Chickadee

The Black-capped Chickadee has a black cap and bib with white sides to the face. Its underparts are white with rusty brown on the flanks. Its back is gray and the tail is normally slate-gray.
You are looking for a unique custom cache container that chickadee's would call home.
Make sure to take care of how you retreive and rehide the cache.
Be mindful of muggles that might be fishing in this area.