RockyRacoon
Well-known member
Hi again, another close group in evolution terms. Larus gulls this time, I am doing a personal project find out about these! So can anyone help?!
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Gulls this time Larus (1 Viewer)
- Thread starter RockyRacoon
- Start date
Rasmus Boegh
BF member
Jake Apps said:
It would be possible to write hundreds (if not thousands) of pages regarding what you ask... So, please specify your question.
Hi Jake,
I think Rasmus's sentiment might be why you've not had any other answers on this. In other words, Gulls make Crossbills look straightforward! :eek!: Even if you narrow it down to the 'Herring Gull group' it's still fantastically complex. Interesting though.
Have you thought of looking at Redpolls or maybe Chiffchaffs? Still pretty complicated (and unresolved) but I reckon that might be more manageable than gulls and you might get a more specific response from BF folks.
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I think Rasmus's sentiment might be why you've not had any other answers on this. In other words, Gulls make Crossbills look straightforward! :eek!: Even if you narrow it down to the 'Herring Gull group' it's still fantastically complex. Interesting though.
Have you thought of looking at Redpolls or maybe Chiffchaffs? Still pretty complicated (and unresolved) but I reckon that might be more manageable than gulls and you might get a more specific response from BF folks.
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Charles Harper
Régisseur
Michael Frankis
conehead
Hi Jake,
I don't know so much about gulls as redpolls or crossbills - but the details are probably fairly similar, with very low genetic divergence between all the different large gulls.
One thing I do suspect, and that is that a lot of the prescriptive characters cited as essential for identification for this, that, 'n' t'other large gull (particularly the exact wingtip patterns) are not yet well researched. They are based often on gulls of unknown origin studied on wintering ranges (or worse, as vagrants!), when the details should be looked at on known origin gulls (i.e., at the breeding colonies). I reckon most large gull taxa have more variation in wingtip pattern than at least some top gull enthusiasts would like to admit. The sort of thing like "this gull can't be an Xxxxx Gull, because the black subterminal band on the 6th primary is 2.761mm long and shaped like a 'd', and to be Xxxxx, it has to be shaped like a 'j' and between 2.762-2.763mm long" - I bet the prescription is based on 3 birds photo'd at an Essex tip, and if they went to a large breeding colony of them in Ukraine and measured a couple thousand birds, they'd find variation from 0-4.5mm . . .
Michael
I don't know so much about gulls as redpolls or crossbills - but the details are probably fairly similar, with very low genetic divergence between all the different large gulls.
One thing I do suspect, and that is that a lot of the prescriptive characters cited as essential for identification for this, that, 'n' t'other large gull (particularly the exact wingtip patterns) are not yet well researched. They are based often on gulls of unknown origin studied on wintering ranges (or worse, as vagrants!), when the details should be looked at on known origin gulls (i.e., at the breeding colonies). I reckon most large gull taxa have more variation in wingtip pattern than at least some top gull enthusiasts would like to admit. The sort of thing like "this gull can't be an Xxxxx Gull, because the black subterminal band on the 6th primary is 2.761mm long and shaped like a 'd', and to be Xxxxx, it has to be shaped like a 'j' and between 2.762-2.763mm long" - I bet the prescription is based on 3 birds photo'd at an Essex tip, and if they went to a large breeding colony of them in Ukraine and measured a couple thousand birds, they'd find variation from 0-4.5mm . . .
Michael
Rasmus Boegh
BF member
Actually, it has been shown that there is a faily large genetic variation in several of the larger gulls. But, the problem is, that it isn't possible to make fixed rules for how much divergence is needed for species recognition. An example: Some species (i.e. several of the Atlapetes Brush-finches) may show a divergence of less than 2% in say, mt-DNA, but clearly be different species as no interbreeding occurs where the distributions meet (if they do). In others (mostly widespread, i.e. some North Hemisphere gulls) there may be a variation of as much as 3%, but still they interbreed freely wherever they meet, meaning that the geneflow is substantial between populations! So, this is a very complicated matter, one that even many biologists have a hard time keeping up with. It would be easy if you could just say; here's the limit; if two populations differ more that x percent, they are different species. Sadly, that is not the way it is! You need more scientific studies involving different tools for analysis. All VERY complicated!
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spanishalex
Active member
Gull taxonomy does seem to be pretty mixed up. It is more due to the problems asociated with species concepts than anything else. Not all populations fit perfectly into the morphological species concept that we use out of convenience to separate closely related birds into distinct groups. In some cases like the gulls you get such a range of different morphologies that the entire population is best viewed as a complex rather than as a set of clearly defined species.
The yellow-legged gulls of the Canaries, for anyone who is interested, currently stand as such:
"The yellow-legged gull Larus cachinnans was previously considered a subspecies of the herring gull L. argentatus but is now considered a separate species in its own right closely linked to the lesser black-backed gull L. fuscus. The subspecies L. c. atlantis breeds on the Canary, Salvage, Madeira and Azores archipelagos. It is also sometimes referred to as L. michahellis atlantis".
The yellow-legged gulls of the Canaries, for anyone who is interested, currently stand as such:
"The yellow-legged gull Larus cachinnans was previously considered a subspecies of the herring gull L. argentatus but is now considered a separate species in its own right closely linked to the lesser black-backed gull L. fuscus. The subspecies L. c. atlantis breeds on the Canary, Salvage, Madeira and Azores archipelagos. It is also sometimes referred to as L. michahellis atlantis".
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