Black-headed Grosbeak (Pheucticus melanocephalus)

I'm not positive what this is, but it is not Pheucticus melanocephalus.

Thank you ! I must say I have been curious from the beginning to find out what is it. As no current entry from Zootierliste seems to fit this one, I basically considered black-headed by default. Will welcome ID tentatives with pleasure !

@Therabu I would say hybrids are possible as well, given how many Cardinalidae appear to be kept in one space.

They arrived fairly recently from seizure and do not think they are breeding yet, at least to my knowledge. Because of this, the array of potential species is broad.