Nocturnal flight calls of Dickcissels and Doppler radar echoes over south Texas in spring

Abstract

Abstract Recording flight calls of migrating birds with one or more microphones provides information on identity of some birds aloft over each microphone and on the time course of their migration, or at least their calling. Doppler surveillance radar observations, on the other hand, provide information on the numbers and sizes of flying animals aloft over a wide area and on speeds, directions of travel, and height in favorable circumstances. Comparison of calls of Dickcissels (Spiza americana) from sound recording stations across south Texas in spring with images from the KBRO NEXRAD (WSR-88D) radar operated by the National Weather Service showed a surprising correspondence between the two kinds of data, both temporally over the course of a night and geographically across about 115 km. Highly significant correlations between call rates and radar reflectivity were obtained for seven sound recording stations but not for two other stations that were too distant for the radar to receive echoes from birds migr...