Results of a first look into the Austrian animal phenological records
Scheifinger, Helfried; Koch, Elisabeth; Winkler, Hans
The year to year variability and trends of animal phenological phases (honey bee, cockchafer, 3 butterfly species, swallow and cuckoo) of the Austrian phenological observational network were related to each other and to mean monthly temperatures over the time period 1951-1998. Insect phases were well correlated with each other (r2 = 0.4 to 0.6) and with temperature (r2 = 0.25 to 0.55), whereas both bird phases were only well correlated with each other (r2 = 0.57), but showed low common variance values with temperature and with other animal phases. The slope of the temperature-pheno regression, also termed as temperature sensitivity of the phenological phase, was high in the case of the insect phases (−3 to −5 days/°C), but low in the cases of both bird phases (about −1 days/°C). All animal phenological time series showed a trend towards later occurrence dates. The trends of the bird phases were even significant (p<0.1). there was a marked discrepancy between the trends of all animal phenological and temperature time series, especially between the insects and temperature: the mean temperature time series of february, march and april with the highest common variance with the insect phases showed a strongly increasing trend (0.027°c/year), whereas the first appearance dates of the insects tended to occur later (0.06 to 0.15 days/year). both bird phases correlated weakly with the mean april temperature (r2 about 0.1). The temperature trend of April was 0.0003°C/year, whereas the trend of the bird phases was 0.2 days/year for the cuckoo and 0.25 days/year for the swallow. From these observations we conclude that a strong temperature sensitivity of the phenological phase based on the year to year variability (in days/°C) does not necessarily result in corresponding trends of temperature and phenological phase. A strong trend of non-atmospheric factors such as population density influencing the animal phases is suspected. Factors other than local atmospheric temperature, like climatic conditions in the overwintering area and on the migration route, probably govern the arrival times of the migratory birds.