Photo by Mark Olsen[/caption] The most common shape for typical seed-eating birds is a short, thick, and conical beak. Think of the classic "triangle" shape. This strong, sturdy beak acts like a ...

Under these drastically changing conditions, the struggle to survive favored the larger birds with deep, strong beaks for opening the hard seeds. Smaller finches with less-powerful beaks perished.

The outer sheaths of birds’ beaks grow continually throughout their lives, but when they are properly aligned, the tips wear each other away and the beak stays straight and normal in length.

Why do you think the average beak depth of the birds increased?Because the drought reduced the number of seeds and finches with bigger beaks were able to eat the larger and harder seeds so more of ...