New research out of the University of Windsor indicates that bright city lights may cause migrating birds to zigzag rather than follow the (darker) course they might otherwise take.
The team, headed by professor Dan Mennill, began their research by accident. Sound recording boxes had been placed around the area during a migration study, and the team noticed that the ones situated near well-lit—urban—areas picked up more bird vocalizations than the ones in dark—rural—ones. Further analysis revealed that more than three times the number of vocalizations occurred in the lit areas than in the unlit areas, indicating that three times more birds passed through the former than through the latter. Why? Perhaps because the lights made it difficult for them to see the stars by which they'd ordinarily navigate.
Being drawn off course causes two problems for migrating birds. First, flying a less-than-direct route uses more of a bird's energy stores than flying a direct route; therefore, birds arriving at their destination are more depleted than they ought to be. Second, flying in a zigzag takes longer than flying directly, which means birds arrive later than they otherwise would—and perhaps miss a key food source or mating period.
What can we do to help restore natural migration routes? For starters, we can turn off any unnecessary outdoor lighting at night. Mennill's team is researching other options, such as changing the intensity of street lights. Whatever they come up with, we're all for it.