Do weather conditions affect the colouration of great reed warblerAcrocephalus arundinaceuseggs?

Abstract

The goal of this paper was to test the hypothesis that weather conditions, such as temperature and rainfall, affect egg colouration in the great reed warbler Acrocephalus arundinaceus. We failed to find strong support for this hypothesis; nevertheless, our results indicate that temperature has an effect on some egg colour characteristics. Eggshell brightness (PC1) increased with increasing temperature at laying and eggs were darker in the colder year of the two-year study. On the other hand, UV-blue colouration (PC2) scores were higher in the warmer year. The amount of rainfall, however, had no effect on eggshell colouration. As there is an indication from other studies that weather may have an effect on egg appearance through the food availability, we encourage further testing the environmental hypothesis in other bird species. If this holds for more bird species, this would have important implications for the hypotheses about the adaptive function of bright eggshell colouration.