At first I thought it must have just been a temporary shift in population. But then I learned the real reason. It was part of a government plan.
As dawn broke on Battersea and St James's Park a week or so ago, men with silenced rifles fired on these jolly birds, killing whole flocks before most of us had had breakfast.
'I cannot believe they could do such a thing. There have always been Branta canadensis on this lake, lamented one old lady as we scoured St James's. 'I like them. I hope they don't start shooting the mallards.
Yet why? Why shoot the birds? The Royal Society for the Protection of Birds said I should get onto the Department of the Environment, headed by John Selwyn Gummer. He grants the licence to kill.
The woman at the information department was firm. Didn't I understand that these creatures were pests? They attack children and animals, she said. (Persephone, now all of 18 months, does not bat an eyelid when a goose gently takes a digestive from between her tiny fingers.) Then there was a pause as she drew herself up for the piece de resistance, the real reason for the slaughter: 'They have a terrible propensity to excrete.
She waited while I took in the full horror. Next, warming to her theme, she went into what can only be described as a Rivers of Blood/
Droppings speech. These curious black and white birds were not indigenous. Not something English born and bred like the canny rook or the plucky little robin. What we have here is an arriviste of a goose. An immigrant.
Didn't I realise that in the Seventies there were only 19,000 of these foreigners? Now there are 60,000 and by the end of the century there could be 100,000. Didn't I appreciate that they excreted every few minutes]
Sentimental do-gooders such as Carla Lane and Paul McCartney could offer to save the 156 geese in Battersea Park but they weren't doing anyone any favours. Even if the Beatle transported all of them in separate Ferraris to his Scottish estate they would soon upset the balance of wildlife and start savaging animals and children.
Just to put this Liverpool upstart in his place, the death sqaud hit before his Schindler-style rescue could be organised.
A Canada Goose working party has been set up, which is ominous. When it was decided to gas West Country badgers as the carriers
of bovine TB, completely needlessly and unscientifically, that was the result of a well-lunched working party. Guilt is shared. Everyone is following the orders of the committee. One can hear the final slap of webbed feet as
my daughter's little friends are marched off to some goose gas chamber.
Who will be next? I watched a Canada Goose the other day and it did not seem to excrete anything like the amount of times the woman at the Department of the Environment claimed. Surely it is a dangerous precedent to establish that an animal which excretes mightily and multiplies must be gunned down.
Take the case of the Secretary of State for the Environment himself, cute, diminutive John Selwyn Gummer. Just the sort of pathetic animal my daughter Persephone would take pity on and offer a digestive biscuit.
But all the breakfast meetings, lunches, dinners, cocktail parties that are part of a Gummer's job (destroying plants and animals and attacking children with new road schemes) in any given year must produce an Everest of Gummer excretia.
And now that he has joined the Roman church, can a Gummer be thought of as 'indigenous? Is he really one of us? Free of contraception of any sort, he can produce as many other Gummers as he likes. Soon the numbers will be unmanageable.
Perhaps as the marksmen take aim, a weeping Gummer may reflect on the absurd consequences of cruel diktats based on excretia.