Underestimated Fatalities of a Cryptic Avian Species of Conservation Concern at Wind Energy Facilities in California, USA.

Accurate information underpins successful ecological science and management. Cryptic species, those that are difficult to differentiate, pose challenges to reliable collection of taxon-specific information. Blackbirds, including tricolored blackbirds (Agelaius tricolor), a cryptic species of high conservation concern, and red-winged blackbirds (Agelaius phoeniceus), an abundant congener, are sometimes killed by wind turbines. We used publicly available survey records to evaluate rates at which blackbirds were reported dead at wind energy facilities in California, USA. We then used genetic species identification of carcasses found to estimate true rates of discovery and of misidentification. Of 329 blackbird fatalities in survey records, most were identified as red-winged (n = 149), "unidentified" (n = 90), or Brewer's (Euphagus cyanocephalus; n = 70); only 13 were identified as tricolored. We also genetically analyzed samples from 40 blackbirds. Of 14 carcasses identified in the field to species, two, including one tricolored, were incorrectly called Brewer's blackbirds (14% misidentification rate). Of the 26 birds called "unidentified blackbird" in the field, 17 (65%) were tricolored, leading to a 19× underestimation of true fatality rate. The state-wide population of tricolored blackbirds is < 1% the size of that of red-winged blackbirds. A large proportion of blackbirds found dead were actually tricoloreds, indicating that fatality rates of this state threatened species may be substantially underestimated. The potential for misidentification or nonidentification may create perverse incentives that undermine conservation and have consequences for on-the-ground management, mitigation, and operations of high-priority infrastructure.