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While the influence of public information sharing on foraging strategies is of growing interest, empirical studies exploring intraguild social information use and facilitation roles between individuals with different trophic specializations remain scarce. Heterospecific facilitation should be more common in specialist foragers, for example, the bearded vulture Gypaetus barbatus, a solitary bone‐eating scavenger. We monitored 133 carcasses of different types/sizes in open and shrubland landscapes in the Spanish Pyrenees to explore bearded vulture foraging in relation to social information transfer and adaptive trophic behavior. We hypothesized that they might (1) feed on carcasses after initial heterospecific exploitation; (2) use heterospecifics to locate and/or exploit carcasses; and (3) prefer old carcasses over fresh ones. We recorded bearded vultures scavenging at 44 carcasses; 95.5% had been previously exploited by heterospecifics (93.2% by griffon vultures Gyps fulvus and 2.3% by golden eagles Aquila chrysaetos) while only two small‐sized carcasses were scavenged without previous heterospecific exploitation. Bearded vultures were not observed scavenging at carcasses used only by mammals. Both griffon and bearded vultures took longer to find carcasses in shrublands than in open landscapes. However, bearded vulture arrival times between landscapes after carcass discovery by griffon vultures were similar. Bearded vultures were more likely to discover a carcass the greater the number of griffon vultures exploiting it. Only 10.4% bearded vulture scavenging events occurred after the third week following heterospecific exploitation, suggesting that recently opened carcasses were preferred. Clearly, heterospecifics play an essential role in bearded vultures foraging success, and griffon vultures are fundamental facilitators for specialist foragers, both in providing visual cues to food location and in opening up carcasses to enable access to food. [ABSTRACT FROM AUTHOR]

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Rural abandonment and subsequent vegetation regeneration ('passive rewilding') are expected to increase worldwide, producing cascades of dynamic socioeconomic, landscape and biological changes. Although landscape characteristics strongly influence the structure and functioning of scavengers, little is known about the ecological consequences of passive rewilding due to woody encroachment (i.e.'landscape closure') on scavenging assemblages. We investigated differences in 'scavenger assemblage composition' (species richness and abundances) and 'scavenging efficiency' (scavenging frequency, detection and consumption times and consumption rates) in a mountain agroecosystem (Pyrenees) undergoing passive rewilding. We monitored 178 carcasses in three landscapes: 'open', 'shrubland' and 'forest', and evaluated the effects of landscape type on 'scavenger assemblage composition' and 'scavenging efficiency' at the community and species levels, while accounting for the influences of carcass size, type and placement time. We also examined whether the locally most abundant and efficient scavenger (i.e. the griffon vulture Gyps fulvus) affects scavenging patterns. We found that landscape type was the main factor governing scavenging dynamics. Overall and average scavenger richness were similar in open and shrubland landscapes, while forests contained the lowest number of scavengers, mainly comprising mammals. Unlike mammals, avian scavenging frequency decreased as vegetation cover increased, especially for obligate scavengers (i.e. vultures). Scavenger abundances were highest in open landscapes, and carcasses were detected and consumed more rapidly in these landscapes. Carcass size did not influence detection and consumption times, although it did affect average scavenger richness, abundances and consumption rates. Consumption rates were higher in open landscapes and were strongly associated with the presence of griffon vultures. Interestingly, we found that griffon vultures influenced scavenging dynamics via facilitation processes. However, woody encroachment could reduce the scavenging role of this species, while favoring mammalian facultative scavengers. Finally, our findings highlight the pivotal role of griffon vultures, mediated by landscape characteristics, in reducing carcass persistence. [ABSTRACT FROM AUTHOR]

The widespread use of second-generation anticoagulant rodenticides (SGARs) and their high persistence in animal tissues has led to these compounds becoming ubiquitous in rodent-predator-scavenger food webs. Exposure to SGARs has usually been investigated in wildlife species found dead, and despite growing evidence of the potential risk of secondary poisoning of predators and scavengers, the current worldwide exposure of free-living scavenging birds to SGARs remains scarcely investigated. We present the first active monitoring of blood SGAR concentrations and prevalence in the four European obligate (i.e., vultures) and facultative (red and black kites) avian scavengers in NE Spain. We analysed 261 free-living birds and detected SGARs in 39.1% (n = 102) of individuals. Both SGAR prevalence and concentrations (ΣSGARs) were related to the age and foraging behaviour of the species studied. Black kites showed the highest prevalence (100%), followed by red kites (66.7%), Egyptian (64.2%), bearded (20.9%), griffon (16.9%) and cinereous (6.3%) vultures. Overall, both the prevalence and average ΣSGARs were higher in non-nestlings than nestlings, and in species such as kites and Egyptian vultures foraging in anthropic landscapes (e.g., landfill sites and livestock farms) and exploiting small/medium-sized carrions. Brodifacoum was most prevalent (28.8%), followed by difenacoum (16.1%), flocoumafen (12.3%) and bromadiolone (7.3%). In SGAR-positive birds, the ΣSGAR (mean ± SE) was 7.52 ± 0.95 ng mL−1; the highest level detected being 53.50 ng mL−1. The most abundant diastereomer forms were trans- bromadiolone and flocoumafen, and cis- brodifacoum and difenacoum, showing that lower impact formulations could reduce secondary exposures of non-target species. Our findings suggest that SGARs can bioaccumulate in scavenging birds, showing the potential risk to avian scavenging guilds in Europe and elsewhere. We highlight the need for further studies on the potential adverse effects associated with concentrations of SGARSs in the blood to better interpret active monitoring studies of free-living birds. [Display omitted] • SGARs were detected in 39.1% of 261 living obligate and facultative scavenging birds. • SGAR prevalence and concentrations were related to the age class and foraging behaviour. • Brodifacoum was most prevalent (28.8%) and the highest ΣSGARs level was 53.50 ng mL−1 • In all SGAR compounds one cis - or trans -diastereomer form was more bioaccumulated. • Exposure of non-target species to SGARs needs urgent risk mitigation measures. [ABSTRACT FROM AUTHOR]

An unexpected human-wildlife conflict between vultures and livestock has emerged in Europe during the last two decades. Farmers attributed changes in vulture behavior, due to food shortages caused by sanitary regulations, to increasing livestock interactions ('vulture attacks'). To disentangle this conflict, we analyzed 683 farmer complaints between 1996 and 2020 in Catalonia (northeastern Spain) and investigated the eco-anthropological factors driving their frequency. We also assessed farmers' perception through 127 interviews. Most complaints (80 %) occurred during the birthing season, mainly involving cattle (76.5 %), followed by horses (14.9 %) and sheep/goats (8.6 %). From 2008 to 2020, vulture-livestock conflicts cost the government €192,000 (~22 % of claims compensated). The frequency of complaints was positively associated with extensive livestock density, griffon vulture Gyps fulvus abundance (breeding and non-breeding), shorter distances to landfill sites and, to a lesser extent, to supplementary feeding stations. In contrast, there was a negative relationship between complaints and the number of griffon vulture breeding pairs, suggesting that long-distance foraging movements by both breeding and non-breeding individuals may play a major role in determining the occurrence of conflicts. Farmers (88 %) said that vultures attack livestock and that attacks had increased in recent years because of significant vulture population increases and food shortages due to sanitary regulations. They considered government policies and compensation ineffective. We highlight the critical need for mitigation in areas with high extensive livestock numbers, particularly during birthing times. Scientific assessments and interdisciplinary awareness campaigns on the coexistence of vultures and livestock are necessary to harmonize biodiversity conservation and agro-pastoral practices in rural economies. [ABSTRACT FROM AUTHOR]

Transhumance is the traditional livestock practice consisting in the seasonal movement of herds between winter and summer pastures. Transhumance have important effects on the ecosystem functions from local to regional scales. Here, we 1) explored the relationship of vultures to transhumant herds, and 2) tested whether there is a shift on the use of space by vultures due to the decline of transhumance. For that, we first assessed whether vultures follow transhumant herds in two mountain areas with transhumant tradition, Pyrenees (Spain) and Andes (Argentina). Second, we compared both systems to determine whether the impact of transhumance on the use of space of vultures is greater in the area where transhumance is still relevant (Andes) than where this activity is in decline (Pyrenees). For this purpose, we analyzed the use of the summer pastures made by 50 griffon vultures (Gyps fulvus) and 18 Andean condors (Vultur gryphus), as assessed by GPS tracking. Our findings showed that both species respond to transhumance by making greater use of summer pastures when herds are present. A higher proportion of condors made use of summer pastures than griffons, and condors individually made a more intense use of it than griffons. Differences could be explained by the fact that transhumance in the Andes is still important while in the Pyrenees is declining and the amount of carrion provided is lower. Given that the abandonment of traditional activities is a phenomenon underway, it is urgent to evaluate the effects it will have on biodiversity conservation. [ABSTRACT FROM AUTHOR]