Green’s Dictionary of Slang

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

1869		Ballarat Courier (Vic.) 10 Dec. 2/3: A good deal has been written [...] on the virtues and vices of sparrows, and although we do not look on ‘Jack Sprag’ as the immaculate friend of the gardener and farmer [...] we feel it our duty to do him the justice of putting forward a theory in his favor.
1918		Marborough Chron. (Qld) 10 Apr. 4/4: That ‘sprig’ is the wrong name for the sparrow, but ‘sprag’ or ‘sprug’ is correct [...] ‘sprag,’ as applied to the little birds, seems to me to have a Scottish twang about it, and if this be so, are we to believe the tiny birds originally came from the land of cakes?
1920		Chron. (Nambour) 25 June 6/4: ‘Sprags,’ as the boys call them, came in for a turn also. These little pests had been increasing and playing up with some of the grain experimental plots.
1935		Dly News (Perth) 16 Jan. 6/5: If the bird were a sparrow, in Sydney and Brisbane it would be called a sprag or spridger; in Adelaide a spoggie; in Melbourne a spriggy.
1950		Advertiser (Adelaide) 25 May 4/7: [I]n Brisbane a sparrow is called a sprag, in Victoria a spadger, in South Australia a spoggie.
1981		G. Lee True Love and How to Get It 65: [U]ntil the sprags gathered in the jacaranda at the close of day.
1993		H. Lunn Fred & Olive’s Blessed Lino 45: We had been shooting sprags and, unfortunately, Kenny had the Daisy Air Rifle instead of me.
2006		ABC Online Forum 3 Aug. 🌐 In Toowoomba, the Common Mynahs have taken over all the sparrows’ nesting places (under the eaves of houses). The sprag population has diminished noticeably.