It does say 'What tree was the partridge sitting on?' rather than 'what was the partridge sitting on?', suggesting that the tree part was already said, so there was no need to type it again.
Also, younger audiences and a majority of the population believe Jesus Christ to be born on Christmas day, as said in the story.
Also, younger audiences and a majority of the population believe Jesus Christ to be born on Christmas day, as said in the story.
Thanks for commenting though.