Some observers have had difficulty identifying male Mangrove Golden Whistlers from Golden Whistlers in areas where the two species overlap, such as in parts of coastal Queensland.; the females are much easier to distinguish. I've had the opportunity recently to closely observe male Mangrove Golden Whistlers in Queensland and Western Australia and it seems that three features safely distinguish them from Golden Whistlers. It can't be assumed that any golden-type whistler in Queensland is Mangrove Golden; I've had both species in mangroves in central coastal Queensland.
In my view the best feature is that the wings of Mangrove Golden appear much greyer due to the broad grey edges to the wing feathers. This is apparent in the bird above, which was photographed in Broome. Also apparent in this bird is the broad golden neck collar, a second feature separating the species from Golden but one that is not so readily apparent.
This is a Golden Whistler photographed near Yandina on the Sunshine Coast. Here, the wings clearly appear blacker than those of Mangrove Golden as the grey edging is narrower. The golden neck collar in this bird is also appreciably more narrow than in Mangrove Golden. The third identification feature is the tail colour, which is jet black in Mangrove Golden and partly grey in Golden. In the Golden Whistler above, the grey upper tail can be seen, although partly obscured by vegetation.. Again, this feature is not always obvious.
In this Mangrove Golden Whistler photographed at Corio Bay in Queensland, the all-black tail can clearly be seen. Again, the wings appear much greyer than Golden.
Another snap of Golden Whistler from the Sunshine Coast, again demonstrating blacker wing feathers. A fourth feature given in reference books is the richer yellow-orange colouration generally of Mangrove Golden Whistler. I think that any such differences are subtle and were not apparent to me in the field.