The Eastern Imperial Eagle is a globally threatened species, represented with not more than 35–40 pairs in Bulgaria. As a facultative scavenger feeding on carcasses and parts of dead domestic and wild animals, this species is extremely vulnerable to poisonous baits and toxic agents, intentionally or accidentally set up in its food. The present study identified electrocution and poisoning as the main mortality factors for the eagles in Bulgaria. We analysed a total of 56 cases among which 44 cases were related to the mortality of non-territorial eagles in different age classes, and we found 12 dead or distressed territorial birds recorded between 1992–2019. The main mortality factor was electrocution, accounted for 30.4% of fatalities. The poisoning was the cause of mortality in 12.5% of the non-territorial and 10.7% of the breeding birds. Some of the cases were laboratory confirmed as intoxication, while the others, based on the history, clinical symptoms and field evidence, indicated poisoning. The most commonly used toxic agents were anticholinesterase’s inhibitors. As a result of a timely therapy applied to the live birds found in distress with symptoms of poisoning, six eagles were successfully treated and released back in the wild. We found that mortality of eagles depended on the age of birds, breeding or dispersal grounds, while season had no significant effect.

Considered extinct as breeding species in the early 2000s, the Saker Falcon was recovered when the first active nest from the new history of the species in Bulgaria was discovered in 2018, formed of two birds that were re-introduced back in 2015. Currently, there is only one confirmed wild breeding pair in the country - the male from 2015 with a female changed in 2020, released again as a part of the programme, in 2016. This is a report on the preliminary results and analysis of the ongoing establishment phase of the re-introduction of the Saker Falcon (Falco cherrug) in Bulgaria - first ever performed for this species in the country and globally. The period studied is 2015-2020. Following the re-introduction activities started in 2011, the current phase is defined by standardised methodology and a unified approach. Analysed and presented are methods for captive breeding and hacking, the breeding performance of the falcons, the number of released individuals, data from the post-fledging dependence period and a model of population growth.

Vultures play a very important role in ecosystems by feeding on dead animals and preventing the spread of pathogens. In the mid-20th century in Bulgaria, all species of vultures experienced a rapid population decline and conservation measures include captive breeding and release via adaptation aviaries. Knowledge of the baseline blood biochemical parameters is crucial for the care, rehabilitation and prior to the release of endangered birds of prey. Plasma levels provide valuable information for the evaluation of the physical condition of animals. Between 2020 and 2022, we took blood samples from captive Bearded, Griffon, Cinereous and Egyptian Vultures in Bulgaria (n = 118). We determined the values of 18 parameters - alanine transaminase, albumin, alkaline phosphatase, amylase, aspartate transaminase, calcium, chloride, cholesterol, creatine kinase, creatinine, glucose, lactate dehydrogenase, magnesium, phosphorus, total bilirubin, total protein, triglycerides and uric acid. This research determined the mean blood biochemical indices for aviary Bearded, Griffon, Cinereous and Egyptian Vultures in Bulgaria and compared the values amongst the four vulture species, to serve in determining clinical pathology and nutrition for scavenger birds of different species, age groups and genders in the country. The results of this study suggested that there are significant differences between many of the indicators of the four vulture species. There are fewer differences in the indicators of different ages of birds of a given species and almost no differences are found between the two sexes of a species. These values could be used by scientists, veterinary pathologists, wildlife rehabilitation centres and other researchers. Furthermore, the use of such parameters in assessing population health may enable conservationists to further research environmental conditions affecting the vultures’ reproduction and survival.

The European Griffon Vulture Gyps fulvus is a large-sized scavenger exploiting carcasses of livestock and wild ungulates and thus having a paramount importance in the natural ecosystems. In this study, we report on an adult Griffon Vulture detected with lead levels in the bones over the threshold. After two years of tracking, the bird died. The corpse’s clinical examination and radiography detected the presence of two embedded lead pellets from a healed gunshot wound in its right wing. Quantitative laboratory analysis of lead in bone and liver samples evidencing subclinical/chronic lead intoxication of the Griffon Vulture could potentially be a result of the long-term exposure to the lead originating from the pellets in its wing.

We collected blood samples from 44 Western Saker Falcons (Falco cherrug cherrug) and 68 Eastern Saker Falcons (Falco cherrug milvipes) in captivity at two facilities in Bulgaria to evaluate the health of individuals involved in a reintroduction project, and to gain insight into appropriate veterinary care and treatment of the birds. We compared the values of 18 biochemical parameters between the two subspecies and also between females and males. We found significant differences between the two subspecies for some of the parameters tested; however, they likely resulted from different feeding regimes at the two breeding facilities—one housing most of the Western Saker Falcons and the other all the Eastern Saker Falcons. Further tests should compare the biochemical values between birds of the two subspecies housed in the same facility. We also found significant differences in the biochemistry of female and male falcons across some parameters tested. After 20 yr without a record of Saker Falcons (Falco cherrug) nesting in Bulgaria, this globally endangered species has been successfully breeding there since 2018 as a result of an ongoing reintroduction project. By establishing baseline information on the differences in the biochemistry of Saker Falcons, our research may guide future studies of this rare species and aid veterinary care and treatment of the birds breeding in captivity.