How absurd you can make Old McDonald had a farm e-i-e-i-o
And on his farm he had some plants e-i-e-i-o
With a puff puff pass here
And a Bogart there
here a puff puff pass
there a puff puff hold puff puff puff puff "pass it already"
Everywhere puff puff cloud of smoke e-i-e-i-o
I don't think that I have seen the Onion in years but duck cannibalism seems to be pretty well known and if you find the reference suspect, you can find other references to it in a number of known business and science sites.
Even the New South Wales Department of Industry states...
Although cannibalism can begin in ducks of any age, ducklings over 4 weeks old are more prone to develop this vice. The underlying reasons for birds turning to cannibalism are not known, but it is associated with boredom and is aggravated by:
lack of ventilation