The author, who looks after the Wood, was not at all pleased and came with his son to attempt to scare them away. Gunshot nor barking dogs could shift them so they were shot.
Apparently, they would have destroyed the pool: frogs, moorhens and any mallard that landed so they were killed.
The gander was shot first in an attempt to force the female to fly off. She did not. She faced the guns so they killed her too, to "end her grievous suffering at the loss of her life-long mate".
The pool was more important.
Seems Canada Geese are not welcome birds
