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Relations of Crossbils (1 Viewer)

RockyRacoon

Well-known member
Hi all, another question. What are the relationships and differences of the four European Crossbill species?

Common Crossbill, Loxia curvirostra
Scottish Crossbill, Loxia Scotica
Parrot Crossbill, Loxia pytyopsittacus
Two-Barred Crossbill, Loxia leucoptera

I need lots of information for a school project which I am going to do on this subject! So please help! :t:
 
According to biological definition, different species can not produce fertile offspring. Nowadays they use DNA to determine species (and electron microscope to identify them..). Tendency is now to have different national lists. I guess RSBP provides that in Britain.

Like in Your Acanthis question - I am used to list scotica under Loxia pytyopsittacus - or would be, if I observed one.
 
O.K now I am confused, the Scottish crossbill's head is more like the common crossbills than a parrot, or neck. And the bill is smaller, I would have thought that the Scottish and Common were closer.

How certain is the research that parrot and scottish are the same?

And also for Pete's question the answer for me is no, because I have never seen a common or scottish. But maybe if I saw Common a few times for myself and Scottish once or twice the answer is probably yes!

For me it is very easy to tell Willow warbler and Common Chiffchaff from each other by sight alone, although I usually hear them before see them...
 
Jake,
IMO the Scottish Crossbill is more a fruit of wishful thinking than anything else in order to give the British Isles at least one endemic. These efforts might better be directed at trying to have the Red Grouse split.
 
I think you could be right, strange that the U.K is an island with no endemics. I recently visited Tenerife, in the Canary islands there are six endemics I can think of, that was just the ones I could think of while I was writing this message!
 
Hi Jake,

I guess the reason that Britain has so few endemic species compared to other islands is that it's only relatively recently (in evolutionary terms) that it's been an island (maybe 7-8000 years but someone will know the correct time). That's not much time for separate species to evolve. Other groups of islands have been isolated for much longer and so tend to have more endemics. That's the theory anyway.

Remember that when we classify birds (or anything else for that matter) into species and sub-species we are grouping lots of diverse individuals under one heading. This means that it's always going to be a simplification of reality and conceals diversity between individuals within the same species. All human beings are Homo sapiens, but obviously when we say 'these are all human beings' we are concentrating on what they have in common rather than how they are different. As I say, this means that we simplify reality by the way that we classify.

One other way in which we simplify things when we classify is by pretending that things don't change. If we believe in biological evolution then we believe that lifeforms change over time. Because this change is so slow, we tend to ignore it because in most cases (at least in long-lived organisms) it's almost impossible to see evolution happening in front of us. However, if evolution operates with species X evolving to form species Y and Z (with X possibly still around too), then the separation of Y and Z into proper species obviously doesn't happen overnight but over many thousands and probably millions of years. During that period, it's likely to be very hard to classify the variety of forms evolving from X because they aren't quite a full species but are somewhere in between. When we look at lots of different Xs in different places they can look very different to each other but these differences may be continuous (or clinal) rather than discontinuous. When biologists classify separate species, they are saying that there is a discontinuity (a gap or step) between them (which means that it's difficult for them to produce fertile offspring, for instance). But again, this is a simplification of reality.

This may be what's happening with Crossbills (and I suspect also with groups like Chiffchaffs and large gulls). They are in the process of evolving into separate species. This gives biologists a great difficulty because the differences between the forms of Crossbill are not always discontinuous (i.e. there's lots of overlap and gradations) but the only way they have of classifying them is by pretending that they are discontinuous species.

Hope that helps!
 
Hi Jake,

There's been several threads on crossbills, with a lot of info in them, well worth doing a search through.

The Scottish Crossbill does appear to be a distinct taxon, but at what rank (race or species) it should be treated, is very open to debate. But the fact remains that there are crossbills in Scotland which have a set of call types different from the (yes, wait for it!!!) THREE different call types of Common Crossbill (i.e. Common Crossbill is 3 taxa, not just one!) and also different from the call types of Parrot and 2-barred Crossbills.

Genetically, so far, no difference between any of these six (3 Common, Scot, Parrot, 2-bar) has yet been discovered - the range of variation between individuals of one is greater than the differences between the averages of each type. Two possible reasons for this; first it could just be, they haven't looked at the right part of their DNA yet; the second, that there is occasional gene exchange between all of them (i.e., Andrew's X, Y and Z interbreed occasionally), allowing them to show the same range of DNA. This second is thought the more likely, but it hasn't been confirmed yet (at least not that I'm aware!). They may be six species, or they may just be six races of one species. The jury is not even out yet, they're still listening to the evidence, and will be for some time I expect.

Why is Scottish regarded as closer to Parrot than Common? - two reasons. First, Scot has a feeding ecology more like that of Parrot: it feeds more on pine (and larch) than spruce; Parrot feeds almost entirely on pine, and Common largely on spruce. Though they will all use the less-favourite conifer if their favourite is having a crop failure (better to eat something second-rate, than nothing at all!)

Second, post-glacial vegetation history: pine colonised Britain about 12,000 years ago, from across the (then dry) North Sea; it is more than likely that large-billed, pine-feeding crossbills colonised with it. In Scotland, winters aren't too severe, so the cones don't get frozen rock-hard, but in Scandinavia, they do, so crossbills there need an even larger bill to deal with frozen cones (that's one theory, anyway). At the end of the ice ages, there was no spruce in northern Europe, only further south (Alps, Balkans) and east (central Russia), so no spruce-feeding crossbills anywhere in the area. Spruce later spread north & west to Scandinavia, but never reached Britain naturally (had to wait for man to introduce it). So there were almost certainly well-established pine-feeding crossbills derived from Parrots in Scotland, well before spruce came anywhere near.

The full distribution of Parrot is yet to be determined; there's large-billed crossbills in southeast Europe (Bulgaria etc) and parts of the Mediterranean, which (the ones I saw in Bulgaria) look structurally just like Parrot and (I'm told, for some in the Med), sound like it too.

Michael

PS good luck with the project - I think with all you're getting from everyone here, you'll be able to leave teacher completely behind . . . maybe, try to be gentle on him with all this university-level stuff :king:
 
Here's one possible phylogeny of crossbills (how they evolved over time). Far from definite, but it does fit the observations fairly well, probably better than any other option

Michael
 

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At the risk of being poo-pooed, laughed off BirdForum and lynched by those that disagree, for us folk who see Crossbills (almost) daily, it is relatively straightforward to distinguish between the three currently accepted species in the UK (Parr, Scot and Comm) taking into account only the bill size and call. Unfortunately, there are large Comms, small Parrs and Scot becomes a mid-way stop which is barely recognisable on bill alone. Parr sounds different (much more like Blackbird alarm or GS Woodpecker than Comm Cross), but Crossies are actually fairly quiet, especially when in trees munching away, and although the feeding and food is different, when you have all three species in Scot's Pine forests, the feeding and food is identicle, and everything goes belly-up. This leads to regular sightings of mixed Crossbill flocks, of which the Parrs stand out, the very Comms stand out as being very small billed and the others are regularly put down as Crossbill sp. only. There are often encountered flocks of Scot, which don't tend to have any very large or small billed birds in them, baring in mind that Parr has a far more washed-out, pale colour for most of the time.
Right, I've confused myself now. That's enough.
Feel free to e-mail me for even more nonsense!
 
Just to ensure the mix will take some time to figure out they have to include the various subspecies of Red Crossbill (aka Crossbill) Loxia curvirostra in North America. There is considerable variation in size, colouration, bill size, and song. The northern L.c. minima isn't much larger than a chickadee, with a bill about as big as a Redpolls and L.c. stricklandi of the US Southwest is quite large, with a bill that almost rivals a Parrot Crossbills.

What I find interesting is that the White-winged Crossbill (aka Two-barred Crossbill), L leucoptera, found around the Northern Hemisphere doesn't appear to have any discernable subspecies or races. That makes it appear to fit the bill as a "recently" evolved species, which has spread rapidly to fill a niche in the coniferous forests following the end of the last ice age (10,000 years ago). Seems they haven't been around long enough, or isolated long enough to diverge into races, subspecies, or new species. They all are tremendous wanderers, noted for breeding anywhere, anytime.

I guess we'll all know someday what's going on within the group.

Hal
 
Hi Hal,

There's two races of ww/2b - L. leucoptera leucoptera in North America, L. leucoptera bifasciata in Asia (& far NE Europe). The American race has a stouter bill than the Asian race. In Asia, they're pretty much restricted to Siberian Larch (Larix sibirica, L. gmelinii), but the American race goes for White Spruce (Picea glauca) and Eastern Hemlock (Tsuga canadensis) as well as Tamarack Larch (Larix laricina).

There used to be a third, L. leucoptera megaplaga on Hispaniola (Caribbean), but that's been split off as L. megaplaga now; feeds on Hispaniolan Pine (Pinus occidentalis).

Of Red Crossbills in America, last I heard was for seven taxa (call types / races / species)

Michael
 
I remember my first Parrot,s up in Grampian a few years back.
I was standing under some pines when I heard a xbill call unlike any other I have heard.
I birreled round in time to see a stonking male flying past me.
I reguarly pick up common on call in Lothian, but I am not sure about Scottish.
An interesting arcticle I read recently involved the tape recording of calls of xbills undertaken in Scotland.
One finding was that two Scottish Xbills were found well south of their usual range, I think one was in Perthshire/Fife area with the other near Stirling.
It makes sense really though,presumably the pine crop fails in Scottish xbills territorys also so they then move on to areas NEAR YOU.
Just to confuse matters more.
 
Hi Birdspotter,


Birdspotter said:
One finding was that two Scottish Xbills were found well south of their usual range, I think one was in Perthshire/Fife area with the other near Stirling.
It makes sense really though,presumably the pine crop fails in Scottish xbills territorys also so they then move on to areas NEAR YOU.
Just to confuse matters more.
A 'type C call' bird, i.e., that to which the name Scottish Crossbill is given, was tape recorded & sonagram analysed a couple of years ago in Kielder Forest, Northumbs. Not sure if our county records cttee have done anything with it yet!

Michael
 
Hi Michael,

Am I ever glad you're keeping up on all this! Nice to find the expertise is available.
Must have had a "senior moment" as my son calls it. I Completely forgot the AOU had split off L. megaplaga. Also seem to remember, somewhat hazily, about talk regarding merging or splitting another Caribean WW/T-b race (Antilles?).

Seven Taxa for Red Crossbills over here? Thats it, I have enough trouble with the four in Canada, got a headache, going to bed, probably dream about crossbills for weeks!

Hal
 
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