INTRODUCTION

Raptors are widely regarded as sentinels both for environmental and human health (Movalli et al. 2018). Exposure to pesticides and other toxicants is recognized as one of the most pressing threats to raptors worldwide (McClure et al. 2018, Serratosa et al. 2024). In the tropics, carbamate pesticides (notably carbofuran; Ogada 2014, Alarcón and Lambertucci 2018), nonsteroidal anti-inflammatory drugs (NSAIDs) such as diclofenac (Oaks et al. 2004), and lead (Lambertucci et al. 2011) have been implicated in the death of many raptors, while in temperate regions, cholinesterase inhibitors (e.g., carbamate and organophosphorus pesticides), lead, and anticoagulant rodenticides appear to be the most common toxic agents currently affecting raptor populations (Redig and Arent 2008, Richards 2011, Langford et al. 2013, Nadjafzadeh et al. 2013, Isomursu et al. 2018, Krone 2018, Gomez et al. 2022). In Europe, various assessments have been made of the poisoning of raptors in individual countries (e.g., Parvanov et al. 2018, Moriceau et al. 2022, Sell et al. 2022), or by specific pesticide types (Garcês et al. 2023), but a continent-wide overview of raptor poisoning including the frequency of poisoning with banned and other pesticides is lacking.

The particularly indiscriminate and far-reaching nature of pesticides magnifies their repercussions to raptor populations (Newton 1988, Mineau et al. 1999, Guitart et al. 2010, Richards 2011, Langford et al. 2013, Mateo-Tomás et al. 2020). Ongoing input of toxicants in the environment and pesticide poisoning practices or malpractice can impede conservation efforts to protect raptors (Richards et al. 2017, Coeurdassier et al. 2019), particularly where small, vulnerable, or reintroduced populations occur (Molenaar et al. 2017). Poisoning that occurs in areas of high prey abundance might accelerate population extinction by creating “mortality hotspots,” which then act as population sinks (Delibes et al. 2001). Because raptors are long-lived species with low reproductive rates and delayed maturity, their populations can be especially vulnerable to loss of adult breeding birds, as is often the case with poisoned baiting (e.g., Hernández and Margalida 2008, 2009, Oppel et al. 2021). Consequently, losses due to poisoning have led to population declines of scavenging raptor populations (Tenan et al. 2012, Mateo-Tomás et al. 2020).

A major factor influencing vulnerability to poisoning is foraging strategy and the corresponding diet. Raptors that rely on carrion (i.e., obligate and facultative scavengers) are particularly susceptible to direct or secondary poisoning via contaminated food resources (Berny et al. 1997, Whitfield et al. 2003, Sanz-Aguilar et al. 2015, Krone et al. 2017, Wells et al. 2020). The case for the disproportionate and population-scale harm by poisoning of scavenging raptors such as vultures has been convincingly made (Ogada 2014, Ogada et al. 2016, Mateo-Tomás et al. 2020). Reasons for poisoning include controlling predators of livestock, including raptors themselves, and maintaining populations of game species for sporting interests and pursuits by illegal placement of poisoned baits—a practice that often goes undetected (e.g., Villafuerte et al. 1998, González et al. 2007, Margalida et al. 2008, Parrott et al. 2008, Wells and Ruddock 2009, Smart et al. 2010, Horváth et al. 2011, Burke et al. 2015). Deliberate poisoning is still pervasive in Europe today (Margalida and Mateo 2019) and often related to human-wildlife conflict (e.g., Mateo-Tomás et al. 2012). Hence the most impacted species are mammalian carnivores and scavenging raptors that feed on poisoned baits (e.g., Whitfield et al. 2003, González et al. 2007, Hernández and Margalida 2008, 2009, Tenan et al. 2012, Mateo-Tomás et al. 2020). It is estimated that intentional and unintentional poisoning may be responsible for more than half the total species mortality and local extirpations in parts of the Mediterranean region (Tavecchia et al. 2012, Mateo-Tomás et al. 2020). Poisoning is also often concentrated spatially and temporally, with certain areas or regions experiencing spikes in poisoning events, for example, when illegal predator control peaks locally or seasonally following certain types of human-livestock conflict or concern about the impact of predators on game species populations (González et al. 2007, Newton 2021).

Biomonitoring using birds of prey as sentinel species across Europe has been proposed as a way to evaluate the success of European Union directives to protect humans and the environment from pesticide pollution, but no such pan-European evaluation currently exists (Gómez-Ramírez et al. 2014, Badry et al. 2020, Valverde et al. 2022). Some 182 monitoring programs across 33 European countries collect a variety of raptor samples, including blood and liver samples, and (more commonly) feathers and failed eggs (Valverde et al. 2022). Poisoned raptors are an important source of information about pesticides used with the intent of killing raptors or other predators, and toxico-vigilance and risk assessment studies are essential to expand knowledge about the number of illegal poisoning cases and the substances involved in these crimes. However, many studies focus on one or a few key species, or those in particular localities where persecution is rife. Certain species, such as threatened eagles (facultative scavengers) and vultures (obligate scavengers) may receive a disproportionate amount of attention (e.g., González et al. 2007, Margalida et al. 2008, Lazarova et al. 2020, Sell et al. 2022, Zsinka et al. 2024) and therefore be perceived as being more at risk than they perhaps are relative to others facing an equal or greater risk. Indeed, some species are more commonly reported than others; for some, this may be because they are more widely studied and monitored, more conspicuous, or more likely to be in proximity to humans and therefore more likely to be discovered (Gil-Sánchez et al. 2021). As a result, despite regular reporting of poisoned raptors from European countries and the recent initiation of a network to examine poisoning cases in a coordinated way across Europe (Brochet et al. 2019, Valverde et al. 2022), there remains a lack of accompanying assessment of the seasonal and spatial patterns of poisons used relative to the range of raptor species affected and their diets. Such knowledge is critical to target conservation action when and where it is most needed, to determine the most vulnerable species groups, to complement preventive measures, and to support law enforcement initiatives against deliberate poisoning.

To provide insight into the spatial and temporal patterns of raptor poisoning across Europe, we collected data received from experts working with organizations (nongovernmental organizations, research institutions, ministries) that report raptor poisonings across Europe, spanning 1996–2016. These referred to known incidents of raptor poisoning generated mostly by conflicts with livestock, pigeon, and game management. This time period included the initiation of intensive monitoring for poisoning of raptors over much of Europe and the implementation of important bans on the use of frequently used poisons such as carbofuran and aldicarb. We describe our resulting dataset by reporting on the number of affected species per country and their conservation status according to the International Union for the Conservation of Nature (IUCN) Red List classification (IUCN 2024). We summarize pesticide poisoning based on spatial, temporal, seasonal, species, and diet variation. More specifically, to assess the role of foraging ecology and diet, we classified raptors as either facultative or obligate scavengers, rodent feeders, or those with other diets (e.g., insects or birds). As the detection of multiple pesticides in a poisoned raptor complicates inference of the role of specific pesticides, we categorized poisoned raptors into those with single and multiple detections of pesticides and focused our assessments of spatial and temporal patterns on the main pesticides detected as single substances in poisoned raptors. We also examined whether the proportion of the main pesticides changed over the years, and whether European trade bans possibly reduced the proportion of these poisons detected in raptors. Lastly, we examined the seasonality of poisoning of the most commonly occurring raptors in our dataset.

METHODS

Beginning in 2017, expert colleagues working in raptor conservation or biology in 22 European countries were invited to provide data on poisoning incidents involving raptors (as defined in McClure et al. 2019) for the years 1996–2016 (inclusive). Experts were selected through mutual raptor conservation, toxicology, or wildlife forensics networks, via information on the internet or through previously published articles, or with outreach to others via these primary contacts (i.e., snowball sampling). Experts worked with nongovernmental organizations, ministries or research institutions that lead or financed the data collection and analyses. The analyses were mostly outsourced to laboratories in the respective countries where raptors were poisoned (  Supplemental Material Table S1 (JRR2373_Supplemental_Material_final.pdf)). Data were shared from 31 researchers representing the following countries: Austria, Bulgaria, Croatia, Czechia, Denmark, France, Germany, Greece, Hungary, Ireland, Italy, North Macedonia, the Netherlands, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Switzerland, and the United Kingdom (UK).

Data requested included information on raptors identified as being debilitated or killed by a specific poison (i.e., a single poison), or group of poisons (multiple poisons). The dataset therefore included poisoned raptors, most of which died as a result of the poisoning, while some recovered; all raptors dead or recovered are referred to as “poisoned raptors” here. We distinguished poisoned raptors from “poisoning incidents,” with a poisoning incident referring to one or multiple poisoned raptors at a single location and time. The data collected were part of ongoing raptor poisoning monitoring, and were usually gathered in specific regions where poisoning conflicts were greatest. An overview of the laboratories involved, with type of analyses used and sample preparation where known is in   Table S1 (JRR2373_Supplemental_Material_final.pdf). The data requested included the number of poisoned raptors per species during poisoning incidents, date and location of the incident, and the type of pesticide or toxic substance detected. In certain cases, categorized separately as “unknown” or “nonspecific detection,” analyses were either not carried out or were negative. Instead, the determination of poisoning was inferred from body positioning of the bird(s) when found (e.g., cramp-like twisted limbs, bait in the beak, slimy discharge from the beak), or if the bird was still alive, on the basis of observed muscle twitching, spread wing posture, stiffened neck, dilated pupils, vomiting and seizures. The toxic substances that were detected could have been the principle cause of mortality, debilitation, or may have not have resulted in any of the physiological symptoms described above. Data were collected in a pre-defined Excel spreadsheet, with each row representing a distinct poisoning incident with one or more poisoned raptors. As the number of poisoned raptors was often uncertain, for example because potentially more were estimated to have been affected than found, we report the confirmed minimum number of poisoned raptors here.

Standardization of Data. For our analyses, we parsed out the array of pesticides and accompanying substances as reported to us by contributors in conjunction with each poisoning incident. We separated the data into two categories based on the number of pesticides detected in the poisoned raptors, as “single” or “multiple” pesticides. This approach allowed us to compare cases where a raptor was exposed to one pesticide to cases where a raptor was exposed to multiple pesticides. This approach served to highlight that carbofuran, aldicarb, alpha-chloralose and parathion—i.e., the four most frequently detected pesticides—were encountered as single pesticides in poisoned raptors, but also with other pesticides and toxic substances. Given the heterogeneity of the multiple subset of the data, we opted to focus the analyses of spatial, seasonal, and diet variation on the poisoned raptors with detections of a single substance.

Species, Spatial, Seasonal, and Diet Variation. We grouped poisoned raptors according to their main taxonomic groups: buzzards, honey-buzzards, vultures, eagles, Osprey (Pandion haliaetus), kites, harriers, falcons, hawks, and owls. We determined the number of reported species, the number of reported incidents, and the number of affected raptors by taxonomic group (Ferguson-Lees and Christie 2001). We classified species by their global population status based on their IUCN Red List classification in 2024 (IUCN 2024), which allowed us to quantify the proportion of pesticide-exposed individuals with globally decreasing populations in our dataset. To evaluate the sentinel role of commonly poisoned species for the detection of poison of other raptors, we examined whether the timing of poisoning of the most commonly occurring raptor in our dataset is similar to, and therefore illustrative of, seasonal patterns of poisoning in other species. In addition to separating the data into taxonomic groups, we examined the proportion of poisoned raptors in four main diet groups based on their foraging strategies and corresponding diets (as detailed in Ferguson-Lees and Christie 2001): (1) obligate scavengers: those species that feed exclusively or almost exclusively on carrion, (2) facultative scavengers: species that feed on carrion for a proportion of their diet, but not exclusively so, (3) rodent eaters: those species that feed on rodents, either exclusively or as a (small) part of the diet, and very rarely or not on carrion, (4) other: all other species, i.e., those feeding primarily on mammals other than rodents, birds, reptiles, fish, or insects, or a combination of those. We quantified the proportion of poisoned raptors within each diet group by country. We further examined the overall proportion of poisoned raptors attributed to the various detected substances, and the annual proportion of poisoned raptors by the most frequently detected toxic substances. We included the nonspecific cholinesterase inhibitor group in these analyses, which refers to data that did not identify specific pesticides but instead identified this group of pesticides, which is consistent with the mode of action of carbofuran, aldicarb and parathion. We grouped the poisoning incidents and poisoned raptors by country and month of the year.

RESULTS

Affected Species. In total, 3196 poisoning incidents, encompassing 4437 poisoned raptors were reported, which included 37 species (Table 1). Out of the 4437 poisoned raptors, the fate of 3556 raptors was known, with 95% reported to have died, as opposed to recovering post-debilitation. Buzzards, eagles, vultures, and kites were the most commonly reported poisoned raptor groups, which accounted for 84% of poisoning incidents and 85% of poisoned raptors (Table 1). Eurasian Buzzard (Buteo buteo; 46% of 4437 poisoned raptors), Griffon Vulture (Gyps fulvus; 12%), White-tailed Eagle (Haliaeetus albicilla; 9%), Red Kite (Milvus milvus; 7%), and Western Marsh Harrier (Circus aeruginosus; 5%) were the most commonly reported poisoned raptors, but the number of poisoned individuals per species differed greatly between countries (  Table S2 (JRR2373_Supplemental_Material_final.pdf)).

Table 1.

Species groups represented in the raptor poisoning database (1996–2016) from 22 European countries.

Six species comprising 4% of all poisoned raptors have a threatened global population status (IUCN 2024). Those species with endangered IUCN status included Saker Falcon (Falco cherrug) and Egyptian Vulture (Neophron percnopterus). Those species with a vulnerable status included Eastern Imperial Eagle (Aquila heliaca), Spanish Imperial Eagle (Aquila adalberti), Red-footed Falcon (Falco vespertinus), and Greater Spotted Eagle (Clanga clanga; Table 2). The species with near threatened IUCN status were Pallid Harrier (Circus macrourus), Cinereous Vulture (Aegypius monachus), and Bearded Vulture (Gypaetus barbatus; IUCN 2024). Fifteen of the 37 affected species (i.e., 40% of species) are categorized as having globally decreasing populations (McClure et al. 2018).

Table 2.

Conservation and 2024 IUCN Red List population status of raptor species (n = 37) from the raptor poisoning dataset, 1996–2016, spanning 22 European countries. Diet type: FS = facultative scavenger; OS = obligate scavenger; Ro = rodent eater; O = all other species. IUCN Red List trend and category (2024): LC = Least Concern; NT = Near Threatened; VU = Vulnerable, EN = Endangered. Incidents and Poisoned Individuals: Si = detection of a single substance; Mu = detection of multiple substances; Unk = detection of an unknown substance.

Table 2. Continued.

Country and Regional Differences. Within the dataset, the proportion of facultative scavengers among poisoned raptors was greatest in northeastern Europe (Fig. 1). In contrast, the proportion of obligate scavengers was greatest in the Mediterranean countries. No spatial patterns were detected for rodent-eating raptors and raptors with other diets (Fig. 1). The reported number of affected species per country (n = 1–26 species) and total number of poisoned raptors per country (n = 3–925) varied considerably (  Table S3 (JRR2373_Supplemental_Material_final.pdf)).

Figure 1.

The proportional contribution of 4437 poisoned raptors in different diet groups across Europe. For each country, the proportion of raptors in each diet group is presented.

Detected Pesticides. The dataset contained unknown, nonspecific, or indeterminate pesticides for 903 poisoning incidents with an associated 1321 poisoned raptors (  Table S4 (JRR2373_Supplemental_Material_final.pdf)). Excluding these yielded adjusted totals of 2284 poisoning incidents and 3099 poisoned raptors with known pesticides. Most pesticides were detected as a single substance in poisoned raptors and categorized as singles (n = 2121 incidents involving 2894 poisoned raptors of 33 species in 19 countries;   Table S5 (JRR2373_Supplemental_Material_final.pdf)). Fewer were detected with other pesticides and classified as multiples (n = 163 incidents involving 205 poisoned raptors), which were detected across 85 distinct/unique detection combinations involving 23 species in 8 countries;   Table S6 (JRR2373_Supplemental_Material_final.pdf),   S7 (JRR2373_Supplemental_Material_final.pdf)). Some pesticides were associated with single detections or as multiples (e.g., carbofuran, aldicarb, diazinon), whereas heptachlor, isophenfos, and paraoxon were only encountered with other pesticides.

Forty-one different pesticides were detected in raptors poisoned with a single substance (  Table S5 (JRR2373_Supplemental_Material_final.pdf)). Carbofuran accounted for 48% of 2121 poisoning incidents with detection of a single substance, and for 55% of the 2894 poisoned raptors with a single substance (Table 3). In the case of multiple detections, 34 pesticides were detected with others (  Table S7 (JRR2373_Supplemental_Material_final.pdf)). Carbofuran (and/or its metabolites) was detected in 55% of 163 poisoning incidents with detections of multiple pesticides, and was detected in 57% of 205 poisoned raptors with detections of multiple pesticides (Table 4). Aldicarb was the second most detected substance and reported in 18% of poisoning incidents with a single pesticide and in 14% of raptors poisoned with a single substance (Table 3), and in 22% of incidents and 18% of poisoned raptors with multiple substances (Table 4). Parathion and alpha-chloralose were the other commonly detected pesticides both as single substances (Table 3) and in combination with others (Table 4). Together, carbofuran, aldicarb, parathion, and alpha-chloralose were detected in 86% of poisoning incidents and 85% of poisoned raptors with detection of a single substance, and in respectively 96% and 94% of poisoning incidents and poisoned raptors with multiple detections.

Table 3.

Pesticides detected as single substances in 2894 poisoned raptors associated with 2121 poisoning incidents in 22 European countries (1996–2016).

Table 4.

The four main pesticides encountered with other pesticides, with the associated number of poisoning incidents and the number of poisoned raptors with detections of multiple substances in 22 European countries (1996–2016). For a complete list see   Supplemental Material Table S6 (JRR2373_Supplemental_Material_final.pdf).

The proportion of raptors reported as being poisoned by carbofuran as a single substance appeared to increase over the years, whereas those poisoned by aldicarb and parathion appeared to decrease (Fig. 2). More than half of carbofuran (53% of 1589 raptors poisoned with carbofuran as a single substance) and aldicarb poisonings (52% of 398 raptors) occurred after they were banned from use in Europe (Fig. 3), respectively in 2007 (Decision 2007/416/EC) and 2003 (although eight European countries were allowed an exception to use aldicarb until 2007; Decision 2003/199/EC).

Figure 2.

The annual proportion of raptors poisoned by aldicarb (n = 398 poisoned raptors), alpha-chloralose (n = 250), carbofuran (n = 1589), and parathion (n = 230), 1996–2016, in Europe. Cases include only those with single detections, i.e., no other substances were detected in the poisoned raptors. For comparison, the number of associated raptor poisonings associated with the unspecified cholinesterase inhibitor category (n = 96) is also shown. Lines depict the proportions of the number of raptors poisoned each year out of the total across all years for that specific substance.

Figure 3.

Annual number of raptors poisoned by aldicarb and carbofuran in Europe, before and after their respective bans. Cases include only those with single detections, i.e., no other substances were detected in the poisoned raptors.

Pesticides per Diet Group and Seasonal Differences. Of the 37 poisoned raptor species, 38% were classified as rodent feeders, 30% were facultative scavengers, 22% were others, and 11% were obligate scavengers. Carbofuran was the most commonly detected pesticide across all diet groups (Fig. 4), and was detected in 27 raptor species including three threatened and two near-threatened ones (  Table S5 (JRR2373_Supplemental_Material_final.pdf)). Of 1589 raptors poisoned with carbofuran as a single substance, 94% were scavengers (88% facultative and 6% obligate; Table 5). Of the facultative scavengers reported, 80%, 89%, and 97% were poisoned by aldicarb, alpha-chloralose, and parathion, respectively.

Figure 4.

The proportion of poisonings for rodent feeders (n = 83), obligate (n = 206) and facultative scavengers (n = 2185), and species with other diets (n = 98) as attributed to the most common poisons. Cases include only those with single detections, i.e., no other substances were detected in the poisoned raptors.

Table 5.

Number of raptors poisoned by a single substance of the four most commonly recorded poisons, and categorized by diet. These collectively represent 56% of all pesticide-exposed raptors in the dataset.

Raptor poisoning peaked between January and April, with 37% of 3566 dated poisoned raptors in March and April. Most facultative scavengers were poisoned in March and April, whereas poisonings of obligate scavengers, rodent feeders, and other raptors showed less obvious temporal patterns (Fig. 5a). The poisonings with carbofuran and alpha-chloralose peaked in spring (March–April), but those of aldicarb, parathion, and cholinesterase inhibitors peaked in summer (Fig. 5b). The most commonly poisoned raptor, Eurasian Buzzard, was poisoned most frequently in early spring, like the other often-reported raptors (except Griffon Vulture; Fig. 5c) and like some of the threatened species (Eastern Imperial Eagle, Egyptian Vulture, and Saker Falcon, but not Cinereous Vulture and Bearded Vulture; Fig. 5d).

Figure 5.

Monthly proportion of raptors poisoned in (a) each of the four dietary groups (n = 4425) and (b) by the most common poisons (n = 2563). Lines depict the proportions of the number of poisoned raptors for each category each month out of the total across all months for that specific category. Note that cholinesterase inhibitor falls under data for which nonspecific analyses were conducted and could include any or all of the other compounds, which are also cholinesterase inhibitors. (c) Monthly proportion of poisoned raptors for the most commonly reported species. (d). Monthly proportion of poisoned Eurasian Buzzard and the five most commonly reported threatened and near-threatened species.

DISCUSSION

We reported on pesticide poisoning of 37 raptor species in 22 countries across Europe from 1996 to 2016, a total of 4437 poisoned raptors, constituting one of the most extensive reported datasets of its kind. Given that 53 raptor species regularly breed in Europe, the poisonings affected 70% of Europe's breeding raptors. Almost 6% of all reported poisoned raptors have a threatened or near threatened global population status under IUCN criteria (IUCN 2024), although a focus on Red List status understates the threat that poisoning may pose to raptors in general (Richards et al. 2017). Indeed, in our dataset the most commonly poisoned raptor was the Eurasian Buzzard, which is classified as least concern but is vulnerable to poisoned baiting due to its comparative abundance and widespread occurrence across Europe, as well as its frequent scavenging (Badry et al. 2020). The most reported poisoned raptors were scavengers, either obligate (e.g., Griffon Vulture) or facultative (e.g., Eurasian Buzzard, Red Kite), which was expected based on scavenging raptor species' vulnerability to poisoned baiting (Margalida et al. 2008, Nadjafzadeh et al. 2013, Mateo-Tomás et al. 2012, 2020). Apart from the scavenging species, a wide range of raptor species with other diets were affected, including non-scavenging raptors such as Eleonora's Falcon (Falco eleonorae), Saker Falcons, and Peregrine Falcons (Falco peregrinus). Contrary to poisoned baiting of scavenging raptors that often targets mammalian carnivores, active hunters such as falcons are affected by deliberate poisoning when baits are specially prepared to target them. For example in Switzerland, Germany, UK, Serbia, North Macedonia, and Poland, racing pigeons (Columba livia) have been used as live or tethered baits with toxic substances applied as a paste to the neck or back of the pigeons to kill Peregrine Falcons (Vogler et al. 2015; Northern Ireland Raptor Study Group, O. Krone, M. Velevski, and T. Mizera, unpubl. data).

This dataset includes a preponderance of obligate scavenger poisoning from the Mediterranean region, while facultative scavengers were mainly recorded in other parts of Europe. This is largely a reflection of species' distribution patterns; vultures are mostly absent from or rare in large parts of northwestern Europe where facultative scavengers such as Eurasian Buzzard are instead among the most common and widespread raptors. Additionally, poisoning related to the control of large predators or dogs is particularly common in parts of the Mediterranean region and impacts vultures because they feed on the poisoned carcasses (Ntemiri et al. 2018). Indeed, such illegal poisoning is probably one of the main causes of vulture mortality in Spain (Hernández and Margalida 2008, 2009) and impacts all four European vultures in the southern Balkan Peninsula (Xirouchakis et al. 2000, Ntemiri et al. 2018, Parvanov et al. 2018, Dimitriou et al. 2021, Santangeli et al. 2022).

Data collated here suggest there is substantial seasonal variation in raptor poisoning rates across Europe, with an overall peak in spring. The early spring peak in poisoning of facultative scavengers may be related to the timing or seasonality of predator control activities. For example, poisoning of Spanish Imperial Eagles occurred more frequently in winter and spring, coincident with the months in which poisoned baits are used in illegal predator control by small game managers and for livestock protection (González et al. 2007), and similar results were found for Eastern Imperial Eagle (Lazarova et al. 2020). Bait use in Greece also peaks in March after the end of the hunting season, when illegal antipredator control campaigns targeting foxes are implemented (Ntemiri et al. 2018). Of reported Eurasian Buzzard deaths in the UK in the 1970s and 1980s, 39% occurred in March and April (Elliot and Avery 1991), coinciding with lambing season in upland areas when foxes and crows are targeted by sheep farmers, and when gamekeepers begin to increase predator control on land used for rearing game birds. Deák et al. (2020) observed the majority of poisoning cases occurring in late winter and early spring (February–April), when predator control activities by hunting organizations peak and rural dirt roads became more accessible, facilitating movements of both perpetrators and surveyors in more remote areas. Importantly, this early spring peak in raptor poisoning coincides with the start of the breeding season of most raptors; poisoning at this time can remove established breeders and thus decrease the possibility of successful reproduction in some territories.

Our dataset highlights a variety of different pesticides detected in poisoned European raptors, either solely or alongside other pesticides. Some pesticides were detected more commonly than others, particularly carbofuran, and to a lesser degree aldicarb, alpha-chloralose, and parathion. Although the use of aldicarb and carbofuran is forbidden by law in Europe, as is the use of baits, they remain among the most common poisons used to kill a host of wildlife including raptors across the continent (Kitowski et al. 2021). In the European Union (EU), it has been unlawful to use carbofuran and aldicarb products since 2007, and 2003, respectively, but the management and existence of remaining stockpiles varies among EU countries and the illegal import of these and other pesticides is also possibly ongoing from neighboring countries (e.g., methomyl imported from neighboring countries into Greece; V. Saravia-Mullin unpubl. data). In this dataset, the proportion of raptors reported as being poisoned by carbofuran as a single substance appeared to increase over the years, and more than half of poisonings attributed to carbofuran and aldicarb were reported after their respective bans (Decision 2007/416/EC and Decision 2003/199/EC), suggesting that the bans alone were insufficiently effective to halt the poisoning of raptors.

There are obvious limitations to the dataset used here and biases introduced by the opportunistic search efforts and the variety of analytical methods, as is the case with wildlife poisoning data in general (Fernández-García et al. 2024). We did not acquire information from all laboratories that analyze raptors for pesticide poisoning on a regular basis and as part of wildlife forensics in Europe (listed in Valverde et al. 2022), for example, because laboratories were unable to share such sensitive data. This included data from countries such as Spain, Italy, or France, which all have many pesticide poisoning incidents (Berny et al. 2015, Di Blasio et al. 2020, Rial-Berriel et al. 2021). Obviously, a representative analysis of species affected and pesticides used in Europe would entail a random sample of poisoned raptors from each country, taking into account the relative abundance of each species, and ideally examined using the same methods over the years, which is currently not the case (Gil-Sánchez et al. 2021). Additionally, some laboratories do extensive screenings for pesticides (including several hundred substances), while others restrict themselves to those most commonly misused, or proceed stepwise as analytical investigations are quite expensive. Also, species that are considered suitable and relevant for more expensive analyses in some countries are not examined in other countries. Despite the limitations, we obtained a large sample encompassing 37 species across 22 countries, covering a range of analytical approaches and institutes. We argue that the spatial and temporal scale of our dataset likely provides a representative cross section of the available raptor poisoning data across Europe for the examined time period, reflecting previous findings on frequently used pesticides (e.g., carbofuran; Richards 2011) and based on the predominance of the most widespread European raptor, the Eurasian Buzzard, in our dataset. In addition, the proportions of the main pesticides, notably carbofuran and aldicarb, were found to be consistent across raptors poisoned with either a single or multiple substances, suggesting that the extent of the screening (i.e., for one or more pesticides) had relatively little influence on results with regard to the main pesticides. Regardless of the limitations, the approach we have taken in terms of collation of the data and interpretation of the results, can offer a useful blueprint for others to follow.

Conclusions. Pesticide poisoning is a threat to raptor populations in many parts of the world that continues unabated (McClure et al. 2018). Even so, the extent of raptor poisoning as reported may still generally be underestimated (Gómez-Ramírez et al. 2014) and many cases of raptor exposure to toxicants and poisons are still not currently diagnosed as such. Even when diagnosed, an ongoing issue is that the information will not always be made available to regulatory authorities (Mineau et al. 1999) and if an animal recovers, the poisoning might not be reported at all (Wells et al. 2020). Therefore, an urgent need remains for more comprehensive monitoring of all raptor species affected by poisoning. Monitoring frequently reported species such as Eurasian Buzzard and establishing increased communication with rehabilitation groups about poisoning of this common species can serve as early warning and prevention of poisoning activities, especially because poisoning incidents involving Eurasian Buzzard often coincide with those involving other raptors in spring. Also, far more species than large, threatened raptors may be affected by poisoning (Gil-Sánchez et al. 2021), and the timeframe of poisonings should be more systematically scrutinized relative to important life cycle stages of each species.

Although the effect of poisoning on a range of raptor species has been documented, the reduction in ecosystem services (e.g., carcass removal, and insect or rodent predation; Whelan et al. 2008, Plaza and Lambertucci 2022) and effects on the prey base have been less well studied relative to pesticide poisonings. We recommend these types of ecosystem service assessments, and closer examination of population-level effect on common species such as the Eurasian Buzzard, which may be bearing a heavy load of pesticide poisoning.

SUPPLEMENTAL MATERIAL (available online).   Table S1 (JRR2373_Supplemental_Material_final.pdf): Laboratory or analytical facility involved, types of analysis, and sample preparation by country. “Unknown or inaccessible” refers to information unknown or inaccessible to the reporting contributor/co-author.   Table S2 (JRR2373_Supplemental_Material_final.pdf): Species and number of poisoned raptors by country in 22 European countries (1996–2016).   Table S3 (JRR2373_Supplemental_Material_final.pdf): Total number of poisoned species and individuals reported from individual European countries (n = 22) spanning 1996–2016.   Table S4 (JRR2373_Supplemental_Material_final.pdf): Number of unknown or nonspecific pesticides in the dataset, and correspondingly adjusted totals with known pesticides.   Table S5 (JRR2373_Supplemental_Material_final.pdf): Species reported as poisoned (n = 2894 raptors) during individual poisoning incidents (n = 2121) in 22 European countries (1996–2016) with the associated singularly detected pesticides.   Table S6 (JRR2373_Supplemental_Material_final.pdf): Pesticides detected with other substances (“multiples”), in association with 163 raptor poisoning incidents and 205 poisoned raptors in 22 European countries (1996–2016).   Table S7 (JRR2373_Supplemental_Material_final.pdf): Poisoned raptors (n = 205 raptors) during poisoning incidents (n = 163) in 22 European countries (1996–2016), with the associated pesticides detected in combination with others (“multiples”).