Female Rooster?

[nuthatched]

I know that it seems as though I'm looking at an almost fully grown Rooster and saying that it's a girl, but she didn't look like this at all a couple of weeks ago. She hadn't laid an egg but she was making nests around the yard and refusing to leave her spots for hours. A week ago though her comb got bigger, her feathers darker and pintyer and she stopped sitting in her spots as much. These two pictures are the same bird taken two weeks apart. Is this how roosters develop? I have never kept chickens before.

Everyone develops at their own rate.
Roosters make nests to show their hens the best place to go. He is a he.