LONG-TERM CHANGES OF BREEDING PARAMETERS OF NUTHATCHES SITTA-EUROPAEAIN 2 STUDY AREAS OF NORTHERN GERMANY

Between 1970 and 1995, nestbox data about clutch size, hatching date a nd fledging success were collected for a total of around 1500 first br oods of Nuthatches in two north German study areas (near Brunswick 52. 16 N 10.32 E and near Essen 51.24 N 6.59 E). The average clutch size w as 6.8 eggs (Brunswick), the average hatching date 9 May (Brunswick) a nd 6 May (Essen), and the mean number of fledglings per successful bro od 5.6 (Brunswick) and 5.2 (Essen). Over time hatching dates significa ntly advanced in both areas. Data of further years are needed to clari fy if the recent unusual sequence of early breeding years in the Nutha tch is already a consequence of the anthropogenic ''greenhouse effect' ' or just due to normal variation of weather conditions.