| Summary: | Abstract Globally, populations of several wader species are in decline. However, for most populations, information on abundance, its changes and the causes of declines is insufficient for designing successful management strategies to recover threatened populations. In this thesis I studied the status and population trends, nesting success, genetic structure and viability of a small, declining and threatened Temminck’s stint population in the Bothnian Bay in the northern Baltic Sea. Historical population data, recent population counts in the early 1990s and in 1999–2002 and the demographic data showed that the decline is continuing, paralleled by declines in nesting success, recruitment and adult survival. Decline in nesting success was caused by a coincident increase in nest predation. Depredation was the main cause of nest losses. The common gull (Larus canus) and the ruddy turnstone (Arenaria interpres) were found to be the most important nest predators. I tested if an increase in nest concealment and consequent decrease in visibility lowers the efficiency of the early-departure antipredator behaviour of the species. An expected positive correlation emerged between visibility and flushing distance in the presence of alarm-giving birds, but not without them. This indicates that Temminck’s stint exploits signals from other birds as early warning of an approaching predator. More nests were lost to predation on narrow than on wide shores. The nest predation rate was not related to habitat (natural vs. man-made) nor to differences in microhabitat characteristics associated with concealment. Overall variability of the mitochondrial control region was low in the one northeast Siberian and the three Fennoscandian populations studied. The occurrence of two maternal lineages in all Fennoscandian populations points to mixing of two previously isolated populations. The overall microsatellite genetic structuring (6 loci) in Fennoscandia was low. The pairwise comparison revealed a low but significant degree of ...
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