Population dynamics of the White Stork Ciconia ciconia in Slovenia between 1999 and 2010

Abstract

Population dynamics of the White StorkCiconia ciconiain Slovenia between 1999 and 2010Between 1999 and 2010, an annual census of the White StorkCiconia ciconiabreeding population was carried out in Slovenia using standardised methods. The Stork's population was concentrated in the NE and SE parts of Slovenia. In the 1999-2010 period, the breeding range of its population in Slovenia expanded in NW direction (the Savska ravan region), in SW direction (the Notranjsko podolje and Pivško podolje regions), but the species also colonized a part between Central and SE Slovenia (Dolenjsko podolje). Between 193 and 240 pairs were breeding during the study period, 209 pairs on average (HPa). The largest number of breeding pairs was recorded in 2004, the smallest in 2005. During the study period, breeding pairs (HPa) occupied 350 discrete nests in total. Average number of breeding pairs that raised juveniles (HPm) was 161. The highest fecundity was recorded in 2004, when 534 juveniles (JZG) fledged, the lowest in 2006, with only 219 fledged juveniles. On average, 414 juveniles fledged per year. The breeding pairs' (JZa) average breeding success in these 12 years was 2.02, the highest in 2000 (2.41), the lowest in 2006 (1.09). Average breeding success for the successful breeding pairs (JZm) was 2.57. The highest was in 2007 (2.94), the lowest in 2006 (2.07). The largest number of breeding pairs in 2004 and 2008 can be explained by the favourable fecundity in the population in 2000 and 2004, as juveniles become sexually mature at the age of 3-5 years, and at that age they generally return to the breeding grounds for the first time. The lowest number of breeding pairs and poor breeding success in 2005 and 2006 was caused by late arrival of White Storks to the breeding grounds and by unfavourable weather conditions during the breeding period. The pattern of nests placement did not change generally during the last 12 years. The largest proportion of nests was positioned on various kinds of poles (81%) and on chimneys (18%). In total, 27 area surveyors and 239 assistants helped in census realisation.

Two-fold increase in White Stork (Ciconia ciconia) population in Lithuania: a consequence of changing agriculture?

“…Similarly, in Estonia, the proportion of nests in trees decreased from 68% in 1984 to less than 10% in 2008, while the proportion of nests on electricity line poles increased from 12% to 72% (Ots, 2009). In Slovenia, the last White Stork nest in a tree was recorded in 2008 (Denac, 2010). This same tendency has also been observed in Poland, both in the entire country, where the proportion of nests on electricity line poles increased from 4% in 1974 to 37% in 1995 (Jakubiec and Guziak, 1998), and in different regions of the country (e.g., Daniluk et al, 2006;Kuźniak, 2006;Tryjanowski et al, 2009).…”

“…A similar tendency of White Storks increasingly nesting on overhead electricity line poles and gradually abandoning their former traditional nest sites on roofs of buildings and in trees has been observed over the last decades in several other countries in Europe (Janaus and Stipniece, 2004;Tryjanowski et al, 2009;Denac, 2010;Onmuş et al, 2012). In Latvia, the proportion of nests in trees decreased from 86% to 40% during the period of 1974-1994, while the proportion of nests on electricity line poles increased from 1% to 38% (Janaus and Stipniece, 2004).…”

“…Rather similar breeding success of White Storks has been observed in other countries. In Slovenia, the mean breeding success over the period 1999-2010 was 2.6 young per successful pair (Denac, 2010). In Poland, which holds the largest population of White Storks (BirdLife International, 2004), breeding success in various regions varied between 2.5 and 3.0 young per successful pair in the 1990s and early 2000s (Nowakowski, 2003;Daniluk et al, 2006;Kuźniak, 2006).…”

“…Almost 9000 breeding pairs were registered during the first census (Kisielius, 1974), followed by a gradual decline until a dramatic decrease down to just over 4000 pairs was registered in 1984 (Kazlauskas and Paltanavičius, 1985; but also see Ivanauskas et al, 1997). This decrease coincided with a Europe-wide decrease in the White Stork population in the 1980s (Schulz, 1999;Daniluk et al, 2006;Ots, 2009;Denac, 2010). A number of factors have been found to affect the population size of White Storks both on their breeding grounds and during migration and wintering: wetland drainage, intensification of agriculture, hunting, weather conditions, and increased feeding by White Storks in rubbish dumps (Kanyamibwa et al, 1993;Blanco, 1996;Barbraud et al, 1999;Tortosa et al, 2002;van den Bossche et al, 2002;Berthold et al, 2006;Higuchi et al, 2006;Kruszyk and Ciach, 2010).…”

A preliminary overview of raptor monitoring in Slovenia – an overview of methodologies, current monitoring status and future perspectives

“…The aims of these monitoring programmes were quite different taking into account specific scientific (Tome 2009) or conservation based issues (Polak et al 2004). They were designed either as broad international actions (Božič 2005) or as a way of bird popularization by monitoring of charismatic bird species (Denac, D. 2010). Therefore long-term data on bird or specifically raptor populations in Slovenia are of quite different quality and quantity based on species specific or assemblage-oriented surveys such as Farmland Bird Index counts (Kmecl & Figelj 2012).…”