Managing nesting by Chihuahuan ravens on H‐frame electric transmission structures

Abstract

Electric utility structures occur widely in natural and human-dominated landscapes and are often used by birds for nesting. Nests can cause power outages, fires, and electrocution of birds and their young, particularly if nests occur directly above energized equipment and incorporate metal wire. Chihuahuan raven (Corvus cryptoleucus) nests often contain metal wire and occur over energized equipment. To explore a proactive risk mitigation strategy we deployed novel nest diverters on 51 structures supporting a 230 kV H-frame transmission line in Kiowa and Bent Counties, Colorado, USA, and compared nesting on these structures with nesting on 66 structures without nest diverters on the same line. Chihuahuan ravens placed nest material on 7% of treated structures and 43% of untreated structures and nested on 0% of treated structures and 34% of untreated structures. Chihuahuan ravens were less likely to attempt to nest on, or actually nest on, structures treated with nest diverters. Future research should evaluate nest diverters over larger spatial and temporal scales and compare prey populations in areas where ravens are excluded to prey populations in areas where ravens persist. ß 2012 The Wildlife Society.

Testing nest deterrents for Chihuahuan ravens on H‐frame transmission structures

“…Whereas Dwyer and Leiker (2012) demonstrated that nest deterrents were successful across a single breeding season for preventing nesting by Chihuahuan ravens, we were able to prevent the ravens from nesting over 2 additional breeding seasons. In addition, we were able to prevent nesting over the center phase of H-frame transmission structures on a line segment 17.7 times as long as the treated segments used by Dwyer and Leiker (2012). However, apparently in response to nest deterrents, Chihuahuan ravens successfully shifted nesting to corner structures, and for the first time in the recorded history of this line (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014), to outer phases and to overhead-shield-wire attachment brackets.…”

“…Our study also supported our 3 predictions that there would be fewer nests on structures with deterrents (treated structures), that nests would not occur over the center phase on treated structures, and that Chihuahuan ravens would perch on overhead shield wires. Whereas Dwyer and Leiker (2012) demonstrated that nest deterrents were successful across a single breeding season for preventing nesting by Chihuahuan ravens, we were able to prevent the ravens from nesting over 2 additional breeding seasons. In addition, we were able to prevent nesting over the center phase of H-frame transmission structures on a line segment 17.7 times as long as the treated segments used by Dwyer and Leiker (2012).…”

“…Though our results are consistent with those of Dwyer and Leiker (2012) in demonstrating that nesting by Chihuahuan ravens can be managed with the nest deterrent tested here, our findings should be applied with caution to other species nesting on H-frame transmission structures. Future research combining nest deterrents with nest platforms, and including additional species, such as osprey (Pandion haliaetus), which also nest on power structures and readily accept platforms (APLIC 2006), might help clarify the potential for wide-scale and long-term effectiveness of the nest deterrents described here.…”

“…However, the test occurred on a relatively small scale, and individual Chihuahuan ravens may have been able to avoid nest deterrents by moving within existing foraging areas to nearby structures that lacked nest deterrents. Evaluating how Chihuahuan ravens react to nest deterrents over a larger scale is necessary prior to deploying and relying on the effectiveness of nest deterrents more widely (Dwyer and Leiker ), or considering deployment of nest deterrents elsewhere.…”

Mitigating avian collision with power lines: a proof of concept for installation of line markers via unmanned aerial vehicle

“…The design parameters of our UAV also make it ideal for conducting close evaluations of overhead power line structures (Lobermeier et al 2012). These structures require regular surveys to evaluate potential operational and maintenance concerns before these concerns develop into unplanned emergencies (Li and Ruan 2010;Dwyer and Leiker 2012). However, improvements to our design to reduce weight and improve durability are needed prior to practical widespread use.…”