Bowtruckle

From Hpwiki

A Bowtruckle is a tree-guardian creature of maximum eight inches height. Bowtruckles can be found in forests (England, Scandinavia, Germany) but are difficult to spot. These creatures are normally shy and peaceable, only if their home tree is put at risk by a woodcutter, Bowtruckles can make an attempt to attack the human.

To mollify them, you can offer woodlice or Fairy eggs.