You’ll need nails to make a chicken coop. This guide will tell you where to find the nails. The chicken coop itself can be built quite close by, but the materials for its manufacture can be found at later stages of the game.
Even before you leave your home island, you will see several building plots. One of the possible buildings is a chicken coop. Unfortunately, it is difficult to create it: despite the availability of free land, you need rare materials. Continue with the story tasks until you leave your home island. Head to the port of Calis, the central island of Mary, where you’ll spend most of your gaming time trading with characters, meeting new NPCs and completing multiple tasks.
When you arrive on the island, follow the story quest, performing the tasks of the old lady from the lighthouse. In the end, after 5-10 tasks, she will introduce you to Akaji, the blacksmith who was not originally on the island.
Once Akaji returns to the island, you can find her near the lighthouse, in a large closed area surrounded by a black fence. Talk to her and complete the first task. After that you can study her products. Among other things, there will be nails: 16 coins each. Once you’ve built a chicken coop, you can find chickens all over the world. Look for “star” icons in new map areas. They are often found in the middle of the ocean. When you unlock the tool shed, you can make your own nails.