I think the situation is well known enough in NA to advocate for the split. Paraphyly itself doesn't actually count against recognizing a species...many island endemics for instance are more closely related to a specific subgroup within a wider continental range. It will probably take decades to resolve Old World crossbill taxonomy...I would rather have the South Hills form recognized than wait for studies that may or may appear, especially as the restricted distribution makes the population vulnerable to logging or other human impacts.
I fully agree with Morgan here. Not only is monophyly is not a requirement at the species level (and is especially not expected in 'island' taxa), but other factors are also good for splitting this species. Also, a split of the (South Hills or Cassia) Crossbill has been proposed before (in 2009), and was voted 6 yes to 5 no, and did not pass at the time. If you read the comments on the proposal at the time (available [
here]), I think the 2009 objections can be sorted into three rough categories:
1.
Lack of good vouchering/specimens. This has been somewhat remedied in the interim, with 10 specimens now residing at University of Wyoming.
2.
Preference to deal with the whole Red Crossbill complex at one time. This seems like it is really an opinion situation more than anything else. I would say that, while preferable in some cases (like has happened with groups like the Yellow-rumped Warbler before), with the holarctic monster that is Red Crossbill, I suspect that we might have to wait another hundred years for such a complex-wide solution. For such a complex situation (pun!), I think piecemeal splitting is more appropriate, rather than wait forever. When we have data that supports at least one taxon of the complex that warrants species-level status separate from the rest of the complex, we should split that taxon. Also, for what it is worth, this particular population of crossbills likely won't wait around 100 years for this ultimate solution, and will instead likely shortly be extinct as written about [
here].
3.
Various comments with the data in the paper that the 2009 proposal was based on. This includes issues with some of the AFLP data and potential number of outcrossers/generation, things about associative mating, etc. There has been a lot of work on this South Hills population since 2009, and a lot of these original concerns have been addressed.
As you could probably guess, I am in favor of this split. I have read the papers that underlie it, and I think the authors have done a good job supporting the reproductive isolation from other crossbills and generally shown the distinctiveness of this population. It seems like a good species to me, especially in a way that things like Scottish Crossbill do not.