Green’s Dictionary of Slang

(Aus. und.) a poultry thief, thus v. snagle, to steal poultry.

1895		Crowe Aus. Sl. Dict. 77: Snagling, stealing poultry.
1901		Argus (Melbourne) 20 Sept. 6/4: Among these small fry of the profession may be included the [...] beaker-hunter, and the snagler, who are both on the roost lay, or poultry stealing.