Abstract
Collisions with glass are a serious threat to avian life and are estimated to kill hundreds of millions of birds per year in the United States. We monitored 22 buildings at the Virginia Tech Corporate Research Center (VTCRC) in Blacksburg, Virginia, for collision fatalities from October 2013 through May 2015 and explored possible effects exerted by glass area and surrounding land cover on avian mortality. We documented 240 individuals representing 55 identifiable species that died due to collisions with windows at the VTCRC. The relative risk of fatal collisions at all buildings over the study period were estimated using a Bayesian hierarchical zero-inflated Poisson model adjusting for percentage of tree and lawn cover within 50 m of buildings, as well as for glass area. We found significant relationships between fatalities and surrounding lawn area (relative risk: 0.96, 95% credible interval: 0.93, 0.98) as well as glass area on buildings (RR: 1.30, 95% CI [1.05–1.65]). The model also found a moderately significant relationship between fatal collisions and the percent land cover of ornamental trees surrounding buildings (RR = 1.02, 95% CI [1.00–1.05]). Every building surveyed had at least one recorded collision death. Our findings indicate that birds collide with VTCRC windows during the summer breeding season in addition to spring and fall migration. The Ruby-throated Hummingbird (Archilochus colubris) was the most common window collision species and accounted for 10% of deaths. Though research has identified various correlates with fatal bird-window collisions, such studies rarely culminate in mitigation. We hope our study brings attention, and ultimately action, to address this significant threat to birds at the VTCRC and elsewhere.
Highlights
In the United States, glass is responsible for an estimated 365–988 million bird deaths per year (Klem, 1990; Klem, 2009; Loss et al, 2014)
Our documentation of 240 birds over 20 months suggest that avian fatalities are a significant problem at the Virginia Tech Corporate Research Center (VTCRC)
We found collision victims year-round because the reflective windows did not present a barrier to avoid
Summary
In the United States, glass is responsible for an estimated 365–988 million bird deaths per year (Klem, 1990; Klem, 2009; Loss et al, 2014). Bird strikes are shown to increase in spring and fall when many birds are migrating (Borden et al, 2010; Ocampo-Peñuela et al, 2016), though year-round data is scant (Kummer, Bayne & Machtans, 2016). Building characteristics, such as the amount of glass, affect the likelihood that a collision will occur (Collins & Horn, 2008; Hager et al, 2013). Landscape features around buildings can affect collision rate, with extensive vegetation drawing birds in and reflecting in windows (Klem, 2009; Hager et al, 2008). Disproportionate colliders include Rubythroated Hummingbird, Black-throated Blue Warbler (Setophaga caerulescens), Ovenbird (Seiurus aurocapilla) Brown Creeper (Certhia Americana), Swamp Sparrow (Melospiza georgiana), and White-throated Sparrow (Zonotrichia albicollis) (Ogden, 1996; Hager et al, 2008; Borden et al, 2010; Loss et al, 2014)
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