When you say "sulfur crested" are you talking about the lesser sulfur crested, or the greater sulfur crested?
The lesser sulfur crested cockatoo is the same species as the citron cockatoo... they are subspecies of yellow crested cockatoo.
The nominate species, the Lesser sulfur crested =
Cacatua sulphurea sulpurea
Citron cockatoo =
Cacatua sulphurea citrinocristata
And there is also Abbott's Cockatoo, or medium sulfur crested cockatoo = C
acatua sulphurea abbotti
The greater sulfur crested cockatoo has four subspecies commonly recognised, two located in Australia, the other two in the islands north of Australia (indonesia etc)
Triton Cockatoo =
Cacatua galerita triton
Eleonora Cockatoo =
Cacatua galerita eleonora
Matthew's or Fitzroy Cockatoo =
Cacatua galerita fitzroyi
And the nominate species "Greater sulfur crested cockatoo" =
Cacatua galerita galerita
Only the "yellow crested cockatoo" species have defined yellow-orange ear coverts (cheek patches), though the depth of colour varies depending on the subspecies and the age of the bird. Some galerita have obvious pale lemon/lime yellow ear coverts when they are young, but they mostly lose it and develop almost a dirty look instead.
Because nothing is certain when hybridising, it could be any combination of larger cockatoo with either greater or lesser sulfur. Every baby produced will vary not only depending on the species but also the individual.
Some traits seem to be polygenic and the end result is often what appears to be a moderately blended trait (the crest for example). Other monogenic and bigenic traits will be inherited based on which is more dominant, which is why we often see "stronger traits" passed down during hybridisation. For example the black beak colour of larger 'toos seems to be dominant and when crossed with a smaller species with horn coloured beak, bubs inherit the black beak phenotype
Here is a triton x moluccan hybrid
