Actual status, distribution, numbers and threats for four forest bird species -Tengmalm's Owl (Aegolius funereus), Pygmy Owl (Glaucidium passerinum), Three-toed Woodpecker (Picoides tridactylus), and Capercaillie (Tetrao urogallus) were studied in the territory of the Pirin National Park, Bulgaria, in the years 2001and 2019 For the owls, we used night line transect, 2-5 km in length, with acoustic imitation of species calls (henceforth playback) at each 500 (700) m (38 points in 2001-2002, 80 points in 2019). Daytime line transects, 2-5 km in length, were used for counting woodpeckers and Pygmy Owl. In Capercaillie counts, we searched for tracks in the snow, excrements or feathers. GIS analyses were applied for visualization of habitat association and distribution patterns of the studied species. The numbers and distribution of these species were compared between the two study periods and with existing data from previous studies. In 2019 a total of 29 occupied territories of Tengmalm's Owls, 20 territories of Pygmy Owls, 2 territories of Three-toed Woodpeckers and 16 leks of Capercaillies were found. Decrease in numbers was detected for Tengmalm's Owl (-30.4%) and Capercaillie. These species showed also different spatial pattern of presence between the two study periods. Three-toed Woodpecker population in Pirin NP is very small, not exceeding 10-15 pairs. Pygmy Owl was recorded for the first time during the breeding period in the National Park. The reasons for the differences between the two study periods were discussed. The results indicate some threats (ski tourism development, disturbance by people, sanitary cuttings, etc.) for these birds and can be used for improving the spatial planning of human activities in Pirin NP.
During 2018–2022, the local breeding population of the long-legged buzzard (Buteo rufinus) in southeastern Bulgaria was monitored in the territory of three districts of Sliven, Yambol and Burgas. Diet data were collected in 15 breeding pairs. Overall, we identified 290 prey items. We used three methods for diet analysis that produced different results: (1) collecting prey remains (68 individuals, 23.5%), (2) collecting pellets and skeletal materials (42 individuals, 14.5%), and (3) collecting data on a diet using trail cameras (180 individuals, 62.1%). The dominant part of the diet formed mammalian species (69.3%, ten species and some undetermined Rodentia and other Mammalia). Birds were less represented but with similar species richness (21.0%, 11 species and pigeons (Columba sp.), thrushes (Turdus sp.), undetermined Passeriformes and Galliformes). Compared to birds, the proportion of Reptilia was lower (9.3%, two species). Amphibia were represented only with one specimen of the common toad (Bufo bufo). The dominant diet of long-legged buzzards in southeastern Bulgaria was European souslik (Spermophilus citellus, 31.0%), followed by sibling vole (Microtus mystacinus, 25.5%). Less abundant taxa were undetermined Passeriformes (6.9%), lesser mole rat (Nannospalax leucodon, 5.9%), pigeons (4.5 %), blotched snake (Elaphe sauromates, 3.8%), Balkan green lizard (Lacerta trilineata, 3.5%), European hare (Lepus europaeus, 3.1%), common magpie (Pica pica, 2.8%), Colubridae (1.7%), common blackbird (Turdus merula, 1.4%), domestic chicken (Gallus gallus domesticus, 1.0%) and Eurasian skylark (Alauda arvensis, 1.0%). Spermophilus citellus was the most abundant species in the Yambol district samples and the most abundant species in the data obtained from trail cameras. In the Burgas district, the dominant species was Microtus mystacinus. When comparing the diet spectrum of Buteo rufinus from other authors, birds occurred more frequently than reptiles in our material.
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