On the Bright Side

Bright lights from cities and factories can blot out our view of the stars and disorient some animals. But scientists have found at least one benefit to the constant glare: it helps shorebirds forage more efficiently at night.

The team studied the common redshank, a shorebird that hunts for food in intertidal areas. The birds search visually for their prey during the day. But when night falls, they have to rely on their sense of touch instead, dragging their bills through the mud till they bump into their next snack.

The researchers attached transmitters to 20 redshanks and let the birds loose at an estuary in Scotland. The transmitters emitted pulses at different rates depending on the bird’s posture. Since touch-based foraging requires the bird to keep its head down as it sweeps its bill along the ground, the researchers could use the transmitter pulse rate to figure out each animal’s foraging technique.

During the night, the redshanks spent more time foraging in parts of their habitat with more light, the study authors report in the Journal of Animal Ecology. Four birds, which stayed near a brightly-lit petrochemical complex and bridge, showed similar transmitter pulse rates during the day and night, suggesting they were sticking to visual foraging the entire time. In contrast, other birds’ transmitter pulse rates increased at night, probably because they were foraging by touch instead.

The light from the estuary’s industrial site “created, in effect, a perpetual full moon across the local inter-tidal area,” the team writes. Since visual foraging is more effective than touch-based foraging, the artificial light is probably helping the birds nab bigger meals at night.Roberta Kwok | 28 November 2012

Source: Dwyer, R.G. et al. 2012. Shedding light on light: benefits of anthropogenic illumination to a nocturnally foraging shorebird. Journal of Animal Ecology doi: 10.1111/1365-2656.12012.

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