Ignore Nobrot.  He can't take the sun anymore :-)
Don't quote me but this is how I understand the situation (I'd be glad to be corrected).
The only way you can get a shooting/hunting licence is to be a member of a hunters (casadores) association.  You can (and some do) then shoot anything that has it's back to the sun.  Some of them use shotguns to bring down small birds ???
The irony is that if you have just an air rifle, you aren't allowed to shoot any living thing (not even rabbits or rats) even on your own land.  Some Guardia Civil who saw me with my air rifle on my land told me I had to go to the local town hall for a permit.  I don't know if this is a licence to own a gun or to shoot vermin etc.  I'll let you know when I get around to applying.