Bird word

Hepatic: While the word refers to the liver, it's often used to describe birds that are purplish brown or a dark, dull red. That doesn't explain why the hepatic tanager is so very orange.

Feed those hummers

Keep your hummingbird feeders filled in fall. Our resident species, the ruby-throated hummingbird, will be migrating through and your feeders can help fuel the trip.

Be sure the sugar water in your hummer feeders is clean and fresh. Replace it when it looks cloudy. If you want to make your own, the formula is one part sugar to four parts water. (There's no need to color the nectar.)

And don't worry, feeding hummers won't keep them from migrating. They'll leave when they're ready.

Bird book in brief

Evolution doesn't have to take millions of years. In fact, observing the birds known as Darwin's finches over a span no longer than a scientific career has shown trends toward new species.

Darwin's finches are found on the Galapagos Islands. For decades they've been studied by Peter R. Grant and B. Rosemary Grant, the authors of "How and Why Species Multiply" (Princeton University Press, $35).

Their book is not easy to read. The Grants have written it for people with a serious interest in evolutionary biology. But even though the terminology often is formidable, the basic ideas in the book are accessible and fascinating. That makes reading it worth the effort.