Crossbills (5 Viewers)

[lewis20126]

.) At this time, the conifers were further south, and I would expect that they supported populations of crossbills: the trees and the birds may well have moved north together as the temperature increased; then the range of the trees contracted, Caledonian pine being the only conifer to persist, and a bird population would have become locked in the remnants of forest.

Laurent, I'm sure that is right. I guess we will never know whether the locked in birds were "large-billed", "small-billed" (or "intermediate billed"!) I guess we know nothing of the factors in conifer distribution, cone crops or other factors which lead to speciation of pytyopsittacus diverging from smaller-billed curvirostra like crossbills (which in the Holarctic default bill form)?

A very interesting paper you link to there - a pity the genus Pinus was not included for comparison.

cheers, alan

 

[MJB]

Here, the birds that would have had the best reasons to leave the pine forests and colonize the new plantations, are those with a bill smaller than average—those to which it was hardest to open a thick pine cone, and particularly easier to feed on the newly-planted smaller-coned exotic conifers. If a population experiences a significant preferential emigration of small-billed individuals, the direct consequence that one might expect for the remaining population is an increase in bill size...

Shades of Darwin's Finches, Laurent....
MJB

 

[jurek]

Hi,

Crossbill research is very interesting, but naming species on this basis is, well, eccentric.

I think Scottish pine forests are not isolated for crossbills, and have never been. We know that Parrot Crossbils have no problem flying in and breeding from Scandinavia. There are also captures of crossbills with the scottish bill sizes in England, which nobody can make anything of. Common Crossbills of course, are well known to disperse all over Britain and neighboring countries.

There are no "Scottish" 3C calls in Alan's recordings from the 70's onwards and DNT's recordings are inconclusive.

Is it possible that 3C call simply appeared since 1970's? Can it be detected on any other old crossbill recordings anywhere? Or more broadly, what is relation of older and new crossbill recordings?

 

[lewis20126]

Hi,
I think Scottish pine forests are not isolated for crossbills, and have never been.

It might not take many generations, with even modest isolation (i.e. some in / out migration), for a population of Loxia to adapt bill morphology to a single species of conifer. As MJB says, the plasticity in Darwin's Finches may well be analogous. It would be interesting to know if there was any substantive spatial separation between the distribution of Spruce, Firs (and Larches) and that of Pinus sylvestris.

cheers, alan

 

[Nutcracker]

The Caledonian Pine Forest is only about 9000 years old: http://en.wikipedia.org/wiki/Caledonian_Forest

Presumably the founder population would have been either a large-billed Parrot type Crossbill or a small-billed Common type Crossbill. I guess there would have been some isolation as there would have been few if any conifers in southern England until relatively recently (no native conifers which could support Loxia?). My guess would be a Parrot type coloniser but I'm not too sure about the spread of the various conifers upon glacial retreat, that being the key factor.

cheers, alan

Scots Pine colonised Britain across the North Sea, apart from some small populations in western Scotland (Loch Maree - Shieldaig area) and Ireland (now extinct) which likely survived the last glaciation on ice-free land below current sea level to the west. Scots Pine used to be native in England too, but became extinct through overcutting / grazing in the 16th-17th centuries.

Neither spruce nor larch (nor fir, but crossbills don't use fir) ever reached Britain in the current interglacial until introduced by man in the 17th-18th centuries.

Fairly safe to assume that Parrot Crossbills colonised Britain with Scots Pine; also very likely that Common Crossbill never successfully colonised Britain until spruce and larch plantations started maturing in the mid to late 1700s.

I understand that Abies (fir) and Picea (spruce) were both present at this time in Britain...? (Eg., see pollen evidence, Fig.14-15 (Abies) and Fig.26-29 (Picea) in Terhürne-Berson, 2005.)

Only in previous interglacials, so not relevant to the current situation at all (the pollen maps are not very useful, as pollen can blow hundreds of km easily).

I think Scottish pine forests are not isolated for crossbills, and have never been. We know that Parrot Crossbils have no problem flying in and breeding from Scandinavia.

Yep.

There are also captures of crossbills with the scottish bill sizes in England, which nobody can make anything of. Common Crossbills of course, are well known to disperse all over Britain and neighboring countries.

No reason they shouldn't be just as mobile as other crossbills! A "Scottish Crossbill" call type was also recorded in Kielder Forest (Northumbs, England) a few years ago.

It might not take many generations, with even modest isolation (i.e. some in / out migration), for a population of Loxia to adapt bill morphology to a single species of conifer.

The obvious case to look for is any future development of a thin-billed crossbill adapted to the small cones of Sitka Spruce Picea sitchensis (the most abundant species in UK plantations).

It would be interesting to know if there was any substantive spatial separation between the distribution of Spruce, Firs (and Larches) and that of Pinus sylvestris.

What are you wanting to know?

PS no-one willing to comment on my crossbill sketches?

 

[lewis20126]

Fairly safe to assume that Parrot Crossbills colonised Britain with Scots Pine; also very likely that Common Crossbill never successfully colonised Britain until spruce and larch plantations started maturing in the mid to late 1700s.

That all sounds highly likely.

My point about the extent of separation (i.e. a gap) between (say) Larch distribution and that of Scots Pine was that this separation (if it was substantive) would likely have reduced the extent of mixing between small-billed Crossbills and the Parrot types in the Scots Pines.

cheers, alan

 

[lewis20126]

PS no-one willing to comment on my crossbill sketches?

Don't give up the day job

cheers, a

 

[l_raty]

(the pollen maps are not very useful, as pollen can blow hundreds of km easily).

Ok, thanks--that was the missing piece of info, then.

Fairly safe to assume that Parrot Crossbills colonised Britain with Scots Pine; also very likely that Common Crossbill never successfully colonised Britain until spruce and larch plantations started maturing in the mid to late 1700s.

Fairly safe, then, to assume that crossbills colonised Britain with Pinus sylvestris.
But various southern European/North African populations are associated to Pinus spp, and are not called "Parrots": still unsafe IMO to assume "association to Pinus" = "Parrot Crossbill" outside the range of pytyopsittacus. (Southern populations not as extreme morphologically as pytyopsittacus; but this morphology possibly, if not probably, a more or less direct consequence of sympatry with a small-billed form; few Scottish specimens known to have shown this extreme morphology except in the last two decades.)

We know that Parrot Crossbils have no problem flying in and breeding from Scandinavia.

Yep.

Citing Lindsay once again: "It is now fairly evident that many of the birds that DNT and Alan Knox referred to as "Scottish Crossbill" are in fact what we today call "Parrot Crossbill" here in Scotland" and "Parrot Crossbill is the only real candidate for being the relict Caledonian species - an isolated population of Parrot Crossbill." If true, these Scottish breeding birds have always been there; and if they have always been there, what is the evidence that they flew in from Scandinavia?
(I don't say that it never happens, of course; but you take it as a proven, and I just don't believe that this can be done.)

The obvious case to look for is any future development of a thin-billed crossbill adapted to the small cones of Sitka Spruce Picea sitchensis (the most abundant species in UK plantations).

The problem being that, should this ever happen, we would probably just suddenly "know" that crossbills have no problem flying in and breeding from the Altai...

 

[Farnboro John]

Citing Lindsay once again: "It is now fairly evident that many of the birds that DNT and Alan Knox referred to as "Scottish Crossbill" are in fact what we today call "Parrot Crossbill" here in Scotland" and "Parrot Crossbill is the only real candidate for being the relict Caledonian species - an isolated population of Parrot Crossbill." If true, these Scottish breeding birds have always been there; and if they have always been there, what is the evidence that they flew in from Scandinavia?
(I don't say that it never happens, of course; but you take it as a proven, and I just don't believe that this can be done.)

I'm sure he can answer for himself, but the first Parrot Crossbills I saw in Britain were breeding in the pine belt at Wells Woods in Norfolk, where they were known not to have been until then - they may have flown in from Scotland (though I don't actually believe they did) rather than Scandinavia but they for sure flew in from somewhere - if not proven then very close to it, because there were other records that winter which would amount to nigh-on a total clear-out from Scotland. BB had a good article:

http://britishbirds.co.uk/wp-content/uploads/article_files/V78/V78_N10/V78_N10_P482_505_A118.pdf

Cheers

John

John

 

[Nutcracker]

That all sounds highly likely.

My point about the extent of separation (i.e. a gap) between (say) Larch distribution and that of Scots Pine was that this separation (if it was substantive) would likely have reduced the extent of mixing between small-billed Crossbills and the Parrot types in the Scots Pines.

cheers, alan

Distribution maps (natural distributions, excluding cultivated) of European trees here if it helps. Check Larix decidua, Picea abies, Pinus brutia, Pinus halepensis, Pinus nigra, Pinus sylvestris (other Pinus spp. not much used).

 

[Nutcracker]

BB had a good article:

http://britishbirds.co.uk/wp-content/uploads/article_files/V78/V78_N10/V78_N10_P482_505_A118.pdf

And of course none in central Scotland . . . because the ones there were "Scottish Crossbills" :t:

 

[Nutcracker]

But various southern European/North African populations are associated to Pinus spp, and are not called "Parrots": still unsafe IMO to assume "association to Pinus" = "Parrot Crossbill" outside the range of pytyopsittacus. (Southern populations not as extreme morphologically as pytyopsittacus; but this morphology possibly, if not probably, a more or less direct consequence of sympatry with a small-billed form; ....)

The (currently unanswerable) question is whether these southern thick-billed taxa evolved direct from Common Xb independently from Parrot Xb, or share a common ancestor with Parrot Xb after divergence from Common Xb. Or a mixture of both!

Citing Lindsay once again: "It is now fairly evident that many of the birds that DNT and Alan Knox referred to as "Scottish Crossbill" are in fact what we today call "Parrot Crossbill" here in Scotland" and "Parrot Crossbill is the only real candidate for being the relict Caledonian species - an isolated population of Parrot Crossbill." If true, these Scottish breeding birds have always been there; and if they have always been there, what is the evidence that they flew in from Scandinavia?
(I don't say that it never happens, of course; but you take it as a proven, and I just don't believe that this can be done.)
The problem being that, should this ever happen, we would probably just suddenly "know" that crossbills have no problem flying in and breeding from the Altai...

I'd think it is reasonable to assume there has always been periodic movement of Parrot Xb between Scotland and Scandinavia. From the Altai - well, it's possible, if a ringed Redpoll can move from China to Norway, likely crossbills can do much the same. So yes, I'd agree it'd be hard to prove whether crossbills adapting to Sitka Spruce have evolved in situ or just colonised from another small-coned spruce elsewhere (e.g. Siberian Spruce Picea obovata).

 

[lewis20126]

The (currently unanswerable) question is whether these southern thick-billed taxa evolved direct from Common Xb independently from Parrot Xb, or share a common ancestor with Parrot Xb after divergence from Common Xb. Or a mixture of both!

A "small-billed form" must surely be basal to the large-billed forms given the widespread Holarctic distribution of small-billed birds, so think your first suggestion is more likely, ie that the southern birds in the "Mediterranean forms" evolved from a widespread small-billed form, independently from the Parrot divergence (and likely later than it?).

cheers, alan

 

[Nutcracker]

Agree the small-billed form is ancestral (given that they evolved from redpoll-like birds), but I don't see why the medium-billed Mediterranean forms should have evolved independently (left diagram, below), rather than share a common ancestor with Parrot (right diagram, which I think more likely).

 

[lewis20126]

Agree the small-billed form is ancestral (given that they evolved from redpoll-like birds), but I don't see why the medium-billed Mediterranean forms should have evolved independently (left diagram, below), rather than share a common ancestor with Parrot (right diagram, which I think more likely).

I think it more like that the small-billed birds get stuck on the islands and evolve independently. This happens a lot - have a look at Crested Serpent Eagle island forms in Eastern Asia - a number of smaller island forms (eg West of Sumatra, Ryukyu chain etc) which must have evolved from larger ancestral forms. The same evolutionary drivers on very remote small islands. The Med islands / north African forms of Crossbill are probably responding to the same pressures, which I would guess are limited diversity of cones (Pinus), which would result in similar bill morphology.

cheers, alan

 

[Nutcracker]

I can see your reasoning there, but pines aren't like a series of islands; more a separate widespread habitat which Norway Spruce (larger, tougher cones than any other spruce, except similar-sized Picea smithiana in the western Himalaya) formed a stepping-stone towards. Once crossbills evolved bills large enough to cope with Norway Spruce cones, then they could start moving into pines, and once into pines, could diversify within them.

 

[lewis20126]

I can see your reasoning there, but pines aren't like a series of islands; more a separate widespread habitat which Norway Spruce (larger, tougher cones than any other spruce, except similar-sized Picea smithiana in the western Himalaya) formed a stepping-stone towards. Once crossbills evolved bills large enough to cope with Norway Spruce cones, then they could start moving into pines, and once into pines, could diversify within them.

I was talking about the actual islands (not metaphorical ones!), of the Balearics and Cyprus and (somewhat isolated) North Africa. So bog standard island endemism, with founder populations going off in a similar direction because of similar selective pressures.

Previously, in relation to the northern birds, I had speculated on gaps between conifer distributions (ie areas with no conifers!) reducing contact but that was a slightly separate point (which might be relevant to continental forms). Edit: Or even true island forms (such as the proto-Scottish Crossbill) is it reduces contact with the continental founding population.

cheers, alan

 

[Richard Klim]

Firs

Possibly of interest?

Xiang, Wei, Shao, Yang, Wang & Zhang (in press). Phylogenetic relationships, possible ancient hybridization, and biogeographic history of Abies (Pinaceae) based on data from nuclear, plastid, and mitochondrial genomes. Mol Phylogenet Evol. [abstract] [fig 7]

 

[Nutcracker]

Possibly of interest?

Xiang, Wei, Shao, Yang, Wang & Zhang (in press). Phylogenetic relationships, possible ancient hybridization, and biogeographic history of Abies (Pinaceae) based on data from nuclear, plastid, and mitochondrial genomes. Mol Phylogenet Evol. [abstract] [fig 7]

Of personal interest to me thanks, but probably not to any crossbills! I've never seen, nor heard of, crossbills using Abies (or Cedrus, either) as a significant food source.

 

[Peter Kovalik]

V. M. Loskot. Revision of crossbills (Aves: Fringillidae: Loxia) collected on Commander Islands and Kamchatka. Proceedings of the Zoological Institute RAS, Volume 319 (1), 2015.

PDF (in Russian) here