"Occamies are choranaptyxic. So they – grow – to fill – available – space."
-- Newt Scamander (WFT)
Choranaptyxic refers to the ability of a magical creature to change size to fit the available space, in particular the snake-like bird known as the Occamy (WFT).
References from the canon
- The Occamy that escaped from Newt Scamander's case in New York became as large as the ceiling rafters in the attic of a department store, but when lured by a cockroach treat it re-sized itself to fit into a small teapot (WFT).
"The Occamy is chronatypsic, which is a word I invented. It's sort of a winged serpent, part bird, part snake. It lays eggs of pure silver. All of these creatures are endangered. They can't hide themselves, they don't understand they're supposed to hide" (BTM).
From the Web
"Choranaptyxis" on Harry Potter Wiki