EURING Newsletter - Volume 2, December 1998

EURING PROJECTS

JOINT VOGELWARTE RADOLFZELL – EURING MIGRATION PROJECT:
A LARGE-SCALE RINGING RECOVERY ANALYSIS
OF THE MIGRATION OF EUROPEAN BIRD SPECIES

By Wolfgang Fiedler

RESEARCH CENTRE FOR ORNITHOLOGY OF THE MAX-PLANK SOCIETY ANDECHS AND RADOLFZELL,
RESEARCH UNIT VOGELWARTE RADOLFZELL, BIRD RINGING CENTRE, SCHLOSSALLEE 2, SCHLOSS MOEGGINGEN, D-78315 RADOLFZELL, GERMANY (Email: fiedler@vowa.mpi-seewiesen.mpg.de)

Recent changes in migratory behaviour of bird species show the importance of migration research, and in particular demand documentation of the present state of European bird migration. Moreover, it is usually essential to know the spatial features of seasonal migration in order to investigate ecological, physiological, evolutionary or ethological questions in any particular bird species.

In September 1997 we proposed to EURING a joint Vogelwarte Radolfzell - EURING Migration Project (JVR-EMP) to continue Pan-European ringing recovery analyses. In contrast to the work carried out earlier by Gerhardt Zink and others who did everything themselves, we intend to perform a close cooperation with national specialists. Another innovation is the extensive implementation of the possibilities of electronic data processing and GIS-technology. All 34 EURING member schemes announced cooperation within that project.

The results are to be published as scientific papers in ornithological periodicals, in compilations such as migration atlases, to achieve a broader distribution of the results, and on CD-ROM, to be stored at the EURING data bank for further analyses and use (from the level of checked and corrected rough data).

It has been decided to start with a number of non-passerine species of relatively high public interest, namely White Stork (Ciconia ciconia), Bittern (Botaurus stellaris), Little Bittern (Ixobrychus minutus), Grey Heron (Ardea cinerea), Purple Heron (A. purpurea) and Great White Egret (Casmerodius albus). Up to now, for instance, approximately 25,000 recoveries of the White Stork of more than 15 different national databases have been homogenized, checked, corrected and included into the analysis. A set of tool computer programs for standard analysis routines has been developed and can be distributed among EURING member schemes for their own ringing recovery analyses.

First Results from the White Stork (Ciconia ciconia)

Fig. 1 shows the recent state of data input. Still lacking data or data of low represented areas such as the Baltic States, Ucraine, Romania or France are announced to be sent soon. Recoveries of White Storks ringed in Europe are spread between southern Sweden, Cape Town, Canary Islands and India.

Fig. 1: Ringing localities (left) and recovery places (right) of White Storks presently included into the analysis (data transmission is not yet finished).

Mean migratory directions per 1 x 1 ° geographical cell grids of young storks show the well known migratory divide across central Europe between southwestwards and southeastwards migrating populations until the early 1970ies. In the 1970ies mean migratory directions shifted from southeast to more southern or southwestern directions in parts of Northern Germany and The Netherlands (Fig. 2). The reason most probaly were rising reintroduction projects with imported or handraised birds, winter feeding activities etc. in several parts of Central Europe.

Fig. 2: Directions of departure of White Storks in their first autumn migration. Pooled data for 1x1° cells of geographical longitude and latitude. Birds which were recovered in a northern direction or in a distance less than 50km or which were handraised are exluded. Only grid cells with a sample size >10 birds are shown. Left: data before 1970 (n= 2191), Right: data since 1970 (n= 4432). Large white symbols: >75% of the recoveries in southeastern directions; small white symbols: >50% in southeastern directions; small black dots: >50% in southwestern directions; large black dots: >75% in southwestern directions.

Recoveries of White Storks in their first winter show that some birds of the eastern migrating populations reach South Africa already in november (Fig. 3). On the other hand, december recoveries are spread all over Eastern Africa from Egypt to South Africa. This indicates, that birds may stay farther in the north, probably depending of suitable feeding possibilities. The western migrating populations reach their Central African wintering grounds already in september and do not proceed farther south.

Fig. 3: Recoveries of White Storks during their first winter south of 37° latitude (n= 1577).

White Storks spend their first and second summer after fledging regularly as nonbreeders. The mean distance from the place of birth (which is in most cases the expected breeding ground for the grown up bird) to the recoveries during first summer was, for instance, about 3000 km before 1970 in storks of Northern Germany. For the period since 1970 this distance changed significantly to less than 1000 km (Fig. 4). An equal trend could be shown for birds of Southern Germany and The Netherlands.

Fig. 4: Mean distances per month between recovery localities and the place of birth in White Storks during their first year. x-axis: months; y-axis: distance (kilometres). White symbols and dashed lines: data before 1970, black symbols and solid lines: data since 1970. The lines are polynomial fits with 95% confidence limits. Numbers indicate the sample size per dataplot.

Central European storks spend their second summer in average closer to their place of birth than their first summer. The mean distances between recoveries during the second summer and the place of birth are significantly shorter in the three mentioned populations than the distances in the first summer. In German White Storks mean distances to the place of birth in the second summer are significantly longer than in the following (breeding) summers before 1970. Since 1970 these distances are statistically indistinguishable.

The results shown are only preliminary and might change slightly during more detailed analyses, especially by further completing the dataset. Nevertheless, within JVR-EM Project for the first time migratory behaviour, recent changes in timing and direction of migration and effects of reintroduction projects and probably climatic and environmental changes can be shown at the scale of the whole European White Stork population.

Back to index of EURING Newsletter Volume 2