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A countrywide White Stork (Ciconia ciconia) nest census was carried out in Lithuania in 2009 and 2010 by over 20 observers using standardised equipment and methods. The census revealed that the White Stork population has doubled since the previous census in 1994, possibly due to favourable changes in farming practices, with birds increasingly settling on the overhead electricity line poles and gradually abandoning nests in trees. In total, 21,192 White Stork nests were recorded, of which 18,782 (81.4%) were occupied by breeding birds, compared to 9400 occupied nests recorded in 1994. The mean density of occupied nests in the country was 29 nests/100 km 2 . Electricity line poles were the most common nest sites (49% of all nests), followed by trees (21%) and specially erected poles with nesting platforms (11%). Mean breeding success of White Storks was rather high, with 2.7 young raised per successful pair, suggesting a favourable conservation status for this species in Lithuania.

In this study, we analyzed the breeding success of the White Stork (Ciconia ciconia) in nests built on poles of lowvoltage overhead electricity lines (OEL). Many previously conducted studies have shown the negative impact of the electromagnetic field (EMF) on bird breeding success. Over the past few decades, in many European countries, White Storks have been increasingly observed building their nests on poles of OEL, with electricity lines functioning as a nest support. This means that there is a growing tendency for their nests to be located in zones of increased electromagnetic pollution. Our study results showed that the most significant factors influencing the breeding success of White Storks nesting on poles of OEL are the nest-site, hydrological network density, and distance to arable land. The analysis of White Stork breeding success in the nests built on poles of operating and non-operating OEL revealed a significant difference. Breeding success in the nests having direct contact with electricity lines was found to be the lowest. Our study results suggest that even low-voltage electricity current-generated EMF can produce a significant negative effect on the breeding success of birds nesting directly on electricity lines.Išanalizuotas baltųjų gandrų Ciconia ciconia perėjimo sėkmingumas ant žemos įtampos elektros oro linijų sukrautuose lizduose. Daugelyje ankstesnių tyrimų buvo nustatytas neigiamas elektromagnetinio lauko poveikis paukščių perėjimo sėkmingumui. Europos šalyse per pastaruosius kelis dešimtmečius baltieji gandrai lizdus vis dažniau krauna ant elektros oro linijų atramų. Elektros laidai tampa atrama lizdams, jie sukraunami didesnio elektromagnetinio užterštumo zonoje. Tyrimo rezultatai parodė, kad gandrams perint ant elektros oro linijų atramų, perėjimo sėkmingumą įtakojantys svarbiausi veiksniai yra lizdo vieta, hidrologinio tinklo tankumas ir atstumas iki dirbamos žemės. Lizduose, sukrautuose ant eksploatuojamų ir nebeeksploatuojamų elektros oro linijų atramų, perėjimo sėkmingumas reikšmingai skyrėsi. Mažiausias perėjimo sėkmingumas buvo lizduose, besiliečiančiuose su elektros laidais. Šio tyrimo rezultatai leidžia teigti, kad net ir žemos įtampos (0,4 kV) sukuriamas elektromagnetinis laukas gali turėti reikšmingą neigiamą poveikį tiesiai ant elektros laidų įsikuriančių paukščių perėjimo sėkmingumui.

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