Using point counts to establish conservation priorities: How many visits are optimal?

We conducted point counts three dines during the 1994 breeding season at 48 stations across the northwestern United States, and used cumulative totals from the three visits to rank the sites by two potential indices of conser vation value: species richness and overall abundance of birds. We then reca lculated each of the indices (1) using data from only a single visit to eac h site and (2) using data from only two visits. Rankings based on only one or two visits revealed that eliminating one, and even two of the visits had relatively minor effects on species richness rankings but affected ranking s based on overall abundance more substantially. We also evaluated how effe ctively one or two visits to each site detected particular species of manag ement concern. We conclude that when resources are limited, species richnes s based on point counts conducted during just one ol two visits to potentia l conservation sites may provide a reliable index for prioritizing conserva tion efforts. When the primary objective is to determine the presence or ab sence of a particular species, however, at least two visits may be warrante d. Finally, we conclude that, in general, researchers must be careful when using overall abundance as an index for establishing conservation prioritie s, as values may fluctuate substantially throughout the season.