The present invention relates to a method for spectroscopical in-ovo gender determination of fertilized and incubated bird eggs comprising the steps of: a. providing a number of passages in an egg shell of an egg for allowing entrance into an interior of the egg and/or eXit from the interior of the egg of electromagnetic waves suitable for spectroscopy, b. introducing electromagnetic waves into the interior of the egg c. detecting electromagnetic waves eXiting the egg, d. analysing, by spectroscopy, of the exiting electromagnetic waves at at least one passage of the number of passages, and e. determining the gender of a chicken embryo.
