Aoi Hane Mitsuketa!

The story centers on Haru and Hina, two siblings who live in the city and get along well. One day they find a beautiful blue feather on the road, and they set out to find its owner. A mysterious crow appears before them, and acts as a guide. The three then go on a journey to find the owner, meeting various birds along the way.

(Source: Anime News Network)