Autumn Leaves Protect Birds and the Ecosystem

While it’s tempting to want to clear away the leaves in your yard, scientists urge us to keep them around because of the many benefits they bring to an ecosystem — University of Delaware Entomologist Doug Tallamy and his colleagues in particular, because of their pivotal research into insect population declines and collapsing food webs.

In terms of soil health, decomposing leaves return the sun’s energy that nourishes an entire world of subterranean invertebrates, microbes and fungi that far outnumber their counterparts above.

In addition, those leaves return nutrients to the soil that trees can access through their root systems. Decomposing leaves provide a buffer that can help prevent erosion, too, by preventing the topsoil from drying out and being stripped away.

A particularly compelling argument for leaving the leaves in our yards, however, relates directly to the birds and other animals we see there. Many species of moths and butterflies spend the winter months in cocoons or chrysalises among the fallen leaves, which provide them a snug shelter in which to tough out the snow and cold.

Come spring, those insects will emerge as adults and continue their life cycles (if not eaten by hungry birds).

Think of the ghostly Luna Moth, the magnificent Great-spangled Fritillary, and the Isabella Tiger Moth (whose caterpillar is the beloved “woolly worm” or “woolly bear”); these and other species that we enjoy seeing in the spring and summer months depend on the presence of leaf litter for survival.

Other animals that depend on leaf litter for survival: millipedes, snails and even mated queen bumblebees all do, too. Their abundance creates the critical foundation for our food webs because of the myriad species of birds, reptiles, amphibians and small mammals that eat them.

The Wood Thrush, a species whose eerie, flutelike song is familiar to many of us in New England’s woods, forages almost exclusively in leaf litter in the interior forest — even though it nests 10 to 13 feet off the ground.

Many bird species exercise the same foraging behavior along their migratory routes as they do in their breeding territories — so a returning Wood Thrush is going to look for insects in leaf litter in the spring, giving us a pivotal opportunity to help this bird in our own backyard. This species has declined as much as 60% in Eastern forests in the last half century and is a conservation priority for Audubon Connecticut.

Fortunately, leaf management isn’t an all-or-nothing game. If you don’t want to leave fallen leaves where they are in your yard, you can either rake or blow them to the edges of your landscape, where they will continue nourishing the soil and providing a shelter for small animals.

Additionally, you might consider congregating them in piles beneath large trees on your property, where they will perform the same quiet, yet profound work. With an estimated 40 million acres of lawn in the United States (according to the National Aeronautics and Space Station), we are, as the title of Doug Tallamy’s new book states, nature’s best hope.

Bethany Sheffer is the Volunteer Coordinator and Naturalist at the Sharon Audubon Center.