Window Strikes

Abstract [ presented to Oklahoma Ornithological Society, October 2018 ]

Seasonal monitoring methods, results and goals of bird-window collision monitoring in the central business district of Oklahoma City, Oklahoma
Nathan Kuhnert
Independent researcher
nrkuhnert@safepassageokc.org

Up to about 1 billion birds are likely killed in the United States each year as a result of collisions with buildings. Bird-window collision monitoring has taken place across an approximate 50-acre grid in the central business district of Oklahoma City, Oklahoma during segments of eight migration windows ranging from October 20, 2014 to October 14, 2018. The monitoring coincides with a downtown development explosion where the skyline has grown at a pace not seen since the Great Depression. A total of 81 identifiable species have died from window collisions while 362 birds have been killed and another 66 injured through preliminary analyses.

The Nashville Warbler (Leiothlypis ruficapilla) was the most common window collision species and accounted for 10% of the deaths. Two primary collisions culprits preliminarily analyzed include illuminated glass facades prior to sunrise and reflected vegetation during the day although other hazards including transparent windows were also documented. Approximately 398 party-hours out of 210 monitoring days comprised the effort. The monitoring protocol evolved to place a strong emphasis on comparative mortality among approximately 60 structures. Standardization challenges in the data collection and analysis include inaccessibility to certain collection points, maintenance/security crews and scavengers removing birds prior to the monitoring and a bias of monitoring to the mornings and migratory windows. Additional variables recorded at the incident site include building collision height, date/time, vegetation description, illumination and  reflective properties of the glass and weather conditions. The intent of the analysis is to compare results with previous research in North American cities and provide a basis for local advocacy to consider light management and bird-friendly building design.

 

Total Number of Casualties from both the DEC and OKC Business District Surveys (2014-17)

English Name Fatal Strikes Injured State of the Birds Watch List1 Migrant2 Neotropic Migrant3

 

Blue-winged Teal 1     X  
Rock Pigeon 1        
White-winged Dove 3     X  
Mourning Dove 1 1   X  
Yellow-billed Cuckoo 1     X X
Common Poorwill 1 1   X X
Ruby-throated Hummingbird 5 1   X X
Humbingbird species 5 1      
Virginia Rail 1     X X
Sora 2 1   X X
American Coot 2     X X
Upland Sandpiper 1   X X X
American Woodcock 1 1   X  
Red-headed Woodpecker 1     X  
Yellow-bellied Sapsucker 2     X X
unidentified songbird sp. 4 5      
Eastern Wood-Pewee 1        
Least Flycatcher 1     X X
Eastern Phoebe 1     X X
Scissor-tailed Flycatcher 1     X X
Bell’s Vireo 1   X X X
Red-eyed Vireo 1     X X
Blue Jay 1     X  
Carolina Chickadee 1     X  
Brown Creeper 2     X  
House Wren 6 4   X X
Winter  Wren   1   X  
Carolina Wren 1     X  
Golden-crowned Kinglet 1     X X
Ruby-crowned Kinglet 2     X X
Hermit Thrush 1     X X
American Robin 1        
Gray Catbird 1     X X
Brown Thrasher 4     X X
European Starling 1        
Northern Mockingbird   1   X  
Cedar Waxwing 4     X  
Ovenbird 4 1   X X
Northern Waterthrush 2     X X
Black-and-white Warbler 4     X X
Tennessee Warbler 2     X X
Orange-crowned Warbler 10     X X
Nashville Warbler 24 8   X X
Mourning Warbler 4     X X
Common Yellowthroat 4 1   X X
Yellow Warbler 3     X X
Pine Warbler 1     X X
Yellow-throated Warbler 1     X X
Yellow-rumped Warbler 1     X X
Black-throated Green Warbler 2     X X
Wilson’s Warbler 3     X X
Warbler species 9        
Spotted Towhee 1     X X
Eastern Towhee 1     X X
Cassin’s Sparrow 1     X  
Chipping Sparrow   2   X X
Clay-colored Sparrow 2 1   X X
Field Sparrow 2 1   X X
Savannah Sparrow 1 1   X X
Grasshopper Sparrow 11     X X
Fox Sparrow 2     X X
Song Sparrow 7     X X
Lincoln’s Sparrow 11 4   X X
White-throated Sparrow 3     X X
White-crowned Sparrow 2     X X
Dark-eyed Junco 9 1   X X
Ammadromus species 1        
Sparrow species 5 1      
Summer Tanager 1     X X
Painted Bunting 3     X X
Indigo Bunting 1     X X
Dickcissel 2     X X
Great-tailed Grackle 3     X  
Orchard Oriole 1     X X
House Finch 2        
unidentified species 19        
Species Total –   71           229 38 2 57 47

Examples of birds killed by window strikes in the survey area