A Short Hike

After reaching the top of Hawk Peak, return to your starting location, speak to the Ranger about your trip, and then select the Ranger’s Cabin. You’ll get the option to “sleep”, choose it. You’ll now see the end credits, and the achievement will pop. You’ll be able to continue your adventure where you left off after the credit sequence.

I’m not 100% sure if you need to speak to the Ranger or not before selecting the Ranger’s Cabin, but I did.

After Reaching the top of the mountain head back to where you started at the beginning of the game.

Speak to the bird.

Go in the cabin.

The achievement will pop after the credits.

Once you have climbed to the top of Hawk Peak, you just need to head back to the cabin where you started at the south of the island. Speak to Aunt May who's still sitting by the camp fire, then go over to the cabin and press A, then select Sleep. Once the credits roll you will get the achievement at the end. These guides will help you get all the achievements to reach the End Achievement.

Part 1 - Feather Finder, Remember This Day Forever, Not a Scratch Achievement & Feathers Forever Achievement - Doing this first will make the rest of the achievements easier:

Part 2 - Only You Can Prevent Campfires Achievement, Crispy Achievement, Hawk Peak Achievement and Photo Friends Achievement

Part 3 - Green Thumb Achievement

Part 4 - The Fish are Biting Today Achievement

Part 5 - Parkour Master Achievement and The End Achievement