This dataset contains data from: E. Keith Bowers, Pavel Munclinger, Stanislav Bureš, Lenka Kučerová, Petr Nádvorník, and Miloš Krist: Cross-fostering eggs reveals that female collared flycatchers adjust clutch sex ratios according to parental ability to invest in offspring. Molecular Ecology. Data collectors: Miloš Krist, Pavel Munclinger e-mails: milos.krist@upol.cz, muncling@natur.cuni.cz Dataset is saved as CSV file separated by semicolons. There are no special symbols for missing data. Missing data are simply empty cells in the spreadsheed. The dataset has following columns: 1) Identity - identity of genotyped individual. This is composed from the year (the first four numbers), study plot (a letter), nest-box number (two numbers following the letter), a letter indicating whether the individual was offspring (o), male parent (m) or female parent (f). For offspring additional one or two numbers distinguish it from its nest-mates. Nest-box number refer to nest where the offspring was raised, not where the offspring was produced (i.e. laid as egg). For parents, nest-box number refer to nest they cared for. 2) Ring identity - identity by ring number. This information misses for offspring that died/disappeared before ringing. 3 - 18) These columns contain genotypes for 8 microsatellite loci.