Aussie Finch Forum

I am interested to find out if the western black rumped and the eastern white rumped double bar finches habitats are strictly geographically distinct/separated by a natural specific boundary where between forms there are no double bars in existence or is there a geographic "fade in / fade out" as we move from western areas (Kimberley Region) and to the eastern seaboard? If there are specific boundaries where are they located? If there are not, will they inter breed?

I'm not sure of the boundaries but they may be similar to the yellow bill longtails and the Hecks red bill longtails in the East. I think it is a line drawn South of Darwin where they interact and breed to cause orange billed birds.
I know the two species of double bars have been crossed in aviaries producing black and white rumps and the two species of longtails are regularly crossed in aviaries which is a darned shame by some breeders who don't know what they have in closely related sub species that should be kept pure even though it does happen in the wild

Grassfinches in Australia (Forshaw and Shepherd) : " bichenovii (white rumps) range from the Gregory river at the base of the Gulf of Carpentaria, where there is intergradation with annulosa (black rumps) "

This text was published in 2012, great book

Cheers
Brett