Taxonomic changes to the British List (1 Viewer)

[Mysticete]

Or they will do what ABA has done for Hawaiian/Galapagos and Fea's/Zino's Petrels, and put one spot on the list for a combined species.

 

[Richard Klim]

BOURC-TSC seabird splits

Bill Bourne and Andy Paterson on Seabird-News today...

Splits and lumps

"While the British Ornithologists' Union have suggested rearranging some seabird taxonomy as reported by Angus Wilson (Seabird-news 1790), this needs to be considered in the light of their past record. In the 19th century they fought a losing battle against trinomial taxonomy. When they surrendered to the next generation early in the 20th century they went in for exaggerated species lumping and subspecies splitting, it is alleged in an extreme case involving opposite wings of the same specimen. The doctrine then was that species can be recognised in the field but races only in the hand. Now that it has emerged that this lumped a lot of sibling species they have started splitting everything again. Is this practical? Considering the seabird cases involved:-

Calonectris (Cory's) Shearwaters. There are three forms involved: compared with the nominate one, originally called the Mediterranean Shearwater, Cory's is separable at sea with difficulty, and the Cape Verde more easily. Apart from a marked development of the usual ecogeographical rules they are all basically the same thing in most respects,

Madeiran/ Band-rumped Storm-petrels. It has been known that these included a number of local populations that behaved differently, notably in when they breed, for a long time, but it is not clear how otherwise they can all be told apart, and judging by the number now being reported at sea there may be more populations than have been found yet.

European Storm-petrel. The suggestion that there is a Mediterranean race is revived. I looked at an inadequate series of skins long ago and could see no difference. I suspect that they have seen no more, but I have not kept up with the debate.

Returning to practical considerations, if people try to separate the Calonectris shearwaters at sea, there might be an increase in useful informstion, but it may become less reliable, especially with the large ones. This will predominate with the storm-petrels, where it will be doubtful if such observations are of any use.

Is any useful purpose served by all this taxonomic splitting? The BOU is not an international authority, and on past form in a year or two their next taxonomic committee (on which I used to sit until I got fed up with it) will probably change their minds again. I agree with Dr Robert L. Flood DSc PhD BSc (1st Hons) that it might be better to follow more comprehensive authorities. It remains to be seen if Shirihai & Joiris will provide one.

Bill Bourne

Hi:

Like Bill Bourne, with whose views I concur, I too have I have been following with interest the discussion over the merits of speciation of the now former races of Cory's Shearwater Calonectris diomedea as well as the Band-rumped Storm-petrel Oceandoma castro group. Whilst I have never had any problem with accepting the speciation of Cape Verde Shearwater C. edwardsii as it is demonstrably different in 'at sea' conditions I have had great problems with and accept reluctantly the speciation of C. diomedea and C. borealis. I see both of these annually, often in large numbers, and have done so in Málaga Bay (where I live), the Canary Islands (most recently just N of Lanzarote a week since as well as several years ago), off Cape Hatteras, N.C. and in the Strait of Gibraltar and nearby Atlantic coast.

The justification for diomedea and borealis breeding together on the Chafarinas Islands is explained as 'some mechanisms of reproductive isolation are likely to be involved in maintaining their differences' which does not appear overly explicit. However, as Bill points out, 'at sea' separation of these two new species is not always simple and there is a small number of birds which appear to be intermediate in the white underwing distribution in the primaries and the presence and/or absence of the black outer primary, even with good views. I would much like to know from those more learned if this could indicate the presence of hybrids, and thus the possibility of incomplete sympatric isolation. I have seen such birds in all the above-mentioned areas with the exception of Cape Hatteras but am assured by local ornithologists that they have been seen there too.

With regard to the Band-rumped Storm-petrel splits (I have been watching and photographing these off Lanzarote a week since) and was faced with perplexing problem of a few in active primary moult (moulting 2CY summer non breeders or early moulting summer breeders?) with a far greater number in perfect primary condition (this year’s young birds or adult winter breeders?).

The question of Monteiro's and Cape Verde Storm-petrels seems satisfactory, although of improbable identification possibilities along with Band-rumped if found away from the breeding grounds, although Monteiro's has a small population restricted to the Azores and the Cape Verde species is believed to migrate southwards, so listers must go to see them where they breed. I note, as I am sure that others have, that the proposed Grant's Storm-petrel, a species suggested by Mullarney et al. in Petrels night and day has been left in abeyance by the Committee.

I have no strong opinion on the separation of the Mediterranean and Atlantic forms of Hydrobates but 'at sea' separation is impossible as far as is known, and I have, in theory, seen both these in the past two months.

And finally, a thought on splits: What use is it for the ordinary sea-going ornithologist such as myself if the relevant species can not be separated at sea and what will the effect of this be on defining their distributions? It seems to me that the various works of González-Solis of the University of Barcelona offers the best current solution in this respect.

Good seabirding

Andy Paterson
Torremolinos, España

 

[Ben Wielstra]

I know many people who cannot distinguish between a blackbird and a house sparrow. Does that mean these should be lumped?

 

[njlarsen]

I am not sure about listing and reporting in the UK, but Ebird actively promotes that uncertain sightings that can be determined to pair but not species should be reported and have lots of designators for such pairs (spuhs I think is the designation for such pairs).

Niels

 

[Richard Klim]

I know many people who cannot distinguish between a blackbird and a house sparrow. Does that mean these should be lumped?

Indeed. Ornithologists have been fortunate that for many years it's been feasible to identify most avian species in the field (unlike some other classes) - which has undoubtedly been very convenient for recording purposes. But there's no way that field diagnosability (eg, at sea) should be a requirement for the assignment of species rank.

 

[jurek]

I know many people who can distinguish between Blackbird male and female. Does it mean they should be split?

 

[Kirk Roth]

Indeed. Ornithologists have been fortunate that for many years it's been feasible to identify most avian species in the field (unlike some other classes) - which has undoubtedly been very convenient for recording purposes. But there's no way that field diagnosability (eg, at sea) should be a requirement for the assignment of species rank.

Exactly. Entomologists and botanists have accepted this fact for decades. Rather, the lack of "field diagnosability" is pretty well considered a noncontroversy and a fact of life (so to speak). Its time for ornithology to graduate, regardless of what it means for people's lifelists!

Just wait until we're splitting birds based on chromosome counts...

 

[Mysticete]

Odd...from looking over pelagic bird reports from the east coast, Scopoli's and Cory's appear to be fully identifiable at sea, with a decent look. By "at sea" do they mean seawatching, or a pelagic trip. I could see the former, but then seawatching is pretty much normally provides suboptimal viewing conditions.

I agree that Band-rumped might be difficult, but even there progress has been made in trying to sort out at sea identification, although what forms belong to what species is still a work in progress.

 

[Mysticete]

And don't forget rodents and salamanders, many of which are impossible to separate from closely related species in the field.

 

[MJB]

And don't forget rodents and salamanders, many of which are impossible to separate from closely related species in the field.

Not to the rodents and salamanders concerned...?
MJB

 

[njlarsen]

We know that some birds rely on UV vision to distinguish between closely related species, and I would not be surprised if it is our relatively poor ability to smell stuff that means we cannot separate those rodents.

Niels

 

[SteveO43]

Maybe not a rodent, but I do have a couple Mephitidae on my "Smelled only" list.

 

[njlarsen]

Maybe not a rodent, but I do have a couple Mephitidae on my "Smelled only" list.

Could you identify to species?

The only smelled only species I can remember was a pig that had spent some time in the forest in Dominica -- I have never seen the feral pigs here.

Niels

 

[Kirk Roth]

Odd...from looking over pelagic bird reports from the east coast, Scopoli's and Cory's appear to be fully identifiable at sea, with a decent look. By "at sea" do they mean seawatching, or a pelagic trip. I could see the former, but then seawatching is pretty much normally provides suboptimal viewing conditions.

I agree that Band-rumped might be difficult, but even there progress has been made in trying to sort out at sea identification, although what forms belong to what species is still a work in progress.

Lucky for you Brits, Steve Howell has already done most of the hard work in the IDs for all of the above:

http://www.amazon.com/Petrels-Albatrosses-Storm-Petrels-North-America/dp/0691142114

 

[Kirk Roth]

Maybe not a rodent, but I do have a couple Mephitidae on my "Smelled only" list.

I'm told that Spotted and Striped Skunks have different odors.

 

[Richard Klim]

Lucky for you Brits, Steve Howell has already done most of the hard work in the IDs for all of the above:
http://www.amazon.com/Petrels-Albatrosses-Storm-Petrels-North-America/dp/0691142114

Robb & Mullarney 2008 (Petrels night and day) does a pretty good job, with 36 pages on the Calonectris shearwaters and 36 pages on the band-rumped storm petrels, including plates, sonograms, and CDs with sound recordings.

 

[jurek]

Summing up Cory/Scopoli shearwaters: BOURC-TSC offered few or no arguments why they are more distinctive than previously thought. They are within the limit of what is traditionally considered parapatric subspecies. BOURC-TSC, in fact, changed the definition of species.

Which brings two interesting points.

First, BOURC-TSC may be very skilled in bird identification, but are not to my knowledge equal experts on taxonomic ranking. Species definition goes much beyond bird identification. I don't see how several people can proclaim to have the final word on it and expect all scientific and birdwatching community to obey. Goes against everything what science is about.

Second, split of Cory/Scopoli creates double standards in species rank among birds. To achieve consistency, tens, if not over a hundred, of well-marked races of birds in Western Palearctic need to be split into species. Likely including several American vagrants which in North America are lumped into subspecies.

 

[Richard Klim]

Going Dutch?

There's clearly been a significant change in BOURC's taxonomic approach in the last decade. At the turn of the century, CSNA/Dutch Birding had fully embraced the PSC, whilst BOURC adhered quite strictly to the BSC. But BOURC-TSC's 2003 guidelines for assigning species rank (Helbig et al) effectively positioned BOURC somewhere in between. And in recent years BOURC appears to be leaning even further towards the Dutch model – perhaps unsurprising given that George Sangster is the lead author of the TSC reports.

With a few notable exceptions, BOURC now seems to have a significantly lower threshold for species status than, say, AOU or BirdLife – a comparison between BOURC's guidelines and BirdLife's quantitative criteria for species delimitation (Tobias et al 2010) found the latter to be much more conservative. As Jurek suggests, the adoption of BOURC's guidelines on a wider geographical basis would result in large numbers of splits.

The following additional Dutch splits are of direct relevance to the British List. Given the recent trend, it seems likely that at least some will be adopted by BOURC in due course...

• Cygnus (columbianus) bewickii – Bewick's Swan
• Anser (fabalis) serrirostris – Tundra Bean Goose
• Branta (bernicla) hrota – Pale-bellied Brent Goose
• Branta (bernicla) nigricans – Black Brant
• Lagopus (lagopus) scotica – Red Grouse
• Pterodroma (feae) deserta – Desertas Petrel
• Milvus (migrans) lineatus – Black-eared Kite
• Circus (cyaneus) hudsonius – Northern Harrier
• Charadrius (mongolus) atrifrons – Lesser Sand Plover
• Larus (glaucoides) thayeri – Thayer's Gull
• Sternula (albifrons) antillarum – Least Tern
• Lanius (isabellinus) phoenicuroides – Red-tailed Shrike
• Lanius (excubitor) lahtora – Asian Grey Shrike
• Phylloscopus (trochiloides) plumbeitarsus – Two-barred Warbler
• Sylvia (cantillans) subalpina/moltonii – Moltoni's Warbler
• Zoothera (dauma) aurea – White's Thrush
• Oenanthe (hispanica) melanoleuca – Eastern Black-eared Wheatear
• Motacilla (flava) flavissima – Yellow Wagtail
• Motacilla (flava) thunbergi – Grey-headed Wagtail
• Motacilla (flava) cinereocapilla – White-throated Wagtail
• Motacilla (flava) feldegg – Black-headed Wagtail
• Motacilla (flava) tschutschensis – Eastern Yellow Wagtail
• Motacilla (alba) yarellii – Pied Wagtail
• Motacilla (alba) leucopsis – Amur Wagtail

 

[Mysticete]

Summing up Cory/Scopoli shearwaters: BOURC-TSC offered few or no arguments why they are more distinctive than previously thought. They are within the limit of what is traditionally considered parapatric subspecies. BOURC-TSC, in fact, changed the definition of species.

Which brings two interesting points.

First, BOURC-TSC may be very skilled in bird identification, but are not to my knowledge equal experts on taxonomic ranking. Species definition goes much beyond bird identification. I don't see how several people can proclaim to have the final word on it and expect all scientific and birdwatching community to obey. Goes against everything what science is about.

Second, split of Cory/Scopoli creates double standards in species rank among birds. To achieve consistency, tens, if not over a hundred, of well-marked races of birds in Western Palearctic need to be split into species. Likely including several American vagrants which in North America are lumped into subspecies.

While I will agree that BOURC is weighing the evidence for speciation differently than that of AOU, I do take issue with your statement that they "changed" the definition of species. Given that their are something like one hundred or so different species concepts, I disagree. They are defining species a different way than you might approve, but that doesn't mean they are "wrong". Species concepts and where you draw the limits between closely related forms are not a black and white issue. It's philosophy, not science, and people need to move away from this image that species are fixed entities that exist in nature and are easy to categorize.

 

[jurek]

While I will agree that BOURC is weighing the evidence for speciation differently than that of AOU, I do take issue with your statement that they "changed" the definition of species.

No matter of my personal preferences, BOURC definitely since last few years took a different, narrower view on species than before.

Given that their are something like one hundred or so different species concepts, I disagree. (...) Species concepts and where you draw the limits between closely related forms are not a black and white issue. It's philosophy, not science, and people need to move away from this image that species are fixed entities that exist in nature and are easy to categorize.

I agree that there are many definitions of species (only few of which are practically applicable to living birds), and that constant nature of change of living things means that there will be borderline cases in every species concept.

However, many people even casually interested in nature have a firm idea what "species" is. Which suggests that "species" is a concept which exists in society, and biologists only struggle to define it.

They are defining species a different way than you might approve, but that doesn't mean they are "wrong".

Lets leave aside my personal preferences, OK? I like many ticks as everybody else. Every serious party, if it uses one concept a species, should be able to define clearly why its chosen concept is better than all others. Other than being a novelty.

I can name several arguments why for birds it is very practical to use biological concept of species, apparently used by AOU and formerly by BOURC:
- It makes almost all individuals identifable in the field, helping field research.
- It makes hybrids and intermediate populations rare, avoiding using intermediate rank. Current science copes very poorly with hybrids. For example, if only hybrids exist in an area, does the list stand at X-and-a-half species? If a pure population is in danger of extinction but there is a large hybrid population, would it be a loss of biodiversity or not? These are examples of unsolvable problems.
- It is conceptually important for conservation, because loss of a species is loss of a significant part of genetic varability of the living world.
- It is practically useful for prioritizing conservation, because there are relatively few species. One can also protect subspecies if resources allow.
- It usually well matches layman understanding of different kinds of birds, bringing ornithology closer to general population.


In contrast, I can think of only one practical argument for narrow definitions of species:
- It makes more ticks for twitchers.