Imagine being a bird of passage, genetically wired to use the moon and stars for navigation during the night-long migration flights. Now imagine flying over a city where stars are obliterated by night light of the city below. Such a topsy-turvy world can baffle the most seasoned, be they pilots or birds, who despite themselves head earthwards, thinking they are gaining height instead. The results are disastrous.
In the US alone, an estimated four million migratory birds are killed annually in collisions with artificially lit structures. 
Light and night is a dangerous cocktail in the natural world. Says Goldin Quadros of the World Wide Fund for Nature-India: “Night light affects the breeding capacity of birds in many ways, with altered light-dark hours disrupting ovulation and other processes. In fact, I believe this could be one of the reasons for the declining populations of house sparrows the world over.”
Perhaps the most well chronicled effect of night light is its effect on the nesting of turtles along the coast. Romulus Whitaker, herpetologist and managing trustee of the Madras Crocodile Bank, says, “Nesting turtles as well as hatchlings are attracted to light. But often, females get confused and wary if the intensity of light changes from the previous year and may not nest.” Even worse is the case of the hatchlings. Their survival depends on them reaching the sea as soon as possible. Since the waters appear lighter than land in the starlight, the hatchlings head straight for it. But when the lights of ports and resorts illuminate the other horizon, the turtles head inland, falling victim to predators or vehicular traffic.
This year, a chemical factory in Orissa, Jayshree Chemicals, voluntarily decided to switch off its halogen lights along the coast during the nesting season to give the Olive Ridley turtles a better chance of survival. “People are getting aware, but probably there is not enough being done,” says Whitaker, noting that the rash of resorts along the East Coast Road off Chennai has unbalanced the fragile coastal ecology.
The balance of ecology is such that every change, however small, impacts upon other links in the network. Next time you hear a crow caw raucously in the middle of the night, think again about who is to blame for the artificial dawn it’s welcoming.
Caption: Heading for disaster: Night light can baffle even the most seasoned
