Bert's got this new ruse to get them back from their hunting adventures. I don't get his logic although he claims it works. What he does is get the shotgun out and fire it. He reckons this frightens them and encourages them to return to safety. Safety? What's safe about Bert with a shotgun?
But to get back to the riverside walk. Of course there were lots of other people out too and the nice weather made them all extra friendly. Everyone was commenting on the beauty of the day and one man said -
"It won't last. I think it's one of those pet days."
A pet day is one beautiful day in a spell of nasty weather.