The behaviour and song of birds is much dependent on the sun, the moon and the seasons. Change in climatic temperatures and phases of the moon have known to effect the singing pattern of the birds. That is the reason one finds the literateurs and poets like Kalidas giving references of monsoon clouds and moon effects on the common birds like chatak, papiha, koel, swan. A study done by team of scientists of Gurukul Kangri University led by head of Zoology and environmental science, Dr Dinesh Bhatt has recently been published in international journal named ‘Current Science’ in which the influence of lunar phases on the Asian Pied Bush Chat bird has been studied. It is the first ever study in Indian subcontinent about the moon and its effects on birds singing.
Speaking to The Pioneer, acclaimed ornithologist Dinesh Bhatt said, “We conducted a study in the natural habitats of this tropical songbird, Pied Bush chat. The results indicated that the onset time of dawn chorus by this bird depends of a number of environmental factors.
The moon of second and third day does not effect on the song of these birds while the fourteen day and full moon affects their song making it shorter suddenly.” It may be possible that due to the predator bird like ‘baaz’ vultures, the bird probably reduces the length of its song for the fear of being caught, added Bhatt.
The dawn chorus of these birds is a classic example of the peaks in sexual signaling and territorial displays that occur across a range of varied geographical places says the study. Effect of sunrise timing and other microclimatic changes like variation in temperature, humidity, lunar phases influence the song of the birds.
‘We all know that each bird species has its own particular awakening time and the regularity with which they first sing in the morning is tuned to the timing of sunrise. We noticed that apart from annual fluctuations in sunrise and sunset, moonlight also affects the start of a bird’s singing,” said Dinesh Bhatt. It is known that birds have a highly developed sense of time as their biological clock perceives the quality of light and day length.
The scientists reached to a conclusion that the Pied bush chat bird sings at regular perches, and if there is a sudden directional wind, the males may stop their dawn song chorus as such communication may not be efficient. Hence such directional winds may leave the males sing smaller bouts.
It is mention worthy here that in most of the bird species, before mating, they sing to woo their partners. As per the theory of natural selection, the more beautiful the bird sings, better is the partner he gets. Discussing about his study on Indian bird Jalidar Muniya, Dinesh Bhatt says, there is hypolthalamus in the brain of birds which has photoreceptors which can assess the change in day length and they indulge in mating songs only when after the winter, the days get longer.