November 29, 2012
How Does Light Pollution Affect Wildlife Feeding Habits?
April Flowers for redOrbit.com - Your Universe Online
Night-time satellite images of Earth show that every continent except Antarctica is ringed in a halo of brightly-lit human development, illustrating the fact that coasts and estuaries are among the most rapidly developing areas on the planet.
Coasts are key wildlife sites as well. For example, every year millions of Arctic waterbirds arrive to winter on the UK coastlines. Scientists remain largely in the dark, however, about how these birds respond to the bright lights of coastal cities and industry.
A research team from the University of Exeter, led by Dr. Ross Dwyer, investigated how artificial light affected the feeding habits of the common redshank in the Forth estuary, one of Scotland's most developed and industrialized coasts. Hundreds of thousands of migrating birds make their homes in the estuary's pristine salt marsh and mudflats, co-existing with the major industrial complexes such as the Grangemouth oil refinery and the Longannet power station. The findings of this study were published recently in the Journal of Animal Ecology.
The team measured the amount of artificial light pollution in the Forth estuary at night using satellite images obtained from the U.S. Air Force. This is the first time such military data has been used in animal behavioral research, though it has been used previously to study electrical power consumption.
Dwyer worked out how the light affected the birds' foraging behavior by tagging 20 common redshanks with tiny radio transmitters, which monitored the birds' location and contained posture sensors to detect how often the birds put their heads down to feed.
The common redshank, named for its bright red or orange legs, is a medium-sized shorebird with a greyish brown back and wings in winter and a black tipped orange bill. It patrols estuaries and coastal lagoons in the winter, feeding on mollusks, worms and crustaceans. The redshank is a wary bird, often the first to panic. It has been nicknamed the "sentinel of the marshes" for the noisy "teu-hoo" alarm calls it will give when nervous.
Though Redshank numbers are in decline, the species is still widespread and plentiful in some regions, breeding and wintering across the temperate Europe and Asia. Because of this, they are not considered a threatened species by the International Union for Conservation of Nature (IUCN).
The redshank generally needs to forage both day and night during the winter in order to find enough food to survive. By day, they forage by sight, which provides them with the most food. By night, they normally forage by the less efficient method of locating prey by touch using their bills.
Dwyer and his colleagues, however, found that the artificial light had a major impact on the redshanks search for food. In brightly lit areas, the birds were able to forage longer using sight, rather than touch. These birds also foraged more efficiently than birds in darker areas.
"Artificial light from industrial areas strongly influenced the foraging strategy of our tagged birds. It was as if the 24-hour light emitted from lamps and flares on the Grangemouth oil refinery site created, in effect, a perpetual full moon across the local inter-tidal area which the birds seemed to capitalize on by foraging for longer periods at night and switching to a potentially more effective foraging behavior to locate prey," said Dwyer in a statement.
Other studies contradict these conclusions, finding adverse effects of light pollution on wildlife to be the norm. For example, previous studies have shown that artificial light will cause newly hatched turtles to head away from the sea instead of into it, and seabirds such as petrels will collide with lighthouses and other lit structures.