Proposal (353) to South American Classification Committee

 

Move Anser anser (Graylag Goose) to main list

 

Effect on South American Checklist: This proposal would add an introduced species to the Main List.

 

Background: This Greylag Goose (or the Domestic Goose) Anser anser is considered introduced in the Falkland Islands (Malvinas) (e.g. Fjeldså & Krabbe 1990). Recent sources treating the species as introduced in these islands include Falklands Conservation and BirdLife International: 

 

http://www.falklandsconservation.com/wildlife/fauna_chklst.html
http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=378&m=1 

There are also small feral populations of Greylag Goose in Bogotá, Colombia (Salaman et al. 2008) and others elsewhere throughout the Andes (Fjeldså & Krabbe 1990). For example, BirdLife also lists Anser anser as introduced in Argentina (as well as the Falklands, above). The species is common in domestication and has established feral populations in many countries.

 

Falkland Islands records are the sole basis for this proposal. No other populations referred to in this proposal have been considered in published work to be of sufficient size to be 'established'.

 

Persons looking for a reason to vote no on this one might point to the lack of a detailed population study. I offer no view or special information relating to this proposal, but simply noted the species' omission from the SACC list and feel it ought to be considered for inclusion. See Proposal 352 for discussion of generic issues relating to introduced species and references.

 

Thomas Donegan, May 2007

 

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Comments from Stiles: "NO. What bothers me on these two (including #352) is just what the evidence is for considering these two species really "feral" and "established". True, individuals of some introduced populations in parks or fincas may nest without human assistance - but does this really constitute the establishment of feral populations? I have never seen mallards (or geese - and here one must specify what species as there are several present in at least Colombian parks and fincas) nesting away from humans or independent of humans for at least much of their food and protection, etc. So, I'd like more information before approving these proposals."

 

Comments from Stotz: "NO. I don't know the situation on the Falklands, but in the absence of specific data indicating establishment, I can't vote for this proposal."

 

Comments solicited from Robin Woods: "On pages 141-143 of my Guide to Birds of the Falkland Islands (1988), there is a fairly full description of the species, including voice, food, habitat, status and breeding with records of localities and numbers.  In our 1997 Atlas of Breeding Birds of the Falkland Islands, on pages 72-73,  all the evidence available at the time for recognising the presence of naturalised Domestic Geese is quoted and for want of stronger evidence, I labelled the species as Anser anser.  In my opinion there is no question that the intermittent introduction of domestic geese by several people since the late 18th century has led to complete naturalisation and the establishment of truly wild, self-sustaining populations at several localities.  I consider therefore that this species should definitely be added to the SACC list with the status IN for the Falkland Islands and listed as Feral Domestic Goose 'Anser anser'., not Graylag Goose.

 

"If anyone questions the availability of a population study in response to this backing for Thomas' proposal, they should consult our Atlas where they will find an assessment of the records I was able to collect over the period 1983-1992.  Incidentally, I believe that the possibility of eventual dominance over the native Upland Goose Chloephaga picta is extremely unlikely.  This has been suggested by some observers locally, perhaps because a few feral geese at a much-visited Magellanic Penguin-viewing point for tourists near Stanley have appeared to be rather aggressive."

 

Comments from Remsen: YES. By virtually any criteria for "establishment," Anser anser seems to fit (for Falklands) based on Robin's comments above."

 

Comments from Cadena: "YES. I think that the case for Colombia is rather weak as it doesn't really seem that there is a self-sustaining population here, but the information from the Malvinas leaves no doubt."

 

Comments from Robbins: "YES, based on Robin Wood's comments."

 

Additional comments from Stotz: "I change my vote on proposal 353 to Yes based on Robin Woods' discussion of the situation on the Falklands/Malvinas.  However, I think I disagree with him that we should use Feral Domestic Goose as the English name instead of Graylag Goose."

 

Comments from Nores: "YES, especialmente por las razones dadas por Robin Woods. En Argentina figura en la lista de Mazar Barnet y Pearman como introducido, pero yo no se si hay seguridad de que la especie nidifique libremente en la naturaleza. Yo he visto nidificando a esta especie en una laguna en Córdoba, pero la laguna estaba al lado de una casa y los gansos, aunque volaban dentro de la laguna, eran evidentemente de la casa."

Comments from Zimmer: "YES, and groan! Could there be anything less inspiring to vote on?"

 

Comments from Schulenberg: "NO. I'm not satisfied by the evidence of an established population on the Falklands Islands. I should say at the outset that I never have been to the Falkland Islands. Almost all that I know about the birds there is from the literature.

 

"To my knowledge, Anser first was reported from the Falklands by Woods in 1988 (Woods, R. W. 1988. Guide to birds of the Falkland Islands). I'm not sure when Woods first became aware of the presence of this goose on the Falklands, only that it was not mentioned at all in the earlier guide (Woods, R. W. 1975, Birds of the Falkland Islands).

 

"Woods 1988 traces the origins of this population back to a pair, apparently unsuccessful breeders, that was "taken to" West Point Island in 1935, and a pair "of the curly-feathered 'Sebastopol' breed imported to West Point" in 1944. Numbers reportedly reached "about 50" by 1955, and "over 130" by October 1983. What catches me short is the description in Woods 1988 of those 130-odd birds that were carefully counted in 1983: "Fifty-seven were pure white, 68 brown/white smooth-feathered, three white Sebastopol and four brown/white Sebsatopol birds were counted."

 

"Also, by 1983, the birds had spread beyond West Point Island to nearby sites. The 1997 Atlas provides little new information. The geese have spread to new localities on the Falklands, but the total population remains small (although it was estimated to be in the range of 300-600 pairs). More importantly, there is no new information on the plumages of these birds.

 

"I'm not aware that SACC has any formal guidelines on criteria for recognizing a population as established. And I'm not aware of any other body having as one of the criteria that the feral population in question should have reverted to "wild" type. No doubt these geese are breeding on the Falklands. Otherwise, all I know is that between 1944 and 1983, these geese still retained the look of barnyard geese, not the "wild" type. I don't know if I just am way off the mark in guessing how many generations it might take for "wild" phenotypes to reemerge in the absence of selection for them, or if the persistence of "barnyard" types suggests that, breeding notwithstanding, a steady stream of ongoing introductions is helping to maintain this population. But despite evidence of some level of local breeding, I have trouble bringing myself to vote in favor of this as an established population, based on the little that I know about the Falklands situation."

 

Additional comments from T. Donegan: "With respect to Tom Schulenberg's comments, as noted in the Mallard proposal, the fact that an introduced population shows leucisms or domestic plumage traits should not affect its status.  Columba livia is on the SACC list, and many South American populations of that species are melanistic or leucistic (not just the captive ones).  Although one might not like these or other alien invaders very much, rejecting the inclusion on the SACC list of a long-established population of 300-600 birds (=No vote) is not sensible.  Such strong data is not available for many of the introduced passerines already on the SACC list."

 

Comments from Jaramillo: "NO - I agree with Schulenberg here that I am more comfortable accepting a wild type population than one that is clearly domestic in origin and phenotype. One reason is aesthetics, and I realize that is not very objective, but then again there is always some subjectivity in what we do and particularly in cases like these. I understand T. Donegan's point, and I think it is a good one, perhaps we should evaluate Rock Dove (Pigeon if you want to call it that) more closely, and in particular it should be assessed carefully in country lists to clarify if the populations are indeed truly wild or being maintained by releases. With these geese, one of the problems I have is that they may be maintained or at least partially maintained by farm escapees; at least it is not clear if this has been entirely discarded as a possibility. Overall I would rather not ever accept feral and domestic phenotype birds at all, but realize that we have some grey, or should I say gray areas here. There is a great deal of difference to me between releasing wild type Graylags from Europe, versus barnyard escapees of Greylag type domestic geese. It may well be just an aesthetic difference in the end, but I think it does also have some biological relevance."

 

Additional comments from Stiles: "In view of Robin Woods's comments, I will change my vote on this one to YES. If the geese are now feeding and breeding away from humans and (this is to me a key point) expanding on their own into additional "wild" areas, then they should be considered "established". (This is not occurring in Colombia with either geese or mallards, to my knowledge). Regarding aesthetics, I do not regard "wild-type" plumage as particularly relevant here - the situation is not necessarily comparable to that in, say, fruit flies where the "wild-type" phenotype is tied to multiple developmental pathways. If mutant plumage type birds can survive, breed and spread along with "wild-types" without continual human releases, they are simply not being selected against as ferals. Here plumage coloration is a much more superficial feature that may not have anything to do with survival and breeding possibilities: the birds simply may not be "programmed" to select wild-type plumage over other, unrelated attributes. The Rock Dove illustrates this point perfectly. Cities, with their ledges, crevices and crannies in manmade structures, are now "natural" habitats for this species, which has apparently spread on its own into this habitat worldwide - it seems far-fetched to postulate separate human introductions in every city! While they feed mostly on human scraps and refuse, most of this is not specifically provided for them by humans and if people everywhere were to stop feeding bread in city parks, I very much doubt that Rock Doves would rapidly go extinct in cities worldwide. House Sparrows have declined in many areas as horses were replaced by motor cars and horse dung as a source of seed became scarce - but they are a long way from extinction, including in areas where they are naturalized!"

 

Comments from Pacheco: "YES. Parece-me claro que a espécie -- ainda que derivada de um estoque doméstico -- está estabelecida nas Falklands."