It’s 2 a.m. You’re snoozing in bed. The sun hasn’t risen, but the robin has. It is tuk-tuk-tuk -ing at an unnatural hour, waking you up. If this has happened to you, you’re not alone. Around the world, streetlights, store signs and skyscrapers are pouring artificial light into the night, and all that extra illumination is prompting birds to tweet for nearly an extra hour a day on average, according to a sweeping analysis of more than 4 million birdcall recordings.