While you might be most familiar with “robin’s egg blue”, many species of birds lay blue-colored eggs. Why might this have evolved? Although scientists can’t go back in time to observe the emergence of blue eggs, they can think carefully about which properties might be most different between blue and non-blue eggs… which is what these researchers did. They found that blue eggs absorb just the right amount of light to warm the egg, but not allow it to get too hot. Egg-cellent!