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Eggshell surface of birds constitutes a suitable environment for bacteria which may have an important impact on the embryo. One important determinant for bacteria development is humidity. We predict bacterial loads on eggshells to be higher in birds breeding in wet environments (e.g. marsh habitats) in comparison to species breeding in other (dry) habitats, assuming that eggs of wetland birds are more likely faced a higher degree of humidity due to increased evaporation and water contact. To minimize damage through bacteria female birds are known to develop several defence strategies including allocation of antimicrobial substances into the eggs. Here we aim to show whether habitat dependent differences in eggshell bacteria loads do exist, more specifically, whether bird species breeding in wetland habitats have to cope with higher bacterial loads on their eggs and whether maternal investment into egg immune defence may have evolved as a counterstrategy to protect embryos from bacteria penetrating the egg shell. Our results reveal eggshell bacteria loads in wetlands to be a multiply higher than in dry habitats. There is no obvious difference in parameters related to maternal egg immune defence investment which seems to be even lower in wetland habitats. In this context alternative possibilities of factors influencing studied parameters are discussed.