Window Strikes in Ornithology

The City of Philadelphia, Bird Safe Philly (a coalition of nonprofits led by the Academy) and the building industry are joining forces to save migrating birds. The announcement today that Philadelphia has become the latest city to join the national Lights Out program couldn’t come soon enough for Nate Rice. 

As the Academy’s ornithology collection manager, Nate is in charge of the institution’s world-class collection of 205,000 bird specimens from over 7,000 species, and some 25,000 tissue samples, all housed on the fourth floor of the museum. Nearly 4,000 bird skins were collected in Philadelphia, with the earliest that are labeled by date going back to 1811, a year before the Academy was founded. Of those, 823 are listed in the database as window strikes and those date back to 1898 from shortly after City Hall first lit the night sky. 

Curious, we asked Nate to fill us in. 

Nate Rice with drawers of specimens. Photo by Keith Russell

How are birds effected by tall buildings? 

Two things can happen when birds are killed at buildings or towers. The obvious is that they directly hit the glass window and are killed instantly or are mortally wounded and die of the trauma a short time after. The second thing that can happen is that migrating birds are distracted by the lights of the building. Migrating birds use stellar navigation as a map and on overcast nights when the evening sky isn’t visible, birds can effectively become confused by the building lights. In such cases the birds just circle the lights until they die of exhaustion. This second case is more typical of communication towers. 

How long has the Academy been collecting birds that have collided with Philly buildings? 

The first recorded “window kills” in Philly come from the 1890s when the City Hall tower was first lit up. There are newspaper articles about that event and the bird kill that followed. Witmer Stone was our curator at that time and salvaged many of those specimens for our collection. We have been collecting window-killed birds in Philadelphia ever since.  

Fast forward to the present. How do you get these birds? 

Generally speaking, they come to us from local residents picking them up and calling us. We do have a small core of volunteers who will monitor downtown buildings during peak migration times in the spring and fall.

Magnolia Warbler

Any from the suburbs? 

Yes, we get salvaged birds from all over the place, including the suburbs and the Jersey Shore. We have even started getting window strikes from other parts of the U.S., mainly from the Pacific Northwest where some of the museums don’t have the capacity to prepare a lot of specimens. We have 1,377 specimens from around the world that are listed as window strikes in our database, with 1,317 from North America, 1,045 from Pennsylvania, and 823 from Philadelphia. 

Ruby-throated Hummingbird

What do you do with them? 

We typically freeze the birds when they arrive, unless they come on a skinning day, and then they may be prepared right away. We make every attempt to prepare each window kill into a museum study skin for use in our research and to become part of the world’s collection of scientific specimens. 

How many have been added to the collection in recent years? 

We have about 250 cataloged specimens dating back to the mid-2000s when the Academy started a dedicated project in partnership with the Philadelphia Zoo and Pennsylvania Audubon Society. We probably have 500 window-killed birds in the freezer yet to be prepared. 

Preparing bird specimens

Have you seen any trends? 

There is a suite of species that show up as window kills more than others: Ovenbirds, Common Yellowthroats, White-throated Sparrows, Gray Catbirds. But changes in climate have proven to cause changes in the ranges of certain bird species around the world. So conceivably we could start to see different species showing up. Migratory bird mortality at windows can cause upwards of one billion deaths of birds each year in the U.S. This combined with drastic changes to the environment may likely put some bird species in a vulnerable position. 

What do you see as the future of project? 

We have been working on this project since the 1890s and have no intention to stop. This is a great way to bring new and fresh material into our collections that would otherwise just be thrown away. Ornithology Curator Jason Weckstein is using these specimens in his ongoing research on birds and their parasites and has even been comparing parasite loads of window-killed birds in Philly with those in Chicago. This also is a great way to get our Drexel students involved in our various programs in Ornithology. They can help with the preparation of the specimens, get experience inputting the data associated with each specimen, then move to the microscope lab to examine what types of ectoparasites were found, and finally to the molecular lab to isolate the blood parasites carried by migrating birds from our region. The nice thing about this is that once the specimens are in the collection, they can be used for all sorts of projects, perhaps decades in the future and on topics we can’t even predict at this time. 

To learn more about Bird Safe Philadelphia and Lights Out Philly, read this post. And check out our previous post about Philly birds

By Carolyn Belardo. Single bird photos by Stephen Maciejewski


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