12/03/2006

On the Wing

Field guide IDs 'Trees of Michigan'

By Kay Charter
Local columnist

Every year, from mid-May through the end of June, I offer a Saturday morning bird hike on Charter Sanctuary. People with all levels of birding expertise, from virtually none to genuine experts, come along for these weekly tours on our 44-acre property.

Sometimes I learn more from the participants than they do from me. Such was the case last year when a woman from Dayton was along for the walk.

About halfway through the tour, she looked up at a tree behind our home and said — more to herself than the rest of us — "Hmmm … compound leaf.” Then she turned to me and asked, "Is that a tree-of-heaven?”

I said that I didn't think so, and hoped fervently that was right since it is a very aggressive alien. At the time, I was certain that it hadn't made its way this far up in our state. (Unfortunately, it has.)

Brought to England from China in the mid-1700s by missionaries, this attractive ornamental was introduced into the United States more than 150 years ago. Tree-of-heaven was immortalized in Betty Smith's popular novel, "A Tree Grows in Brooklyn,” wherein a girl from a struggling family is inspired by the tree's ability to survive. Paradoxically, this plant degrades habitat wherever it invades, reducing or eliminating food value for birds and other wildlife.

Thus my concern, which was not laid to rest until botanist Dave Dister visited this fall and pronounced the suspect to be a very welcome native walnut tree.

If I'd had a copy of Linda Kershaw's book, "Trees of Michigan” (Lone Pine Press, 2006, $20.95), when the woman from Dayton first asked about the tree, it would have been easy to figure out that it was not a tree-of-heaven. The author tells us (and so did Dave Dister) that when the leaf lobes of the noxious tree are rubbed, they give off an unpleasant odor. The leaves of our tree did not do that.

This handy little field guide answered many other questions about trees in our state, such as whether or not the catalpa is native — the seedpods of which my siblings and I tried to smoke as kids. There was a large old catalpa tree in the yard of our southern Illinois home and our parents had said it originated in Asia. Not so according to Kershaw; this tree is as native as the Carolina tribes that gave it its name. Tulip trees, about which I had also wondered, are native as well.

There are, however, a good many non-native willows in Michigan, a fact also unknown to me. The aliens include basket, white, crack, purple-osier and bayleaf willow, all complicating the efforts of those — like my husband and me — who are working to preserve or restore habitats to native plants.

Although the book is relatively small (it would fit easily into a jacket pocket), it is full of valuable information. The introduction alone is worth the modest $20.95 price, informing us of the various roles trees play in our everyday lives, from providing food and shelter to producing oxygen.

Kershaw discusses Michigan's various ecoregions and lists rare as well as invasive tree species. Her book includes easy-to-follow key information and range maps. It also includes excellent illustrations and beautiful, clear photographs. The origin of each tree, an especially important bit of information for conservationists, is noted along with descriptions of branches, trunks, flowers, leaves and habitat.

Interesting trivia is also included, such as the mention of White's novel, the fact that protein-rich leaves of Carolina poplars are fed to livestock and that spicebush berries were used during the 1800s to treat many ailments including expelling intestinal worms (such claims were never verified).

Although a handful of species, including silky dogwood, box elder and common juniper, are missing, this is an outstanding book for anyone interested in knowing more about the trees of our state.

Since incorporating native trees, shrubs, flowers and grasses into personal landscapes is helpful to migrating bird species, this book should be on every birder's shelf. My copy is already dog-eared from leafing through it.

Trees of Michigan would be a terrific holiday gift for anyone interested in knowing more about the Michigan's natural resources.

Kay Charter is executive director of Saving Birds Thru Habitat, an organization dedicated to teaching people how to help migrating birds whose populations are declining