I don't think so. Why do you say this?
Because researchers kept meticulous track. Why wouldn't it be so? The various breeds/species differentiated to match beak morphology to food supply specialization. If the environment hasn't changed significantly, the forces that brought about the specialization will penalize half or more of your offspring for having the sub-optimal beak configuration.
um, viable, in this context, has a larger meaning than just breathing on their own, it is a measure of the long term success of a given line of descent.
I don't think so. Why do you say this?
From the major study done on Darwin's finches:
A longitudinal study of Darwin's finch populations on a Galapagos island shows that hybrids exhibit higher fitness than the parental species over several years.
From: Grant, P.R., and Grant, B.R. (1992). Hybridization in bird species. Science 256: 193-197. Selected Abstracts