Green’s Dictionary of Slang

mutton-bird n.

also mutton-bird eater
[SE mutton-bird, an edible species of puffin, found on the Bass Strait (between Tasmania and the mainland)]

(Aus.) a native of northern Tasmania.

[Aus]Baker Popular Dict. Aus. Sl. 48: Mutton-bird, a resident of Northern Tasmania. Also, ‘mutton-bird eater’.
[Aus]A. Chipper Aussie Swearers Guide 66: Mutton Bird Eater. A Tasmanian.

In derivatives

muttonbirdy (adj.)

old-fashioned, unworldly.

[NZ]B. Crump ‘Fred’ in Best of Barry Crump (1974) 296: Scratcher went on clucking and winking and making outrageously seductive, old-fashioned, muttonbirdy remarks that were supposed to be provocative.