Birder crossing with firearm.

Whatever you do, do not bring your firearm into the border station unless requested. When we crossed at Pigeon River for our fall fishing trip last year, a group of hunters brought their cased rifles into the building. One of our guys was in there paying duty on our extra beer and he said the agents really let the hunters have it. Obviously its a very big no no. 

Go to the Canadian border website.   There is a form that you will need to fill out in triplicate,  Do no sign it you will do it in the presence of the customs officer.   I think you can have up to 2 or 3 guns on the form.  In the past I took two across on the same form.  They will authorize and you will be responsible for carrying that form on your person.   Unless something has changed you don't need anything to cross back into the states with those declared firearms.  If you have a bear or a moose then you will likely need to complete paper work to declare.  Other wise when I went bird hunting no issues.  Just make sure you follow applicable regulations for animal identification.  IE a wing retained on the bird.  Things change so double check.  It cost $50 Canadian that is for all guns listed.  Not a big deal to cross with a long gun into Canada.  There are some restrictions so do your home work. 

I'm not sure what forms may be needed but I know you can't bring a handgun into Canada.