Chirping birds can be a delight to wake up to in the morning, unless they’re up and at ’em a little too early. But don’t blame our feathered friends—they may just be confused about what time it is, a new study suggests. Ornithologists observed six common species of birds to see how artificial light and traffic noise affect their daily songs. After recording them at dawn and dusk in various environments, researchers found that whereas noise has little effect on them, light pollution can change the timing of their songs. For instance, in areas with more artificial night light emitted by street lamps, European robins (pictured above) and blackbirds can start singing up to 1.5 hours earlier than sunrise, and great tits chirp an hour earlier than normal. The effect was not as strong at dusk, with some birds only tweeting about 10 minutes later than usual. The finding, published this week in Behavioral Ecology, suggests that birds’ perception of day length is rattled by artificial light, but the disruption of the natural pattern may not be entirely bad. The researchers think that because singing attracts mates, an earlier start in the day may make them more successful at reproduction.