ACME: A Partially Periodic Estimator of Avian & Chiropteran Mortality at Wind Turbines

Abstract

Estimating the mortality of birds and bats at wind turbines based on periodic carcass counts is challenging because carcasses may be removed by scavengers or may be missed in investigators' searches, leading to undercounting. Existing mortality estimators intended to correct for this offer wildly different estimates when search intervals are short. We introduce a new estimator that includes many existing ones as special cases but extends and improves them in three ways to reflect phenomena discovered in the field: * Decreasing removal rate by scavengers as carcasses age; * Diminishing proficiency of Field Technicians in discovering carcasses as they age; * Possibility that some (but not all) carcasses arriving in earlier search periods may be discovered in the current period. It is this feature that makes the new estimator "partially periodic". Both point estimates and 50% and 90% Objective Bayes interval estimates are provided for mortality. The new ACME mortality estimator will significantly improve the accuracy and credibility of mortality estimates for birds and bats near wind turbines.