Green’s Dictionary of Slang

(Aus.) a sparrow, esp. the House Sparrow, Passer domesticus.

1899		Kipling ‘An Unsavoury Interlude’ in Stalky & Co. 81: ‘You’ve no more brains than spidgers’.
1930		Smith’s Wkly (Sydney) 29 Mar. 27/6: The sparrow – common in most parts of Australia – must own more nicknames than any other bird. Here’s eleven of ’em anyhow: – ‘Chirper,’ ‘dadger,’ ‘diggie,’ ‘padjie,’ ‘sprig,’ ‘spriggie,’ ‘spadger,’ ‘spoggie,’ ‘sproggle,’ ‘spidger,’ ‘titter,’ – and what some of the farmers call him at seeding time would fill a book.
2008		Birding-Aus 21 Nov. 🌐 I’ve only twice heard people calling them by other names, both by people over 70. ‘Spidgie’ and ‘squidgie’ were the names used, and neither mentioned whether they meant Tree or House Sparrow, and it’s possible that they didn’t know there were more than one kind.