Population decline in the Rustic Bunting Emberiza rustica in Norway

Abstract

Since the expansion of the Rustic Bunting (Emberiza rustica) westwards in northern Europe during the 19th and 20th centuries, declines have been reported in Fennoscandia. The Norwegian population was 100-500 breeding pairs in 1994. We carried out censuses to detect Rustic Buntings in Norway during 2008-12, and compared these results with previous records to evaluate recent population changes. Transect censuses made along 15 km of optimal habitat (swamp forest along rivers) yielded 18 territories during 1972-78, but in 2008 we found only 5 territories, and none since 2011. We also detected Rustic Buntings in 21 of 74 previously-occupied sites (one or more records during 1963-2007). During the study period 2008-12, we recorded Rustic Buntings in 41 sites, with a maximum of 47 territories in 2008. However, from 2008 to 2012 we detected a decline of 82% (yearly decline of 34% ± 9%; 95% CI). Local extinctions occurred in at least 31 sites. The current known population size is 13 territories in 9 sites, and the true population size may be only slightly larger. About half of all territories were associated with beaver dams, but the rate of decline during 2008-12 did not depend on dams. Extinctions could be attributed to habitat loss or change in 9/53 sites (1 logging, 1 cultivation, and 7 loss of a beaver dam). We suggest that the population decline of Norwegian Rustic Buntings is due to factors operating during migration or in wintering areas.