Behavior of Hawaiian Petrels and Newell's Shearwaters (Aves: Procellariiformes) Around Electrical-Transmission Lines on Kaua‘i Island, Hawaiian Islands

Abstract: Understanding the behavior of birds around tall structures such as electrical-transmission lines, communication towers, and wind turbines is important in assessing the potential effects of those structures on bird populations; it is especially important for threatened or endangered species. We studied responses of the mostly crepuscular/nocturnal Hawaiian Petrel (Pterodroma sandwichensis) and the mostly nocturnal Newell's (Townsend's) Shearwater (Puffinus newelli; Aves: Procellariiformes) to coastal and near-coastal transmission lines on Kaua‘i Island, Hawai‘i, USA, in 1992–2002. Hawaiian Petrels responded to transmission lines significantly more often (19.1% of the time; N = 209) than Newell’s Shearwaters did (7.4%; N = 392), responded significantly more often with decreasing distance from a line, and responded significantly less often if a study-site was dark (i.e., unlit by ambient lights from nearby towns) than if it was light (i.e., lit by ambient lights from nearby towns), regardless of whether the sky was light (i.e., daylight or crepuscular light conditions) or dark (nocturnal light conditions). In contrast, Newell’s Shearwaters showed little variation in response rates by distance or by whether the study-site or sky was light or dark. Hawaiian Petrels mostly responded to transmission lines by changing flight velocity and flight altitude, whereas Newell’s Shearwaters mostly responded by changing flight direction and flight altitude. The higher response rates and more-buoyant flight characteristics of Hawaiian Petrels than Newell’s Shearwaters may contribute to lower rates of fatality of Hawaiian Petrels than Newell’s Shearwaters at coastal and near-coastal transmission lines on Kaua‘i.