Factors influencing detection of nesting crested caracaras

Management of crested caracaras (Caracara cheriway), focuses on nests identified during surveys. If no nests are found, management can be suspended. Thus, false negatives can have substantial consequences. We surveyed 49 breeding territories to assess factors with the potential to cause false negatives in detecting nests of crested caracaras and in observing adult birds. The probability that a nest would be detected on any given visit increased by about 0.5% for each hour of observer experience up to about 70 hours (our maximum). Experience did not affect the probability of observing an adult. The probability of detecting a caracara nest or observing an adult caracara decreased by 2.0–3.5% each hour after sunrise that a visit began. If visibility during any portion of a visit was obscured by fog or rain, the probability of detecting a nest decreased by as much as 60%, and the probability of observing an adult caracara decreased by about 50%. We provide a tool managers can use to calculate the likelihood of successful surveys. We recommend that managers disregard negative results from surveys conducted under conditions that are unlikely to yield positive results, and repeat those surveys under better conditions. © 2011 The Wildlife Society.