Dogs shed hair for warm weather; snakes outgrow their old skin and lobsters their shells; people's worn-out skin rubs off; and birds shed their old worn-out feathers. All birds molt: some once a year, some more often; some feather by feather, a few (like the penguin) all at once; some grow their feathers back fast, some slowly. New birds have no feathers, but they grow fast. A few big strong feathers are called flight feathers. There are hundreds of smaller ones underneath. This book is like one of the smaller ones. It could fill in some spaces between the stronger entries in the series but it is not essential.