Grey's Anatomy, Season 8

Meredith:
[voiceover]: I don't know how those birds do it. Travel thousand of miles without getting lost. Banging into windows, being eaten by cats. But every spring they are always here. I guess they come back to what they know. People say it's pretty cool watching them go. They say you can actually see the moment when at some mysterious signal, all at once, the birds decide to leave. So maybe I've been missing out. Whatever. There's always next year.