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Winter 2020
Black vulture conflict and management in the United States: damage trends, management overview, and research needs
Bryan M. Kluever
Morgan Pfeiffer
Scott C. Barras
Brett Dunlap
Lee A. Humberg
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Black vulture conflict and management in the United States: damage trends, management overview, and research needs
Bryan M. Kluever, U.S. Department of Agriculture, Wildlife Services, National Wildlife Research Center, Florida Field Station, 2820 East University Avenue, Gainesville, FL 32641, USA [email protected] Morgan B. Pfeiffer, U.S. Department of Agriculture, Wildlife Services, National Wildlife Research Center, Ohio Field Station, 6100 Columbus Avenue, Sandusky, OH 44870, USA; and School of Natural Resource Management, George Campus, Nelson Mandela University, George, South Africa Scott C. Barras, U.S. Department of Agriculture, Wildlife Services, Virginia State Program, P.O. Box 130, Mosely, VA 23120, USA Brett G. Dunlap, U.S. Department of Agriculture, Wildlife Services, Tennessee/Kentucky State Program, 537 Myatt Drive, Madison, TN 37115, USA Lee A. Humberg, U.S. Department of Agriculture, Wildlife Services, Indiana State Program, 901 W. State Street, West Lafayette, IN 47907, USA
Abstract: Contrary to rapid declines of many vulture (Accipitridae, Cathartidea) species worldwide, black vulture (Coragyps atratus) populations are increasing and expanding their range in North America. Vultures exhibit complex behaviors and can adapt to any human- dominated landscape or land use. These traits, combined with population growth and range expansion, have contributed to increased human–vulture conflicts. Our goal was to summarize the current status and trends in human–black vulture conflicts (hereafter human– vulture conflicts), review available management strategies, identify knowledge gaps, and provide recommendations to enhance management and understanding of this species and the associated conflicts. We found human–vulture conflicts are increasing in agriculture (livestock), private and public property (both personal and infrastructure-based), and threats to human health and safety. The greatest increases in conflicts were reported in agriculture and private and public property damage. Regarding livestock depredation, good progress has been made toward assessing producer perceptions of the conflicts, including estimates of economic damage and mitigation strategies, but a basic understanding of the underlying mechanism driving the conflict and advancing strategies to mitigate damage is lacking. For damaged property, little information is available regarding economic losses and perceptions of stakeholders who are experiencing the damage, and most of the tools recommended for mitigating this damage have not been rigorously evaluated. Regarding human health and safety, recent research quantifying flight behavior of black vultures has direct implications for reducing aircraft collision risks. However, it is unclear what factors influence roost site selection and the most effective means to leverage the sensory ecology of the species to mitigate risks. We identify additional knowledge gaps and research needs that if addressed could increase managers’ understanding of black vulture ecology and facilitate enhanced management of this species while simultaneously allowing for the species to provide valuable ecosystem services.
Key words: behavior, black vulture, Coragyps atratus, ecology, human health and safety, infrastructure, livestock depredation, property damage, range expansion, United States
Globally, many vulture species (Accipi- of the continental-level declines vary. For tridae and Cathartidea) have recently experi- example, in India and Pakistan, a veterinary enced population and/or distribution declines drug known as dicoflenac has been identified (Ogada et al. 2012a, Thiollay 2017, Santangeli as the primary driver (Green et al. 2004). In et al. 2019). Sixty-nine percent of all vulture Africa, non-target mortality, poaching, and the species occurring in Africa and Eurasia have incorporation of vulture parts in the traditional been identified by the International Union for medicine trade have been implicated as factors Conservation of Nature as near-threatened, contributing to declining vulture populations threatened, endangered, or critically endan- (Ogada et al. 2016, Botha et al. 2017). gered (BirdLife International 2020). The causes New World and Old World vultures serve Black vulture conflict and management • Kluever et al. 377 similar ecological roles yet evolved from dif- tion is more limited, and throughout much of ferent species: New World vultures reportedly the twentieth century, only the southeastern from storks (Ciconiidae) and Old World vul- United States hosted large year-round popula- tures from raptors (Campbell 2014). Vultures, tions (Avery 2004). In recent years, however, the by consuming carrion, provide valuable eco- species has undergone a distribution increase system services, including potentially reducing by expanding its range to the northeastern and the pervasiveness of disease in wildlife (Ogada midwestern United States (Zimmerman et al. et al. 2012b, Beasley et al. 2015) and humans. 2019), and its range is predicted to reduce in Markandya et al. (2008) estimated $2.43 bil- certain areas of South America (Saenz-Jimenez lion USD on average was spent annually on et al. 2020). The reasons for the recent distribu- expenses related to human rabies transmitted tion changes in the United States have not been from feral dog (Canis lupus familiaris) bites fol- clearly identified, but potential contributing lowing the decline of Asian vulture species. In factors include increased food availability and terms of ecosystem services, the turkey vulture climate change (Buckley 2020). (Cathartes aura) was estimated to remove $700 In addition to a spatial expansion, black vul- million USD worth of organic waste material tures have increased in abundance, including per year (Grilli et al. 2019). Despite their valu- in areas of historical occurrence. According to able ecological roles, the same behavioral traits the Breeding Bird Survey (BBS), from 1966 to that have enabled some vultures to adapt to 2015 black vulture annual indices of abundance anthropogenic landscapes have also exacer- increased in the southeastern and midwestern bated human–vulture conflict in both rural and portions of the United States by an average of urban settings on several continents (Avery 3.75% (95% CI 2.93–4.49) and 9.04% (95% CI 2004, Toledo et al. 2013, Margalida et al. 2014, 5.06–12.36), respectively. The reported largest Washburn 2018, Duriez et al. 2019). and smallest black vulture populations esti- In the United States, extant vulture guild mated for a state are Florida and Ohio, USA diversity is low when compared to South with estimates of 1,149,817 and 4,569, respec- America, Eurasia, and Africa, comprising only tively (Zimmerman et al. 2019). 3 species, the California condor (Gymnogyps The phrase “human–wildlife conflicts” californianus), turkey vulture, and black vul- describes any negative interactions between ture (Coragyps atratus). The California condor humans and wildlife, including those that is listed as federally endangered in the United are either real or perceived, economic or aes- States and Mexico, persisting only in portions of thetic, social or political (Messmer 2000, 2009). California, Utah, Arizona, and Baja California, Human–wildlife conflicts can be categorized by USA (Finkelstein et al. 2020). The turkey vulture the primary resource affected and/or the threat is distributed seasonally throughout the major- associated with the conflict. For instance, the ity of South America, Central America, Mexico, broad categories of agriculture (e.g., crops, live- and the United States, extending northward to stock), natural resources (e.g., threats to sen- the southern portions of most Canadian prov- sitive species), property (e.g., residential and inces (Buckley 2020). Where black and turkey industrial infrastructure), and human health vultures co-occur, they may comingle generally and safety (e.g., wildlife–aircraft collisions) while foraging, soaring, loafing, and roosting have been established as a means to identify (Sweeney and Fraser 1986, DeVault et al. 2005), and thereby guide efforts to address wildlife yet exhibit differences in fine-scale habitat selec- conflict (Conover 2001, Reidinger and Miller tion (Holland et al. 2017). Thus, several of the 2013). We have elected to use these categories to knowledge gaps and opportunities we discuss report on our findings regarding human–vul- in this paper for achieving a better understand- ture conflict. ing of black vulture ecology and management Here, we provide a synthesis on the current are also applicable to turkey vultures. status of knowledge for human–vulture con- Black vultures, though not as widely dis- flicts, with a focus on management and research tributed as turkey vultures, range throughout in the United States. We focus on the black vul- much of South America, Central America, and ture (hereafter vultures; Figure 1) because the Mexico (Buckley 2020). Their northern distribu- species population increase and range expan- 378 Human–Wildlife Interactions 14(3)
Figure 1. The 3 vulture species occurring in the United States, the black vulture (Corogyps atratus; A), the turkey vulture (Cathartes aura; B), and the California condor (Gymnogyps californianus; C). Images from the Cornell Lab of Ornithology Macaulay Library (photos A, B, and C courtesy of B. Sullivan, A. Kambhampati, and K. Trouton, respectively). sion have resulted in more reports of conflicts lina, South Carolina, and Tennessee, USA) from than other vulture species occurring in the 2010 to 2019. Data access was approved by R. United States. Our objectives are to: (1) describe L. Hudson and provided by J. M. Weiskittel by trends of human–vulture conflict, (2) summa- querying the Management Information System rize the conflict and management approaches Database (MIS; accessed April 30, 2020). These by the major types of resources affected, and (3) data included a category for the type of resource identify basic and applied research needs that if being protected (e.g., aircraft, residential build- carried out should increase knowledge of vul- ing, industrial building, swine [Sus scrofa], cattle ture ecology and biology, leading to enhanced [Bos taurus], etc.). From these data, we parsed the management efficacy. human–vulture conflict by the major resource categories described above. Methods We accessed the Federal Aviation Admini- In May, 2020, we contacted the U.S. stration (FAA) Wildlife Strike Database Department of Agriculture (USDA), Animal (https://wildlife.faa.gov/home; accessed June Plant and Health Inspection Service (APHIS), 16, 2020) and searched for aircraft collisions Wildlife Services (WS) Eastern Regional Office involving only black vultures from 2010 to (Raleigh, North Carolina, USA) and requested 2019, which included a monetary component. all instances of requests for assistance relating We selected 2010 as our earliest reporting year to vulture conflicts within the jurisdiction of the because reporting of damaging bird–aircraft U.S. Fish and Wildlife Service (USFWS) Southeast collisions became more robust in the 2010s Region 4 (Alabama, Arkansas, Florida, Georgia, following the forced landing of Flight 1549 in Kentucky, Louisiana, Mississippi, North Caro- the Hudson River in 2009 and the subsequent Black vulture conflict and management • Kluever et al. 379
Figure 2. Requests for assistance relating to black vulture (Coragyps atratus) conflicts in the United States submitted to U.S. Department of Agriculture, Animal Plant and Health Inspection Service, Wildlife Services, parsed by major categories of resources affected for states within the jurisdiction of the U.S. Fish and Wildlife Service Southeast Region 4 (Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, South Carolina, and Tennessee, USA) for 2010 (n = 115) and 2019 (n = 325). The resource category of natural resources protection is not displayed because calls for assistance were <1% for this category for both years. awareness campaigns by the FAA and USDA tus.” From these records, we next queried 1 of (Dolbeer 2015). 2 additional keywords: “management” and Also in June 2020, we requested from the “conflict.” We examined >100 papers and used U.S. Navy (USN) and U.S. Air Force (USAF) the expert elicitation to select what we felt were the reported vulture strikes to military aircraft for most germane papers for inclusion. Because we the same temporal span (2010–2019). The USN were interested in both historical and contem- provided this information by way of the Naval porary works on black vulture management, Safety Center (accessed June 22, 2020), and the we did not set a date range for our searches. USAF provided this information by way of their USAF Automated System database (accessed Results and discussion June 22, 2020). A. L. Bowe, D. P. Sullivan, B. R. Requests for technical assistance and Burnham, and J. E. Higgins provided military depredation permits bird strike summary data. According to the USDA, APHIS, WS, MIS, in In May, 2020, we contacted the USFWS 2019 there were 325 requests to WS to provide Migratory Bird Program (Falls Church, Virginia, technical assistance to mitigate human–vul- USA) and requested summary information for ture conflict in the aforementioned states. This the number of USFWS depredation permits represents nearly a 3-fold increase in requests issued for vultures nationwide from 2015 to 2019. since 2010 (n = 115). The resource categories The USFWS monitors depredation permits by most affected by human–vulture conflict are way of their Service Permit Issuance and Tracking human health and safety, property, and live- System Database (SPITS). E. L. Kershner pro- stock (Figure 2). According to MIS data, vul- vided the summary data (accessed May 14, 2020). tures do not pose a threat to natural resources To report on the current state of the litera- (e.g., adversely affecting a species of conserva- ture regarding human–vulture conflict and tion concern) because reports were <1% of the management in the United States, we searched total. In addition, there appeared to be a tran- 2 internet-based literature databases, Google sition taking place where a greater proportion Scholar and Web of Science, from August 15 of requests for technical assistance were associ- to September 15, 2020. For each database, we ated with the property and agriculture resource conducted initial keyword searches using the categories than human health and safety search terms “black vulture” and “Coragys atra- (Figure 2). In 2019, according to the SPITS data- 380 Human–Wildlife Interactions 14(3) base, USFWS issued 435 depredation permits ior of the species. Black vultures have been authorizing lethal take of vultures nationwide, described as inefficient predators, with some a 26% increase from 2015. predation events lasting 6 hours (average 3 hours and 26 minutes) from the start of the Agriculture interaction to the death of a lamb (Ballejo et Although black vultures are predominantly al. 2020). An alternative explanation of a long scavengers, they have been observed to consume duration associated with subduing prey could live prey including sea turtles (Dermochelyidae, be that it is part of a predatory strategy of wear- Cheloniidae), skunks (Mephitidae), opossums ing down prey. While not examined here, it is (Didelphidae), birds, fish, and livestock (Baynard important to note that human perceptions of 1909, McIlhenny 1939, Mrosovsky 1971, Dickerson scavengers have been shown to influence the 1983, Lowney 1999). Black vultures have been degree of perceived vulture conflict (Duriez et identified by U.S. livestock producers as a threat al. 2019, Ballejo et al. 2020). through depredation of neonate cattle, horses Integral to managing vulture livestock depre- (Equus ferus caballus), sheep (Ovis aries), goats (Capra dations is a better understanding of behavioral aegagrus hircus), domestic swine, and farm-raised ecology of the species. Specifically, black -vul deer (Odocoileus virginianus; Lowney 1999, Avery tures exhibit bolder behaviors than other vul- and Cummings 2004). For cattle, black vulture ture species (Buckley 1996). For example, black predation has reportedly occurred in 18 U.S. states vultures routinely displace turkey vultures located in the southeast and southwest United and/or alter the social hierarchy at carcasses States (Spires 2014). In Florida, 38% of surveyed when both species are present, including when cattle ranchers reported experiencing vulture pre- turkey vultures are numerically dominant at dation that, on average, exceeded $2,000 USD of sites (Haskins 1972, Buckley 1996). Further, damage (Milleson et al. 2006). Also, in Tennessee, black vultures participated in more interac- a survey of agricultural extension agents revealed tions with neonate livestock than any other that 89% of counties had recurring issues of vul- avian scavenger observed during 311 hours of ture predation on livestock (Spires 2014). In Texas, field observations in lambing season (Ballejo et where black vultures have historically occurred al. 2020). Depredation of neonate livestock by and also expanded (Parmalee 1954, Avery and vultures may be a combination of active preda- Cummings 2004), a shift by livestock produc- tory behavior, where neonates attempt to avoid ers from wool varieties of sheep to hair breeds, being preyed upon but are still pursued, or a capable of lambing multiple times per year, has “case of mistaken identity” where neonates are made year-round breeding more commonplace listless to the point that vultures perceive them (Morgan 2016), increasing the likelihood of as carrion (Duriez et al. 2019). Whether preda- encounters between black vultures and lambs. tory behavior exhibited by vultures is learned In areas where black vultures have expanded or innate is unknown. their range, less is known regarding impacts to The indirect effects of predation and preda- livestock. Although for states in the northeast tion risk have received much attention in the United States that generally produce less live- ecological literature, but research has primarily stock than the states black vultures have histori- focused on wild ungulate-large carnivore sys- cally occurred, reported losses due to predatory tems (Creel and Christianson 2008, Laundre et birds have been low (USDA 2015). Latteman al. 2014). Evaluating indirect effects of livestock (2019) reported that vulture livestock depre- depredation has been reported as a research dation was occurring in the Midwest. In addi- priority (Howery and DeLiberto 2004). Cattle tion, vulture depredation has been definitively have been shown to temporarily decrease for- identified as the cause of mortality for several aging behavior following depredation of neo- calves in southern Indiana (G. Burcham, Heeke nates by mammalian carnivores (Kluever et al. Animal Disease Diagnostic Laboratory, Purdue 2008), and wolf (Canis lupus) depredation risk University College of Veterinary Medicine, per- can affect cattle weight gain (Steele et al. 2013). sonal communication). For vultures, and raptors in general, knowledge Reports of vulture livestock depredations of the indirect effects of predation and predation may be confounded by the predatory behav- risk is lacking. In Brazil, Toledo et al. (2013) found Black vulture conflict and management • Kluever et al. 381 the presence of vultures at cattle birthing sites spatial extent, vegetation cover types adjacent altered the behavior of cows and calves; contact to and comprising operations, husbandry prac- time between cattle and calf decreased and cattle tices employed, and local abundance of vultures vigilance increased. In Florida, Humphrey et al. likely all contribute to both the magnitude of (2004) observed a single event of a cow engaging black vulture depredation risk and the efficacy in antipredator behavior to thwart black vultures of mitigation strategies. from depredating its calf. Mitigating human health and safety risks Mitigating agriculture depredation Compared to reporting vulture damage to Multiple strategies have been employed to livestock, documentation of collisions between mitigate the threat of livestock depredation by aircraft and vultures is relatively comprehen- vultures at livestock parturition areas. These sive given the possibility that a collision might include harassment/hazing of birds using result in the loss of human life (Blackwell and pyrotechnics, propane exploders, shooting Wright 2006, Pfeiffer et al. 2018a). Between 2010 near birds, effigies, chasing with vehicles and and 2019, 188 black vulture strikes, including 6 lasers, the elimination of food attractants by vulture carcasses found in air operation areas livestock producers, lethal removal of a subset of civil airports, were voluntarily reported to of black vultures through trapping or shooting the FAA Wildlife Strike Database. Most of these via permitted take, and dispersal of vultures strikes occurred with aircraft traveling within from known nocturnal roost sites in proxim- the United States; however, 6 observations ity to parturition sites (MIS, unpublished data). were from inbound flights from Honduras An integrated approach, where multiple tools and Panama to the United States. There were are used simultaneously or sequentially imple- 9 human injuries related to 4 vulture strike mented, is the standard practice if the mitiga- incidents during this time period. In addition tion is employed by WS, and lethal removal to human injuries, structural damage to the is not authorized by the USFWS unless used aircraft itself from bird strikes can threaten in tandem with nonlethal approaches (i.e., as human safety. Black vulture strikes with civil a reinforcing stimuli; USFWS Form 3-200-13). aircraft have resulted in $10,287,190 USD of This integrated approach is also recommended reported damage between 2010 and 2019. to producers who elect to mitigate the damage During the same time period, black vultures themselves. Harassment and lethal shooting were involved in 264 collisions with USAF coupled with effigy display is one of the most aircraft, which resulted in no human injuries commonly implemented integrated approaches but $27,106,300 USD in damage according to employed by livestock producers. data from USAF mandatory mishap report- However, what is known of the efficacy of ing. For the USN, 63 black vulture strikes were livestock depredation mitigation strategies for reported, which resulted in $85,716,438 USD in vultures is largely based on producer surveys damage. Black vulture strikes were responsible rather than field-based investigation conducted for $123,109,928 USD to civil and military avia- in a robust manner. In Florida, only a small num- tion from 2010 to 2019. ber of cattle producers employed guard dogs, Given these statistics, black vultures have the but this technique was the most effective strat- third highest relative hazard score (metric that egy reported, with attractant removal and shoot- estimates the probability of damage from a bird ing being the second and third most effective, strike) for military aircraft (Pfeiffer et al. 2018a) respectively (Milleson et al. 2006). In Wyoming, and ranked in the top 11 riskiest species (based USA, producers reported the most effective on severity and probability of a bird strike) for strategies for mitigating depredation of cattle civil aviation (DeVault et al. 2018). In conjunc- and sheep by avian species, and although data tion with their population and range expan- had high variance, shooting and removal by way sions, the number of reported black vulture of trapping appeared the most effective for both strikes to the FAA Wildlife Strike Database is stock types; guard dogs appeared more effective also increasing (Figure 3). for sheep whereas stalling animals at night was Prevention of black vulture strikes with air- more effective for cattle (Scasta et al. 2018). The craft is difficult because most vulture strikes 382 Human–Wildlife Interactions 14(3)
Figure 3. Frequency of black vulture (Coragyps atratus) bird strikes with civil aviation in the United States according to Federal Aviation Administration Wildlife Strike Database, 2010–2019. occur outside of the airport environment, or 2007, Mee et al. 2007). Further, regurgitation of ≥152 m above ground level, which is common non-food items is transmitted to nestlings (Mee for vultures (DeVault et al. 2005, 2016). In fact, et al. 2007, Pfeiffer et al. 2017). However, it is the highest recorded bird–aircraft collision uncertain if black vultures are ingesting or sim- was with a Rüppell’s vulture (Gyps rueppelli) at ply manipulating material. Most of the material 11,278 m (Laybourne 1974). Therefore, prom- that vultures have damaged emit the following ising mitigation methods include landscape compounds: hexanal, octanal, undecane, and modification (Pfeiffer et al. 2018b, although nonanal, which are common in vinyl and plas- see Pfeiffer et al. 2020 in regard to landfill loca- tic (Mauldin et al. 2003). tions) and aircraft lighting that increases detec- Specific items observed being damaged by tion of the oncoming aircraft by the vulture vultures include but are not limited to seat and evokes an avoidance behavior (Blackwell cushions, roof shingles, caulking sealant, and et al. 2012, Goller et al. 2018). Identification of the rubber portion of windshield wiper blades management areas by quantifying incursions (Mauldin et al. 2003). Complaints about damage of vulture and aircraft flight paths is another by black vultures commonly include damage to current management option (Avery et al. 2011, industrial and residential rooftops and vehicles Novoselova et al. 2020). On-the-ground meth- at or near commonly used loafing and roost- ods such as dispersal of roosts close to the air- ing sites. Vulture damage to boats from tearing port using pyrotechnics and effigies and collec- upholstery in Virginia from 1994 to 1996 resulted tion of carcasses still need to be evaluated in in $19,600, or $3,217 per incident (Lowney 1999). terms of changes in strike risk. Due to the myriad types of property and site-specific characteristics that can be- asso Mitigating property damage ciated with vulture damage to property, the The ingestion of non-food items has been types of mitigation tools employed are vari- recorded for multiple vulture species (Houston able. Tubemen (Lindell et al. 2018) and motion- et al. 2007, Mee et al. 2007). Explanations of this activated sprinklers (Evans 2013) have been behavior include: (1) misidentification of mate- utilized, but their reported efficacy remains rials as bone fragments used for diet supple- anecdotal. For the latter, the sudden onset of a ments, (2) to facilitate pellet formation, and sprinkler triggered by the vultures’ movement (3) exploration of food options (Houston et al. can startle them and increases their latency to Black vulture conflict and management • Kluever et al. 383 return to the site. The sound of the sprinkler, to changes in North America have not been sight of the water stream, and unpredictability clearly identified for this species. Such efforts of the stimulus may cause a synergistic deter- are needed for vultures in North America to rent effect. Sprinklers have been successful forecast potential future distribution increases, against vultures on roofs of houses, on boat and in turn, areas where conflict may occur. docks, and around backyard patios (Avery Similarly, the behavioral and movement ecol- and Lowney 2016). Effigies can be but are not ogy of black vultures inhabiting range expan- always effective at dispersing offending black sion areas have not been explored. Because vultures from the area where property is being factors such as resource availability may differ damaged if a roost site is in proximity of the in these areas, birds may use these landscapes area/objects being damaged (Tillman et al. differently than areas of historical use. Further, 2002). Traditional harassment methods utiliz- individuals of avian populations undergoing a ing sound as the primary deterrent coupled distribution expansion and occurring toward with lethal shooting as reinforcement are still the periphery of the species distribution have the most commonly utilized techniques. been shown to be more aggressive than more insular occurring conspecifics (Duckworth and Knowledge gaps and research needs Badyaev 2007). Determining whether this phe- Despite being one of the most abundant raptor nomenon occurs in black vultures is germane, species in the United States, black vultures are as more aggressive birds may more frequently identified as an understudied species (Buckley conflict with humans. 2020). Recent advancements toward increas- Vultures often congregate at large commu- ing our understanding of vulture ecology and nal roosts (Prather et al. 1976), the behavior management have been achieved and include facilitating the transfer of food patch knowl- efforts focused on vulture movements (Avery edge, thermoregulation, and reducing the risk et al. 2011, Holland et al. 2019), development of of predation (Beauchamp 1999). This behav- allowable take models to help inform the deci- ior can also lead to increased conflict in areas sions of migratory bird management agencies within proximity of the roosts (Blackwell et al. (Zimmerman et al. 2019), the ecological role of 2007). Vulture roosts can contain >500 vultures vultures (Hill et al. 2018), and genetic diversity (Prather et al. 1976). However, to date, inves- and population connectivity (Wostenberg et al. tigations focused on understanding vulture 2019). In spite of these works, given the rise of selection criteria for these “mega-roosts” are conflict with humans, there is still a need to fill absent (Sweeney and Fraser 1986). Anecdotal basic knowledge gaps on life history and ecol- evidence suggests vultures may preferentially ogy, to better understand the drivers of the vari- select roost sites (Rabenold 1987), but to our ous conflicts, and to test existing and develop knowledge a use versus availability framework new management strategies. has not been employed to investigate vulture Current modeling approaches can both iden- roost selection. tify factors contributing to changes in species Tools such as distribution modelling have distribution and predict further change (Snow the potential to determine preferred landscape et al. 2017, Tombre et al. 2019, Saenz-Jimenez characteristics (Martens et al. 2020), which et al. 2020). The BBS and Christmas Bird Count, would be important for planning urban roost longitudinal data sets comprising a large North dispersal. More specifically, it may be possible American spatial extent, have been used to that newly developed models for identifying document and describe the North American and predicting avian nest locations (Bracis et black vulture distribution expansion (Latteman al. 2018, Picardi et al. 2020) can be leveraged to 2019, Zimmerman et al. 2019). Climate change gain a firmer understanding of roost selection. is forecast to indirectly reduce the black vul- Understanding why vulture roosts appear and ture range in South America by way of facili- where they might appear in the future can help tating increased interspecific competition with managers plan for a dispersal event following Andean condors (Vultur gryphus) and favoring roost management activities and help deter- more mountainous regions (Saenz-Jimenez mine areas on the landscape more likely to con- et al. 2020); however, the factors contributing tain roosts in the future. 384 Human–Wildlife Interactions 14(3)
Population estimates and allowable take and field investigations (Breck et al. 2011, Elser models (Runge et al. 2009) for black vultures et al. 2019). Research focused on doing the same have been recently generated for the United for vultures and livestock producers could be States where the species occurs (Zimmerman used to validate and/or develop correction fac- et al. 2019). However, in these estimates there tors for producer-generated estimates of loss, is greater uncertainty (i.e., variance) in areas which could ultimately affect livestock indem- where black vultures have become established nity programs. Gaining a better understanding more recently. This is primarily attributed to less of producer perceptions of the vulture–live- data being available as model inputs. If vultures stock conflicts, especially in areas where black continue to increase numerically and expand vultures have recently become established, is spatially into states such as Pennsylvania and also warranted. Movement and resource inves- Indiana, currently available population and tigations focused on vultures in agricultural, allowable take estimates may be misrepresen- urban, and suburban dominated landscapes is tative, by way of underestimation. This bias also needed, as nearly all black vulture space represents a management challenge that could use investigations to date have had an airport/ potentially be rectified by generating more spa- airfield nexus. Finally, robust testing of new tially specific population estimates using mark- strategies to reduce black vulture livestock resight techniques and models (McClintock et depredation, damage to property, and risks to al. 2009). This technique has been employed human health and safety are needed. to robustly estimate abundance and density for several avian species (Hurley et al. 2013) Bridging research and management including raptors (Smith et al. 2015), but this The need for applied research to conduct method has not been validated for a gregari- investigations in a manner that creates robust, ous wide-ranging raptor species like black vul- defensible science can create research findings tures (Monadjem et al. 2014). We recommend that are not immediately translational to man- this approach be explored for black vultures agement efforts or tool development. Managers because if successful, resultant recalibration of often apply the sensible practice of using an population and allowable take estimates could integrated damage mitigation approach, where provide greater management flexibility. a suite of damage mitigation tools is used in Vulture damage to property due to their affin- concert or proceeding one another based on ity for damaging synthetic materials remains site-specific considerations (Conover 2001, poorly understood. Mauldin et al. (2003) iden- Reidinger and Miller 2013). This strategy does tified and collected the volatile compounds not always lend itself well to providing data emitted by several vulture-damaged items and capable of being analyzed in a manner that pro- attempted to develop a synthetic materials vides inference regarding the individual and/or mimic (SMM), but SMM bioassay trials were synergistic effectiveness of each tool. inconclusive. Determining whether this behav- For vultures, an emblematic example is ior is olfactory, aural, or tactile driven will allow research conducted to date on roost site disper- researchers to develop and test novel mitigation sal, whereby investigators have largely exam- strategies. Recent advancements in volatile com- ined the singular effects of important mitiga- pound research can offer pathways toward bet- tion tools such as effigies (Avery et al. 2002, ter understanding whether this behavior is olfac- Tillman et al. 2002) but have not included treat- tory based (Lubes and Goodarzi 2007). Further, ments incorporating multiple contemporarily contemporary strategies aimed at mitigating this employed mitigation tools or stimuli such as ini- damage type, including automated sprinkler tial roost dispersal by way of pyrotechnics and systems and inflatable tubemen (Lindell et al. lasers followed by placement of effigies. Without 2018) on flat roofs need to be robustly evaluated. incorporating multiple experimental treatments Myriad opportunities exist for better under- including both integrative and singular stimuli, standing and managing the vulture livestock the ability to defensibly determine the most depredation conflicts. Investigators have been effective tool combinations and quantify if syner- successful at comparing loss estimates of both gistic effects of integrative approaches are occur- crops and livestock measured by producers ring will continue to be elusive. Several advance- Black vulture conflict and management • Kluever et al. 385 ments and adoptions, including the practice of 19:58–63. modeling messy field-based data using Bayesian Avery, M. L., J. S. Humphrey, T. S. Daughtery, approaches that rely on previous knowledge J. W. Fischer, M. P. Milleson, E. A. Tillman, and (Jessop 2020) have the potential to help bridge W. D. Walter. 2011. Vulture flight behavior and this gap along with a robust study design that implications for aircraft safety. Journal of Wild- incorporates a novel and control stimuli. life Management 75:1581–1587. Avery, M. L., J. S. Humphrey, E. A. Tillman, K. O. Conclusions Phares, and J. E. Hatcher. 2002. Dispersing Based on our synthesis of the current status vulture roosts on communication towers. Jour- of black vulture management and research in nal of Raptor Research 36:45–50. the United States we contend that important Avery M. L. and M. Lowney. 2016. Vultures. Wild- advancements in research have been achieved life Damage Management Technical Series, in recent years that have increased manage- U.S. Department of Agriculture, Animal and ment efficacy. However, the general upward Plant Health Inspection Service, Wildlife Ser- trajectory of human–vulture conflicts warrants vices, National Wildlife Research Center, Fort additional investigations that shed new light on Collins, Colorado, USA. knowledge gaps regarding biology and ecology Ballejo, F., P. I. Plaza, and S. A. Lambertucci. of the species and applied works aimed at devel- 2020. The conflict between scavenging birds oping novel or improving existing damage miti- and farmers: field observations do not support gation strategies. Performing the latter in close people’s perceptions. Biological Conservation coordination with vulture damage management 248:108627. practitioners can help ensure these works are Baynard, O. 1909. Notes from Florida on Cath- translational (i.e., adaptable by field personnel). arista urubu. Oologist 26:191–193. Beasley, J. C., Z. H. Olson, and T. L. DeVault. Acknowledgments 2015. Ecological role of vertebrate scavengers. 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Steele, J. R., B. S. Rashford, T. K. Foulke, J. A. Bryan M. Kluever is a supervisory research Tanaka, and D. T. Taylors. 2013. Wolf (Canis wildlife biologist within the USDA, APHIS, Wildlife Ser- vices, National Wildlife Research lupus) predation impacts on livestock produc- Center (NWRC). As the NWRC tion: direct effects, indirect effects, and implica- Florida Field Station Leader, he and his team of dynamic natural tions for compensation ratios. Rangeland Ecol- resource professionals employ ogy & Management 66:539–544. observational, experimental, Sweeney, T. M., and J. D. Fraser. 1986. Vulture and captive animal/pen wildlife research to come up with robust, roost dynamics and monitoring techniques in common sense solutions to hu- southwest Virginia. Wildlife Society Bulletin man–wildlife conflict issues. He received his B.S. degree in wild- 14:49–54. life and fisheries from the Univer- Thiollay, J. M. 2017. Decline of African vultures: a sity of Nebraska, M.S. degree in rangeland ecology and need for studies and conservation. Ostrich 88:3. management from the University of Arizona, and Ph.D. degree in wildlife biology from Utah State University. Tillman, E. A., J. S. Humphrey, and M. L. Avery. 2002. Use of vulture carcasses and effigies to Morgan B. Pfeiffer is a research biologist reduce vulture damage to property and agricul- at the USDA, APHIS, Wildlife Services, National Wildlife Research Center in Sandusky, ture. Pages 123–128 in T. M. Timm, and R. H. Ohio. Her research interests Schmidt, editors. Proceedings of the 20th Verte- include understanding species plasticity, movements, and behav- brate Pest Conference, Davis, California, USA. ior in anthropogenic landscapes. Toledo, L. M., M. da Costa, A. Schmidek, J. Jung, Her current research involves J. Ciryllo, and V. U. Cromberg. 2013. The pres- evaluating unmanned aircraft sys- tems (UAS) technology for wildlife ence of black vultures at the calving sites and hazard management. its effects on cows’ and calves’ behaviour imme- diately following parturition. Animal 7:469–475. Scott C. Barras (photo unavailable) is the state director of the USDA Wildlife Services program in Tombre, I. M., T. Oudman, P. Shimmings, L. Griffin, Virginia, where he has served for the past 13 years. He and J. Prop. 2019. Northward range expansion and the program staff work daily to resolve human–wild- life conflicts with a wide variety of species throughout in spring-staging barnacle geese is a response Virginia. He earned a Ph.D. degree in fisheries and to climate change and population growth, me- wildlife from Utah State University. He is a member of The Wildlife Society and serves on the Virginia Invasive diated by individual experience. Global Change Species Advisory Panel. Biology 25:3680–3693. U.S. Department of Agriculture. 2015. Cattle and Brett G. Dunlap is the state director for the USDA Wildlife Services (WS) program in Tennessee calves death loss in the United States due and Kentucky. His professional to predator and nonpredator causes. Report experiences have focused on #745.1217. U.S. Department of Agriculture, Ani- wildlife/human dimensions, wild- life education/outreach, predator mal and Plant Health Inspection Service, Vet- management, and numerous erinary Services, Center for Epidemiology and aspects of wildlife damage man- agement. He has been a TWS Animal Health, Fort Collins, Colorado, USA. member since 1989 and a TWS Washburn, B. E. 2018. Human–raptor conflicts in Certified Wildlife Biologist since urban settings. Pages 214–229 in C. W. Boal 1995. He earned a B.S. degree in wildlife and fisheries sciences from Texas A&M University and an M.A. de- and C. R. Dykstra, editors. Urban raptors: ecol- gree in biology from Sam Houston State University. He ogy and conservation of birds of prey in cities. is a past president of the Tennessee Chapter of TWS and serves as an adjunct professor for the University of Island Press, Washington, D.C., USA. Tennessee at Martin and Tennessee Tech University. Wostenberg, D. J., J. A. Fike, S. J. Oyler-McCance, M. L. Avery, and A. J. Piaggio. 2019. Develop- Lee A. Humberg is the state director for USDA, APHIS, Wildlife Services in Indiana. He earned ment of microsatellite loci for two New World his B.S. (2000) and M.S. (2006) vultures. BMC Research Notes 12:6. degrees from Purdue University investigating wildlife crop depreda- Zimmerman, G. S., B. A. Millsap, M. L. Avery, J. R. tion. For the last 14 years, he has Sauer, M. C. Runge, and K. D. Richkus. 2019. worked for the federal govern- Allowable take of black vultures in the eastern ment, including positions with the Department of the Army, U.S. United States. Journal of Wildlife Management Forest Service, and USDA Wildlife 83:272–282. Services. He currently directs wildlife conflict mitigation programs associated with aviation safety, public utilities and infrastructure, human health and safety, agricultural Associate Editor: George M. Linz damage, and natural resource protection.