NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

This study was supported by the U.S. Department of Agriculture, Agricultural Research Service (USDA-ARS) under Award No. 59-0790-3-201 and the U.S. Geological Survey (USGS) under Grant Agreement No. 03HQGR0131. The content of this publication does not necessarily reflect the views or policies of the USDA-ARS or USGS, nor does mention of trade names, commercial products or organizations imply endorsement by the U.S. Government.

Cover: Design by Van Nguyen. Photo credits clockwise from top left: hummingbird by W. May; sphinx moth by W. May; bat by Merlin D. Tuttle, Bat Conservation International, reprinted with permission; bee by David Inouye, University of Maryland, College Park.