Davor Ćiković

Migration of Central and East European Acrocephalus Warblers at the Eastern Adriatic Coast: An Analysis of Recoveries

Migration of Central and East European Acrocephalus Warblers at the Eastern Adriatic Coast: An Analysis of Recoveries Migration routes and origins of the Reed Warbler (Acrocephalus scirpaceus), Great Reed Warbler (A. arundinaceus) and Sedge Warbler (A. schoenobaenus) populations migrating through the eastern Adriatic coast were investigated by analysing recoveries of birds ringed or found at two eastern Adriatic wetlands during autumn migration. There were 75, 104 and 63 long-distance recoveries for these three species, respectively. Great Reed Warblers from central and eastern Europe and Sedge Warblers from countries surrounding the Baltic Sea use the eastern Adriatic wetlands as stopover sites and continue their migration across the Mediterranean. Some Great Reed Warblers use south-western route during their return migration. Reed Warblers of unknown origin, presumably from eastern Europe continue their migration through south-western route to Spain (mean distance - 1329.3 ± 118.0 km, n = 20; mean azimuth - 251.05 ± 4.91°, n = 20; mean velocity - 63.25 km/day, n = 16). Local breeding Reed Warblers migrate southeast along the eastern Mediterranean (azimuth 117.53°). Eastern Adriatic coast represents a crossroads for migratory warblers using south-western, south-eastern and central Mediterranean flyways.

Nest Site and Nest-Hole Characteristics Used by Great Spotted Woodpecker Dendrocopos major L. in Croatia

ABSTRACT: Great Spotted Woodpecker is the most abundant and widespread European woodpecker species, and it thus contributes the most to the number of excavated tree holes — an important habitat resource for secondary hole users. However, majority of nest site characteristics data comes from boreal and temperate forests, with lack of information from Southern Europe. In this article, nest sites of the Great Spotted Woodpecker have been investigated in the continental forests of Croatia — a previously understudied area of this species range. A total of 41 active nest-holes found in the breeding seasons 2003 and 2004 are described. Nest-holes were mainly positioned below the crowns, in injuries of branch abscission. Nesting tree species were not used randomly: wild cherry Prunus avium in hill and pedunculate oak Quercus robur in riverine forests were preferred while hornbeam Carpinus betulus and maples Acer sp. were avoided. While tree species used for nesting vary across the Great Spotted Woodpecker range, and thus cannot be used as a uniform nest site predictor, defected wood spots on a tree, like scars of branch abscission, are identified as an important nest site clue and a habitat feature that is spatially more consistent. Nestholes dimensions acquired in this research could not be clearly differentiated from those given for the other parts of the continent.

Habitat-dependent effect of a rare predator on apparent survival of male Black-headed Bunting

Both habitat changes and predation can cause population declines in farmland birds. Habitat changes may allow novel or invasive alien predators to establish populations in new environments, which can have major ecological consequences for native prey species. We studied effects of a novel avian predator, the Montagu’s Harrier (Circus pygargus), on the survival of male Black-headed Buntings (Emberiza melanocephala). Between 2011 and 2015, survival of 35 territorial Black-headed Bunting males was monitored and their apparent survival in years with and without predators was computed. The apparent monthly survival (reported ± SE) was very high during the breeding seasons when Montagu’s Harrier was not present (0.957 ± 0.035) as well as in nonbreeding periods (0.981 ± 0.011). It was significantly lower during the breeding season of 2013 when Montagu’s Harrier was present in the area (0.600 ± 0.136). Changes in habitat structure due to alteration in agricultural practice and temporal changes in weather conditions have presumably enabled Montagu’s Harriers to breed in the study area and led to increases in the importance of birds in Montagu’s Harriers diet. The appearance of Montagu’s Harriers in the study area strongly coincided with the steep decrease in the apparent survival of the male Black-headed Buntings. The lack of appropriate response in male Black-headed Buntings made them extremely vulnerable to attacks of this aerial predator. Effet lie a lhabitat dun predateur rare sur la survie apparente du Bruant melanocephale mâle RESUME. Les modifications de lhabitat et la predation peuvent tous deux etre en cause dans les baisses de population doiseaux champetres. Les modifications de lhabitat peuvent permettre a de nouveaux predateurs ou des predateurs etrangers envahissants detablir des populations dans de nouveaux paysages, pouvant du coup entrainer des consequences ecologiques graves pour les especesproie indigenes. Nous avons etudie les effets dun nouveau predateur aviaire, le Busard cendre (Circus pygargus), sur la survie des Bruants melanocephales (Emberiza melanocephala) mâles. Entre 2011 et 2015, la survie de 35 Bruants melanocephales mâles territoriaux a ete suivie et leur survie apparente avec ou sans predateurs a ete calculee selon les annees. La survie apparente mensuelle (rapportee ± erreurtype) etait tres elevee au cours des saisons de nidification ou le Busard cendre netait pas present (0,957 ± 0,035) ainsi quen dehors de la saison de reproduction (0,981 ± 0,011). Cette survie etait tres faible durant la saison de nidification de 2013 (0,600 ± 0,136) alors que le Busard cendre etait present dans le secteur. Les changements de la structure de lhabitat, attribuables aux modifications des pratiques agricoles, de meme que les changements temporels des conditions meteorologiques ont apparemment permis au Busard cendre de se reproduire dans laire detude et ont mene a laugmentation de limportance des oiseaux dans la diete du busard. Lapparition du Busard cendre dans laire detude a coincide grandement avec la diminution importante de la survie apparente des Bruants melanocephales mâles. Le manque de reactions appropriees de la part des bruants mâles les a rendus extremement vulnerables aux attaques de ce predateur aerien.

Distribution, density and habitat relationships of the Ural Owl Strix uralensis macroura in Croatia.

We surveyed the Ural Owl Strix uralensis macroura from 1993 to 2007 to determine the geographic range of the species in Croatia and to provide information on its density and habitat preferences. We conducted playback surveys at 365 survey points within 19 plots (total survey area 1070 km2) systematically covering all of the major forest types in Croatia. Surveys were also carried out at 144 calling stations arranged in transects and at 133 stations scattered over larger areas. Playback surveys were conducted twice at stations in plots and along transects, and once at scattered stations. A total of 234 Ural Owl territories were located. We estimate the total population of the Ural Owl in Croatia to be 700–1000 pairs, and include an updated map of its distribution. The owls occurred in Dinaric fir—beech forests, montane beech, Sessile Oak Quercus petraea and Common Oak Quercus robur forests. The majority of the population, around 80%, was located in Mountain Croatia, where mixed Dinaric fir—beech forests predominated, at densities ranging from 1.1 to 5.4 pairs/10 km2 (average 2.3 pairs/10 km2). The highest density was found in the Plitvice Lakes National Park, in forests that have not been commercially logged for more than 50 years. Approximately 20% of the total population was found in the western part of Lowland Croatia, in the zone of beech and Sessile Oak-hornbeam forests, with average density of 0.9 pairs/ km2, as well as in Common Oak forests, with density of 0.7 pairs/10 km2. In Mediterranean Croatia the Ural Owl was found only in the mountainous zone of thermophile beech forests. There we recorded a density of 0.3 pairs/km2 and estimate the population at 15–25 breeding pairs constituting approximately 2% of total population in Croatia.