The role of tower height and guy wires on avian collisions with communication towers

Abstract

Every year an estimated 4–5 million migratory birds collide with communication towers in the United States. We examined the relative risks that tower support systems and tower height pose to migrating and other birds. We collected data comparing tower support systems (guyed vs. unguyed) and tower height categories in Michigan during 20 days of the peak of songbird migration at 6 towers in September–October 2003, 23 towers in May 2004, 24 towers in September 2004, and 6 towers in both May and September 2005. We systematically and simultaneously searched for bird carcasses under each tower and measured carcass removal and observer detection rates each season. Of those towers, 21 were between 116 and 146 m above ground level (AGL, medium) and 3 were >305 m AGL (tall). During the five 20‐day sample periods we found a mean of 8.2 bird carcasses per guyed medium tower and a mean of 0.5 bird carcasses under unguyed medium towers. During four 20‐day sample periods we detected a mean of 34.7 birds per guyed tall tower. Using both parametric and nonparametric tests (Mann–Whitney U‐test, Kruskal–Wallis test, and Tukey's Honestly Significant Difference multiple comparison procedure) we determined that unguyed medium towers were involved in significantly fewer fatalities than guyed medium towers. We detected 54–86% fewer fatalities at guyed medium towers than at guyed tall towers. We found 16 times more fatalities at guyed medium towers than at unguyed medium towers. Tall, guyed towers were responsible for 70 times as many bird fatalities as the unguyed medium towers and nearly five times as many as guyed medium towers. These findings will provide managers and regulators, such as the US Fish and Wildlife Service, with quantitative data; thereby, allowing them to effectively work with the Federal Communications Commission in siting and authorizing tower placement. © 2011 The Wildlife Society.

Factors influencing experimental estimation of scavenger removal and observer detection in bird–window collision surveys

“…Contrary to expectations based on previous studies (Gehring et al. , Boves and Belthoff ), we found no effect of season on searcher efficiency. However, unlike previous research, our survey areas exhibited minimal seasonal changes in vegetation cover, and further, we did not perform observer detection trials in winter when conditions influencing detectability may have differed more dramatically.…”

“…This observer detection bias has been systematically assessed for many mortality sources and may increase with extensive vegetative cover, poor light conditions, inclement weather, and observer fatigue or inattentiveness (Gehring et al. , Korner‐Nievergelt et al. , Mathews et al.…”

Collision avoidance by migrating raptors encountering a new electric power transmission line

“…Large, heavy-bodied species such as swans, pelicans, herons, and cranes are generally thought to be more susceptible to transmission line collisions than smaller, more maneuverable species (APLIC 2012). Nocturnal migrants have not been well studied, but also may be susceptible, particularly within migration corridors (Rogers et al 2014), and especially in light of their susceptibility to collision with other types of tall anthropogenic structures (Drewitt and Langston 2008, Kerlinger et al 2010, Gehring et al 2011. Relatively small duck and grouse species are also vulnerable to collision because of their high flight speed, low altitude, and flocking flight, in which the view of upcoming obstacles is obscured by leading birds (APLIC 1994, Bevanger andBrøseth 2004).…”

Bird and bat mortality at short, monopole cell towers in Rock Creek Park, Washington, D.C., USA

“…A review of wind turbine‐related bat mortality found no studies documenting bat carcasses at the shorter meteorological towers (Arnett et al 2008). All things being equal, shorter unlit and unguyed towers seem to kill fewer or no birds, but there is still a need for more data on short towers to use in the meta‐analyses of tower studies (Gehring et al 2011).…”