Red Crossbill Taxonomy

  • Status quo
  • Remove North American “subspecies” and replace with call types
  • Promote Observation Field for call types.

0 voters

I tried getting community opinion before on the forum but that topic went completely by without comment. Perhaps by adding a poll, I can gain a better idea of what the community wants and therefore, convince bird curators to take action on a faulty taxonomy. So I’ll run down the pros and cons of each option above.

Quick history lesson on this amazing little finch. The current taxonomy is in accordance to latest change in 1937, that nine subspecies are present in North America. These subspecies are entirely based upon bill size and perhaps very subtle body proportion differences. In a realistic point of view, this does nothing for the iNat community and is completely useless. Especially since the ranges of several of these had strong overlap in breeding range, breaking rule number one on subspecies diagnosis that subspecies don’t have range overlap or very little overlap.

Groth (1988) proposed that instead of naming subspecies by bill size, how about using the structure of several distinct flight calls to diagnosis subspecies. That year, he announced the 8 “call types” of Red Crossbills. The flight calls will get an id every single time because unlike subtle and mostly undetectable bill size, you can id calls to distinct populations. Ever since, Benkman (1999) named Type 9 which has been elevated to species status as the Cassia Crossbill, Irwin (2010) found Type 10 and finally, Matt Young and Tim Sphayr (2017) described Type 11.

The big question is, with call types recognition going back 33 years, why hasn’t the taxonomy been updated? It is simply because museum specimens can’t vocalizations. One might presume that benti is Type 2, but that’s just it, an assumption. But fact of the matter is, a Type 5 crossbill is unlikely to be with a flock of Type 8, simply because it’s not his flock by sound and feeding behavior. This leads to reproductive isolation and therefore, speciation.

Status Quo

  • Follows Clements Checklist
  • That’s literally it.


  • Subspecies diagnosis is faulty and does not represent true geographical variation.
  • Leads to many erroneous ids if one tries to identify by bill size and if one tries to apply a call type to a named subspecies.

Remove North American “subspecies” and replace with call types

  • More accurately represents what the subspecies taxonomy should be.
  • Disagreements in ids will be limited to none, especially if subject is recorded.
  • Call types are universally used as the primary id mark of distinct populations.
  • Since our understanding on the reproductive isolation and interaction of these call types has been strongly aided by citizen science, we can our fair share and help scientists out.
  • Crossbills seem to cling so strongly to their type, we might see the species split into more species and the early 20th century taxonomy is going to become obsolete.


  • Does not follow Clements Checklist
  • Scientific names will be informal (ex. *Loxia curvirostra “Type 1”)

Promote Observation Field for call types

  • Will still follow Clements Checklist


  • Max Kirsch created an observation field 5 years ago to accommodate call types. Yesterday, I added the first observation to that OF, meaning it was not promoted well.
  • Inconvenient
  • Unlike an observation field used to document hawk morphs or birds with bands, call types represent very distinct geographical variation and should not be contained in an observation field.

I feel lucky to ID a bird as a Red Crossbill; the other version seem beyond my capabilities. So I don’t really care how Red Crossbills are further divided except for this: I want “Red Crossbill” to be the species; don’t split it at the species level.


Wouldn’t call types be better managed with observation fields?

The high majority of observations will either be cases where observer skill and/or circumstances do not allow call type ID’s to be made.

If the expectation is that the ID’s be done based on geography, this will just be another example of implementing circular reasoning about range and ID like with other subspecies.

Leave it as an observation field.


The split is inevitable, the species as it is now is paraphylletic. The only reason the split hasn’t happened is because no one is quite sure yet which call types are full species and which ones aren’t.

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I just added the field to all of my Red Crossbill observations.

well, that gets into taxonomy and how it works. The split is inevitable in some databases, but that does not hold that iNat has to use that taxonomy. But at risk of descending into the same rant i always do i will leave it at that.


Discussion about how to deal with a specific taxon should really be done via a flag on the relevant taxon.


If it must split, it must split (that’s still controversial as far as I know). If it does, it will be important for iNaturalist to have a “Red Crossbill Complex” option, even it it includes something else to avoid paraphyly. (How essential it is to avoid paraphyly at the species level is another controversial issue.)


Can you move the poll to the end of the post? It’s distracting, and confusing until you read the rest of the topic.

Do these call types have taxonomic names? The thing about subspecies is that they are taxonomic entities that we can track in the literature etc. Most people may disagree on whether they are correct, but they are valid for now. I don’t know anything about these species/subspecies but as I understand it, the call types cannot be linked to a name and nobody knows which are actually distinct. Is that right? If so, then trying to add in undescribed species here on iNat is just going to cause confusion. iNat follows outside resources so that it can have some sort of stability, but that does mean that it won’t follow new or suspected taxonomic changes. If these subspecies haven’t formally been synonymised yet, they should remain on iNat even if they’re a bit useless. Observation field is the way to go!

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There’s no formal names for most of the types. A few like types 2 and 10 have names, but that’s it.

I’ve tried but the bird curators wouldn’t even let the topic be discussed because it’s “following the Clements Checklist.”

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No the call types do not have taxonomic names. As mentioned previously, it’s because specimens do not call, and since these birds are incredibly nomadic, one cannot say a specimen collected from California in 1937 is Type 5 or Type 2 based on a skin alone. And we make assumptions on what subspecies might be applied to which type (ex. Type 2’s core range is the Intermountain West, and matches moderately well with subspecies benti) but the ranges of the types are hardly concordant with subspecies ranges. The only call type we know for certain can be applied to a subspecies is Type 11 with mesoamerica. But nearly all of the birding community follows call types rather subspecies because unlike the subtle and subjective differences in purposed subspecies, call types can be identified vocally and ecologically. A Type 2 crossbill has a large bill specialized to crack open the cones of hardpines like ponderosas (hence the alternative name Ponderosa Crossbill), jeffrey, lodgepole pines. While a Type 10 (Sitka Spruce Crossbill) has a small bill that feeds on the soft, flecky cones of spruces and firs. But that’s why are becoming reproductively isolated because they follow the calls of their pack because they know where the food he can get into is. Hopefully that makes sense.

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So the main problem here is simply that these call types aren’t taxonomic units, so they’re not actual species/subspecies, at least as currently recognised. It may well be that they are more valid than the current subspecies, but until the scientific work gets done we won’t know for sure. Scientists in the past decided that the subspecies were valid, and until someone does the work to change that (and to determine whether it really does need to be changed), those are the subspecies we have. But call types are certainly useful, so we should track them with an observation field for sure! Then when they do get assigned to a particular subspecies, we can go through and make the necessary changes.


That sounds as if you are saying that the species as it is now consists of several lineages descended from the same common ancestor. Which looks circular to me, as the species could be defined as descendants of that common ancestor.

Didn’t you just say that the bill size was not a reliable guide to subspecies? It looks to me like Ponderosa Crossbill and Sitka Spruce Crossbill correspond to workable subspecies, whether or not they fall within currently delineated subspecies.

Hence, it looks to me like the real work is to try to correlate call types with physical types, and re-delineate the subspecies that way.

It isn’t because it’s incredibly subjective. Yes, there is variation in bill sizes but not to a reasonable identifiable extent. It’s like saying you can identify Sharp-shinned Hawks from Cooper’s Hawks by size, even though small male Cooper’s overlap size variation with female Sharp-shinned. Or you can tell a Northern Bald Eagle from a Southern Bald Eagle because you can notice a 3 inch size difference in a 35 inch long raptor. Just because there are size differences doesn’t mean one can accurately assess size in the field. In fact, that’s one of the first rules of birding is never assume the size of the bird is correct.

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To put it in visual perspective, here’s a photo of a Type 2 Crossbill, a type of “large-billed” crossbill, compared with a “small-billed” Type 10 Crossbill. Both crossbills were confirmed to their types by audio recordings. And keeping in mind there’s medium-billed types as well, you can see with even very good quality photos, you cannot reliable use bill size to identify two types apart, let alone 11 of them.


Very interesting! Clearly there’s still a lot of work to be done then and I definitely agree with you, those bill sizes look very much the same. Until they get formally named though observation fields are the way to go. iNat doesn’t really work with undescribed species or suspected taxa etc.

Plus that “Sitka Spruce” type is on a Lodgepole Pine.