Wild Bird Window Strikes in a Zoo Setting: Lesions, Predispositions, and Abatement Practices
Department of Pathology, Smithsonian National Zoological Park, Washington, DC, USA
Endeavors to create an enhanced zoo visitor experience have often resulted in enclosures lined by clear glass panels that create an unobstructed view of the exotic species within these walls. This clear view also, unfortunately, appears to birds to be physically unobstructed and often results in fatal, in-flight collisions.1 In the 17 months from November 2005 through March 2007, window strike fatalities comprised 74 of the 226 (32.7%) wild birds submitted for necropsy at the National Zoo. The most common lesions observed in birds that struck windows included fractures of the liver and rupture of the pericardium with subsequent hemorrhage into the coelomic cavity. Gross head and neck trauma was relatively uncommon. Seasonal peaks of activity have occurred in December–January and February–March. A sharp rise was seen in the number of window strike bird deaths after 19 untreated glass panels were installed in a new sloth bear habitat in September, which is outside of migratory season. The next migratory season, recorded window strike fatalities in the area were reduced to zero following application of UV-reflecting stickers to the panes in an esthetically pleasing, vertical gradient pattern. The same year, a regular mortality spike was recorded during the December–January peak in a “control” enclosure around lemurs treated with only one hawk silhouette per pane. UV-reflecting stickers are effective in abating avian mortality due to window strike when applied in an appropriate concentration and pattern and may even enhance the zoo visitor experience.
1. Klem Jr. D., D.C. Keck, K.L. Marty, A.J. Miller Ball, E.E. Niciu, and C.T. Platt. 2004. Effects of window angling, feeder placement, and scavengers on avian mortality at plate glass. Wilson Bull. 116: 69–73.