Bird friendly buildings could save millions

The infrastructure that provides people with essential services sometimes has a surprisingly large side effect on other species. Seemingly benign buildings may be one of the deadliest serial killers.

People have long observed birds collide with windows at their home or office. The cumulative effect of all those collisions across America has previously been estimated to range widely from 100 million to 1 billion birds killed a year. A new study to be published in  The Condor analyzed previous studies and datasets for a clearer consensus. The result, even with some uncertainty remaining, was still a whopping 365 to 988 million birds.

The potential impact of those numbers on bird populations is difficult to understand without a reference point. All U.S. bird species combined probably far exceed one billion individuals. However, some species are more likely than others to crash into buildings, and the consequences for those smaller populations might be significant. Several migratory species, including the Worm-eating Warbler, Painted Bunting, and Wood Thrush, are in decline and highly vulnerable to collisions.

Collision risk also differed with the type of building. Less than one percent of mortality came from high rises that intrude into long-distance flyways. Low-rises posed the largest threat, accounting for 56 percent of the collision deaths, followed by 44 percent for residences. Homes and apartment buildings are obviously more common than skyscrapers, and they also occur more often in higher quality bird habitat. Short flights between trees and other vegetation may be when birds mistake a reflection of the sky for an escape route from a predator or a territory neighbor giving chase.

As bird habitat and urban development continue to overlap, bird encounters with more buildings will be unavoidable. The good news is that individuals can help prevent collisions through small modifications. The National Audubon Society recommends stationing bird feeders away from windows, adding decals to windows, angling glass downward to reflect the ground, and installing bug screens year round. Developers can take responsibility, too. The San Francisco Planning Commission adopted Standards for Bird-Safe Windows to offer alternative designs to new buildings. Once we assist birds’ ability to navigate the built environment, the next step will be to help them escape the number one killer: cats. Miles Becker | 13 January 2014


Source: Loss, S.R. et al. 2014. Bird–building collisions in the United States: Estimates of annual mortality and species vulnerability. The Condor  doi: 10.1650/CONDOR-13-090.1

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