Invisible: Dead Birds and Windows
Birds killed by windows, the programs trying to count them and their final, museum resting place.
This story was originally reported and drafted in fall 2019. It went unpublished until April 2021. I’m publishing it now without no further reporting and a bit of editing to remove some confusing references to 2019.
By Andrew Blok
One autumn day in any of the last few thousand years, a chimney swift in Michigan joined dozens or thousands of others and flew south to become a chimney swift in South America for the season.
On a more recent autumn morning, a volunteer walked around Michigan State University’s College of Law to see if any swifts (or sparrows or warblers or other migratory birds) had their migration (and life) abruptly ended by the building’s windows.
Often there are none. But, students and volunteers gathered close to 90 birds during 2019's fall migration. (Though the student, Oliver Autrey, questions whether his fellow students monitored their routes as often as expected of them.) That’s 90 of the 365 million to 998 million birds that die each year from window collisions, largely during spring and fall migrations.
On this particular morning Autrey, a Michigan State zoology student finds two. The first—a blue jay, he speculates—has been reduced to a scattering of feathers and possibly carried off by a scavenger. (Or a predator, Autrey says. With so little left of the bird, it’s uncertain whether a window killed it even though its feathers are right below one.) The second is some kind of warbler. In tact with a windows on two sides, cause of death here is more certain.
Buildings are dangerous for birds (“There really are dead birds everywhere,” Autrey said), but relatively small changes could make them much safer.
Sometimes birds are injured or killed because of the Windex effect. Glass is invisible to birds. Reflected vegetation or a tree on the other side looks like a suitable perch.
Sometimes windows are all too visible. Birds are confused or attracted by buildings that light up the night sky. The NASCAR Hall of Fame killed hundreds of birds during one night of fall migration in 2019. The annual 9/11 Tribute in Light is regularly temporarily shut down to allow the birds attracted by the colossal beams of light to disperse. When the lights are shut off, birds continue on their way. So, too, when buildings go dark after dark.
On a dark, cold October morning in Grand Rapids, Michigan, volunteers meet to walk a designated route: permits, baggies and cameras in hand. They’re part of a Grand Rapids test run of Michigan Audubon’s building monitoring program and searching for window collisions around building in the downtown area.
They note when each building lights up for the day, or whether it went dark at all. Each observation communicates implicit concern: Is it too early for those lights to come on? Did those overnight lights lure and kill any birds?
They croon sympathy for the two dead birds they find: house sparrows. Non-migratory and non-native, but indicative of the problem facing birds more precipitously situated.
A maintenance worker cleaning outside city hall says she sometimes sees dead pigeons, but will keep an eye out for other birds. Shortly before, the volunteers peeled a sparrow from the sidewalk. It had been there for long enough to start decomposing, apparently invisible.
The birds collected in and around East Lansing and Michigan State University are delivered to the Michigan State University Museum. They’re stored in a freezer, double-bagged in Ziplocs, waiting to be counted and prepared as study skins for the museums collection.
In the spring, students will dissect well-preserved specimens and remove their internal organs and any fat and oil which ruin the prospects of long term storage. Done properly, a museum specimen can last a long time.
In the fall they practice on pigeons.
Pamela Rasmussen, an ornithologist and instructor at Michigan State whose students collect the birds as volunteers, can prepare a study skin in under an hour. In their first attempt, it takes students several hours over multiple days.
The pigeons aren’t part of the window collision monitoring, but are useful training tools because of their size.
After they are dissected and cleaned, the birds are stuffed with cotton and given cotton eyes. They’re sewn into a specific position that will allow researchers to get accurate, standardized measurements of length, wing length, tail size and more. Birds that enter the museums permanent collection are laid flat in shallow drawers in huge cabinets.
When it comes time to count the birds volunteers and students have collected over fall migration, Rasmussen and Linnea Rowse, conservation program coordinator at Michigan Audubon, meet at the MSU Museum. They identify each bird (or confirm the ID done by the collector), file its paperwork and decide whether or not it’s museum collection quality or not (A bird that dies and is collected shortly after: museum quality. A bird that begins to decompose: not.)
Each bird has a fact sheet filled out by the volunteer that collected it detailing species, the building it was collected from and time of day and how much time volunteers spent out looking for birds. This will help identify dangerous buildings and what makes them so, Rowse said. Eventually it could be used to educate those buildings’ owners, who can save birds and money by turning out lights.
The frozen birds hit the table like small rocks. It’s a surprise every time it happens. A louder, more solid echo of the window collision that killed them.
Birds of all sorts have been collected this year. A lot of white throated sparrows. Also, a few wood thrushes, birds with a beautiful, haunting song that are already pressed as suitably sized woods become harder to find. A grasshopper sparrow: a small, Michigan bird of special concern. A sora: a secretive marsh bird, more often seen than heard.
After it’s counted, each bird goes back in its bag and back in the freezer to wait for spring when they’ll be prepared to enter the permanent collection. Then they’ll sit, for years if all goes according to plan, in drawers in cabinets in the back room of the museum. They’ll be there, in their standardized pose, for scientists to study.
Nearly a billion birds is a lot to die by window collisions. With all the buildings and all the birds in North America, there are bound to be a few such deaths. But many could be avoided dressing windows with visual deterrents like films or decals. Shutting off a building’s lights during migration makes it less attractive and confusing to birds.
There are 31 lights out programs throughout North America, which make cities safer by dousing lights during important bird migrations. The data gathered in Michigan Audubon’s monitoring program can be used to make the case to building owners and operators for shutting down nighttime lights or adding visible markers to particularly dangerous windows, Rowse said.
When that case is successfully made, birds will have one fewer obstacle to contend on their twice-yearly intercontinental flights.
Andrew Blok is a freelance environmental journalist, writer and member of his local Audubon chapter.
