I'd say they are juvenile Herring Gulls for pics 1-3 and adult Herring Gull for the last picture. Any of you others want to confirm it or give your opinion?
There has been a fair amount of Cackling Geese seen recently in PA. I'd say their bill size looks about like Cackling Geese and their overall size in comparison to the Mallards. I see them together often and Canada Geese are much bigger than Mallards. At least the goose in front of the small duck on the right has a short bill.