Flight Activity of Bats 79 



Three telemetry periods, each spanning five nights, were 

 conducted in each year. In 1990 male bats were radiotracked from 2 

 to 6 June (n = 9 bats), 16 to 20 July (ti = 10), and 6 to 10 August 

 (n = 11). In 1991 females were tracked from 10 to 14 May (n = 9), 17 

 to 21 June (n = 10), and 5 to 9 August (n = 11). Bats were tracked 

 from both fixed and mobile stations. Fixed stations were positioned 

 on the top of cliffs enclosing a hollow with either a bachelor or 

 maternity roost. Distances between fixed stations averaged 857 m 

 in 1990 and 509 m in 1991. Mobile stations were along road routes 

 throughout the surrounding areas. Three TRXlOOOs receivers (Wildlife 

 Materials, Inc., Carbondale, Illinois) were used to locate bats, with an 

 additional TRX2000s receiver used in 1991. Receivers were coupled 

 to a 3- or 5-element yagi antenna. Signals were searched for at 

 20-minute intervals from sunset to sunrise. Bats may have been 

 detected in multiple intervals by more than one receiver. 



Telemetry data were organized into nightly rates of bat activity by 

 converting signal responses into mean nightly detection frequencies 

 (NDF) calculated as 



t n 



NDF = 2(2 (dlo)ln)t l 



;=1 i=\ 



where NDF = mean nightly detection frequency, t - number of time 

 intervals post-sunset, n - number of bats with transmitters, d - number 

 of receivers detecting a bat in an interval, and o - number of 

 receivers operating in an interval. 



Patterns of activity were also derived for each sampling period by 

 converting signal responses to mean detection frequencies per time 

 interval (TIDF) calculated as 



k n 

 TIDF = 2 ( 2 (dlo)ln)k x 

 7 = 1 i"=l 

 where TIDF = mean detection frequency per time interval, and k - 

 number of days sampled. 



Nightly environmental conditions were obtained from the 

 Heidelberg, Kentucky, weather station located 11 km, from the bach- 

 elor roost. The foraging radius of bats from the bachelor and maternity 

 colonies was large (Adam et al. 1994), rendering sampling for environ- 

 mental conditions throughout the study site impractical. Data for 

 eight variables were analyzed: daily maximum temperatures (°C), daily 

 minimum temperature (°C), total precipitation the day of sampling (cm), 

 total precipitation on the day preceding sampling (cm), average daily 



