How different reproduction of different pairs can be? Some adult Short-toed Eagles occupy the same sites from year to year. They had yet been identified in 2011 by photos taken since 2006 and according to previous and new observations. The birds had got indexes A11, B11 etc. although, in spoken communication we give them more harmonious names: for example, K11 is Barry, B11 is Ospry, and so on. Then later pictures of the individuals repeatedly got into the annual photo galleries. The natural identifying details are general plumage patterns, shapes of heads, wings, beaks and general silhouettes in flight from certain angles as well as signs of moulting. The number of the examined images should be enough to select the details and to collate them. Thus, now it is possible to compare the mean reproduction – – of pairs of individuals identified from year to year for certain, definitely without replacements of mates and without clear differences in objective conditions for breeding.