Green’s Dictionary of Slang

(orig. Aus.) dog excrement, esp. when very old; thus barker’s nest, a pile of dog excrement.

1985		B. Humphries Traveller’s Tool 70: You just have to tread in one of the ever-popular Barker’s Eggs which litter British pavements.
1988		McGill Dict. of Kiwi Sl. 13/1: barker’s egg dog turd [...] barker’s nest pile of dog turd.
1993		Aus. Word Map 🌐 barker’s egg canine faecal matter, usually in unwanted locations like lawns and footpaths: Your mutt keeps laying barker's eggs on my lawn!; Sorry mate, I just trod on a barker's egg.
1999		Roger’s Profanisaurus 3 in Viz 98 Oct. 4: barker’s eggn. Poodle shit. A dog turd so old it has gone white.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].
2023		S. Kempner on X 10 Dec. 🌐 Also...who was Shadow Brexit Secretary when that ‘impossible to understand’ stance was created? This era is dog eggs.