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This is Scientific American’s 60-Second Science, I’m Cynthia Graber. This’ll just take a minute.

Songbirds sing to entice¹ mates, and the timing² of those songs is often regulated by sunlight. But that timing is getting thrown off—by streetlamps. That’s according to research published in the journal Current Biology.

Scientists at the Max Planck Institute for Ornithology³ in Germany studied five common forest-breeding songbirds. Males in four species started singing significantly earlier in the morning if they lived near streetlights than did their deep forest-dwelling kin⁴. And for one species studied, males were more successful at attracting extra-pair mates. Those are females other than the male’s primary nest-mate with whom they sire offspring.

Sounds great, right? Well, the researchers say, not so fast. They note that the males may be weaker, because they get less sleep due to the lights. And so females who used to take early singing as a sign of virility⁵ may be attracted to weaker males who simply can’t sleep because the lights are on. The early singing may also put the males at greater risk of predation.

The researchers say we don’t understand the long-term effects. But they add a hopeful note—companies are developing new streetlamps with reduced light pollution, which could also help songbirds get their z’s.

Thanks for the minute, for Scientific American’s 60-Second Science, I’m Cynthia Graber.