May 13, 2001: Beaking and Feathering Out
On May 12 it rained, and so Julie didn't take any photographs. But now, on May 13, see how much the babies have developed in just two days! Their flight feathers are starting to poke through. Each one grows inside a sheath--a protective tube similar in shape to a tiny drinking straw. When the feathers get a little larger, the sheaths will start crumbling off, and the feathers will open up.
Also notice how the beaks are starting to grow. And soon these babies' eyes will start opening and they'll get their first glimpses at the big world.
Q. Before they open their eyes, how do they recognize their parents? How do they know their parents have arrived with food?
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Q What
percentage of a mother robin's body weight is her brood of newly-hatched
babies? What percentage of a mother hummingbird's body weight is her brood?
Do you think this may be related to the reason that robins lay four or
five eggs while hummers lay two?
Four newly-hatched robins weigh about 22 grams, which is about 29%
of their mother's weight. Five baby robins weigh 27.5 grams, 37%
of their mother's weight.
But just
two newly-hatched hummers weigh 1.24 grams, which is about 35%
of their mother's weight. This may be why female robins manage to lay
twice as many eggs as hummers.
See the next Robin Nest Photo Lesson and discussion of today's questions.
