Birds making final stop at bus shelters

Friday, June 23, 2017

The gift of flight leaves birds without the need to hop on public transit systems for transportation. However, more and more of our feathered friends have been seen at bus stop shelters.

The only problem is, the birds are not waiting for the blue route to take them downtown. They are lying lifeless after having flown into the aesthetically pleasing glass walls.

After noticing a number of bird corpses lying near bus stop shelters in Stillwater, researchers in Oklahoma State University’s Department of Natural Resource Ecology and Management began to investigate.

“We already had some evidence it was happening right here in Stillwater,” said Corey Riding, NREM doctoral student. “There’s a shelter near my house where I had seen dead birds, so I knew birds were colliding there.”

Riding partnered up with NREM research technician, Christine Barton, and under the direction of Scott Loss, assistant professor of global change ecology and management in NREM, the team designed a scientific study that had an obvious, yet strangely unique, urban focus.

“Wildlife in urban areas face many human-related threats to their survival. For birds, collision with glass on manmade structures is a major hazard, killing hundreds of millions of birds in North America every year,” said Loss, who has studied bird mortality caused by wind turbines, buildings, cats and everything in between. “Although research has investigated factors associated with bird collisions at buildings, no prior studies have looked at bird collisions at glass-walled bus shelters.”

From May through September 2016, Barton led the effort to survey for bird carcasses and collision evidence at 18 of the 36 bus shelters in Stillwater. She found 21 incidents of collision evidence on the shelters, like feathers stuck to the glass, as well as 13 intact bird carcasses.

The indirect collision evidence suggests not all birds that collide ultimately die, that some birds die outside of view or scavenging animals remove some bird carcasses before they are found. The team tested the scavenging theory by placing bird carcasses near bus shelters to see how long it took scavengers to remove them.

“We found there was a 25 percent chance bird carcasses were removed before we could get to them,” said Barton. “After accounting for scavenger removal, we actually estimate at least 34 birds are killed each year between May and September by collision with the 36 bus shelters in the City of Stillwater.”

Most of the bus shelters in Stillwater are relatively similar in size, with three to five clear panes of glass each. However, the amount of glass on the shelter was still positively related to numbers of dead birds, as was the amount of open lawn surrounding shelters.

“We found several bird species, including mockingbirds and cardinals, as well as a Scissor-tailed Flycatcher and Cooper’s Hawk; however, the most commonly killed birds were House Sparrows and House Finches, species that usually adapt well to urban areas,” said Barton. “This was surprising because studies of bird-window collisions show nonurban migratory species to be most vulnerable. This could have occurred because there are more urban birds foraging in the mowed grass around shelters, or because the bright lights that attract nocturnally migrating birds to buildings are not used at shelters.”

It is difficult to extrapolate the results from this study to a national or even state level, but the fact remains birds often collide with glass-heavy bus shelters.

“A clear conclusion that arises from our study is bus shelters with large amounts of glass kill more birds, so making this glass more visible to birds or reducing the amount of glass used in the first place should help reduce collisions” Barton said.

A paper from this study was published in PLOS ONE, the “world’s first multidisciplinary Open Access journal.”