Variation in eggshell traits between geographically distant populations of pied flycatchers Ficedula hypoleucaGeographical variation in egg mass and egg content in a passerine birdClutch-size variation in Western Palaearctic secondary hole-nesting passerine birds in relation to nest box designVariable responses to large-scale climate change in European Parus populationsBrominated flame retardants and organochlorines in the European environment using great tit eggs as a biomonitoring toolLarge-scale geographical variation in eggshell heavy metal and calcium content in a passerine bird (Ficedula hypoleuca)The design of artificial nestboxes for the study of secondary hole-nesting birds: A review of methodological inconsistencies and potential biasesGeographical trends in the yolk carotenoid composition of the pied flycatcher (Ficedula hypoleuca)