Flying is obviously a unique attribute of the birds which had to be achieved through the evolutionary struggle of millions of years. Birds fly for different reasons. The first stage of flight is take-off. It is crucial, because a steady and perfect take-off results in a perfect flight for them. Grey Heron can take-off from shallow water, wetland reed bed and floating hyacinth and other vegetation too. It is a wonder how such a tall bird weighing just over one kilogramme can take-off in a fraction of second.
I had been studying Grey Herons Ardea cinerea and I observed the birds for several days in the months of September and October of last year, between 7 to 10 in the mornings, all the while ferrying around in a fisherman's boat. I was especially trying to understand the mechanism behind their take-off methods. Normally, the whole phenomenon of flying of any bird can be differentiated in various stages. The initial stage is obviously the “Take-off” stage. And this is followed by climbing, diving, bounding, gliding, soaring, hovering and lastly, landing.
All the water birds do not take-off in the same way. Ducks and cormorants take-off directly from the surface of a water body. They initially run over the water surface and flap their wings very fast on water for initial lift. Then they achieve frontal velocity in air by fast upward and downward strokes of their wings.
Grey Herons do not follow the process that ducks do. They have much longer legs. Dr. Salim Ali wrote in his book Handbook of the birds of India and Pakistan about take-off of Grey Herons in detail. He wrote – “The initial take-off from the perch is clumsy and accompanied by an awkward stretching of the long neck, vigorous laboured flapping of the wings, and by much swaying and balancing with the long loosely dangling legs. The launching is preceded by a slow swing or waggling of the tail up and down, as if to assist in the process. The bird then flexes its legs and springs upward. Once in the air it flies strongly with steady flaps of the broad wings, neck characteristically folded back in a flat ‘S’, head drawn in between the shoulder, legs trucked under the tail and trailing behind.”
Here are some of my observations on the take-off of the Grey Herons along with some sequential photographs.
I have observed mainly four types of take-offs.
1. Process 1 – keeping the legs more or less straight, fully spreading the wings right upward, they float their bodies in the air at an angle of 45 degrees to the ground. Then they flap their wings vigourously downwards which helps them to lift their bodies upwards in the air quickly. (Look at the Image – 1 to Image - 3)
Process 2 – They utilise the strength of their legs for the initial thrust by first bending their legs to a great extent and fully spreading their wings upwards and then lifting their bodies in the air. Then they flap their wings vigourously downwards and they move forward. In this case also, their bodies make an angle of 45 degrees to the ground level. (Look at the Image – 4 to Image – 6)
Process 3 – They keep their legs vertically straight, bring the bodyline at an angle of 45 degrees and then flap their wings with a great thrust in such a way that the extreme end portion of the wings move forward to a large extent. This creates a large pressure in the surrounding air and helps them to lift their bodies upward in the air. After this, they flap their wings very fast and move forward. (Look at the Image – 7 to Image 9)
Process 4 – Here it is more or less same as the first one; the only difference is that the bodyline makes a narrower angle, much less than 45 degrees to the ground and after this take-off they do not fly very high up in the air and remain close to the ground or water surface. (Look at the Image – 10)
Besides the above observations, I would like to mention here some other general observations.
1. In every situation the head and bill always remain horizontal to the earth to navigate.
2. During take-off, the shoulder or the inner part of the wings work hard. But during flight only the extremities do the main work.
3. Its long neck stretches to a large extent so that the center of gravity of the body is maintained in the front portion of the body.
Equipment used – Canon 7D + Canon 500mm F4 + Monopod
Place – Mathura Beel, West Bengal, September-October 2015
Author: Samrat Sarkar