NREL - National Renewable Energy Laboratory

Avian collision mortality at 50- and 60- m guyed towers in central California

Publication TypeJournal Article
Year of Publication2012
JournalThe Condor
KeywordsContra Costa County, Solano County

By searching for carcasses weekly year round, we estimated rates of avian fatality from collision with ten 50-m and eight 60-m temporary meteorological towers supported by guy wires near wind turbines at the Altamont Pass (n = 3) and Collinsville Montezuma Hills (n = 15) wind resource areas in central California. All towers were searched out to 55 m, beyond the farthest guy-wire anchors. Estimates for the total number of fatalities were based on searchers’ efficiency and scavengers’ removal rates determined empirically at one of the wind farms. In 1632 searches (90.7 ± 5.4 per tower; 136.0 ± 2.8 per month), we found 85 carcasses of 19 species, for an average of 2.8 carcasses per tower per year. When adjusted for searchers’ efficiency and scavenging, fatalities per tower per year were 6.8 ± 1.1 for all birds. Icterids, the Horned Lark (Eremophila alpestris), pipits, and sparrows accounted for 60% of carcasses, whereas night-migrating songbirds accounted for only 7% of carcasses. This level of mortality likely did not result in population effects because fatalities were spread among many, mostly common species and the towers were temporary structures. Because the towers we studied were similar in structure to guyed communication towers of the same height, our findings are likely applicable to those structures in California. There is currently no other empirical information available on fatality from towers of these heights and support systems, even though they are one of the most common types of such towers in California and elsewhere.

TagsCalifornia; Utility Scale; Passerines (general); Birds (general); 2012; Journal Article