The respected readers may very well ask how I deducted that the bird was yawning and was not doing something else. This is true that there are some limitations in arriving at some specific conclusions out of the mere observations at the birds for a few moments. Even keeping this in mind this particular behavior of the birds may be explained in a new perspective.

Firstly, I was very close to the bird but did not hear any sound coming from it. It was certainly not making any sound.

Secondly, one may think that it was displaying the “open mouth threat-gesture” in anticipation of some impending danger. Now we will go back to the observation that I mentioned in the beginning of my article. Sauer and Sauer have observed that the gular sack contracts upward during open mouth threat gesture whereas it hangs downward during yawning.
If we give a little attention to the picture we will see that the gular sack is freely hanging downwards. If we see minutely in the first picture it will be clear that the tongue of the bird has come out of its mouth to a great extent which might very well happen at the time of open mouth threat-gesture. But it is obvious that the more a bird opens its mouth the more its tongue comes outside in either case of yawning or of open mouth threat-gesture.

Thirdly, the posture of standing of the bird is worth observing. Had it intended to open its mouth this way to give a open mouth threat-gesture it certainly would not remain standing on a single leg in such a careless manner like this, it would have stood on both the legs with sufficient alertness.

Now I will try to describe under what circumstances a bird is more likely to yawn and under what circumstances during my observation the bird opened its mouth this way.

Generally, yawning is a thermoregulatory mechanism which takes place due to the fluctuations of the temperatures of the body or/and the brain. But we know this is hypothesis only. It is the result of some of the successively happening neuro-chemical interaction in the brain. In the case of the birds this is very complicated and very less talked about fact. Recently three ornithologists Andrew C. Gallup, Michael L. Miller, Anne B. Clark carried out research works on Budgerigar .They have discovered that the birds are less likely to yawn under the circumstances of regulated temperatures.

But the tendency of yawning increases as the temperature increases. Again in high temperatures the tendency is coming down and at the same time the gular fluttering increases. Some of us might have witnessed this in cormorants, egrets while they are resting. Gular fluttering is a mechanism of the birds for adapting to the surrounding high temperatures. Therefore it is assumed that yawning is primarily a process of maintaining a balance between the temperatures of the body and the increase in the surrounding temperatures.

Also, yawning is closely related to the physical tiredness. During yawning the birds take long and deep breaths and then exhale which forces the lungs to perform more. The blood circulation to the brain increases. The supply of oxygen to the body increases. The tiredness goes away.

On many occasions the birds are seen to yawn while they are performing some comfort behaviours. They also may yawn before or after preening or stretching during their leisure time. It stopped preening after it yawned and all these activities took place while it was in a restive mood standing on a single leg.

I did not observe the bird for a long period and I had no opportunity to note down the fluctuations of the surrounding temperatures. So it is difficult to decide under which circumstances the bird was yawning. There are some scopes of more research works. The Openbills generally flock in groups. This bird was standing alone in a vast water body. So I did not have any chance to observe its comfort behaviours while it remains in a group. I am telling this for the particular reason that the ostriches remaining in a group are known to start yawning when they see one bird in the group yawning a number of times.

Yawning acts as a social stimulus among them. So, it is obvious that to maintain a balance of their body temperature with their surrounding temperature and to express a feeling of security with some comfort behaviours in their surroundings they may yawn.

When the ostriches take rest they have been seen to yawn just after overcoming some small dangers and to go to rest again. We cannot strike out this logic in the case of this Openbill because it was obviously in a condition of resting as it was standing on a single leg and primarily might very well have taken our large boat for a possible threat. Whatever may be the reasons, we yawn and the birds yawn as well, and this is a proven truth now.

Papers cited:-
1. Yawning and other maintenance activities in the South African Ostrich by E. G. Franz Sauer and E. M. Sauer.
2. Yawning and thermoregulation in budgerigars, Melopsittacus undulates by Andrew C. Gallup, Michael L. Miller, Anne B. Clark.

Written in Bengali and photographed by Samrat Sarkar.
Translation into English by Biswajit Debnath

This article has already been published in a National science Magazine. Although I am sharing this article in this forum for wider portion readers, researchers and naturalist and activist. I have done many such observations and documentations in the wetland of Mangalajodi and Chilika. Chilika has huge biodiversity. The Chilika lake and Mangalajodi wetland is now under serious threat as a Seaplane project will be executed there which will have enormous adverse impact on the fragile ecosystem of Chilika as well as Manglajodi. Many of such beautiful species will disappear from Mangalajodi permanently. Please raise your voice against Seaplane project.

STOP SEAPLANE PROJECT. SAVE CHILIKA. SAVE MANGALAJODI. SAVE BIODIVESITY.