Initial deadline for comments: 31 January 2012.
BirdLife species factsheet for White-winged Scoter (prior to the taxonomic change)
White-winged Scoter Melanitta fusca has been split into M. fusca, M. deglandi and M. stejnegeri following a review of recent literature (Livezey 1995, Garner et al. 2004, Sangster et al. 2005, Collinson et al. 2006, AOU 2010) and museum specimens by the BirdLife Taxonomic Working Group. Prior to this taxonomic change, the polytypic species M. fusca was listed as being of Least Concern on the basis that it was not thought to approach the thresholds for Vulnerable under any of the IUCN criteria.
Following the taxonomic change, all three species are still regarded as having extremely large ranges and hence do not approach the thresholds for Vulnerable under the range size criteria (B and D2: EOO of less than 20,000 km2, combined with a declining or fluctuating range size, habitat extent/quality or population size, and a small number of locations or severe fragmentation). Their population sizes are also large (probably >500,000 individuals in M. deglandi, which has the smallest population; Wetlands International 2006), and hence do not approach the thresholds for Vulnerable under the population size criteria (C and D1: fewer than 10,000 mature individuals with a continuing decline estimated to be at least 10% over ten years or three generations, or with a specified population structure).
Therefore, the only relevant criterion is A, which relates to reductions in population size. Until recently, there was little evidence to suggest that any of these taxa were declining sufficiently rapidly to approach the threshold for listing as Vulnerable under criterion A (at least a 30% decline over ten years or three generations, whichever is longer).
This species breeds in Scandinavia and western Siberia to the River Yenisey, and winters mostly in the Baltic Sea and along the coasts of Western Europe (c.1 million birds; Wetlands International 2006), with only an estimated 1,500 birds wintering in the Black Sea and Caucasus (Wetlands International 2006). Since surveys in 1992-1993, when the estimate of the north-west European wintering population of M. fusca was updated to c.1 million birds, an apparent decline of c.60% (3.7% annually) has been detected in the Baltic Sea, with counts in 2007-2009 putting the wintering population at c.373,000 individuals, down from c.933,000 in 1992-1993 (Skov et al. 2011). Extrapolation of the data implies that this is equivalent to a decline of c.77% over three generations, estimated at 23 years (based on a generation length of c.7.5 years; BirdLife International unpubl. data).
The Baltic Sea is the most important wintering area in the world for this species, holding c.93% of the global population in 1992-1993. It seems unlikely that the proportion of the total north-west European wintering population present in the Baltic has dropped from 93% to 37% (see Skov et al. 2011), thus a rapid decline has probably taken place. This is supported by reports of probable declines elsewhere in its range, e.g. in the UK (Holt et al. 2011)
It is possible that the lower numbers recorded in the Baltic (and possibly elsewhere in north-western Europe) relate not to a population decline, but to changes in the species’s winter distribution. In recent decades, many waterfowl species have responded to global climate change by ‘short-stopping’, i.e. taking advantage of warmer conditions to winter closer to northern breeding areas than was previously possible. M. fusca may have been affected by this phenomenon, and there is some evidence for a partial northwards shift in the species’s distribution within the Baltic (Skov et al. 2011). However, this is not capable of explaining the whereabouts of the c.600,000 birds ‘missing’ from the Baltic. It is possible that some birds may now be wintering in the White Sea or Barents Sea off north-western Russia, but there is no evidence for this.
Assuming therefore that the decline recorded in the Baltic is genuine, then globally the species may be declining at a rate of more than 70% over three generations, which would qualify the species for uplisting to Endangered under criterion A. Comments would be welcomed.
This species breeds in Canada, Alaska and the very north of the contiguous United States, and winters mainly off both the Atlantic and Pacific coasts of North America, reaching farther south than when breeding. Most indices have indicated population declines; however, it has not been possible to reliably estimate the magnitude of the declines (Sea Duck Joint Venture 2003). The species is said to have declined nearly to the point of extirpation in the prairie biome. However, the number of birds formerly occupying this portion of the range cannot be estimated. Data from the US Fish and Wildlife Service–Canadian Wildlife Service breeding waterfowl survey indicate that the combined population of all three scoter species along survey transects in the western boreal forest may have declined by as much as 75% since the 1950s. However, it is not possible to separate trends specific to M. deglandi and the magnitude of the decline for this species cannot be ascertained. Trends have not been apparent in other parts of the species’s breeding range. Mid-winter inventory data do not indicate any trends on the Pacific coast and only weakly show a decline on the Atlantic coast. However, these surveys are said to track scoter populations poorly and all three species are combined in one count (Sea Duck Joint Venture 2003). Contrary to many other studies, analysis of Christmas Bird Count data overall indicates an annual increase of 1.20% between 1965-1966 and 2005-2006 across about half of its range (Butcher and Niven 2007), implying that this species may in fact qualify as Least Concern. Comments would be welcomed.
This species breeds in central and eastern Siberia east of the River Yenisey, and winters along the coasts of East Asia. It is estimated to number 600,000-1,000,000 birds; however, population trends are apparently unknown (Wetlands International 2006). Information is requested on this species’s population trends to assist in the assessment of its threat status against criterion A.
Further information is requested and comments are invited on whether the population of M. fusca is likely to have declined at a rate equivalent to 50-79% over the past three generations, and thus whether it qualifies for listing as Endangered under criterion A. Under the same criterion a decline of at least 30% over three generations would qualify the species for Vulnerable, while a decline approaching 30% (typically 20-29%) would qualify the species for Near Threatened. Comments are also invited on the potential listing of M. deglandi as Least Concern.
American Ornithologists’ Union (2010) Fifty-first Supplement to the American Ornithologists’ Union Check-list of North American Birds. Auk 127: 726-744.
Butcher, G. S. and Niven, D. K. (2007) Combining Data from the Christmas Bird Count and Breeding Bird Survey to Determine the Continental Status and Trends of North American Birds. Ivyland, PA: National Audubon Society.
Collinson, M., Parkin, D. T., Knox, A. G., Sangster, G. and Helbig, A. J. (2006) Species limits within the genus Melanitta, the scoters. British Birds 99: 183-201.
Garner, M., Lewington, I. and Rosenberg, G. (2004) Stejneger’s Scoter in the Western Palearctic and North America. Birding World 17: 337-347.
Holt, C. A., Austin, G. E., Calbrade, N. A., Mellan, H. J., Mitchell, C., Stroud, D. A., Wotton, S. R. and Musgrove, A. J. (2011) Waterbirds in the UK 2009/10: The Wetland Bird Survey. Thetford, UK: BTO/RSPB/JNCC.
Livezey, B. C. (1995) Phylogeny and Evolutionary Ecology of Modern Seaducks (Anatidae: Mergini). Condor 97: 233-255.
Sangster, G., Collinson, J. M., Helbig, A. J., Knox, A. G. and Parkin, D. T. (2005) Taxonomic recommendations for British birds: third report. Ibis 147: 821-826.
Sea Duck Joint Venture (2003) Species status report. http://www.seaduckjv.org/meetseaduck/species_status_summary.pdf
Skov, H., Heinänen, S., Žydelis, R, Bellebaum, J., Bzoma, S., Dagys, M., Durinck, J., Garthe, S., Grishanov, G., Hario, M., Kieckbusch, J. K., Kube, J., Kuresoo, A., Larsson, K., Luigujoe, L., Meissner, W., Nehls, H. W., Nilsson, L., Petersen, I. K., Roos, M. M., Pihl, S., Sonntag, N., Stock, A. and Stipniece, A. (2011) Waterbird Populations and Pressures in the Baltic Sea. TemaNord 2011: 550. Copenhagen, Denmark: Nordic Council of Ministers.
Wetlands International (2006) Waterbird population estimates. Fourth edition. Wageningen, The Netherlands: Wetlands International.
The following input from Dr. Gennady Grishanov was forwarded to us on 30 January 2012: Melanitta fusca Grishanov Jan12
The following letter was received on 31 January 2012: Melanitta fusca Lehikoinen et al. Jan12
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