P.c.sinensis....? (1 Viewer)

HH75 said:

From memory, the late Clive Hutchinson's Birds of Ireland refers to tree-nesting carbo here, in the west of the country I think, but I'd have to take another look. Plus, at many freshwater colonies in Britain pioneered by sinensis, carbo are now dominant. So perhaps not as 'major' a difference in breeding requirements as you imply.

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I believe that at Abberton and Walthamstow, Sinensis is the dominant ssp? I think the last article/report (BTO?) I read, suggested 80/20% split in favour of sinensis at Abberton, and how certain can we be that the 20% were not dark sub-adults (5 years to mature..I believe?) surely they weren't ID'D on the gular angle, or the larger size (overall and bill?). When as stated the gular pouch has to be relaxed, all that precise information gleaned from a ''bobbing'' boat in the face of a stiff Northerly wind through bins or imaged, I couldn't reconcile the veracity of that data. If Steve Lister's comment regarding the Cormorants at Rutland are to be accepted, that no size difference was observed between Carbo and Sinensis? The whole situation regarding this taxa is beginning to emerge as a ''Can of Cormorants''.

KenM said:

I believe that at Abberton and Walthamstow, Sinensis is the dominant ssp? I think the last article/report (BTO?) I read, suggested 80/20% split in favour of sinensis at Abberton, and how certain can we be that the 20% were not dark sub-adults (5 years to mature..I believe?) surely they weren't ID'D on the gular angle, or the larger size (overall and bill?). When as stated the gular pouch has to be relaxed, all that precise information gleaned from a ''bobbing'' boat in the face of a stiff Northerly wind through bins or imaged, I couldn't reconcile the veracity of that data. If Steve Lister's comment regarding the Cormorants at Rutland are to be accepted, that no size difference was observed between Carbo and Sinensis? The whole situation regarding this taxa is beginning to emerge as a ''Can of Cormorants''.

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I am sure that nobody would just make an assumption that carbo moved in to colonies pioneered by sinensis, Ken, counter-intuitive as it is. And I doubt anyone is extrapolating based on sloppy data either. I seem to recall that DNA and birds measured and examined in the hand were involved in determining the mixed nature of many Cormorant colonies, and the increasing proportion of carbo in these over time. Yes, intergrades/hybrids will muddy the water, but there are surely genuine unequivocally-proven carbo nesting in these freshwater colonies.

HH75 said:

I am sure that nobody would just make an assumption that carbo moved in to colonies pioneered by sinensis, Ken, counter-intuitive as it is. And I doubt anyone is extrapolating based on sloppy data either. I seem to recall that DNA and birds measured and examined in the hand were involved in determining the mixed nature of many Cormorant colonies, and the increasing proportion of carbo in these over time. Yes, intergrades/hybrids will muddy the water, but there are surely genuine unequivocally-proven carbo nesting in these freshwater colonies.

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Yes, I would hope that there is indisputable evidence to support this, I'm still finding it difficult to adjust to the concept that a once "all black, rocky ledge marine loving Cormorant....should "gate crash" a smaller ssp from a freshwater "background", positively by comparison, festooned with an excess of white filoplumes and make in evolutionary terms, a "lightning" adaptation to tree nesting? For that to be so, I would expect the resulting hybrids to be biased towards the superior structure of carbo? All in all, requiring a quantum leap of faith, from my "historical" perspective.

KenM said:

and make in evolutionary terms, a "lightning" adaptation to tree nesting?...All in all, requiring a quantum leap of faith, from my "historical" perspective.

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Again, note my comments based on data from Hutchinson's Birds of Ireland. This was published in the mid-late 1980s, and the data referring to tree-nesting carbo in western Ireland may predate the time of publication substantially also. I don't have access to my copy right now, so I don't know off hand.
Given this fact, it is possible that tree-nesting carbo in Ireland weren't a completely novel phenomenon. Perhaps the taxon breeds in trees elsewhere in its range, for all I know it could do (it does in Britain now, of course). But many areas in which carbo is found lack sufficient trees...Iceland, for one. That, in combination with past persecution of Cormorants, may have reduced the frequency of the habit, but the tendency to nest in trees may have remained, latent, within populations. Or perhaps the British carbo are only spreading to freshwater habitats to breed of late, but even then, the habit would not be a 'lightning' adaptation, seeing as how it was known from over here already.

KenM said:

a once "all black, rocky ledge marine loving Cormorant"

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Also, this...carbo wasn't once 'all black'. Peter has provided numerous links to birds far outside the possible genetic influence of sinensis, in Iceland and the US, with heads that could hardly be described as all black.

Have you actually read the paoer linked to above by Mark Lewis?

I quote jost a couple of paragraphs (citations removed to improve readability):

" Until the 1940s, inland breeding was reported from just six sites, in Cumbria, Dorset, Kent, Norfolk (two) and Suffolk... At several of these sites, human persecution is thought to have curtailed breeding activity. The relative inaccessibility of coastal colonies in England probably allowed the coastal, cliff- nesting population to remain at a reasonably high level during this period."

...

"The establishment of an inland-breeding population of Cormorants in England between
1981 and 1995 has been well documented It is relevant to point out that inland breeding has also taken place in Scotland and Wales (in the latter country for centuries), and that there are tree-nesting Cormorants in Ireland. These colonies are, however, believed to be of the nominate race carbo, and are not part of the recent development in England discussed here."


...

"Although there is evidence that Continental birds (sinensis) have influenced the development of an inland-breeding Cormorant population in England considerably, ringed
Cormorants of the nominate form carbo,origi-nating from British colonies, have also been
observed at inland colonies during the breeding season (between April and June). These have included three birds from St Margaret’s Island (Pembrokeshire), two from Grune Point
(Cumbria) and one from the Farne Islands (Northumberland)."


...

"Further confirmation that mixed colonies of carbo and sinensis occur at inland sites in
England comes from DNA analysis."

I appreciate that much of what I have cited does not agree with what you thought you knew about the two taxa, but if you expect a discussion I think you need to be more specific in what reason there is not to trust aspects of ths paper, and I think `it does not fit with what I've been thinking for decades' is not really conducive to a debate on these issues.

Andrea

In a past thread (2012) Brett Richards mentioned a paper that speculated that there was a third subspecies of cormorant in the north Atlantic http://www.birdforum.net/showthread.php?t=245427. This has also been explored by Martin Garner in Birding Frontiers.

The article by L Marion and J Le Gentil is really quite instructive and suggest that the new subspecies P. c. norvegicus has more pronounced filoplumes than P.c. Carbo and similar gular angle. There are other differences and I can't help wondering if these birds are more widespread than suggested by the article. Occurrence in the UK has been suggested. The full text can be found via Google and well worth reading!

Ecological segregation and population structuring of
the Cormorant Phalacrocorax carbo in Europe, in relation
to the recent introgression of continental and marine
subspecies
L. MARION and J. LE GENTIL
Evolutionary Ecology (2006) 20:193–216

HH75 said:

Again, note my comments based on data from Hutchinson's Birds of Ireland. This was published in the mid-late 1980s, and the data referring to tree-nesting carbo in western Ireland may predate the time of publication substantially also. I don't have access to my copy right now, so I don't know off hand.
Given this fact, it is possible that tree-nesting carbo in Ireland weren't a completely novel phenomenon. Perhaps the taxon breeds in trees elsewhere in its range, for all I know it could do (it does in Britain now, of course). But many areas in which carbo is found lack sufficient trees...Iceland, for one. That, in combination with past persecution of Cormorants, may have reduced the frequency of the habit, but the tendency to nest in trees may have remained, latent, within populations. Or perhaps the British carbo are only spreading to freshwater habitats to breed of late, but even then, the habit would not be a 'lightning' adaptation, seeing as how it was known from over here already.

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I quote from Birds in Ireland: "During the 1968-1972 period of the Breeding Atlas they (Cormorants) were proved to nest inland in Clare, Galway, Kerry, Roscommon and Donegal. The largest inland colonies are on Lough Scannive (218 nests) and Lough Cutra (166 nests) in Galway". Earlier, there was reference to "inland breeding birds" nesting "on islands in lakes or in trees".

HH75 said:

I quote from Birds in Ireland: "During the 1968-1972 period of the Breeding Atlas they (Cormorants) were proved to nest inland in Clare, Galway, Kerry, Roscommon and Donegal. The largest inland colonies are on Lough Scannive (218 nests) and Lough Cutra (166 nests) in Galway". Earlier, there was reference to "inland breeding birds" nesting "on islands in lakes or in trees".

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Would we know Harry if they were ''Classic'' carbo (all dark), or with variable frosting during this period?

cheers

Looking through a publication from the early 1970's I found a photo of Cormorants nesting on the Farne Islands. Although this one photo does not prove anything it seems to shows a group of "black headed" British rock nesting Cormorants circa 40 years ago. The article was in a popular magazine of the period (World of Birds - Volume 1), edited by John Gooders.

second picture in the linked thread shows a bird on a cliff in cornwall with extensive white on the head

http://www.birdforum.net/showthread.php?t=302388

http://www.birdforum.net/attachment.php?attachmentid=538871&d=1428348527

shhh said:

second picture in the linked thread shows a bird on a cliff in cornwall with extensive white on the head

http://www.birdforum.net/showthread.php?t=302388

http://www.birdforum.net/attachment.php?attachmentid=538871&d=1428348527

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Thanks for that shhh, am yet to see an image of a bird as above, sitting on a "cliff" nest in a maritime/marine situation.

Cheers

KenM said:

Thanks for that shhh, am yet to see an image of a bird as above, sitting on a "cliff" nest in a maritime/marine situation.

Cheers

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some of the birds in this picture are still showing a lot of white:

http://jonathanmclachlan.co.uk/wp-content/uploads/2012/04/L1034614.jpg

Theres some info on the position of carbo / sinensis in Wirral and Cheshire here.
http://www.deeestuary.co.uk/news.htm

p.s. The amount of white filoplumes on the neck and head are dependant on age, not taxon. carbo differs from sinensis in the shape of the feathering on the malare and gular areas.