Bird eggs

Last night we watched another fascinating episode in PBS's Nature series hosted by David Attenborough. This one was about bird eggs, the variety of their characteristics, and the birds that make them. For example, the cuckoo doesn't make its own nest and hatch its eggs. It lays the egg in the nest of another bird -- a different species and mimicking the color and shape of its eggs -- and that bird hatches it (if successful).

Nothing was said about how the host behaves after the cuckoo egg hatches. Per Wikipedia, the cuckoo chick is much larger than a chick of the host species, but the host doesn't discriminate against a cuckoo chick. The host feeds a cuckoo chick as if it were the host's own.

The entire episode can be viewed online until May 8 here.

Bird Eggs and Wings

A NY Times article caught my attention. Why Do Bird Eggs Have Different Shapes? Look to the Wings. The article relates egg shape to "flight ability," but doesn't explain what that means. Speed? Stamina? Maneuverability? Efficiency?

Having recently returned from New Zealand, it made me wonder about kiwis. Kiwis can't fly and have tiny stubby wings. The article suggested to me a kiwi egg would be more spherical, less elongated, and not pointy. It isn't pointy as I expected, but it is elongated similar to an egg of a wondering albatross, which has great flying ability and huge wings, at least in length, relative to their body size.

By the way, while in New Zealand I was surprised when I saw an x-ray image that showed egg size relative to the mother's body size. Why Is the Kiwi’s Egg So Big?

We also saw an albatross breeding ground on the Otago Peninsula near Dunedin. About the only time they spend on land is for breeding. The rest is in air or on water. They migrate eastward encircling Antarctica in the process. They fly long distances expending very little energy by soaring (using the wind with minimal wing movement).