Solution
The late Andreas Helbig summarized his
work in Bauer et al. (2005) : The Western (Atlantic) form of Western Reef Heron
Egretta [garzetta] garzetta gularis seems to be a southern subspecies of Little Egret Egretta [garzetta] garzetta. Similar to
Snow Goose and 'Blue Goose' which originally were geographically separate
populations of the same species, the southern subspecies of Little Egret
(gularis) occurs predominantly in the dark morph. In contrast, the Eastern (Indian Ocean) form of Western Reef Heron Egretta
schistacea (formerly Egretta gularis schistacea) seems neither closely related to Little
Egret nor to
'Western' Western Reef Heron (better 'Southern' Little Egret, this name is my personal input), but seems to
be a different species and not even a member of the superspecies Egretta
[garzetta]! On the other hand the Madagascar form Egretta [garzetta] dimorpha might be a separate species within the
superspecies Egretta [garzetta]!