Some mtDNA-based stuff attached.
Green is Old World, ochre is New World.
So best fit is four crossbill species: L. curvirostra (Common Xb) & L. bifasciata (Two-barred Xb) in Old World, and L. minor (Red Xb; Brehm 1846, oldest New World plain-winged Xb name) & L. leucoptera (White-winged Xb) in New World :t:
Any plans to get this published formally? Looks worthwhile to me.