We found the Hazel nuts under an oak tree. They were cracked open not nibbled. So we thought that squirrels had done this.
Squirrels open the nut and find another one and crack it and do it again and store them for winter and sleep until summer and take them out of the ground some times they plant them instead of eating them. If they do not find them a new tree might grow.
Hazel nuts have a cover over it and squirrels take the nut out the cover and eat the nut in side of it.