WHEN ARE GOSHAWKS NOT THERE? IS A SINGLE VISIT ENOUGH TO INFER ABSENCE AT OCCUPIED NEST AREAS?

摘要: We tested the efficacy of three methods (historical nest search, broadcast and tree transect search) for detecting presence Northern Goshawk (Acdpiter gentilis) at occupied areas during 1994 breeding season using only a single visit to previously known area. used detection rates in probability model determine how many visits are required have confidence reporting absence goshawks. The purpose this study is understand if goshawks robust enough managers rely on them making land management decisions that may impact goshawk areas. Blind tests were conducted throughout western United States. Results similar among with going undetected 36-42% after visit. These results indicate area inadequate provide reliable information occupation. Our showed each method repeated or transect) four (broadcast) times, can be inferred high level confidence. Conclusions regarding occupation sampling should made utmost caution. Classifying as vacant, when fact present, serious concern leads spurious conclusions. Land habitat-altering not establish Possibilities improving nesting include multiple independent same method, sequence techniques combi- nation yield an improved cumulative detection, developing new yielding higher detection. historical search obtained best results, followed by search.