Imperial Cormorant (1 Viewer)

On January 7, John Boyd rearranged the cormorants: http://jboyd.net/Taxo/changes.html :

"The cormorants have been rearranged in accordance with Kennedy et al. (2000). Further, King Cormorant, Phalacrocorax albiventer, was merged into Imperial Cormorant, Phalacrocorax atriceps; Antarctic Shag, Phalacrocorax bransfieldensis, and South Georgia Shag, Phalacrocorax georgianus, were split from Imperial Cormorant, Phalacrocorax atriceps."

I am fine with the whole rearrangement, but I am wondering about the 2 splits. Is there any recent study that would support this opinion ?

I'm not aware of any recent study, but bransfieldensis and georgianus are split by (at least) Orta 1992 (HBW1), Monroe & Sibley 1993, Enticott & Tipling 1997 (Photographic Handbook of the Seabirds of the World), Mazar Barnett & Pearman 2001 (Annotated Checklist of the Birds of Argentina), Couve & Vidal 2003 (Birds of Patagonia, Tierra del Fuego & Antarctic Peninsula), Jaramillo 2003 (Birds of Chile), Pugnali 2008 (Checklist of the Birds of Argentina, Antarctica & South Atlantic Islands) and Cornell/Clements.

But Jaramillo remarks:

• Phalacrocorax bransfieldensis - "Recent literature affords species status to this taxon, separating it from Imperial Cormorant. The two differ biometrically, in plumage and behavioural repertoire (Siegel-Causey & Lefevre 1989, Holocene records of the Antarctic Shag (Phalacrocorax [Notocarbo] bransfieldensis) in Fuegian waters). However a thorough molecular study is required to independently corroborate or refute the species-level hypothesis of these two forms."
  
• Phalacrocorax georgianus - "Recent literature often affords species status to this taxon, separate from Imperial Cormorant. The details for considering this, and Antarctic Cormorant, separate from Imperial Cormorant or from each other are unclear. Molecular work is needed to determine relationships within this group."

AOU SACC also notes:

• "Some recent authors (eg, Siegel-Causey 1988, Siegel-Causey & Lefrevre 1989, Sibley & Monroe 1990, Orta 1992, Jaramillo 2003) have considered the subspecies bransfieldensis of Antarctica and South Shetland Island to deserve recognition as a separate species from Phalacrocorax atriceps. Proposal needed."

Richard

Richard Klim said:

[...] bransfieldensis and georgianus are split by (at least) [...]

Click to expand...

I'm not sure I would use South American references here, because they presumably only cover atriceps, "albiventer", bransfieldiensis and georgianus, thus offer an incomplete treatment of the group. Among the sources that cover the range of the entire group, HBW1 and Cornell/Clements further split nivalis (Heard Shag), purpurascens (Macquarie Shag), and melanogenis (Crozet Shag). (And so does Shirihai 2002: A complete Guide to Antarctic Wildlife.)

My understanding is that the former "traditional" treatment (e.g., still recognized in H&M3) used to lump white-cheeked taxa in one species (Ph. atriceps, incl. bransfieldiensis, georgianus and nivalis), and black-cheeked taxa in another (Ph. albiventer, incl. melanogenis and purpurascens; sometimes also verrucosus, although this one differs from all the others on other grounds). But the current trend is to dismiss albiventer (black-cheeked) as a morph of atriceps (white-cheeked), based on apparent lack of reproductive isolation in sympatry, and lack of osteological differentiation in South America - in which case this dichotomy doesn't hold anymore and the entire construction presumably falls down...

In a treatment that lumps atriceps with albiventer, splits bransfieldiensis and georgianus, but does not split nivalis, melanogenis and purpurascens, where are the latter three supposed to end up? (And why?)

l_raty said:

In a treatment that lumps atriceps with albiventer, splits bransfieldiensis and georgianus, but does not split nivalis, melanogenis and purpurascens, where are the latter three supposed to end up? (And why?)

Click to expand...

Well, Sibley & Monroe 1990 (and Monroe & Sibley 1993), and Enticott & Tipling 1997 recognise as species:But I don't know how this was justified! Probably just a consequence of leaving unsplit forms lumped with the senior (nominate) group member as a simplistic default position?

Richard

Imperial/King Cormorants in Patagonia

On a visit to Chile in October 2008, all of the dozens of birds seen well on/near Isla Grande de Chiloé were white-cheeked (Imperial/Blue-eyed) types; but the overwhelming majority of the hundreds lining the jetties at Punta Arenas on the Strait of Magellan were black-cheeked (King) types.

Can anyone (particularly our Southern Cone specialists) give any further insight into the status of these interesting birds (subspecies, races, colour morphs...), eg: Where approximately is the main transition zone? Have the respective ranges changed over time? Are there significant mixed colonies anywhere? Are mixed pairs frequent? How common are Imperial/Blue-eyed types on the coast of Argentina?

And what is the current consensus on whether Patagonian King-type birds should be considered to be 'albiventer', or just a colour morph of atriceps sensu strictu (with true albiventer restricted to the Falkland Islands - as per Harrison 1983, Orta 1992, Enticott & Tipling 1997 and Cornell/Clements)?

Richard

Richard asks a good question. Essentially, the white cheeked creature is Pacific, and the Dark-cheeked creature is Atlantic. So in Chiloe there will only be White-cheeked ones, in Puerto Natales in the southern Fjords they are white-cheeked and every so ofte a dark cheeked one is there. In the Strait of Magellan they are mixed up, and proportion of dark cheeked birds increases as you head closer to the Atlantic. The work of Pamela Rasmussen is what you need to look up for some data on this. I have no idea what is going on, but I don't buy that they are color morphs. If anything they are two separate populations (subspecies? species?) that have a zone where they hybridize. I guess the issue is that the young are not intermediate but are one or the other cheek type. Someone has to head down and figure out if these are separate genetic populations, or what. My guess is also that the birds on the Falklands are probably something else altogether. For further mysteries in the old publications on Cape Horn, and I can look up the author, he mentions that there were two types of Imperial Cormorant there. One that was larger and shy, flew from the colonies when observers approached. Then there was a smaller creature that was very tame. What do we do with that info? It is all very confusing - cheers Alvaro Jaramillo.

I was looking at the information in this thread and the info in Jaramillo's Chile Guide and tried to make some sense of one thing: Both Antarctic and South Georgia Shags are said to occur on South Sandwich and South Orkney Islands, but there also is a note on them being allopatric. I cannot make those two things connect to one meaning?

thanks
Niels

njlarsen said:

Both Antarctic and South Georgia Shags are said to occur on South Sandwich and South Orkney Islands, but there also is a note on them being allopatric. I cannot make those two things connect to one meaning?

Click to expand...

I suspect that this might be an error in Alvaro's guide.

Couve & Vidal 2003 (Birds of Patagonia etc) gives:

• Antarctic Shag - Antarctic Peninsula, South Shetland & Elephant Islands
• South Georgia Shag - South Georgia, South Orkney & South Sandwich Islands

Orta 1992 (HBW1), Enticott & Tipling 1997 (Seabirds of the World), and Cornell/Clements are consistent with this.

Does anyone know what Shirihai 2002 (Antarctic Wildlife) has to say?

Richard

Richard Klim said:

Couve & Vidal 2003 (Birds of Patagonia etc) gives:

• Antarctic Shag - Antarctic Peninsula, South Shetland & Elephant Islands
• South Georgia Shag - South Georgia, South Orkney & South Sandwich Islands

Orta 1992 (HBW1), Enticott & Tipling 1997 (Seabirds of the World), and Cornell/Clements are consistent with this.

Does anyone know what Shirihai 2002 (Antarctic Wildlife) has to say?

Richard

Click to expand...

He gives the same distribution.

Thanks for the clarification.

Niels

Well, I quoted from the sources that I had to hand – but I still reckon that there's some rather over-zealous/simplistic pigeon-holing (shag-holing?!) going on with these taxa...

Richard

Rock & Imperial Shags

Calderón, Quintana, Cabanne, Lougheed & Tubaro (in press). Phylogeography and genetic structure of two Patagonian shag species (Aves: Phalacrocoracidae). Mol Phylogenet Evol. [abstract]

[Related: Magellanic Cormorant attacks ornithological innuendo!]