5th Annual NTCC Tree Sale, now under way, offers many trees native to the U.S. Click “Native” to filter your search while you shop. And remember, fall and winter are the best times to plant a tree in Nashville!

Joanna Brichetto is a certified Tennessee Naturalist in Nashville, where she writes about everyday wonders in everyday habitat loss. Her essays have appeared in Brevity, Fourth Genre, The Hopper and other journals; and her current project is an urban-nature almanac called Hackberry Appreciation Society. Follow her on Instagram (@Jo_Brichetto) and at SidewalkNature.com.