Searcher Bias and Scavenging Rates in Bird/Wind Energy Studies

Karin Sinclair, Karin Sinclair (NREL Technical Monitor)

Research output: NRELSubcontract Report


Estimates of animal fatalities in wind developments are biased to unknown degrees by inefficiencies of observers and by the removal of carcasses by scavenging animals or other actions before their detection by observers. This report summarizes results of searcher efficiency and scavenging, thus providing a guide for workers designing or interpreting bird/wind energy studies. Searcher efficiencyis highly variable, with several studies reporting relatively low rates (i.e., 35%-50%) and several studies reporting relatively high rates (i.e., 75%-85%) of recovery. The few studies that tested vegetation type indicated that efficiency is influenced by the height and type of vegetation present. It is evident that relatively small birds are being missed at high rates, with most studies likelyunderestimating the fatality of small birds by 50%-75%. Results also indicate that corrections for observer efficiency need to be based on vegetation type, plant phenology (season), and bird (or bat) size. Studies of scavenging rates were also highly variable and were influenced by bird size and season. Results did show a trend toward a substantial (50%-75%) loss of carcasses of small to midsizebirds within one to four weeks; even large raptors will disappear after a month or so.
Original languageAmerican English
Number of pages9
StatePublished - 2002

Bibliographical note

Work performed by White Mountain Research Station, Bishop, California

NREL Publication Number

  • NREL/SR-500-30876


  • avian research
  • research bias
  • scavenging rates
  • searcher bias
  • wind energy


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