VALIDATION TESTS OF AN AMPHIBIAN CALL COUNT SURVEY TECHNIQUE IN ONTARIO, CANADA

Amphibian call count surveys in Ontario use a common survey protocol. We evalu- ated the precision and accuracy of data collected by these methods. Multiple observers monitored the same routes to determine inter-observer variation. Inter-observer agreement in evaluation of calling intensity and occurrence was generally high, and the experience of the observer affected estimation of both calling intensity and the number of individuals calling. There was no significant increase in inter-observer agreement in evaluation of calling intensity or occurrence with 5-min versus 3-min surveys. Longer surveys rarely resulted in the identification of species not heard in the first 3 min. Surveys of 30-60 min duration indicated that return for effort declined sharply during the second minute of the survey, although new species were sometimes heard after as long as 15 min. Simultaneous intensive and extensive monitoring was performed on populations of Fow- ler's toads (Bufo fowleri) in southern Ontario and bullfrogs (Rana catesbeiana) in central Ontario to determine whether there was a relationship between calling intensity and chorus size or population size. We found a linear relationship between call counts and chorus size in both species. We conclude that the data generated with the call count surveys were adequately precise, but accuracy remains to be validated. Further investigation of the relationships among population size, chorus size, calling intensity, and environmental factors are required to determine whether extensive monitoring of calling amphibians can be used as an index of actual population size. However, until that time, we recommend that calling amphibian surveys be used as the first part of an integrated program using extensive monitoring to identify areas where populations may be declining, and intensive monitoring to confirm or refute reports of declines. EXTENSIVE monitoring programs using volunteer observers in conjunction with professional biologists are currently being used in Canada and the United States in an attempt to detect fluctuations and trends in both the abundance and distri- bution of amphibian populations using standardized techniques. Amphibian call count surveys have been implemented in Quebec, Ontario, Manitoba, Saskatche- wan, New York, Pennsylvania, Ohio, Mich- igan, Indiana, Wisconsin, Illinois, Minne- sota, Missouri, and Iowa. The amphibian call count protocol used in Ontario is a point-count method that relies primarily upon the efforts of volunteer observers. Three-minute surveys are conducted along routes consisting of up to 10 permanently marked stations. Because of the difficulty of estimating distance in the dark, no at- tempt is made to limit the calls counted to a fixed distance around each survey point. Stations are set at intervals of at least 500 m to minimize the risk of counting indi- viduals more than once. Surveys begin 0.5 h after sunset and are completed no later than midnight. Each route is surveyed three times during the spring and early summer, with the dates of surveys depend- ing on the latitude of the route. Ontario has been divided into north, central, and south regions demarcated at the 43rd and 47th degrees of latitude. The three survey periods are 15 days in dura- tion and are set a minimum of 15 days apart. Participants are asked to survey dur- ing specific weather conditions. Minimum air temperatures for surveying are 8 C (first survey), 13 C (second survey), and 21 C (third survey). At each station, nartici-