The Motivational Organisation Controlling the Mobbing Calls of the Blackbird (t uRd Us Mer Ula)

Abstract

Abstract1. The change from the low intensity mobbing call 'duck' to the high intensity call 'tix' involves the addition of what is probably the first overtone and a slight rise in pitch of the fundamental tone. The first change has a lower threshold than the second. 2. Bouts of calls are usually associated with flights and commonly begin a little before take-off. 3. At or near take-off there is a change (the 'flight effect') which tends to initiate calling if it has not begun, and to accelerate it and/or cause the change from 'duck' to 'tix', if it has. 4. Experimental prolongation of flight prolongs calling and promotes the change to a 'tix' type of call. 5. Bouts of calls given when perched are accompanied by activity of the system controlling flight, which does not reach the threshold for take-off.