In this task, you are given a paragraph, and your job is to generate comma-separated entities present in the given paragraph. Generate entities from a given passage in such a way that (i) they are present in the paragraph, (ii) they are non-duplicate, (iii) they underwent a state change during the process. Avoid creating entities that (i) aren't present in the process paragraph and (ii) aren't significant.

Example input: Magma rises from deep in the earth. The magma goes into volcanos. The volcanos pressure the magma upwards. The pressure causes the magma to push through the surface of the volcano. The lava cools. The lava forms new rock. New magma is pressured to the surface of the volcano. The volcano bursts through the rock the formed after the last eruption.
Example output: magma ,lava ,new rock
Example explanation: The entities are present in the process paragraph and they undergo state change. So, this is a positive example.
Q: A male and female bird mate. The female lays eggs. The eggs are incubated by the parents, by sitting on them, for weeks. The bird hatches from an egg. The parents feed them as the continue to grow. Develop flight feathers. The parents teach them to fly. After learning to fly they leave the nest to live on their own. The next year they breed beginning the cycle again.
A:
eggs ,bird ,flight feathers