Artificial City Light Impacts the Foraging Behaviors of Blackbirds

Scientists have long known that artificial light can impact the behavior of animals. Now, they've discovered that light can increase foraging time in black birds. Not only are birds in city centers active considerably earlier, but are also active for longer than their relatives elsewhere.

In this case, the researchers studied about 200 blackbirds in Leipzig. The scientists caught the birds, measured them, individually ringed them and then released them. Then, over the period of 35 days, the scientists specifically observed individuals during their foraging activities.

"On the short days in March, the blackbirds in the forest stopped foraging almost one hour before their counterparts in the well-lit city," said Anja Rub, one of the researchers, in a news release. "The longer the days grew, the smaller the difference became. In the summer, there were just a few minutes' difference between city and forest birds."

That's not all the researchers found. The increased light creates more of a division between males and females; because males have larger eyes, they forage even longer than the females. In addition, it turns out that artificial light at night has a major part to play in the biorhythms of city blackbirds. It allows them to extend their daily activities, but this doesn't seem to physically benefit them. The scientists believe that as well as light, the availability and quality of food and the risk of being eaten are also important factors.

Light doesn't just influence biorhythm in the city, though. Even in many conservation areas, the sky has become lighter that originally at night due to neighboring settlements and cities. This means that the environment is changing and causing species to shift their behaviors. This, in turn, makes it important to understand what these shifts are in order to better target conservation efforts.

The findings were published in the Journal of Ornithology.