Abstract
An intensive research of the Lesser Spotted Eagle biology is conducted in Slovakia since the 80ties of the 20th century. A lot of attention has been paid to the process of cainism. Despite this strong feature in the species bionomy, scarcely cainism is overcome and 2 young fledge from a single nest without human intervention. In 1981 the first finding of this kind was recorded in Slovakia. Since then until the year 2008 there were 64 records of this kind out of 1775 surveyed productive breedings recorded in Slovakia. In the mentioned time period, it represents 3.61 % on average (in individual years it varied from 1.15-9.65 %) when 2 young fledged from a single nest without human intervention.