Causes of admission to a raptor rehabilitation centre and factors that can be used to predict the likelihood of release

Trends in Admissions and Outcomes at a British Wildlife Rehabilitation Centre over a Ten-Year Period (2012-2022)

Millions of animals pass through wildlife rehabilitation centres (WRCs) globally each year, some dying in captivity, others euthanised, and some released into the wild. Those caring for these animals are generally well-intentioned, but skills, knowledge, and resources may be limited, potentially compromising animal welfare. WRC databases provide an opportunity to provide an evidence base for treatment and conservation efforts. 42,841 records of animals admitted over a 10-year period to a British WRC were analysed. More birds (69.16%) were admitted than mammals (30.48%) and reptiles and amphibians (0.36%). Most admissions were in the summer (48.8%) and spring (26.0%) months. A total of 9 of the 196 species seen made up 57% of admissions, and hedgehogs were the most common species admitted (14% of all admissions and 20% of mammals). Juvenile animals (35.5%) were admitted more frequently than 'orphans' (26.0%) or adults (26.4%). 'Orphaned' was also the predominant reason for admission (28.3%), followed by 'injured' (25.5%). 42.6% of animals were eventually released back to the wild, 19.2% died in captivity, and 37.2% were euthanised; 1% of outcomes were unknown. The prognosis was better for orphaned animals than for those admitted because of injury. Unexpected natural deaths in captivity were found to decline over the period of study, consistent with improved early triage. These findings can be used to focus veterinary and WRC training and seasonal resources on the species and case types most likely to be successfully rehabilitated and released. The findings also have the potential to contribute to our understanding of anthropogenic impacts, historical and regional variations in ecosystem health, and resultant implications for animal welfare.

Evaluation of Thermal Antinociceptive Effects of Intramuscular Hydromorphone Hydrochloride in Great Horned Owls (Bubo virginianus)

Across the Americas, great horned owls (Bubo virginianus) are often presented to veterinarians for conditions requiring pain management. Although recent studies have evaluated opioid drugs in raptor species, information in Strigiformes is lacking. The objective of this study was to evaluate the analgesic effect and duration of action of hydromorphone hydrochloride, a full µ-opioid receptor agonist, in great horned owls. In a randomized, blinded, balanced crossover study, 6 adult birds (5 females and 1 male) received hydromorphone (0.3 and 0.6 mg/kg) or saline (0.9% NaCl) solution (0.03 mL/kg; control) in the left pectoral muscle, with a 7-day washout interval between treatments. Each bird was assigned an agitation-sedation score, and the thermal foot withdrawal threshold (TFWT) was measured at predetermined times before (t = 0 hours) and after treatment administration (t = 0.5, 1.5, 3, and 6 hours). Measurements of the TFWT were obtained with a test box equipped with a thermal perch, which delivered a gradually increasing temperature 40-62°C (104-143.6°F) to the right plantar surface of the owl's foot. Compared with controls, hydromorphone at 0.3 mg/kg dose resulted in significantly higher mean TFWT at 0.5 hours (P < 0.001), 1.5 hours (P = 0.003), and 3 hours (P = 0.005), whereas the 0.6 mg/kg dose resulted in significantly higher mean TFWT from 0.5 hours (P = 0.035) to 1.5 hours (P = 0.001). Both hydromorphone doses were associated with a significant change in the agitation-sedation score (P = 0.001), consistent with mild to moderate sedation. Two owls were observed tremoring after administration of the 0.6 mg/kg dose, which was not noted after the 0.5-hour timepoint; no other adverse effects were identified. This study offers scientific evidence to support the use of a µ-opioid agonist in great horned owls for pain management. Pharmacokinetics and other pharmacodynamic studies of other pain models evaluating hydromorphone and other opioid drugs in this species are still needed.

Anthropogenic threats to owls: Insights from rehabilitation admittance data and rodenticide screening in Texas

Owls (Strigiformes) provide myriad ecosystem services and are sentinels for ecosystem health. However, they are at continued risk from anthropogenic threats such as vehicle collisions, entanglement with human-made materials, and exposure to anticoagulant rodenticides (ARs), a widespread pesticide known to affect owls. Texas is an important region for numerous migratory and non-migratory owl species in the United States (US), yet assessments of threats owls face here are lacking preventing the development of informed conservation strategies. This study coupled assessment of admittance data from two wildlife rehabilitation centers in Texas with AR liver screening to (1) identify which species of owls are commonly admitted, (2) evaluate seasonality of admittance, and (3) assess causes of admittance for owls in Texas. Between 2010 and 2021, 1,620 owls were admitted into rehabilitation, representing eight species of which the Great-horned Owl (Bubo virginianus) was the most common. For all owls combined admittance rates were highest in the spring, driven by an influx of juveniles (n = 703, 43.40%). The leading cause of admittance amongst species was 'no apparent injury' (n = 567, 34.94%). Where clear diagnoses could be made, the leading causes of admittances were 'entrapment in human infrastructure' (n = 100, 6.11%) and 'collision with vehicles' (n = 74, 4.56%). While the admittance data did not reveal any cases of AR poisoning, liver screening demonstrated high incidences of AR exposure; of 53 owls screened for ARs, 50.94% (n = 27) tested positive with 18 showing exposure to multiple ARs. Brodifacoum was the most frequently detected AR (n = 19, 43.18%) and seven owls (25.93%) tested positive within lethal ranges. Our results suggest that owls in Texas are at risk from myriad anthropogenic threats and face high exposure rates to ARs. In doing so, our results can inform conservation strategies that mitigate anthropogenic threats faced by owls in Texas and beyond.

Diurnal raptors at rescue centres in the Czech Republic: Reasons for admission, outcomes, and length of stay

Rescue centres play an important role in the protection of raptors living in the wild by caring for injured or debilitated animals and abandoned young with the aim of returning them to the wild. A total of 22,538 raptors were admitted to 34 rescue centres in the Czech Republic in the years 2010-2019, with an increasing trend during the monitored period (rSp = 0.7333, p < 0.05). The most frequent reasons for their admission were other injuries and fractures (26.52%), the admission of young (22.98%), and the admission of raptors injured by electric shock injuries (20.51%). It proved possible to release 42.45% of admitted raptors back into the wild, the majority of which (91.05%) were released using the hard-release method. Foster parents were used in 1% of cases and a replacement nest in 0.2% of cases involving the rearing of young. In spite of all the care provided at rescue centres, a total of 39.97% of raptors admitted either died or had to be euthanized. Among them, most raptors were euthanized or died due to injuries caused by collision with a vehicle, electric shock injuries, and other injuries. This generally occurred shortly after admission (a median of two days). The importance of the work of rescue centres lies not merely in returning injured raptors back into the wild (which proves possible in around half of all cases), but also in obtaining information about the factors endangering raptors in the wild and contributing toward a decline in their populations. The findings provide information about human-wildlife interactions in the Czech Republic and their implications for conservation as well as on the effectiveness of rescue centres to successfully treat and subsequently release raptors back into the wild.

Causes of Raptor Admission to the Wildlife Rehabilitation Centre in Abruzzo (Central Italy) from 2005–2016

The purpose of this retrospective study was to describe the causes of morbidity and mortality in free-ranging raptors admitted to a wildlife rehabilitation center (WRC) in Abruzzo Italy from 2005 to 2016 and the associated risk factors. A total of 2496 free-ranging raptors were included in the study. We analyzed the raptors’ medical records, epidemiological information, bird characteristics, cause of admission, final diagnosis, and outcome. The prevalence rates of nocturnal and diurnal raptors were 49% and 51%, respectively. Nocturnal raptors showed trauma as the primary cause of admission (45.8%, 558/1219), followed by nestling (including birds on their first flight attempt or presumed abandoned by their parents) (39.2%, 478/1219), and starvation (5.6%, 68/1219). Diurnal raptors showed trauma (73.1%, 934/1277), starvation (12.1%, 155/1277), and nestling (5.8%, 74/1277) accordingly. A description of the dangers for wild birds of prey in the Abruzzo region was provided to assist in the planning of rescue and rehabilitation activities in the WRC. Finally, the cause of admission, GAP, and BCS can be used as prognostic factors during the bird entry process.

Surviving the Urban Jungle: Anthropogenic Threats, Wildlife-Conflicts, and Management Recommendations for African Crowned Eagles

Larger carnivores often trigger human-wildlife conflicts that arise from perceived threats to humans and domestic animals’ safety, which generate the need for management and removal strategies. These issues become especially challenging when humans and wildlife coexist close to one another, for example, in urban landscapes. African Crowned Eagles (Stephanoaetus coronatus) are powerful forest raptors that breed within the metropolitan green-space system of Durban and Pietermaritzburg, South Africa. Negative human-wildlife interactions can occur because eagles occasionally predate on pets, such as cats (Felis catus) and small dogs (Canis lupus familiaris), and provisioning domestic stock to nest sites has previously been quantified. Here, wildlife management becomes critical, usually aimed at reducing or eliminating causes of economic or social harm, but have to be balanced against conservation goals regarding threatened species. In this study, we (i) identified causes of harm or loss of Crowned Eagles because of injuries (n = 53 incidents; 31 mortalities); and (ii) describe interactions with negative perceptions to human livelihoods, particularly concerning predation on pets and livestock. Anthropogenic causes of mortality were more likely to be reported than remote natural deaths, which provides important opportunities for mitigation measures. Most avoidable are electrocution on utility poles, persecution via gunshot wounds and poisoning (targeted or secondary), while collisions with anthropogenic structures, such as glass panes, vehicles and fence wires, are more challenging to mitigate. Out of 44 verified Crowned Eagle vs. pets and livestock conflicts, we documented 19 dog attacks (2012–2020), with detrimental impacts on social perception and acceptance of urban eagles. Pet and livestock conflicts were primarily associated with juveniles and immature eagles (83%). Of these, 19% occurred during September alone, which marks the end of the post-fledging dependency period; 70% occurred outside the breeding season. We provide management recommendations regarding various categories of Crowned Eagle human-wildlife interactions. For example, activities such as rehabilitation and falconry can coordinate to achieve a high standard of public support and conservation outcomes for Crowned Eagles. Finally, we discuss using different management intervention strategies, including rehabilitation, falconry, re-wildling processes, and lethal control of specific “problem” individuals toward achieving the goal of sustainable, healthy Crowned Eagle populations that coexist with humans in urban landscapes.

Modification of the third phase in the framework for vertebrate species persistence in urban mosaic environments

Urbanisation is rapidly transforming natural landscapes with consequences for biodiversity. Little is documented on the response of African wildlife to urbanisation. We reviewed case studies of vertebrate species' responses to urbanisation in KwaZulu-Natal, South Africa to determine trends. Connected habitat mosaics of natural and anthropogenic green spaces are critical for urban wildlife persistence. We present a novel modification to the final of three phases of the framework described by Evans et al. (2010), which documents this sequence for vertebrate species persistence, based on the perspective of our research. Species in suburbia exhibit an initial phase where behavioural and ecological flexibility, life-history traits and phenotypic plasticity either contribute to their success, or they stay at low numbers. Where successful, the next phase is a rapid increase in populations and distribution; anthropogenic food resources and alternate breeding sites are effectively exploited. The modified third phase either continues to spread, plateau or decline.