Has the Greylag Goose Anser anser started to arrive earlier in Uppland?

Abstract

The first arrival day of Greylag Geese Anser anser at two sites in Uppland, the province north of Stockholm, Sweden, during 1992—2002 was analysed. There was an almost significant change towards earlier arrival at both sites and for the combined observations (P=0.063). The influence of some factors that possibly could affect the date of arrival was studied, i.e. temperature on date of arrival, mean temperature in March, size of the Swedish population, and size of the local breeding population. Regression analysis showed that the size of the Swedish population had a significant influence on the first arrival date (P=0.050). As the regression of date of arrival on temperature was almost significant it is likely that temperature also influences date of arrival. Observations from one of the sites showed that the earlier arrival had not caused any change in the time of hatching. A significant relationship between number of days between the observation of first brood(s) and first arrival day was found (P<0.001).