The present invention relates to a method for non-destructively identifying a characteristic of a Gallus Gallus domesticus embryo in ovo the method comprising : (a) obtaining a sample of material associated with an egg comprising the embryo and (b) measuring a score value for the presence of and concentration of at least a first biomarker in the sample indicative of the characteristic of the embryo and (c) applying a threshold to the score value and concentration obtained in (b) to identify the characteristic for the embryo associated with the presence and concentration of the biomarker wherein an at least first biomarker comprises an amino compound having a molecular weight in the range of from 140 to 190 g/mole wherein step (c) further comprises : (i) correlating each relevant biomarker signal with a reference biomarker by matching the spectrum of each correlating signal with the expected spectrum of the correlating reference biomarker using a similarity measure to define at least one positively correlating signal; (ii) measuring the intensity of each positively correlating signal and scoring its absolute and/or relative signal intensity; and (iii) applying a threshold to the score value obtained from a similarity function to determine the correlated embryo characteristic.