Influence of duration on the frequency discrimination of Bobwhite Quail (Colinus virginianus).

In attempting to parcel out the components within calls that may have functional significance or "message value", the present study of the series pitted "best audible" frequencies of Bobwhite Quail against one another in a frequency discrimination task, and further looked at these frequencies relative to their durational limits. The tasks set for the birds were difficult. In Expers. I and II, 8 adult quail discriminated between frequencies which presumably have independent significance (the 1.0-kc/s of the adult separation call, and the 3.5-kc/s of the chick "lost" call) at lessening durations (200-30 msec). In Exper. III, duration discrimination was tested at single frequencies. The tasks were related in several ways to "real call" situations like those met by birds under field conditions. Mean frequency discrimination performance was about 75%-correct when the standard and comparison tones were both 200 msec in duration, about 65% when both were at 100 msec, and at chance levels at shorter durations. This was true whether the standard tone remained at 200 msec (Exper. I) or was shortened along with the comparison tone. The limit of durational discrimination at both peak frequencies was also of the order of 100 msec. Thus, quail can discriminate the frequency of peak frequency signals that vary in duration down to a limit of 100 msec., but as the task becomes more difficult (i.e., reduced duration or similar frequency content) decreased sensitivity might have to be offset by enhancement of other signal parameters.