Untersuchungen zur Eiqualität bei der Kohlmeise (Parus major) in Abhängigkeit von der Bodenbeschaffenheit

Summary

Since the beginning of the 80's it has been evident that the immission of acidifying gases damages the ecosystem ‘forest’. The studies carried out since then mainly addressed the effects on invertebrates of aquatic ecosystems, on soils and vegetation.

So far very few studies have been conducted which deal with the effects of acidification on indigenous forest birds. In the Netherlands, thin-shelled as well as porous eggs and a lower breeding success were found in areas with soil poor in calcium.

In our study areas around Schlüchtern we also observed occasional eggs which had no eggshells at all or which dried out completely during hatching. These observations suggested a closer study of the effects of calcium availability on breeding biology.

The favourable location of the Schlüchtern study areas between Spessart, Vogelsberg and Rhön with different geological formations provides good preconditions for establishing whether the various levels of calcium availability due to the different soil conditions affect the breeding biology of the Great Tit. In two study areas with different geological characteristics various aspects of egg quality in the Great Tit are compared: egg volume, eggshell thickness along with the loss of mass caused by evaporation, clutch-size and hatching rate. In a limestone area with a better calcium supply, the egg volume was larger, the shells were thicker and the mass loss of the eggs at constant temperature was smaller than in a sandstone area. Hatching rate was not affected. Clutch-sizes and hatching rates do not show any differences in the two study areas.

Zusammenfassung

In zwei Untersuchungsgebieten mit unterschiedlichem geologischem Untergrund wird die Eiqualität bei der Kohlmeise im Hinblick auf die Gelegegröße, die Eigröße, die Eischalendicke sowie die damit verbundenen Masseverluste der Eier und die Schlüpfrate verglichen. In einem Muschelkalkgebiet mit einer besseren Ca-Versorgung lassen sich höhere Eivolumina, größere Eischalendicken und ein geringerer Masseverlust der Eier bei konstanter Temperatur feststellen als in einem Buntsandsteingebiet. Dies wirkte sich allerdings nicht auf die Schlüpfrate aus. Die Gelegegröße und die Schlüpfrate zeigen keine Unterschiede zwischen den Untersuchungsgebieten.