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.

Birds have feathers and a beak and lay hard-shelled eggs. Many birds are able to fly using their wings, but others such as ostriches are flightless and unable to fly. Some birds like penguins ...

“normal” beaks (examples shown of a petrel and a gull) and a bird with a tactile bill-tip organ (a tinamou, close relative of ostriches and emus and which has an ancestral bill-tip organ ...