Scottish Crossbill - Yes? No? Never? (1 Viewer)

[Farnboro John]

No opinion on the Scotsbill, but if you are interested in crossbill taxonomy, I would suggest looking for threads in the Bird Taxonomy forum. Quite a bit of discussion on this and related topics have occurred there.

The trouble is that the Crossbill enthusiasts expect everyone to accept their belief in a thousand separable, distinctive call types being meaningful identifiers of bird populations in an irruptive nomad, in a world where Great Tits and Chaffinches have distinctive dialects every few dozen miles in mixtures of residents and migrants where everyone knows they are single species. You'll get no sense out of those threads.

John

 

[Tiraya]

The trouble is that the Crossbill enthusiasts expect everyone to accept their belief in a thousand separable, distinctive call types being meaningful identifiers of bird populations in an irruptive nomad, in a world where Great Tits and Chaffinches have distinctive dialects every few dozen miles in mixtures of residents and migrants where everyone knows they are single species. You'll get no sense out of those threads.

John

In the US, they have more separation than I expected. It is not only call, but that the populations are fairly large, and said calls always correspond to a diet and breeding range. These nomadic flocks still tend to stick together. It's not a matter of dozens of miles with them, but more akin to hundreds...

I am not sure where I stand on the matter, only that in Europe, it seems to be messier even though there's less proposed species.

 

[wolfbirder]

Its a shame Lindsay Cargill (?) doesn't interact with birders any more, for his knowledge regards the existence of a distinctly separately-breeding Scottish type-Crossbill, is second to none, having handled/rung hundreds of such birds.

I don't think the exhibited updating research categorically rules out the existence of a Scottish Crossbill, but it just says more research is required. Their remark that this new N20-type call is the only call that 'might' identify a separate Scottish Crossbill population is not that new..........even I managed to record such a call at Boat of Garten woods when I went there two years ago, and was well aware that excitement type C calls were no longer defining, and I also managed to distinguish by ear, the difference between N20 of 'putative' Scotsbill and similar N2 and N15 calls of Common's. I don't believe this paper necessarily takes us any further backward or any further forward, to me it simply (and perhaps rightly) questions the original assignment of Scottish Crossbill as a full species, until further research is completed. Again, Lindsay, I think it is fair to say, was the man to go to. But he seems to have fallen out of birding altogether and hence with birding authorities too. From my recollection, he was clear that there was a distinct Scottish Crossbill type that bred separately from Common or Parrot and that could be assigned by call, or via bill depth and wing measurements in the hand, as well as by body size. He also remarked that with the 3 species, their moult was related to their breeding cycle, which was dependent on the food sources they were able to feed on. I recall him saying that in winter you get mixed flocks, but that they soon fragmented into their respective types, and that in his strong opinion, 'Scotsbill existed, but that it might not be exactly what we currently think it is'. He was adamant assortative breeding occurred.

I think there is little doubt that Parrot and Common occur, just as Arctic and Lesser Redpoll do, but its the middle bits that remain difficult to precisely define and distinguish. Even as far back at 2003, he suggested that 'the most likely candidate for a hybrid was a bird that gave Excitement call C.' Lindsay said a lot about Crossbills at the time, so to quote him for little bits here and there may misrepresent what he was trying to say about things. I think it is fair to say that although he was adamant that 3 species existed, he routinely acknowledged that further work was needed to determine what exactly defined them.

So, the newer N20 call may be just that..........but more work is required.

But of course, I genuinely don't know if Scotsbill (or Arctic Redpoll for that matter) should be given a full separate species assignment or maybe just a sub-species one, but at least morphologically there is clear distinction between Arctic, Common, and Lesser Redpoll, and critically for their full species status, even where they overlap they do not interbreed (other than very isolated instances) and that is why they are given full species status, as far as I understand. Perhaps species separation in Redpolls has not been for long enough for the required % DNA diversion, but this is why I feel the former can be more important than the latter at times (distinct selective breeding where populations overlap, rather than DNA % divergence).

I also personally favour separation on morphological differences, but then Northern Long Tailed Tit (ssp caudatus) are only classed as a sub-species because they overlap and interbreed in Denmark for instance. Should Masked Wagtail, which is a distinctly different morph, be a separate species? I guess White Wagtail was merged back because they interbreed with Pied.

So I guess, in simple terms, the key criterion separating full species from sub-species is defined primarily by geography? If populations overlap and they do not interbreed then they are afforded full status, but if populations do not overlap then they are classed as sub-species. Is this fundamentally correct? Sorry to be a simpleton.

 

[James Lowther]

So I guess, in simple terms, the key criterion separating full species from sub-species is defined primarily by geography? If populations overlap and they do not interbreed then they are afforded full status, but if populations do not overlap then they are classed as sub-species. Is this fundamentally correct?

Not really. If populations overlap and do not interbreed then that’s a good indication they are separate species as you say. But if similar taxa don’t overlap then in order to determine if they are best treated as separate species you need to examine other lines of evidence to determine if they are reproductively isolated I.e. if they WOULD interbreed given the chance. That’s obviously quite difficult but that’s the principle.
Cheers
James

 

[jurek]

I don't think the exhibited updating research categorically rules out the existence of a Scottish Crossbill, but it just says more research is required.

Hi, existence of Scottish Crossbill was disproven by genetic studies. Cheap large scale genomic sequencing is a method which was not available until the last decade.

this new N20-type call is the only call that 'might' identify a separate Scottish Crossbill population

excitement type C calls were no longer defining

I think this can be a valid discovery - that call types of crossbills appear and disappear fluidly. This would be similar to many other learned sounds produced by animals.

It seems that a library of crossbill calls has been collected over several decades in Britain. An interesting research would be to compare the full spectrum of calls recorded every year. The interpretation would be that different call types appear, spread and (presumably) disappear, not an constant elusive bird with a constant call which different studies found to be different.

Such call types could easily fool a researcher making a short-term study into claiming there are constant different populations, if the researcher chooses not to use genetic data.

 

[wolfbirder]

Hi, existence of Scottish Crossbill was disproven by genetic studies. Cheap large scale genomic sequencing is a method which was not available until the last decade.





I think this can be a valid discovery - that call types of crossbills appear and disappear fluidly. This would be similar to many other learned sounds produced by animals.

It seems that a library of crossbill calls has been collected over several decades in Britain. An interesting research would be to compare the full spectrum of calls recorded every year. The interpretation would be that different call types appear, spread and (presumably) disappear, not an constant elusive bird with a constant call which different studies found to be different.

Such call types could easily fool a researcher making a short-term study into claiming there are constant different populations, if the researcher chooses not to use genetic data.

Hi Jurek

I totally understand the point about DNA, and if one chooses that to be absolutely and finitely defining then so be it. I totally get why most would accept that.

I just think that assortative breeding is equally defining. It tells you that certain species recognise themselves as different. I'm not saying this is the case here, though I suspect Lindsay Cargill certainly would, I'm just making the general point that whilst genetic study is an extremely valuable tool to identification, maybe separation has occurred in relative recent times.

 

[opisska]

So when interracial marriage was taboo, homo sapiens was actually several species?

 

[Phil Andrews]

A (in)famous British birder advocated "at least 10 species of human" a few years back.

 

[opisska]

Five species in India alone when the caste system was in full power?

 

[edhunter]

interesting thread this at times like a Viz cartoon,, seems not to grasp at all the vocal types of Crossbills and the already published stuff as if its not even been deeply considered or researched at all.

Crossbills do in the Uk suffer from lack of effort regarding sound recording ...its likely due I would think to the uncertainty of Scot bill everyone has switched off and the lack of sound recording effort made is as birding culture here not just for xbills . To read a very good comparison to Calls - FC and EC avesrares this works, the Scot bills I recorded 2 years ago fit very well to this ( no ecs recorded). If you get Fcs or ecs which do not match on anything email me or them.

One big problem with Crossbills is everyone is not sharing the data and the publications are late after writing.... too publication or some choose to to do this at ten year intervals which stops progress for other Crossbill folk then you at end . the birders ..think its all BS by the looks of this thread above

"Crossbill research would make an interesting study of bad practices in science. Notorious is cherry-picking arguments and publications for versus against the split. Another is selection bias. 20. century ringing manuals report many intermediate individual crossbills, but 21. century birder records and photos show almost exclusively classic Common and classic Parrot Crossbills. Intermediates are selectively not reported."

Harsh comments with no idea of the current reality of Crossbill knowledge , myself I do not bother to put out vagrant crossbill types as the last years have shown since if you cannot tick it ....noone is interested, but since "flava wags " is the trend ( not much difference here regarding call separation.....although Crossbill vocal types is far easily separable) hopefully this will change in the future

There was a very interesting influx of crossbills this autumn winter involving birds from way east. In October in Wales we got some 3 N9s previously around 4 Uk ( coincided to birds near Paris and Germany) records , these came in same group as multiple N5s again first Welsh records just 3 in uk - all from way east. These initially arrived with N8....east( rare in Wales) more regular in England, also some N3s again a very rare Welsh one with previously just 6 occurences ( a central Europe type)

The birds that followed after the autumn much anticipated (to the similar " sibe acc " winds) are far more interesting and happened with major Coal tit irruptions also in Scan. Viz mig ( Low numbers) Crossbills irrupted as far as Wales for several weeks after that even when Thrushes dried up. They all have disappeared in the last week ...these were particularly interesting in many ways. Maybe someone reading this has recordings to add to the picture??? They just left Wales....maybe back nin England soon., Hope so ...they did not just miss England. please contact me if you have such recordings

This post just to open your eyes to that Crossbill folk ...who are as rare as these birds in the uk.... are still at it and certainly not blinkered and certainly not cherry picking we are trying to work out these birds vocally -

Scot xbill wise the Welsh N15 does not impact identification from recordings

all the best
Ed

 

[wolfbirder]

I learnt how to recognise N20 calls and sono-grammed them in Boat of Garten Woods, Speyside in 2021, quite distinctive I thought though it took 3 weeks of listening to them prior. Also saw what were clearly Commons, and others near Grantown on Spey that were clearly Parrots.

Also had 4 large billed Crossbills near Bridgnorth, Shropshire issuing N6 calls in December 2020.

I did a report of what I saw on Speyside which was reported here: -

A return to Scotland to try to see Scottish Crossbills

I spent a superb four nights in Speyside at the end of April, based at Grantown On Spey, ultimately seeing nearly all my targets including 3 Capers, 16 Black Grouse, 3 White-billed Divers, American White-winged Scoter, 7 Parrot Crossbills, and 3 'putative' Scottish Crossbills. I say 'putative'...

www.birdforum.net

 

[jurek]

Harsh comments with no idea of the current reality of Crossbill knowledge , myself I do not bother to put out vagrant crossbill types as the last years have shown since if you cannot tick it ....noone is interested,

You confirmed exactly one of the reasons of the criticism. If out-of-place records are selectively not reported, how one can trust the pattern?

This seems to be the bias in the community, for which individual birders have little influence - but this does not make the bias real. I commented before that a science result can be fake without any single person being dishonest - simply by selective reporting / verification.

 

[01101001]

Harsh comments with no idea of the current reality of Crossbill knowledge , myself I do not bother to put out vagrant crossbill types as the last years have shown since if you cannot tick it ....noone is interested, but since "flava wags " is the trend ( not much difference here regarding call separation.....although Crossbill vocal types is far easily separable) hopefully this will change in the future

Yes, you can tick them, but only 'A', 'B', 'C', 'D', 'E', 'F' and 'X' types (as per the original The Sound Approach classification):

Sign in

ebird.org

EDIT: Not sure how it translates to the 'N' system: maybe you know or it's written somewhere in the internet?

EDIT 2: Not much overlap, it turns out (from the link above: avesrares).

 

[01101001]

Apart from those already mentioned at avesrares:

• B (Bohemian) 🔊 = N1,
• C (Glip) 🔊 = N4,
• D (Phantom) 🔊 = N7,
• X (Parakeet) 🔊 = N8,

it also looks like the following could be true:

• A (Wandering) 🔊 = N3,
• E (British*) 🔊 = N6,
• F (Scarce) 🔊 = N13.

(I based my assumptions on 'Similar FCs', 'Similar ECs' and 'Distribution' sections from avesrares, plus Part 8: Twitching and taxonomy - The Sound Approach.)

@edhunter Please check the last three lines for obvious mistakes or overinterpretations.

EDIT: *for which eBird mistakenly uses the name 'Parakeet' for the second time

EDIT 2: Unfortunately, crossbills are thin on the ground where I live; anyway--in case I managed to catch up with one--do the authors of the blog post still accept submissions of new recordings to their database?

EDIT 3: Also (some of those most probably have innacurate data):

• Altai 🔊 = N9,
• Corsican 🔊 = S2*,
• Tien Shan 🔊 = E1,
• Himalayan 🔊 = E2,
• Japanese 🔊 = E3,
• Dalat 🔊 = E5;

potential call types:

• Cyprus 🔊 = S3,
• North African 🔊 = S6,
• Balearic 🔊 = S22.

*the English version of this description is farther above

Index of all call types described in the article: avesrares. (Just in case, everything in my post and both articles above concerns the Palearctic only.)

 

[phototroph]

That it and Scottish Crossbill are genetically identical to Common Crossbill. Which means that they constantly interbreed with Common Crossbills.

Do you have the paper showing this to hand? I'd be interested to know the author's methodology. There are several examples of 'good' eco-morphologically distinct species of moth that have indistinguishable mtDNA sequences, for example.

 

[pbjosh]

Here's the synopsis from BotW under systematics history o L scotica:

"Forms a species group with L. curvirostra and L. pytyopsittacus, and all have sometimes been considered conspecific. Present species almost identical to L. curvirostra in wing, tail, bill and tarsus measurements, and overlaps in wing and bill measurements with L. pytyopsittacus, but intermediate in bill shape (a feeding adaptation). Feeding behaviour (and excitement call) apparently sufficient to isolate it partially from L. curvirostra, with no hybridization known where ranges overlap; but hybridizes with L. pytyopsittacus, and genetic evidence reveals limited differences between all three forms in Europe, indicating incomplete reproductive isolation. Captive and wild birds mate assortatively mainly on basis of bill size and flight and excitement calls, but extent of hybridization in wild not fully known; further research required, especially into resource polymorphism in Loxia as an explanation of the many similar cases within L. curvirostra where subspecies vary somewhat in bill size and vocalizations (latter perhaps as a function of former, or simply from vocal copying) but which remain capable of interbreeding when cone-crop failures force irruptions (under this scenario even L. pytyopsittacus would be treated as a subspecies)."

The same summary for L pytyopsittacus:

"Forms a species group with L. curvirostra and L. scotica, and all have sometimes been considered conspecific. Has hybridized with former, and recently found to hybridize with L. scotica. Recent genetic studies indicate limited differences between the three in Europe, indicating that they are not in total reproductive isolation, but differences in bill size and in flight and excitement calls considered sufficient to restrict widespread interbreeding; further research required (see under L. scotica)."

There are various studies / publications stating that eg Crossbills in the N African mountains, some islands, the Sierra Madre of Mexico are genetically more distinct from other groups of Red/Common Crossbill than Red/Common is from Scottish/Parrot/Cassia. Of course genetic yardsticking is not the defining metric, and particularly in a group like this is hard to apply. Additionally these are young types/taxa and each time there is a climate / habitat change event they appear come back into contact and interbreed and then in stable periods they rapidly diverge to selectively take advantage of differing resources.

But whether that makes them species or not is more philosophical than cut and dry science perhaps.

And the current species boundaries are perhaps as much defined by the politics and people involved in taxonomy of this group as the actual differences between the birds. There's a ton of really cool research, there are people who've dedicated their lives to this, there are a lot of stake holders, and the birds are of course fascinating so it's not surprising that people want to study them. But my personal read of the situation is that some of the people involved in this carry a fair amount of weight in the ornithological community and thus their results / opinions are taken as quite definitive and less questioned. There are a lot of subspecies / cryptic species out there that are not yet separated but that are patently far more distinctive than these Crossbill taxa are, but don't have the same amount of research or the same powerful voices lobbying their cases. The fact that Cassia Crossbill seems to bread assortively is sort of not surprising as a clade/type. It's just a question of whether it's a species and again that's a bit more philosophical but it's got some strong voices behind it.

Most seabird populations on islands breed assortively. There have been discussions surrounding splitting Short-tailed Albatross due to this, and the two subspecies / populations are absolutely morphologically diagnosable, frequently in the field even. And while there are clearly still more cryptic species hiding in the seabirds (ie, likely that at some point "Fuegian" SP will be separated from Wilson's), no one is talking about myriad species of say Leach's SP, Wedge-tailed SW, etc. Though all those birds have great site fidelity, do not widely interbreed, and tend to form monophyletic clades based upon breeding site. A particularly interesting case that is basically unstudied here is what the hell is going on with Tropical Shearwater in the W Pacific. So many "types" that seem to be field diagnosable and regional but then those birds go and wander and various attempts to quantify it (ie, Steve Howell in his book) simultaneously illuminate a lot of the variation but don't necessarily hold up to the ranges / realities of what is being seen as the years tick by and more people pass through these areas on ships. Far far less studied and who knows if it's one polytypic species or stacks of species. But certainly those birds are all showing repeatable morphological distinctions and are breeding assortively according to breeding island. I use these seabird examples a bit to highlight the fact that Crossbills are sort of heavily studied and politically favored in the current taxonomic winds is all

Personally I'm not overly fussed about where the Crossbill species boundaries are drawn, the birds are fascinating no matter how you slice it. I do suspect, though, that the current species boundaries don't best reflect the real world diversity.

 

[pbjosh]

Also from BotW from the Red/Common Crossbill species account, some salient bits:

Regarding prior categorization of N American types into subspecies:
"However, with a few exceptions on the periphery of the distribution (e.g., L. c. percna in Newfoundland, L. c. stricklandi in Mexico, and L. c. mesamericana in Middle America), the remaining subspecies have widely overlapping breeding distributions in the New World (2, 3), violating a basic tenet of subspecific designation, in which breeding ranges must not overlap geographically."

General overview of N American types / the case for Cassia Crossbill:
"Each call type has a range of morphological variation normally found within a songbird species (2, 3), which, combined with evidence of sympatric breeding and assortative pairing (58), led Groth (3) to propose that these call types are cryptic species. However, more recent genetic evidence (10) and the limited evidence of reproductive isolation outside of the Cassia Crossbill (11, 12) indicated that elevation to species status of the remaining call types is premature. For only the Cassia Crossbill is there strong support for monophyly (10) and strong evidence for reproductive isolation: 99.3% of 875 breeding pairs over 6 years were assortative (11, 12). Besides the Cassia Crossbill, Type 6 (L. c. stricklandi), found mostly in Mexico, is the most genetically distinct of the call types (10) and with further study might warrant species status. Neither Type 8 (L. c. percna) nor Type 11 (L. c. mesamericana) have been included in genetic analyses so their genetic distinctiveness remains unknown. However, based on the apparent similarity in ecology of Type 11 to that of the Cassia Crossbill (i.e., both call types rely on seeds in strongly serotinous pines year round), it could warrant species designation."

A summary of the palearctic situation:
"Most of the morphological variation in western Palearctic is between populations near the Mediterranean (especially Cyprus, Mallorca, northern Africa) and those to the north. Genetic studies (25) revealed no genetic differentiation among European vocal types, and stunningly little differentiation even between Parrot Crossbill (L. pytyopsittacus) and co-occurring Red Crossbills (see also Piertney et al. [64]). In contrast, the subspecies confined to areas of Aleppo pine (Pinus halepensis) in southeastern Spain (L. c. hispana), Mallorca (L. c. balearica) and the Atlas Mountains of northern Africa (L. c. poliogyna) are genetically distinct and the latter 2 subspecies are monophyletic (25). Size variation is greatest in central and eastern Asia (32) where additional research is needed."

 

[l_raty]

I once posted an mtDNA tree here, if there is interest.

 

[pbjosh]

I once posted an mtDNA tree here, if there is interest.

Cheers for that, I had forgotten about this effort of yours.

Granted it's mtDNA but taken at face value, it makes a lot of sense: An mtDNA soup in N America, an mtDNA soup in Eurasia, and the biggest difference is between the two hemispheres, rather than the same species in Chiapas as in the Atlas Mountains but magically Scottish, Cassia, and Parrot Crossbills standing out.

 

[david kelly]

This episode of the Life List podcast may be of interest to readers of this thread.

Life List: A Birding Podcast: Understanding red crossbill types and other finches with Matt Young on Apple Podcasts

Show Life List: A Birding Podcast, Ep Understanding red crossbill types and other finches with Matt Young - Apr 10, 2024

podcasts.apple.com

David