Possible cases of hybridisation between Cracticus torquatus and C. nigrogularis
Cracticus torquatus (Grey Butcherbird) and C. nigrogularis (Pied Butcherbirds), including the juveniles, are generally easy to distinguish between. In the adult stages, Grey Butcherbirds have a white throat, a black cap, white lores (between the eyes and beak), an incomplete white collar, and grey plumage across the back. Pied Butcherbirds have a black throat, dark lores, a complete white collar, and black plumage on their backs. The juveniles are both shades of brown, with light coloured lores already visible in the Grey Butcherbird, while in Pied Butcherbirds, the dark throat/bib is faintly apparent as pale brown with a noticeable sharp transition to the lighter colour of the abdomen. Subsequently, there are very few misidentifications on iNat between the two species.
I've been rummaging through iNat observations for mis-id's and I've found some suspicious looking observations marked as Grey Butcherbirds (linked below), that seemingly possess most features that would identify them as Grey Butcherbirds. However, they also all have patches of black in the throat/bib area, with some having more black than expected on the back (obs - 4), and others with diminished lores (obs - 1, 2, 5). All observations are within the vicinity of Perth (19/09/2022 - Observation 18 is in western Victoria, if they are hybrids, it could indicate that hybridisation has occurred more than once between the two species). I've looked briefly on Google Scholar and the UNE library for any papers that discuss hybridisation between the species and found none so far. There's no mention of hybrids in any of the field guides I have either.
01 - https://inaturalist.ala.org.au/observations/65467072
02 - https://inaturalist.ala.org.au/observations/41440785
03 - https://inaturalist.ala.org.au/observations/40360665
04 - https://inaturalist.ala.org.au/observations/108492066
05 - https://inaturalist.ala.org.au/observations/67243862
06 - https://inaturalist.ala.org.au/observations/68597079
07 - https://inaturalist.ala.org.au/observations/127816336 (added 25/07/2022, pale back, white lores, patchy throat)
08 - https://inaturalist.ala.org.au/observations/127093449 (added 20/08/2022, another possible example)
09 - https://inaturalist.ala.org.au/observations/120294777 (added 20/08/2022, another possible example)
10 - https://inaturalist.ala.org.au/observations/106465823 (added 20/08/2022, another possible example)
11 - https://inaturalist.ala.org.au/observations/101399494 (added 20/08/2022, another possible example)
12 - https://inaturalist.ala.org.au/observations/105016159 (added 20/08/2022, another possible example)
13 - https://inaturalist.ala.org.au/observations/41440785 (added 20/08/2022, another possible example)
14- https://inaturalist.ala.org.au/observations/19490811 (added 20/08/2022, another possible example)
15 - https://inaturalist.ala.org.au/observations/23872139 (added 20/08/2022, another possible example)
16 - https://inaturalist.ala.org.au/observations/42152529 (added 20/08/2022, another possible example)
17 - https://inaturalist.ala.org.au/observations/14760326 (added 20/08/2022, another possible example)
18 - https://inaturalist.ala.org.au/observations/135641738 (added 19/09/2022, first example I've seen outside of the Perth area, spotted by @ricardosimao )
19 - https://inaturalist.ala.org.au/observations/142621160 (added 23/11/2022, spotted by @tristak87, thanks @george_seagull )
20 - https://inaturalist.ala.org.au/observations/146509601 (added 14/01/2023, first example in the list from the east coast, Brisbane)
It may be a case that this is variation within the species, differences in ontogeny between eastern and western populations, or I'm just outright mistaken; however, at the moment I'm curious about these observations and I suspect they may be hybrids between Grey and Pied Butcherbirds.
I've tagged a few people below that have identified a lot of Butcherbirds to see what knowledge and thoughts you fine people have.
@thebeachcomber @george_seagull @ratite @twan3253 @deborod @joshuagsmith @jadonald @louisb
References
Cayley, N.W. (1946). What bird is that? A guide to the birds of Australia (11th ed.). Australia: Halstead Press Pty Ltd.
Flegg, J., Madge, S. (1995). Reader digest photographic field guide to the birds of Australia. Australia: Reader's Digest (Australia) Pty Ltd.
Leach, J.A. (1926). An Australian bird book. Melbourne: Whitcombe & Tombs Ltd.
Menkhorst, P., Rogers, D., Clarke, R., Davies, J., Marsack, P., Franklin, K. (2021). The Australian bird guide (Revised ed). Australia: CSIRO Publishing.
Morcombe, M. (2000). Field guide to Australian birds. Australia: Steve Parish Publishing Pty Ltd.
Simpson, K., Day, N., Trusler, P. (1989). Field guide to the birds of Australia. Australia: Penguin Books Australia Ltd.