Rethinking Europe's White-bellied Storm-Petrel and Cape Gannet

In two recent issues of Dutch Birding (see citations below), Pierre-André Crochet and Marcel Haas published short articles arguing for (declaring?) for the removal of White-bellied Storm-Petrel (Fregetta grallaria) and Cape Gannet (Morus capensis) from the Western Palearctic list.

It isn't clear to me whether these pronouncements come in an official capacity (as the article titles would suggest) or merely recommendations of concerned members of the ornithological community. Regardless, both cases are compelling and the story of the Cape Gannet provides a particularly interesting lesson in retrospective interpretation of specimen data.

White-bellied Storm-Petrel: The addition of White-bellied Storm-Petrel is based on a sight report made at sea (23.48 N, 22.01 W, 17 Aug 1986) between the Canary and Cape Verde Islands. Expert evaluation of the description by Mike Imber, Tony Palliser and Paul Scofield concluded that the description is not sufficient to rigorously exclude Black-bellied Storm-Petrel (F. tropica). As an interesting aside, Crochet and Haas mention a 'white-bellied' population of Black-bellied Storm-Petrels nesting on Tristan da Cunha in the South Atlantic. Tristan da Cunha seems a reasonable point of origin for non-breeding birds venturing into the North Atlantic but the taxonomic status of these populations seems confusing and ultimately might impact future records. In Albatrosses, Petrels and Shearwaters of the World (2007 Helm/A&C Black/Princeton UP), Derek Onley and Paul Scofield state that both Black-bellied (F. t. melanoleuca) and White-bellied Storm-Petrel (F. g. leucogaster) nest in the archipelago and that the latter are morphometrically closer to Black-bellied than other populations. I would be interested to hear more about these birds and whether there are any DNA studies that might address their affinities. Photographs of either species taken at sea near the islands might also be interesting. Getting back to the main thread, another concern with the Western Palearctic sighting is the fact that three unambiguous Black-bellied Storm-Petrels have been now been photo-documented off North Carolina USA (31 May 2004, 16 July 2006 & 23 June 2007), further reinforcing the necessity for a water-tight description or better still photographs or specimen to document occurrence in the WP.

Cape Gannet: Inclusion of Cape Gannet is based on a single ring (band) return with a wonderfully convoluted back story. The ring information was transmitted by the Moscow Ringing Center to SAFRING in Cape Town stating the ring number, 30 May 1966 recovery date and recovery locality "21:40 N, 13:55 E". In the SARING records, '17deg 00, Western Sahara' was hand written over the locality information, the reason being that 21:40 N, 13:55 E is in the desert of northern Chad!

Crochet and Haas consider it likely that a Russian fisherman submitted the original ring information to the MRC, as there was an extensive Soviet fishing fleet operating off Africa. They are troubled, however, by the fact that the original coordinates were most likely wrong. Rather than making up new coordinates (as appears to have been done by anonymous author of the hand written note) they considered the common mistake of mixing up N and S or E and W. Swapping E & W puts the gannet much further into the desert but changing the N/S coordinate to 21:40 S, 13:55 E places the bird a few miles off the coast of Namibia where Cape Gannet is abundant. Indeed the MRC has many Cape Gannet ring recoveries from this area made by Soviet trawlers. They quote Terry Oatley of SAFRING "It is far more likely that the Russian Ringing Center mislabelled the latitudinal co-ordinates N out of force of habit (since the vastmajority of recoveries processed by them are from the northern hemisphere, and the same error was finding its way into the Euring data band when I visited it in 1994)". This strikes me as an elegant piece of detective work and provides the simplest reinterpretation of the original coordinates.

Apparently there are no other credible reports of Cape Gannet from the Western Palearctic but I recall an article in BIRDWATCH magazine some years back discussing sightings of candidates from southern Spain. What's the story there? Like many seabird enthusiasts on the eastern seaboard of the United States, I keep an eye on migrating Northern Gannets in hopes of finding a Cape. Given the movement of both species towards the tropics, vagrancy would not seem impossible.

Crochet, P-A. and Haas, M. (2008) Western Palearctic list update: deletion of White-bellied Storm-Petrel. Dutch Birding 30(2):103-104.

Crochet, P-A. and Haas, M. (2008) Western Palearctic list update: deletion of Cape Gannet. Dutch Birding 30(1):17-18.

I thank Brian Patteson for updating me on the NC storm-petrel sightings.