Max Planck Institute for Ornithology study: Are blackbirds that sleep with night lights early breeders?

This year, Holyoke’s downtown Red-tailed Hawks built their nest directly under a building’s security light. (c) Greg Saulmon

The latest issue of Audubon Magazine includes a short piece about research on the impact of city lights on urban birds.

The research, which involved blackbirds, was performed by scientists working with Jesko Partecke, a researcher with Germany’s Max Planck Institute for Ornithology. The institute has posted its own summary of the research here.

In a nutshell: For ten months, the researchers exposed blackbirds to a constant light intensity at night. Birds exposed to light had gonads that grew a month earlier than birds who slept in the dark. The birds with night lights also had testosterone levels that rose earlier, and they began singing around one hour earlier each day. At the end of the breeding season, they molted earlier.

“All of this indicates that, from a seasonal perspective, the animals are ready to breed earlier,” Partecke writes in the Max Planck Institute summary. “These findings are clear evidence that the artificial light we find in towns and cities can dramatically change the seasonal organisation of wild animals.”

Lead researcher Davide Dominoni told Audubon that one implication is troubling: urban birds that breed and lay eggs too early might not be able to find adequate food supplies for their offspring.

The research makes me wonder about the implications for this year’s brood of Red-tailed Hawks. As shown in the photo above, the adults built their nest this year directly under a building security light that stays on all night.

Will that somehow impact the development of this year’s brood? Or, is the nesting season too short to have an impact? And: Is it possible that the adults deliberately chose a well-lit location as an additional measure of security against potential predators?