TY - JOUR
AU - Medway, Lord
AB - 258 SHORT COMRIUNICATIONS IBIS 107 LACK OF ULTRASONIC FREQUENCIES IN THE CALLS OF SWIFTLETS (COLLOCALIA SPP.) It has already been demonstrated that certain species of swiftlet (Collocalia spp.) can orientate acoustically in darkness, apparently by echolocation (Medway, ' njature ' 1959 : 1352-3; Novick, ' Biol. Bull.' 1959 : 497-503). The facultative vocalization is audible to man as a series of sharp clicks uttered in rapid succession in irregular bursts, having the general effect of a loud intermittent rattle. Spectrographic analyses of tape- recordings of the rattle-like calls of several species have indicated that the component frequencies fall within the range 1.5-5.5 K/cs., and do not extend into the ultrasonic range characteristic of the echolocating calls of bats (see Griffin, ' Listening in the Dark ', 1958, Yale Univ. Press). There has however been some doubt whether the apparatus used in making these recordings of swiftlets would have responded to higher frequencies in the ultrasonic range, and the possibility that the call heard by man represents merely the audible components of a much wider range of frequencies, extending into the ultrasonic range, has not formally been eliminated. However in October, 1964, we had the opportunity to test for the 
TI - LACK OF ULTRASONIC FREQUENCIES IN THE CALLS OF SWIFTLETS (COLLOCALIA SPP.)
JF - Ibis
DO - 10.1111/j.1474-919X.1965.tb07305.x
DA - 1965-01-01
UR - https://www.deepdyve.com/lp/wiley/lack-of-ultrasonic-frequencies-in-the-calls-of-swiftlets-collocalia-JZVgCh5eGX
SP - 258
EP - 258
VL - 107
IS - 2
DP - DeepDyve
ER -