Tagged Animals
 

Could someone explain the deal with killing a tagged animal such as a deer or duck.

Most tagged wildlife are marked for research. They will generally have a phone number to call and/or address to send the tag to.
By calling you are helping to improve the future management of the species and in some cases perhaps making yourself some money. Some tags in some studies have a money reward assigned to the tag number when called in.

R.S. Bodenhorn