Saker falcon populations suffered severe declines, especially in the second half of the 20 th century. During the period between 2004 and 2018, the species became extinct in Bulgaria as a breeding ...species. After that, a reintroduction program was implemented with birds originating from central Europe. We studied the main behavioral characteristics of both wild sakers from the local population of the species in SE-Bulgaria and these of the reintroduced birds which started breeding in the same region in a wild in 2018. We collected numerous observations on the territorial, hunting, and breeding (parental) behavior of that species. Territorial attacks against 16 bird species were recorded with prevailing numbers against kestrel ( Falco tinnunculus ) and imperial eagle ( Aquila heliaca ). The main hunting strategies of the species included attacks against sousliks ( Spermophilus citellus ) in their numerous colonies in the study area. Various species of birds were also captured and brought in the nest. Adults were feeding the nestlings in 31.5-55.3 min intervals depending on their age. In the morning hours (7 am - 12 pm) the duration of the feeding of the nestlings is lower - 11.35±3,5 min on average, compared to the afternoon (12 pm - 5 pm) - 18.81±6,81 min. After the disappearance of a female in 2021, the male alone fed and cared for three nestlings during a period of 19 days. The male stopped feeding the nestlings after finding another female and consequently all the nestlings were found dead.
The Barn Owl (
Tyto alba
Gould, 1837) is a rare and endangered species in Bulgaria, included in the Red Data Book (Golemansky 2015) as “Vulnerable”, with national population estimated at 200–700 ...pairs. Barn Owl presence was surveyed using sound provocation during the night at 161 points in 52 small to medium-sized settlements in Sliven and Yambol districts (Thracian plain, SE Bulgaria). The studied territory was about 1190 km
2
. The habitats presented in a 3-km radius around the presence and potential absence points were statistically analysed. The species was found to be a quite common breeding species in the study area – a total of 56 Barn Owls were registered, at 50 points (31.1%), in 31 settlements (62% of all studied). Clear defensive behavior was observed against the source of the sound in many occasions. The average density of the population was 4.2 occupied territories / 100 km
2
. The occupied locations were situated mostly in settlements laying in deforested lowland areas (far from large forest patches), with flat or hilly relief, covered by agricultural lands, pastures and steppes. The number of presences was found to be scarce in villages along heavily used motorways. Traffic-caused mortality of Barn Owls is commented as a probable explanation.
During 2018–2022, the local breeding population of the long-legged buzzard (
) 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 (
sp.), thrushes (
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 (
). The dominant diet of long-legged buzzards in southeastern Bulgaria was European souslik (
, 31.0%), followed by sibling vole (
, 25.5%). Less abundant taxa were undetermined Passeriformes (6.9%), lesser mole rat (
, 5.9%), pigeons (4.5 %), blotched snake (
, 3.8%), Balkan green lizard (
, 3.5%), European hare (
, 3.1%), common magpie (
, 2.8%), Colubridae (1.7%), common blackbird (
, 1.4%), domestic chicken (
, 1.0%) and Eurasian skylark (
, 1.0%).
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
. When comparing the diet spectrum of
from other authors, birds occurred more frequently than reptiles in our material.
Blood parasites of migrating yellow wagtails of two subspecies—
Motacilla flava feldegg
and
Motacilla flava flava
—were studied on a sample of 473 birds caught in spring and autumn periods in ...Bulgaria. We controlled eight “migration waves” (flocks captured in different evenings) of yellow wagtails for four parameters—average body mass, average fat level, average wing length, and average prevalence of different hematozoan species. Gametocytes or meronts of a total of six species of hematozoa belonging to three genera were identified—
Haemoproteus motacillae
,
Haemoproteus anthi
,
Plasmodium relictum
,
Plasmodium subpraecox
,
Plasmodium cathemerium
, and
Tryponosoma avium
. Mixed infections were detected in 31 cases, of which 14 were of
H. anthi
/
H. motacillae
type. Parasite species composition was similar in the two studied subspecies of
M. flava
. We did not find any significant differences in the overall infection prevalence or number of infecting parasites between
M. f. flava
and
M. f. feldegg
. Parasite prevalence and the number of co-infecting parasites in spring were much higher than in fall. Season had a strong influence on the prevalence of
H. anthi
and
H. motacillae
, and for both, there was a marginally significant interaction between subspecies and season, but not a season-independent influence of subspecies. Males of
M. f. feldegg
had a significantly higher overall blood parasite prevalence and prevalence of
H. anthi
than females. Sex-related differences in the prevalence of other parasites were not significant. Migration waves of yellow wagtails differed in overall infection status and in
H. motacillae
prevalence, but not for
H. anthi
prevalence. We also found significant differences in fat score, weight, and wing length between the studied migration waves of the yellow wagtails. Fat scores of birds infected with different hematozoa were lower compared with those of the non-infected birds. This only marginally was true for body weight and was not the case for wing length. Overall, infected birds were in worse condition (estimated as the residual weight after regression with wing length) compared with the non-infected birds, but after controlling for seasonal effects, the differences in condition appeared to be due to migration season and did not significantly differ between infected and non-infected birds caught in the same season.
The ruddy shelduck (Tadorna ferruginea) is a species of great conservation importance within its European breeding grounds. Tadorna ferruginea is included in the Red Data Book of Bulgaria (2015) in ...the category “Critically Endangered”. The species is qualified as “Near Threatened” in EU27 countries as a whole. Recent data from the Balkan parts of the species range indicate its considerable enlargement. During the last 10-year period, the presence status of the ruddy shelduck during winter changed from incidentally wintering in low numbers to regular and even locally abundant wintering species. The numbers of T. ferruginea migrating over the Eastern Balkans increased substantially, especially during autumn. The reasons of these expansion of the species are discussed.
The area of Coastal Dobrudzha in NE Bulgaria is well known for its richness of vagrants. A long-term research project was started at a location at Durankulak Lake, on the northern Black Sea Coast, ...aiming to obtain data on the characteristics of autumn migration of passerine birds and on the presence of vagrants there. A total of 20 mist nets with an overall length of 200 meters were set between August and October in two different habitats - reed bed and broad-leaved forest. In 2019, a total of 9344 birds of 84 species were caught and ringed. In 2020, the number of the birds caught increased to 13786 of 93 species. Vagrants such as dusky warbler (Phylloscopus fuscatus), yellow-browed warbler (Phylloscopus inornatus) and red-flanked bluetail (Tarsiger cyanurus) were captured in 2020. Detailed information about these findings is given in the present work.
Hunting behavior was studied in a small breeding population of Red-footed Falcons in SE-Bulgaria and in a transitory migrants of the same species. A total of seven types of hunting strategies were ...performed by the Red-footed Falcons which can be rapidly switched from one to another in relation to the available type of prey, the speed and direction of the wind. It was recorded that the hovering series were longer in calm weather (wind speed < 2 m/s) and in strong winds (over 5 m/s) than in moderate winds (2 – 5 m/s). Difference was found in the mean length of the hovering series between the migrating and local breeding Red-footed Falcons. The hunting success of the finished attacks of the Redfooted Falcons was in overall 59.6 %.
Large flocks of Yelkouan Shearwaters (Puffinus yelkouan Acerbi, 1827) were reported to migrate along the northern Bulgarian Black Sea coast in the winter. On 06.02.2021, a total of 15,488 Yelkouan ...Shearwaters were counted for one hour after midday at Dobrudzha campsite, Shabla. During February 2021 and 2022, some smaller flocks were also observed. In the past, such big concentrations of Yelkouan Shearwaters in the Black Sea have been reported only during the spring, summer and rarely autumn. The possible explanations for such a winter influx of the species are discussed.
•We studied stand variables determining presence of Semi-collared Flycatcher.•Forest stand age and portion of broad-leaved cover determined species presence.•22.3% of Bulgarian forests show a ...predicted habitat suitability higher than 50%.•Suitable forests are older than 75, hence exceeding age of commercial logging.•Reduced logging of old-growth stands foster presence of Semi-collared Flycatcher.
Intensive forest management has caused a decline in the numbers of birds specialized on old growth. Understanding how forest stand attributes influence the distribution of these specialists has hence become a prerequisite for sustainable forest management. In this study, we evaluated the conservation value of managed forests for old-growth forest specialists using the poorly studied Semi-collared Flycatcher as an example. We applied a boosted generalized additive model to identify forest characteristics that determine the occurrence of the bird in Bulgaria. We found that on a national scale, forest stand age and percent cover of broad-leaved forests best explain the breeding distribution of the flycatcher. Although, forest stands became suitable habitat at an age of around 70 years for this species, stands in the interior forest featuring trees older than 160 years and composed of more than 80% broad-leaved trees were preferred by the species. At a local scale, the amount of dead wood positively influenced nest site choice of the flycatcher. In total, 22.3% of all studied broad-leaved forests in Bulgaria showed a predicted habitat suitability higher than 50%. High-stem forests that are old enough to develop old-growth characteristics had the highest potential to serve as habitat for the Semi-collared Flycatcher in Bulgaria. Therefore, we conclude that a decrease in logging of forests stands older than 160 years decreases the risk of decline of the Semi-collared Flycatcher.
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 2001−2002 and 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.
PDF
