In Kakariko Village during the Child era, you will find an NPC next to a pen who will ask you to find all 7 of her Cuccos.
Find each one, carry it back and throw it into the pen next to her. When all seven are home, she gives you an Empty Bottle. Here are the locations:
Cucco #1
By the village entrance.
Cucco #2
In the construction site by the Cucco Lady.
Cucco #3
On the pile of bricks to the east of the Cucco Lady. Hit it with the slingshot or boomerang to get it down.
Cucco #4
Inside a wooden crate near the centre of the village. Roll into it to break it.
Cucco #5
On the main path up to Death Mountain Trail, just past the wooden tower. Sometimes it will be in the tower to the left of the guard.
Cucco #6 & 7
Grab one of the previous Cuccos and go up the stairs to the windmill. Then continue past the entrance door and jump with the Cucco to clear the wooden fence. Next, go up the stairs on your left and throw the Cucco you used to get there over the fence, then pick up another Cucco in the area where you landed. The final Cucco can be found by climbing up the ladders on your right, where you landed after gliding over the fence.
