So, have you ever seen a partridge in a pear tree?
Almost certainly not, because partridges, being particularly plump and full of meaty goodness, are much safer crouching invisibly on the ground.
Well, nearly invisible:
Chukar Partridge. Photo by Karunakar Rayker
So why else do you rarely partridges in pear trees?
Because partridges tend to live in open fields and moors.
Because they tend to eat seeds and not great big juicy pieces of fruit.
Because they're not passerines.
They're not what?
Oh, a passerine is a perching bird. If you're a passerine (as about half the species of birds in the world are), then if you go to sleep and someone sneaks up behind you and tries to knock you off your perch, you automatically cling on. Non-passerines fall off. (Non-passerines (like pigeons) do quite often sit in trees, though.)
Above all, you don't find partridges in pear trees because, according to Greek legend, the first partridge appeared when Daedalus threw his nephew Perdix off the sacred hill of Athena in a fit of rage. So now all partridges, remembering Perdix's catastrophic fall, keep near the ground, neither building their nests in the trees nor flying far off the ground.
And what's with the pear tree?
Well, no one knows, but pear tree does sound a lot like Perdix, doesn't it?
Word To Use On The First Day of Christmas: partridge. This word comes from the Old French perdriz, from the Greek perdrix.