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Peterson Field Guide to Bird Sounds of Eastern North America, Nathan Pieplow, Houghton Mifflin Harcourt Publishing, softcover, 593 pages, index, illustrated, $28 — This is part of the Peterson Field Guide Series. The book contains spectograms of 520 bird species. A spectogram is a visual representation of sound. I would not find this book helpful. However, it makes reference to more than 5,400 audio files of these birds available streaming on the web at

www.petersonbirdsounds.com. Those I would find helpful.

Beaks, Bones, & Bird Songs: How the struggle for survival has shaped birds and their behavior, Roger J. Lederer, Timber Press, hardcover, 280 pages, index, with photos and maps — Lederer has taught biological sciences, including ornithology, at the college level. His subject — behavior as guided and created by evolution — is one that interests me significantly. The adaptability of birds is fascinating, how the world's 10,000 bird species fit so perfectly into 10,000 slots. How did it come to be that five different species of warblers can feed in the same coniferous tree, each at a different location? Lederer doesn't answer that question, instead exploring a broader set of subjects that describe challenges birds face and solutions they find. It is a good overview of bird life. His web site is at ornithology.com.