4 Week Mark

They are growing fast! Head to toe, their body size is now very close to that of an adult. But they have a long way to go in terms of muscle development, strength and feathers. As their wing feathers grow in, expect to see a lot of flapping to help build the muscles they will use in flight. Because they are mostly sedentary up until the time when they fly for the first time, while they might be the same size as an adult they are usually a bit heavier.
Here you can see the brown juvenile feathers are coming in.