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Lessons Learned from a Literal Migrant Trap: Bird Collisions on a University Campus
Timothy O’Connell, Monika Burche@e, and Emily Clark Natural Resource Ecology and Management, Oklahoma State University
Most carcasses are photographed in situ and then photographed again when ready to be frozen for later use. Age, sex, fat content, and other a;ributes (e.g., brood patch) and measurements are recorded prior to freezing.
Background and ObjecGves
Birds frequently collide with windows in buildings of educaAonal and corporate campuses. This is a subtly different phenomenon from window collisions around homes and at skyscrapers along major migraAon corridors.
Much research into collisions has focused on the physical features of buildings that influence collisions and the careful sampling of carcasses to quanAfy rates of observer detecAon and removal by scavengers or other agents. The ostensible purpose of this sampling is to increase the accuracy and precision of numerical esAmates of collision mortality. We illustrate here that there are addiAonal reasons to collect such data, including the carcasses themselves.
Right: SpaAal distribuAon of trapped and dead birds at the NRC, Aug.–Nov. 2012.
Methods
From 2009–2012, I conducted near daily searches for window-‐killed birds at the Noble Research Center (NRC) on the campus of Oklahoma State University in SAllwater. The NRC is located in a wide open area of parking lots and lawns, but its complex shape draws birds toward both reflecAve and “pass-‐through” expanses of glass.
Le[: Such a waste -‐ Lincoln’s Sparrow. We cannot eliminate window collisions enArely, but we can try to put the bodies of these unfortunate vicAms to be;er use.
The Noble Research Center on the campus of Oklahoma State University in SAllwater, OK. There are 206 separate glass facades > 1.5 m wide on this building.
Most “trapped” birds are unable to be caught by hand, and have an excellent chance of recovery. I have “saved” approximately 36 birds this way.
Above le[: This Carolina Chickadee has been measured and its a;ributes recorded. Above right: the same chickadee ready for temporary internment in the freezer.
Results of every survey (posiAve and negaAve data) are posted to a website, along with photographs, analysis, commentary, and links to key advances in window collision research and conservaAon: birdsmack.wordpress.com:
I leave some carcasses in situ to gather data on removal rates. The best specimens and those under-‐represented in our holdings are prepared as museum skins for the OSU CollecAon of Vertebrates. Other specimens of species not needed for our collecAons are used for dissecAons in Ornithology.
Above, from le[: Specimens awaiAng curaAon in the CollecAon of Vertebrates (COV); this Sprague’s Pipit and molAng Indigo BunAng were valuable addiAons to the COV; students much prefer dissecAon of wild birds of mulAple species, such as this Yellow-‐billed Cuckoo, to dissecAon of Rock Pigeons prepared in formalin.
Results, Discussion, Lessons Learned
From 2009–2012, I confirmed collision mortality of 122 individuals of 42 species. Almost all were migrants that would otherwise not be recorded near the NRC due to the lack of appropriate habitat, e.g., Whip-‐Poor-‐Will (eastern), Sora, Canada Warbler, and Black-‐throated Green Warbler. Most frequently found were Lincoln’s Sparrow (18) and Grasshopper Sparrow (15). Compared to data from eBird, Lincoln’s Sparrow encountered 21% of the Ame it occurred in the county in spring; 58% of the Ame in autumn.
Le[: Moving this Orange-‐crowned Warbler to a secure locaAon away from the NRC gave it the chance to recover and conAnue on its journey. Anecdotal evidence suggests that some birds die from the exhausAon and stress of being “trapped” by the building’s shape as opposed to simply hikng a window at high speed.