Article taken and adapted from Goose News The newsletter of the Goose and Swan Monitoring Programme, Issue no.10, Autumn 2011
After several years of very poor breeding success, the Greater White-fronted Goose, Anser albifrons flavirostris population that breeds in west Greenland finally returned to the Scottish wintering grounds with no less than 22.9% of the aged sample of geese on Islay being birds of the year, the most since the record breeding season of 1985. Islay holds approximately half of the geese that winter in Scotland, and between 1996 and 2008 they returned with less than average proportions of young in 11 out of 13 seasons. This resulted in the overall population size rapidly declining following the peak in numbers at 35,700 in winter 1998/99.
Declines in the small global population in the early 1980's led to protective legislation enacted to stop hunting on the winter quarters. Following that change in the law, the population increased at approximately 6% per annum until it reached the peak in 1998/99. Since 1983, the population has not been legal quarry on the wintering grounds, although small numbers were still being taken in Greenland and some 3,500 were shot each autumn in Iceland.
Renewed concern for the well being of the population has resulted in considerable activity since the mid-2000's. An international action plan for the species was drafted in 2009 in readiness for adoption by the Range States as a formal single species action plan under the African-Eurasian Waterbird Agreement.
The population has been protected in Iceland since 2006 and since 2009 in Greenland. There is little more that can be done to reduce "unnecessary sources of mortality".
So what is the cause of poor breeding success since the mid-1990's? Greenland White-fronted Geese already consistently produce proportionally fewer young in relation to the number of potentially fecund adults than do most of the circumpolar populations of Greater White-fronted Geese.
Several hypotheses have been put forward to explain the recent particularly low breeding success, including the effects of climate change, disease, enhanced predation rates on nests or young, and competition from Canada Geese which have increased rapidly in abundance on the west Greenland nesting grounds (where White-fronts were formerly the only numerous goose present in summer).
Weather conditions in west Greenland have been unusual in several springs since 1995. Differences in sea surface temperatures in the northern Atlantic Ocean have deflected frontal systems further north across the Atlantic, tending to deposit more precipitation in west Greenland than was formerly the case. In eight of the years between 1996 and 2008, this meant very heavy snow during April and May prior to the arrival of the geese in spring, resulting in low reproductive success in those years. In contrast, 2009 and 2010 were relatively dry and warm compared to most recent years.
The summers of 2009 and 2010 were also very warm, which is also known to positively influence breeding success, since in years with relatively little spring snow, breeding success on Islay tends to correlate with summer temperatures in central west Greenland.
The spring of 2010 was exceptionally mild and snow-free in west Greenland, so geese arrived to good feeding conditions. Exceptionally warm temperatures persisted throughout the summer and probably also contributed to high reproductive success in that year
Despite the high proportions of young recorded in Scotland over the 2010/2011 winter, the Wexford Slobs had only 14.7% of young (slightly above the recent average), as was the case elsewhere in Ireland.
Nevertheless, it is encouraging to see that some parts of the population can still perform when the conditions are suitable for breeding.