Georgi Popgeorgiev - Academia.edu (original) (raw)

Papers by Georgi Popgeorgiev

Пернатые хищники и их охрана, Oct 30, 2018

Пернатые хищники и их охрана, Oct 1, 2018

Water Air and Soil Pollution, Mar 17, 2021

In this study, basic erythrocyte sizes in P. ridibundus individuals inhabiting a polluted area (h... more In this study, basic erythrocyte sizes in P. ridibundus individuals inhabiting a polluted area (heavy metals, nitrates, nitrites, and ammonium) in southern Bulgaria were evaluated. The erythrocyte cells’ parameters, erythrocyte length (EL), erythrocyte width (EW), length/width ratio (EL/EW), and erythrocyte size (ES), and nuclear parameters, nucleus length (NL), nucleus width (NW), NL/NW ratio, nucleus size (NS) and NS/ES ratio were either measured or calculated. The data obtained were compared with the data from identical measurements made in frogs inhabiting a reference site. In this study, an authentic reduction was established, of the basic erythrocyte-metric cells (EL, EW, EL/EW ratio, and ES) and nuclear (NL, NW, NL/NW, and NS) parameters in P. ridibundus individuals that inhabit the polluted industrial area east of the city of Plovdiv. In those frogs’ blood, oval and spherical erythrocytes circulate. For the erythrocytes from frogs in the polluted site, a significant reduction was found in the nucleus/cytoplasm ratio. Those changes can be seen as adaptations enlarging the contact surface and the oxygen capacity of the erythrocytes in conditions of hypoxia. The results of our research once again emphasize the importance of hematological investigations and specifically of the blood cell morphology as reliable biomarkers in ecotoxicological research in the field.

Biodiversity and Conservation, 2017

The management of Arctic migrant geese is complex, because they frequently use landscapes under i... more The management of Arctic migrant geese is complex, because they frequently use landscapes under intensive human use, and are conflict species in multiple respects. Some populations are of high conservation concern, but they also cause agricultural damage, are quarry for hunters, and may be particularly sensitive to infrastructure developments. In Bulgarian Dobrudzha, large wintering populations of greater white-fronted geese Anser albifrons and red-breasted geese Branta ruficollis feed in agricultural land, and cause management dilemmas. We developed linear models to investigate fine-and mesoscale foraging habitat selection of geese foraging on winter wheat in the area, and used these models to make suggestions for zoning landscape use in order to reduce conflict and conserve geese. Habitat selection was scale-dependent. Geese selected fields that were near to major roosts and had low proximity to roads and tree-lines, which may be a proxy for hunting disturbance. We found some evidence for selection of wheat fields with high nutritional quality. Within fields, geese strongly avoided features which cause landscape 'clutter': power-lines, tree-lines and wind-turbines, but primarily over distances of less than a few hundred metres. Optimal management might involve encouraging goose populations to feed in areas close to roosts, by means of agri-environmental measures and creation of hunting-free refuges. This would allow efficient use of agri-environment funds, might reduce conflict with farmers, and would mean that infrastructure development-Communicated by Dr. Grzegorz Mikusinski.

First survey on the invasive Pond slider (Trachemys scripta) in Bulgaria: historic development an... more First survey on the invasive Pond slider (Trachemys scripta) in Bulgaria: historic development and current situation Prvo istraživanje invazivne crvenouhe kornjače (Trachemys scripta) u Bugarskoj: povijesni razvoj i trenutno stanje

Herpetology Notes, Jan 27, 2017

Northward). from the Balkan Mountains, the species was found in natural sites only along the Blac... more Northward). from the Balkan Mountains, the species was found in natural sites only along the Black Sea coast, Ruse town and at the Orlova chuka cave (Kovachev, 1912; Unjian and Ivanov, 1966; Tzankov et al., 2009). Microclimatic features are considered to confine its distribution. Three subspecies of M. kotschyi are known from Bulgaria: M. k. bibroni inhabits the valleys of the Struma and Mesta ivers n southwestern Bulgari M. k. rumelicus is known from the regions of Plovdiv

Zoology and ecology, Sep 24, 2018

Commercial trade in Pond sliders (Trachemys scripta scripta and T. s. elegans) is the most import... more Commercial trade in Pond sliders (Trachemys scripta scripta and T. s. elegans) is the most important factor responsible for their wide distribution in ecosystems where they are nonnative. Pond sliders have been very popular pets in Bulgaria since 1990 and can be still obtained commercially for several Euros from pet shops or via the Internet. There is a tendency for these turtles to be kept until maturity and then released into the wild. In the present study we used questionnaires to investigate awareness among the people in NE Bulgaria of the dangers related to housing Pond sliders as pets and the environmental risks presented by releasing them into the wild. Additionally, we studied patterns in the trading of Pond sliders in Bulgaria and the prevalence of these non-native turtles in the water catchments of NE Bulgaria. Our data revealed a very low level of awareness and competence among the respondents concerning the biology and the status of the Pond sliders. We also provide data on an unrestrained trade in Pond sliders and identify 15 new localities where Pond sliders were detected in the wild of NE Bulgaria.

Nature and Conservation, Jul 7, 2023

Although Morimus asper, in particular the ssp. funereus, is considered as widespread throughout B... more Although Morimus asper, in particular the ssp. funereus, is considered as widespread throughout Bulgaria, a current national mapping of the species is missing. Thus, here we present the first exhaustive study on the distribution of M. asper in Bulgaria. Our research combined 967 georeferenced presence records from scientific publications, from the museum collection of the National Museum of Natural History-BAS, as well as authors' and citizen scientists' field observations. An Ecological Niche Model (ENM) was generated using software MaxEnt to identify the potential distribution of the species based on niche suitability. The potentially suitable area for the species was 26% of Bulgaria (29 059 km 2). The main predictor variables in M. asper's ENM assessed by а Jackknife test were the distance to mixed Fagus-Carpinus forests, the mean forest age, the mean tree height, the maximal temperature during the hottest month and the altitude. The percentage contribution to the model of the first two variables was also the largest-respectively 40% and 11%. The remaining variables contributed less than 10% each. Furthermore, we recommend some changes to the current species monitoring methodology to the National Biodiversity Monitoring System.

Figure 1. Phylogenetic tree resulting from the Bayesian inference (BI) analysis of three mitochon... more Figure 1. Phylogenetic tree resulting from the Bayesian inference (BI) analysis of three mitochondrial and three nuclear genes concatenated. Nodes were considered supported when Bayesian posterior probability was ≥ 0.95 and maximum likelihood (ML) bootstrap values ≥ 70. Lengths of branches connecting the split between Platyceps collaris and Platyceps najadum and the crown nodes of those species are not proportional to the rest of the tree and the scale, which is indicated by their partial transparency. The two clades, the Balkan–Anatolian and the Levantine, are highlighted in the tree with the red and green shading, respectively. Four species of Telescopus used to root the tree are not shown. Each tree tip is connected by a dashed line with the locality of its sample, which is marked by a number (for details, see Table 1). Type localities are marked with stars: P. collaris collaris in green, P. collaris rubriceps in white and Coluber rubriceps thracius in pink. The potential current...

Figure 2. Phylogenetic network from SPLITSTREE, showing the reticulate relationships within the t... more Figure 2. Phylogenetic network from SPLITSTREE, showing the reticulate relationships within the two clades of Platyceps collaris, the Balkan–Anatolian clade (red) and the Levantine clade (green). Numbers in circles are locality numbers shown in Figure 1 and detailed in Table 1. Bootstrap support values for major nodes ≥ 70 are indicated. The specimen depicted is from Ropotamo, Bulgaria.

Pond sliders (Trachemys scripta) have become a popular pet in Bulgaria since 1990. Through the ye... more Pond sliders (Trachemys scripta) have become a popular pet in Bulgaria since 1990. Through the years a number of released specimens were observed in the wild. Although the negative effects on native turtles have been studied extensively elsewhere, no specific studies (besides brief reports) have addressed the invasion of T. scripta in Bulgaria. The present study is based on over 25 years of field monitoring and represents the first source of detailed information on the distribution of the Pond slider in Bulgaria. A total of 293 UTM (10×10 km) squares with habitats suitable for freshwater turtles were surveyed. We collected 64 records for 173 individuals, from 19 UTM squares. From all observed individuals, only two were from the nominate subspecies – the rest belong to T. s. elegans. In our study only one subadult was observed. To date no successful hatching has been recorded, although successful overwinterings have been registered. We discuss various mitigation measures that must be...

Journal of Ornithology, 2016

Avian scavengers are declining throughout the world, and are affected by a large number of threat... more Avian scavengers are declining throughout the world, and are affected by a large number of threats such as poisoning, electrocution, collision with man-made structures, direct persecution, changes in agricultural practices, landscape composition, and sanitary regulations that can reduce food availability. To formulate effective conservation strategies, it is important to quantify which of these factors has the greatest influence on demographic parameters such as territory occupancy and breeding success, and whether quantitative models can be transferred across geographic regions and political boundaries. We collated territory and nest monitoring data of the endangered Egyptian Vulture Neophron percnopterus in the Balkans to understand the relative influence of various factors on population declines. We monitored occupancy in 87 different territories and breeding performance of 405 territory-monitoring years between 2003 and 2015, with an overall territory occupancy rate of 69% and a mean productivity of 0.80 fledglings per occupied territory. We examined which of 48 different environmental variables were most influential in explaining variation in territory occupancy and breeding success in Bulgaria and Greece, and tested whether these models were transferrable to the Former Yugoslav Republic of Macedonia. Territory occupancy and breeding success were affected by a wide range of environmental variables, each of which had a small effect that may not be the same across political boundaries. Both models had reasonably good discriminative ability [area under the receiver-operated characteristic curve (AUC) for territory occupancy = 0.871, AUC for breeding success = 0.744], but were unsuccessful in predicting occupancy or breeding success in the external validation data set from a different country, possibly because the most influential factors vary geographically. Management focussing on a small number of environmental variables is unlikely to be effective in slowing the decline of Egyptian Vultures on the Balkan Peninsula. We recommend that in the short term the reduction of adult mortality through the enforcement of anti-poison laws, and in the long term the adoption of large-scale landscape conservation programs that retain or restore historical small-scale farming practices may benefit vultures and other biodiversity.

international workshop on the management and restoration of Hermann's tortoise populations an... more international workshop on the management and restoration of Hermann's tortoise populations and habitats" are published in the framework of the LIFE project number LIFE 08NAT/F/000475 "Toward an integrative management in favour of the terrestrial tortoises in Var – Creating tools for the managers of natural habitats in Europe" By the Station d'Observation et de Protection des Tortues et de leurs Milieux (SOPTOM) Chelonii®is a journal published by SOPTOM, with an editing committee, to promote and develop information on chelonians and their conservation. This scientific publication includes congress proceedings, monographs, synthesized documents and papers. Half of the journal will deal with chelonians from the European and Mediterranean region and French-speaking countries. However, the journal is open to unusual texts by all chelonians specialists. It is supervised by the SOPTOM's scientific administrator with the assistance of scientific counselors for eac...

Communications in Soil Science and Plant Analysis, 2001

... system, Milford, MA, consisting of Maxima controller, 510 pump, 710B autosampler, and 490 UV ... more ... system, Milford, MA, consisting of Maxima controller, 510 pump, 710B autosampler, and 490 UV detector) analysis [6]6. Locke, MA, Gaston, LA and ... of cosolvent on the extent of dissociation, coupled with cosolvency effects [8]8. Lee, LS, Bellin, CA, Pinal, R. and Rao, PSC 1993. ...