Spring migration of waterbirds and raptors at Medvedce reservoir (Dravsko polje, NE Slovenia)/ Spomladanska selitev vodnih ptic in ujed na zadrževalniku Medvedce (Dravsko polje, SV Slovenija)

Abstract

Spring migration of birds, particularly waterbirds and raptors, was monitored from dawn till dusk from an observation point located on the levee on the northern side of the Medvedce reservoir (Dravsko polje, NE Slovenia) in three separate years (1-17 Mar 2009; 25 Mar-10 Apr 2011; 28 Feb-12 Apr 2012). In all three years, 42,045 individuals of 89 species (66 waterbirds, 23 raptors) migrated over the site. 38,238 of these were waterbirds. The most numerous species was Lapwing Vanellus vanellus (11,813 individuals), followed by Blackheaded Gull Chroicocephalus ridibundus (10,515 individuals). In total, 3807 migratory storks, raptors and Cranes Grus grus were counted. Harriers (2303 individuals) were by far the most numerous group. The prevailing direction of migration was SW-NE. Half of all migrating birds were observed in the altitudinal belt between 10 and 100 m above ground level. Harriers were mostly observed up to 100 m above ground level, whereas storks, other raptors and Cranes were observed most often in the altitudinal belt between 100 and 500 m above ground level. The highest numbers of waterbirds were observed between 10 and 100 m above ground level. In the first five hours after sunrise, 61.3% of all waterbirds, 44.0% of all storks and raptors and only 20.5% of Cranes were observed. Although other parts of Dravsko polje have never been studied in such detail, it is possible that a significant portion of migrating birds from a larger area gathers at this site. This study confirms the importance of the area for migrating and staging birds, especially for Great Egret Ardea alba, Marsh Circus aeruginosus and Hen Harriers C. cyaneus, Osprey Pandion haliaetus, Crane, Ruff Calidris pugnax and Black-headed Gull that all reached at least 0.1% of their respective biogeographic populations. Internationally significant are particularly the numbers of migrating Marsh (1079 individuals in 2012) and Hen Harriers (408 individuals in 2012), as there are only few sites where these species migrate in such high numbers in spring.

The MallardAnas platyrhynchosin Slovenia: a review with an estimation of its current population

“…For the presentation of annual dynamics of the Mallard individuals, broods and temporal dynamics of females, the year was divided into ten-day periods according to Bordjan & Božič (2009a). Data from sites with multiple-year monitoring were averaged across years for each ten-day period.…”

“…The more even the yearly distribution of Mallards, the lower the maximum percentage in ten-day periods. Phenological periods were used according to Bordjan & Božič (2009a).…”

“…The Mallard has a high occurrence frequency, often reaching 100%. Frequencies below 100% are usually the result of complete freezing of individual water bodies, such as at Medvedce before 2009 (Bordjan & Božič 2009a) and at Ormož Basins Nature Reserve (L. Božič pers. comm.…”

Novi podatki o razširjenosti navadne česnovke Pelobates fuscus (Laurenti, 1768) v Podravju (SV Slovenija)

“…Kljub temu, da so Medvedce obiskali številni naravoslovci (npr. Bordjan & Božič 2009), novih opažanj navadne česnovke ni. Prav tako tam nikoli ni bilo sistematičnih raziskav dvoživk.…”

Occurrence of the Red Kite Milvus milvus in Slovenia

“…In the early 1990s it was listed as a rare bird in the breeding and wintering periods by the National Rarities Committee (Komisija za redkosti 1993). Although it occurs more often during migration, it was listed as a rare visitor in overviews of birds on Ljubljansko barje (Tome et al 2005), at Medvedce reservoir (Bordjan & Božič 2009), at Lake Cerknica (Bordjan 2012b), at Vrbje fishpond (Gamser & Novak 2013), in Ljubljana and surrounding areas (Tome et al 2013) and at Sečovlje saltpans (Škornik 2012). An increased number of sightings was reported only for the Medvedce reservoir (Bordjan 2012a).…”