Post-collision impacts, crippling bias, and environmental bias in a study of Newell's Shearwater and Hawaiian Petrel powerline collisions

Abstract

Powerline collisions have been identified on Kaua'i as a potential contributing factor to the large-scale decline of both Hawaiian Petrel (Pterodroma sandwichensis) and Newell's Shearwater (Puffinus newelli), but the scale of the powerline collision problem is unknown. From 2012 to 2020 we conducted observations for seabird powerline collisions across Kaua'i, documented grounded seabirds, and assessed crippling and environmental biases -both poorly studied facets of powerline collision research. We directly observed 121 powerline collisions and detected 89 grounded seabirds. While some collisions resulted in birds falling lifelessly out of the sky, most resulted in seabirds flying or gliding outside of the search area. This means that traditional ground searches would underestimate total collisions by 78-88% if not accounting for crippling bias. We tested environmental bias by comparing our ability to conduct searches for grounded birds, "searchability", across multiple variables. Environmental bias resulted in significant reductions in searchability across regions, environment types, and powerline heights. Furthermore, observed collision rates were significantly higher at powerlines that had very low to zero searchability. Forty-three percent of observed collisions occurred at unsearchable powerlines (mainly spanning steep valleys), equating to an estimated 3170 seabird collisions that could not be detected through ground searches. We detected powerline collisions in every region of Kaua'i, in every environment type, and at all powerline heights monitored. Our results show that crippling bias and environmental bias are the mechanisms that concealed the geographic distribution of collisions and the scale of the powerline problem from grounded bird searches, ultimately preventing the detection of thousands of collisions. The data collected for this study are critical for assessing the scale of seabird powerline collisions and quantifying the biases inherent in traditional ground searches. Collisions de Puffins de Newell et de Pétrels des Hawaï avec les lignes électriques : impacts postcollision, biais inhérent aux blessures et à l'environnementRÉSUMÉ. Les collisions avec les lignes électriques sur Kaua'i ont été identifiées comme facteur contribuant potentiellement à la baisse à grande échelle du Pétrel des Hawaï (Pterodroma sandwichensis) et du Puffin de Newell (Puffinus newelli), mais l'ampleur de ce problème est inconnue. De 2012 à 2020, nous avons été témoins de collisions d'oiseaux marins avec des lignes électriques sur Kaua'i, documenté les oiseaux marins trouvés au sol et évalué les biais inhérents aux blessures et à l'environnement -deux facettes peu étudiées dans les études sur les collisions avec les lignes électriques. Nous avons assisté à 121 collisions avec des lignes électriques et détecté 89 oiseaux marins morts au sol. Si certaines collisions ont été fatales sur le coup pour les oiseaux marins, la plupart des oiseaux ont continué à voler ou à planer en dehors de la zone de recherche. Ce résultat in...

Behavior of Hawaiian Petrels and Newell's Shearwaters (Aves: Procellariiformes) Around Electrical-Transmission Lines on Kaua‘i Island, Hawaiian Islands1

“…Because even small errors in avoidance rates for these types of structures can have a very large effect on predicted fatality rates from preconstruction studies (Chamberlain et al 2006, understanding the avoidance behavior of birds around these structures will be especially important in assessing the potential effects of those structures on birds, especially on endangered species such as Hawaiian Petrels and Newell's Shearwaters. Although it is clear from several studies that both Hawaiian Petrels and Newell's Shearwaters collide with transmission lines on Kaua'i (Cooper and Day 1998, Podolsky et al 1998, Travers et al 2021, we found that, during the peak evening and morning activity periods, a substantial proportion of petrels and a small proportion of shearwaters detect and respond to coastal and near-coastal transmission lines under normal ranges of weather conditions and visibility. We agree with others (Chamberlain et al 2006, however, that detailed avoidance data are needed to understand and model fatality risk with confidence.…”

“…It is clear that collision rates are low, both at these coastal and near-coastal transmission lines and at the mostly inland lines studied by Travers et al (2021). We recorded only one collision in 2,106 total Hawaiian Petrels, Newell's Shearwaters, unidentified shearwaters, and unidentified petrels/shearwaters seen flying near lines on 637 sampling sessions during ∼300 h of sampling, suggesting that collisions may be on the order of ∼0.0005 collisions/bird seen near a coastal or nearcoastal transmission line and ∼0.003 collisions/h of sampling effort.…”

“…In all cases, collisions clearly are a rare event, making estimates of collision rates difficult to quantify with accuracy. On the other hand, such small numbers can become large numbers when calculated across the entire island over a year (Travers et al 2021).…”

“…Occasional fatalities have been recorded at electricaltransmission lines near the summit of Haleakala -, Maui Island (Hodges 1992), at wind turbines on Maui Island (Tetra Tech 2020), at fences high on Mauna Loa on Hawai'i Island (Swift 2004), and at a fence high on Lana'i Island (anonymous reviewer of this paper, in litt.). In contrast, fatality rates at inland transmission lines on Kaua'i Island appear to be high (Travers et al 2021). Weather conditions during these occasional fatality events often are not known, so it is unclear how often poor visibility is involved in such fatalities; however, the fairly frequent occurrence of fog near the summit of Haleakalaat night (RHD, pers.…”

“…Keywords: collision, collision-avoidance behavior, conservation, Hawaii, petrel, powerline, shearwater THE CONSTRUCTION OF TALL STRUCTURES such as electrical-transmission lines, communication towers, and wind turbines often results in the fatality of birds of various species (e.g., Anderson 1978, Avery 1978, Winkelman 1995, De Lucas et al 2004, Desholm and Kahlert 2005, Manville 2005, Everaert and Stienen 2006, National Research Council 2007, Longcore et al 2008, Gehring et al 2009). In the Hawaiian Islands, the federally endangered Hawaiian Petrel ('Ua'u; Pterodroma sandwichensis) and the federally threatened Newell's Shearwater ('A'o; Puffinus newelli; Aves: Procellariiformes) have been killed at electrical-transmission lines (Telfer et al 1987, Hodges 1992, Cooper and Day 1998, Podolsky et al 1998, Travers et al 2021 and wind turbines (Tetra Tech 2020). These two crepuscular/nocturnal seabird species nest only in the Hawaiian Islands and have undergone significant population declines in historical times; they still nest on all of the Main Islands but now are restricted primarily to scattered, small colonies in mostly inaccessible locations (Day and Cooper 1995, Raine et al 2017, Ainley et al 2020, Simons and Hodges 2020.…”