Comparison of daily avian mortality characteristics at two television towers in western New York, 1970-1999

Recent increases in the demand for communication towers have renewed interest in the impact of these towers on birds, particularly during migration. The objective of this Study was to investigate avian mortality at two television towers (WGRZ and WKBW) in western New York from 1970 through 1999. Daily mortality totals ranged front 1 to 1.089 birds. The majority of the kill events were small, involving 10 or fewer birds: however. the majority of birds died in larger kill events. Both kill events and the numbers of individuals salvaged peaked in September. Patterns in avian mortality at the towers that we Studied were consistent with normal migration events, during which the number of birds migrating varies substantially between nights. The two towers differed significantly in kill characteristics. At the WGRZ tower, median daily mortality generally ranged from I to 10 birds and was Usually lower than at the WKBW tower. The size of kill events varied across the 3 decades, with no very large kill events (> 500 birds) occurring in the 1990s. Because most birds salvaged in the 1970s and 1980s were killed in medium and large kill events, the absence of any very large kill events in the 1990s Could explain the previously published decline in birds salvaged at these towers.