The invention pertains to a method for grading individual poultry hens in a flock, wherein the method comprises the following steps: - when a hen is present in or adjacent to a laying nest, applying a mark to that hen, which mark is invisible to the hens of the flock, - after a marking time period which is at least as long as the expected time interval between the laying of two subsequent eggs by a single hen, determining which hens of the flock do not have a mark, therewith grading the hens into a first class of hens which have at least one mark and a second class of hens which do not have a mark.
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