Okay, "native" may be a bit misleading; I'm talking about what kind of "wild" animals and plants you'd find in the streets of Sigil.
Thus far, I only know of these;
Cranium rats.
Pigeons(Black Marians' entry in uncaged mentions them dropping feathers in the fountain.)
Lim-lims(!).
Razorvine.
I'll assume that stray pets (cats, dogs, alligators, squirrels and parrots) and such live in the big city like here on Earth, but are there any iconic "Sigil-animals" I've missed?
*e* Oh yeah, also; I'm not a native english-speaker. The stem, that is, the cutty part of razorvine, is the thick part of the plant that the leaves sit on, right?
From In the Cage:
Executioner Ravens (huge, gray-feathered ravens)
Aoskan hounds (fierce two-headed dogs)
Arcadian ponies (native to Arcadia, but commonly used in Sigil)
Skinrat (a nonpsionic cranium rat; their sweat acts as a potion of diminuation)
From Torment:
Trocopotaca (giant albino crocodile living in Sigil's sewers)
From the Mimir:
Sigilian Pigeon
Cager Pony
Scarling
From Dragon Magazine Annual #3: (small animals suitable for Sigil)
Acid pigeons
Piranha Ant
Polyroach
Rat Burglar
Stone Termite
Dragon #259: Worry-Wart
Dragon #238: (fantasy sewer creatures suitable for Sigil)
Necromantic Sludge
Plague Moth
Albino Crocodile
Water Cat
Lich's Blood