ABSTRACT — Bird strikes were recorded at the windows of commercial and private buildings to study the effects of collision mortality on birds, and several experiments were conducted to evaluate methods of preventing collisions between birds and glass panes. Two single houses that were systematically monitored annually killed 33 and 26 birds, respectively. Collisions at one house in the same 4-mo period (September- December) in consecutive years resulted in 26 and 15 fatalities, respectively. At least one out of every two birds were killed striking the windows of these single dwellings. The records from these homes also revealed that window strikes are equally lethal for small and large species. The annual mortality resulting from window collisions in the United States is estimated at 97.6-975.6 million birds. Experimental evidence indicates that complete or partial covering of windows will eliminate bird strikes. If parts of the window are altered, objects or patterns placed on or near the window must be no more than 5-10 cm apart and uniformly cover the entire glass surface. Eliminating bird attractants from the vicinity of windows will reduce or prevent strikes by reducing the number of birds near the glass hazard. If removal of attractants is unacceptable, place them within 0.3 m of the glass surface; birds are drawn to the attractant on arrival and are not able to build up enough momentum to sustain serious injury if they hit upon departure. My experimental results further reveal that the common practice of placing single objects such as falcon silhouettes or owl decoys on or near windows does not significantly reduce bird strikes. Window casualties represent a potentially valuable, but largely neglected source of data capable of contributing information on species geographic distributions, migration patterns, and various other studies requiring specimens.

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