Nesting by the Eurasian eagle owl (Bubo bubo) in a nest of the whitetailed eagle (Haliaeetus albicilla)

Abstract In 2011 and 201 2 two breedings by a pair of Eurasian eagle owls were observed in an old white-tailed eagles’ nest at Blatná Polianka in the Senianske rybníky SPA. The nest was situated in a grey poplar tree 1 5-20 m above the ground in a treebuffer by the rivulet Okna, in open lowland landscape without woodland, just with linear tree vegetation and scattered trees. In 2011 incubation of the clutch was observed and the female was present in the nest even at the end ofApril, when the fledglings were probably already present in the nest, but no more data on their further success were obtained. In 201 2 the pair of Eurasian eagle owls bred in the same nest again, but in May the nest was already abandoned and we suppose predation of the clutch, probably by ravens. This occasion is the third known breeding attempt by the Eurasian eagle owl in a raptor nest built in a tree, and the first known occasion of breeding in a white-tailed eagles’ nest in Slovakia. The obtained data also document the further spreading of the species in the Dolný Zemplín region into unusual habitats of a lowland agricultural landscape with very few trees. Abstrakt V rokoch 2011 a 201 2 bolo zistené hniezdenie páru výra skalného v starom hniezde orliaka morského pri Blatnej Polianke v CHVÚ Senianske rybníky. Hniezdo sa nachádzalo na topoli sivom 1 5-20 m vysoko v brehovom poraste riecky Okna, v nížinatej otvorenej krajine bez lesov, len s pásmi líniovej zelene a roztrúsenými stromami. V roku 2011 bola pozorovaná inkubácia znášky a samica bola prítomná v hniezde ešte aj koncom apríla, kedy už boli pravdepodobne vyliahnuté aj mládatá, ale bližšie údaje o úspešnosti hniezdenia neboli zistené. V roku 201 2 hniezdil pár výrov v tom istom hniezde, ale v máji bolo už opustené a predpokladáme znicenie znášky krkavcami. Jedná sa o tretí známy prípad hniezdenia výra v dravcom hniezde a o prvý známy prípad hniezdenia výra v hniezde orliaka z územia Slovenska. Súcasne potvrdzujeme týmito údajmi šírenie sa výra na Dolnom Zemplíne do doteraz netypických biotopov v agrocenózach.