Some species of birds react to climate change by reducing the distance they travel during migration. The Odra River Estuary in the Baltic Sea is important for wintering waterfowl and is where we investigated how waterbirds respond to freezing surface waters. The most abundant birds here comprise two ecological groups: bottom-feeders and piscivores. Numbers of all bottom-feeders, but not piscivores, were negatively correlated with the presence of ice. With ongoing global warming, this area is increasing in importance for bottom-feeders and decreasing for piscivores. The maximum range of ice cover in the Baltic Sea has a weak and negative effect on both groups of birds. Five of the seven target species are bottom-feeders (Greater Scaup Aythya marila, Tufted Duck A. fuligula, Common Pochard A. ferina, Common Goldeneye Bucephala clangula and Eurasian Coot Fulica atra), and two are piscivores (Smew Mergellus albellus and Goosander Mergus merganser). Local changes at the level of particular species vary for different reasons. A local decline of the Common Pochard may simply be a consequence of its global decline. Climate change is responsible for some of the local changes in the study area, disproportionately favoring some duck species while being detrimental to others.

This paper focuses on relationships between the North Atlantic Oscillation Index (NAO) and the ice conditions in coastal lakes (Jamno, Bukowo, Gardno and ebsko) of the southern Baltic Sea. The data on ice conditions included : date of first ice appearance (F), date of last ice disappearance (D), number of days with ice (N), length of the ice season (in days ; S) and maximum ice thickness (H) during the given winter. The period examined covers the winters from 1960/61 to 1999/2000. The monthly values of the NAO index for the same period were applied in accordance with Jones et al. (1997). Correlation and regression analysis methods were applied to determine and study the relationships between NAO (independent variable) and the parameters of ice conditions (dependent variables). The strongest relationships, with a linear correlation coefficient exceeding -0.80, were obtained for the date of the last ice disappearance (D) in ebsko Lake (-0.853) and Gardno Lake (-0.828) for the JanuaryMarch period. In contrast, the relationships between the NAO index and the date of first ice appearance (F) are much weaker. They are statistically significant only in November and early winter (Nov.-Dec., Nov.-Jan.). The correlation coefficients in the coastal lakes of the Southern Baltic Sea coasts generally increase eastwards, a phenomenon related to the severity of winters and to the increasing continuity of ice phenomena during a given winter in this direction.

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St re s z c z en i e. Na podstawie material6w archiwalnych IMGW z okresu 40letniego (1946/47-1985/86) i w oparciu o metod<'; analizy korelacji i regresji badano wplyw warunk6w termicznych i anemologicznych na utworzenie sit'; pierwszego lodu w trzech wybranych rejonach strefy przybrzeznej (Gdynia, Rozewie i Mi

This paper focuses on relationships between the North Atlantic Oscillation (NAO) Index in selected months and periods and the ice conditions along the southern coast of the Baitic Sea. The data on ice conditions, including the number of days with ice (L) and the length of ice season (counted in days; 8|. cover 25 observation regions located between Arkona in the West and Kaliningrad in the East for winters ofthe 1950/51-1989/90 period. The NAO Index, understood to be the difference between normalized values of atmospheric pressure in Gibraltar and Reykjavik, was applied.Correlation and regression analysis methods were applied to determine and study the relationships between NAO (independent variable! and the parameters of ice conditions L and S Idependent variables). The linear relationships recorded for sheltered basins (Szczecin Lagoon, Puck Bay Small, Vistula Lagoon) were stronger than those calculated for unsheltered ones (e.g., open Baltic Sea coast). The majority of relationships of ice conditions (L and S) to winter monthly NAO values, particularly for January (NAO,) and February {NAOi,) in sheltered basins, are statistically significant, some of them even at the level of a ~ 0.01. The linear correlation coefficients, in most cases, were included within the range from -0.3 to -0.7. The strongest of them were calculated for January and February and encompassed the range from -0.5 to -0.7. The strength of these relationships tended to increase when particular months were connected into several-month periods of NAO Index, especially during the January-March and December-March periods. During these periods the correlation coefficients were usually in the -0.7 to -0.8 interval. In addition, the relationships ofthe NAO index with L were distinctly stronger than those with S. The strongest relationships, with linear correlation coefficients exceeding -0.80. were obtained for the number of days with ice rLi in protected areas, e.g.. in Vistula Lagoon for a period of December-March (NAO^^,,.,,,! and in Puck Bay for January-March period (NAO, 1, 1). These relationships are weaker in unsheltered area.s, where tbe correlation coefficient does not exceed the value of -0.75. The strongest of them concern the estuarine regions of large rivers (Dziwnow, Swibnol and bays (Migdzyzdrojei, whereas the relationships between the NAO Index and L and 8 did not differ significantly from each other in unsheltered basins. However, for the NAO periods of December-March and January-March, they were stronger with S than with L.The correlation coefficients show a decreasing tendency eastward along the southern Baltic Sea coast from Pomeranian Bay to Gdansk Bay (northward ofthe Hel Peninsula). They become stronger in the western part ofthe Gulf of Gdansk and in the mouth ofthe Vistula and again decrease eastward. During some extremely severe or very mild winters, the extreme ice conditions do not always match the extreme NAO index values. During extremely severe winters, the ice cover could exist for a relatively long period, which is a ...