What is smaller than the width of a dime and weighs less than half a gram? That would be the egg of an Allen’s hummingbird. This tiny bird lays tiny eggs and lives in tiny nests. We are fortunate ...

Scientists may have just cracked the mystery of why bird eggs come in all shapes and sizes: it has to do with the bird's ability to soar up in the sky — and the body changes wrought by years of ...