template_unit_fauna_decorative.xml has no parent, therefore its current name is misleading. Furthermore, it doesn't make sense to define values only to have them replaced or disabled by its only one child (gaia/fauna_hawk.xml).
This patch:

• moves the template to template_bird.xml and updates its child accordingly (cf. D1733)
• merges the attribute values from the hawk into it, keeping only the actor there (cf. D1774)

Check if nothing is overlooked and everything still works.