Papers by Stoycho Stoychev
Species’ range shifts and local extinctions caused by global change lead to community composition... more Species’ range shifts and local extinctions caused by global change lead to community composition changes. At large spatial scales, ecological barriers, such as biome boundaries, coastlines, elevation, and temperature gradients, can influence a community's ability to shift. Yet, ecological barriers are rarely considered in global change studies, potentially hindering predictions of biodiversity shifts. We used data from two consecutive European breeding bird atlases to calculate the geographic distance and direction between communities in the 1980's and their nearest compositional equivalent in the 2010’s and modelled their response to barriers. The ecological barriers affected both the distance and direction of bird community composition shifts, with coasts and elevation having the strongest influence. Combining ecological barriers and community shift projections can identify ecological corridors that facilitate shifts of species and communities under global change.
ABSTRACT The Natura 2000 network has been created across the European Union to enhance the conser... more ABSTRACT The Natura 2000 network has been created across the European Union to enhance the conservation of biological diversity together with regional sustainable development. Although it covers 18% of the area of the 28 member states (Bulgaria being amongst the countries with the highest coverage, with 34.4%), there is still uncertainty about its long-term effectiveness. Here, we summarise the results of 18 contributions representing Supplement 5 of Acta zoologica bulgarica. These studies have been conducted primarily under the project “Conservation of globally important biodiversity in high nature value semi-natural grasslands through support for the traditional local economy” (2007–2011) in Bulgaria. The reviewed studies cover two Special Protection Areas, Ponor and Besaparski Ridove, within the Natura 2000 network and discuss current inventory and conservation topics on various elements of local biodiversity, such as open and forest habitats, vascular plants, invertebrates, amphibians, reptiles, birds, bats and terrestrial small mammals. A wide range of threats was identified, some of them being site- or group-specific while others were common and related mainly to habitat loss and degradation. The common nature of the environmental problems demonstrates the main challenges to the implementation of Natura 2000 in Bulgaria and the urgent need of management plans for the network sites. In order to fulfil the purpose of the ecological network for more efficient conservation of biodiversity in Bulgaria, the most important priority measures include ensuring a legislative mechanism for adequate management, regular monitoring and better control.
Slovak Raptor Journal, 2014
A long-living species like A. heliaca has a natal dispersal period lasting several years. This pe... more A long-living species like A. heliaca has a natal dispersal period lasting several years. This period is crucial for the survival and conservation of the eagles. In this study we present mortality factors and the survival rate of juvenile and immature A. heliaca from Bulgaria as established by satellite telemetry. A total of 20 juvenile A. heliaca were fitted with GPS/Argos transmitters in their nests in Bulgaria. Fourteen birds were tracked till their death and the bodies were found. Tracking allows the survival rate of juvenile and immature A. heliaca to be estimated for the first time. It is 59.1% for the first calendar year, 83.3% for the second calendar year and 80.0% for the third calendar year. The main mortality factor for juvenile and immature A. heliaca from the Bulgarian population is electrocution, which caused 59.0% of the mortality cases. Other threats identified are shooting, poisoning and collisions. Most of the fatalities of these tracked eagles occurred in Bulgaria...
The Birds of North America Online, 1997
The northern goshawk is the largest of the three North American accipiters, or forest hawks. Fema... more The northern goshawk is the largest of the three North American accipiters, or forest hawks. Female goshawks are similar in size to the common red-tailed hawk (Buteo jamaicensis), whereas male goshawks are somewhat smaller. Like all accipiters, goshawks exhibit short, rounded wings and a long tail compared to those of buteos such as the red-tailed hawk. The goshawks' wings are more tapered or falcon-like and its tail is broader than that of its closest relative, the Cooper's hawk (A. cooperii). The wing beats of the northern goshawk are heavy and deep like those of some of the larger species of buteo. The call of the northern goshawk is a series of loud, piercing "cacks" that can be heard from nearly a mile away. Adult northern goshawks are pale blue-gray on the back and whitish underneath with fine charcoal-colored barring. Juveniles are brown above with a narrow, tawny bar across the upperwing and buff-colored below with broad, dark vertical streaking on the breast and belly. Juvenile goshawks obtain adult plumage during their first molt, which occurs in their second year of age. All ages show a diagnostic broad, white superciliary (eyebrow) line. Eye color changes from yellow in juveniles to blood red in adults. The sexes are nearly identical in plumage.
650-750 pairs. Increasing in range and numbers. Patchy and dispersed distribution over the countr... more 650-750 pairs. Increasing in range and numbers. Patchy and dispersed distribution over the countryq mainly in the plain and low-mountain areas.
Ornis Hungarica
The spatial ecology of the Eurasian Griffon Vulture (Gyps fulvus) has been a subject of scientifi... more The spatial ecology of the Eurasian Griffon Vulture (Gyps fulvus) has been a subject of scientific interest for long due to its conservation status, critical ecosystem role, gregarious lifestyle and complex foraging behavior. The trans-border Eastern Rhodope Mountain in Bulgaria and Greece holds an increasing population of the species and one of the largest on the Balkan Peninsula. We used high-frequency GPS data from 13 Griffon Vultures from this population to study their movements, home range size and its seasonal or age specific dynamics. The overall foraging home range (95% kernel) was 3,204 km2 and the core area of activity (50% kernel) was 256.5 km2. We found high seasonal variation of the home range size. Vultures were foraging over larger areas in the summer and spring but their activity was limited to four times smaller areas in winter. We found no age specific variation in the home range sizes but the non-adult vultures showed tendency to conduct exploratory movements far ...
Acrocephalus
The Goosander Mergus merganser was not recorded breeding in Bulgaria till recently. We present he... more The Goosander Mergus merganser was not recorded breeding in Bulgaria till recently. We present herewith the very first record of the species breeding in the country and estimate the size of its breeding population in Bulgaria. Thus, we propose a change in its status in the country with more effort to be invested in the survey of this small, isolated population.
Many populations of long-distance migrants are declining and there is increasing evidence that de... more Many populations of long-distance migrants are declining and there is increasing evidence that declines may be caused by factors operating outside the breeding season. Among the four vulture species breeding in the western Palaearctic, the species showing the steepest population decline, the Egyptian Vulture Neophron percnopterus, is a longdistance migrant wintering in Africa. However, the flyways and wintering areas of the species are only known for some populations, and without knowledge of where mortality occurs, effective conservation management is not possible. We tracked 19 juvenile Egyptian Vultures from the declining breeding population on the Balkan Peninsula between 2010 and 2014 to estimate survival and identify important migratory routes and wintering areas for this species. Mortality during the first autumn migration was high (monthly survival probability 0.75) but mortality during migration was exclusively associated with suboptimal navigation. All birds from western breeding areas and three birds from central and eastern breeding areas attempted to fly south over the Mediterranean Sea, but only one in 10 birds survived this route, probably due to stronger tailwind. All eight birds using the migratory route via Turkey and the Middle East successfully completed their first autumn migration. Of 14 individual and environmental variables examined to explain why juvenile birds did or did not successfully complete their first migration, the natal origin of the bird was the most influential. We speculate that in a declining population with fewer experienced adults, an increasing proportion of juvenile birds are forced to migrate without conspecific guidance, leading to high mortality as a consequence of following sub-optimal migratory routes. Juvenile Egyptian Vultures wintered across a vast range of the Sahel and eastern Africa, and had large movement ranges with core use areas at intermediate elevations in savannah, cropland or desert. Two birds were shot in Africa, where several significant threats exist for vultures at continental scales. Given the broad distribution of the birds and threats, effective conservation in Africa will be challenging and will require long-term investment. We recommend that in the short term, more efficient conservation could target narrow migration corridors in southern Turkey and the Middle East, and known congregation sites in African wintering areas.
a long-distance migratory raptor
The Thrace geographical region comprises territories of three states and covers an area of about ... more The Thrace geographical region comprises territories of three states and covers an area of about 70,000 km2. At the end of the 19th century, the Eastern Imperial Eagle ( Aquila heliaca ) was widespread throughout the region, occupying a variety of habitats. The mid-20th century marked the beginning of its dramatic decline, and in the latter half of the century the birds breeding in Northern Thrace amounted to 15-20 pairs, Eastern Thrace harbored scattered pairs along the lower reaches of the Maritsa River, while in Western Thrace the population was estimated at 6-10 pairs only. Since 2000, the systematic conservation activities implemented by Bulgarian NGO’s have improved the status of the Imperial Eagle in Bulgaria (Northern Trace). At the same time, in Western Thrace (the Greek part), only one pair was confirmed by the Dadia Reserve. Since 2008, intensive field research in European Turkey identified an abundant and stable population of the species. In Bulgaria, 44 different breedi...
Slovak Raptor Journal
This study presents the results of conservation measures undertaken and their impact on the easte... more This study presents the results of conservation measures undertaken and their impact on the eastern imperial eagle population in Bulgaria. The species is distributed in the south-eastern part of the country, as there is only one known pair in central Bulgaria. During the period 2009-201 3, 28 different breeding territories were occupied. The population increased by 20%, as the number of pairs that occupied breeding territories increased from 20 in 2009 to 24 in 201 3. In general, the mean values of the breeding parameters of the eastern imperial eagle population for the period 2009-201 3 were as follows: productivity (P) 1 .03±0.1 8; breeding success (BS) 1 .1 8±0.21 ; and fledgling success (FS) 1 .68±0.1 6. The annual survival rate of breeders varied from 0.795 to 0.932. The most important factor causing the mortality of immature eagles was electrocution. Shooting and poisoning have become important mortality factors, too. Guarded pairs had a higher mean breeding success (1 .32±0.8...
This study presents the results of conservation measures undertaken and their impact on the easte... more This study presents the results of conservation measures undertaken and their impact on the eastern imperial eagle population in Bulgaria. The species is distributed in the south-eastern part of the country, as there is only one known pair in central Bulgaria. During the period 2009–201 3, 28 different breeding territories were occupied. The population increased by 20%, as the number of pairs that occupied breeding territories increased from 20 in 2009 to 24 in 201 3. In general, the mean values of the breeding parameters of the eastern imperial eagle population for the period 2009–201 3 were as follows: productivity (P) 1 .03±0.1 8; breeding success (BS) 1 .1 8±0.21 ; and fledgling success (FS) 1 .68±0.1 6. The annual survival rate of breeders varied from 0.795 to 0.932. The most important factor causing the mortality of immature eagles was electrocution. Shooting and poisoning have become important mortality factors, too. Guarded pairs had a higher mean breeding success (1 .32±0.8...
The data on the status of the Masked Shrike Lanius nubicus in Bulgaria is summarized. The researc... more The data on the status of the Masked Shrike Lanius nubicus in Bulgaria is summarized. The research carried out by the authors and literature data for the periods 1963−1990 and 1991−2005 on the map of Bulgaria with UTM squares are presented. The northward and westward expansion of the species’ breeding range is quite obvious, e.g. along the Maritsa River. The authors estimate the population of the Masked Shrike in Bulgaria to be 600−800 pairs.
270-320 pairs. Increasing in numbers and range. Dispersed and grouped all over the country, more ... more 270-320 pairs. Increasing in numbers and range. Dispersed and grouped all over the country, more dense at the open, dry and with abundant reptiles regions of Bulgaria.
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Papers by Stoycho Stoychev