Noise by made by thousands of bats as they swirl out of sinkhole; later noise made as they fly back into hole the next morning (0600, 19Aug1960). The whirr of the wings sounds like wind; there is also a crackling noise. Mostly Mexican Free-tailed bats. Some Cave Swallows flying out as last bats go in on 19 August.
L. Irby Davis
27 Mar 1960
- 9 Miles NE of Rock Springs; "Devils Sinkhole"
- 30.059089 -100.108988
- 610 meters
- NAGRA III-B
- Electro-Voice 650
- Parabola 101.6cm/30.5cm (40in/12in)