. The Canadian field-naturalist. Natural history. Bear Crow (A 'E a. 2 ra "5 â visual survey â¡ pitfall traps gj funnel traps. June July August Figure 1. Encounter and capture rates for the Wood Frog at Bear Creek and Crow Creek using visual surveys (a), and pit- fall and funnel traps (b) for the three monthly sampling sessions combined. Monthly encounter and capture rates for the Wood Frog using visual surveys (c), and pitfall and funnel traps (d) for the two sites combined. Total time devoted to visual surveys was h at Bear Creek and h at Crow Creek. Trapping
. The Canadian field-naturalist. Natural history. Bear Crow (A 'E a. 2 ra "5 â visual survey â¡ pitfall traps gj funnel traps. June July August Figure 1. Encounter and capture rates for the Wood Frog at Bear Creek and Crow Creek using visual surveys (a), and pit- fall and funnel traps (b) for the three monthly sampling sessions combined. Monthly encounter and capture rates for the Wood Frog using visual surveys (c), and pitfall and funnel traps (d) for the two sites combined. Total time devoted to visual surveys was h at Bear Creek and h at Crow Creek. Trapping effort totaled 216 pitfall and 156 funnel trap-nights at Bear Creek, and 188 pitfall and 140 funnel trap-nights at Crow Creek. Discussion We documented substantial differences in the per- formance of the four sampling techniques. Live and automated call surveys largely failed. The proposed AFBMP schedule for sampling streams simply does not coincide with the breeding season of anuran amphibians in boreal Alberta. Calling begins in late April, peaks in May and only Bufo species (which we did detect) continue breeding into June (Russell and Bauer 2000). Although relatively quick and easy, call surveys make little biological sense in this program. Pitfall and funnel trapping sessions resulted in few amphibian records, accounting for only 10% of the total number of individuals. This was a disappointing performance considering that the two workers required 18 h and h to install the full suite of pitfall and funnel-trap arrays, respectively. Using our pitfall trapping effort and design (16 traps in 4 arrays), two overnight trapping sessions were required to yield a 70% probability of capturing one Wood Frog. Funnel traps never even reached this level of performance. Trapping offers a reliable tech- nique at sites where low travel costs and easy access permit sampling over an extended time period, par- ticularly in upland habitats where amphibian densi- ties are relatively lo
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