I believe that this was originally a
marching cadence in the
US military, although it exists in many, many forms, currently.
This version is the most suited for chanting while marching, and is probably the most well known:
A yellow bird
with a yellow bill
Was perched upon
my window sill
I lured him in
with a piece of bread
And then I smashed his little head
The doctor came
to check his head
"Indeed" he said
"this bird is dead"
Author unknown
If, instead of chanting this, you are planning on reading it to some poetry afficionados, I would advise using a calm, relaxed voice for the first six lines, and then a BRUTAL, ENRAGED PSYCHOTIC voice for the seventh. And then add insult to injury by reading the bit about the doctor.