~ A bird whose display call is made by wings
by P M Lad
Lesser Florican is one of the most fascinating birds of India. It is not only very beautiful but also mysterious. It is seen only during breeding season. Nothing is known about its whereabouts during non-breeding period.
Another peculiarity is its jumping habit. Its arrival is noticed by jumps. It stands at place, looks round and jumps to a height of 1.5 to 2 meters. It also makes a frog-like croaking call during the jump. This jump is used to set up a territory i.e. warning to other males also an information to females about its location.
A Florican may jump up to 600 times in a day. Recently a bird was observed jumping 150 times in an hour. The call can be heard from 300 to 400 meters.
How is this powerful call made? Florican is otherwise a silent bird. It makes a sort of whistling sound while taking to wings when surprised. The female makes hissing sound when near a male at the time of laying eggs.
We were certain that the sound is made by wings. Video pictures revealed that 9 bits of sound are made during a jump which takes less than a second The call period is 0.55 sec. The sound bit interval is 0.06 sec. The sound bit duration is 0.006 to 0.016 sec. The frequency varies from 450 to 2700 per sec.
Primaries rotated round carpel joints
We tried to photograph the wing movement It was noticed that primaries are rotated around carpel joint during a wing beat by an angle of nearly 220 degrees and back. This fast reverse movement in less than 0.04 to 0.06 sec generates sound. We were reminded of the sound made by the hunter of the ringmaster in a circus. In day to day life when we long shake a wet towel before hanging it on a wire. We are familiar with sound made by the towel. Half the primaries are modified for this purpose. They are soft and can bend both ways which is necessary for production of sound. The carpel joint is also capable of very fast round movement of primaries. The wing muscles are also modified for complex and very fast movement of the wing and primaries simultaneously.
Showing modified primaries