Heck's Shaft tail Grassfinch

This is one of two new spouses for my solitary Heck's Grassfinch who lost its mate last year. As yet they have not met as the new arrivals are acclimatising in the indoor section of my aviary. However I have a nasty feeling that they are not only both males, but different types of Grass finch which will not hybridise even if they are opposite sex! Hmmm.