Abstract
We evaluated the collision risk of Galapagos Petrels Pterodroma phaeopygia with a wind energy development recently constructed in the highlands of San Cristóbal Island, Galapagos. Trained observers recorded the movements of petrels at dusk and dawn from the wind project site, and from control sites located along ravines that host nesting colonies. Collision mortality was also assessed by monitoring circular plots and transect lines located under human-made structures. Petrel flight activity showed a bimodal pattern, with the majority of the movements recorded in the hours previous to sunrise. Most petrels (96%) moved along major ravines that descend from the highlands to the south–southeastern coast of the island. Significant differences in passage rates were found between the project and control sites, with only five petrels recorded on the site selected for turbine installation. Although our data suggest that wind farms will not be more detrimental to petrels than other existing man-made structures, a word of caution is made because even very low levels of additional mortality might be significant for a species with such low productivity and slow maturation rates. Moreover, some other possible indirect effects on habitat change and disturbance might occur that were not assessed in our study. A post-construction monitoring program should be implemented to adequately assess long-term effects on petrels and to enable these uncertainties to be satisfactorily addressed.