Milvago Chimango Research Articles

Long-term directional changes in urban bird communities of Mar del Plata City, Argentina

Urban environments have been characterized by their temporal stability of resources, which could promote stability in bird composition. Several studies have found that bird communities in urban environments persist over the years, showing a similar species composition in the short term. However, studies analyzing continuous changes in urban communities over the long term are scarce. This study aimed to analyze the stability or directional changes (instability) in bird communities along an urban gradient. Bird counts were conducted in urban, suburban, and periurban areas over 8-10 years in 2002-2019. Changes in species composition were analyzed over periods ranging from one year to the next, to changes from one year to the seventeenth. Urban bird communities were more similar between years than suburban and periurban communities. Compositional changes were greater as time lags increased, indicating directional compositional shifts. The magnitude of these changes was similar across the urban gradient. The Chimango Caracara (Milvago chimango), the Picazuro Pigeon (Patagioenas picazuro), the Rufous Hornero (Furnarius rufus), and the Red-bellied Thrush (Turdus rufiventris) significantly increased their abundances during the period, while the House Sparrow (Passer domesticus) significantly decreased its abundance. Regional changes in species abundance, urban vegetation succession, and biotic interactions could explain the changes in bird communities.

Assessing Knowledge of the Caracaras: Compiling Information, Identifying Knowledge Gaps, and Recommendations for Future Research

ABSTRACT Because information availability and management are essential components of wildlife conservation, we sought to compile literature published since 1900 on the caracaras, a group of nine extant species, eight of which occur only in Central America and South America. Our findings revealed that the number of sources and therefore, the amount and types of information available varied considerably among the caracara species and among countries where these raptors occur. Most sources represented studies conducted in Argentina, the United States, Brazil, and Chile, and many focused on the more common species, for example, the Crested Caracara (Caracara plancus) and the Chimango Caracara (Milvago chimango). Most sources published in the early 20th century focused on breeding and feeding ecology and natural history. Since the 1960s, the number of studies published per decade has increased, and since the 1990s, more studies have addressed a broader range of topics including behavioral ecology, demography, infectious agents, parasites, contaminants, biomedicine, and taxonomic relatedness among the caracara species and other falcons. Aside from the Striated Caracara (Phalcoboenus australis), which recently has been the subject of intensive research, other species in the genus Phalcoboenus (the Mountain Caracara [P. megalopterus]; the White-throated Caracara [P. albogularis]; and the Carunculated Caracara, [P. carunculatus]) remain little known, as do the two forest-dwelling caracaras, the Black Caracara (Daptrius ater) and the Red-throated Caracara (Ibycter americanus). Knowledge gaps exist for all the caracaras; research is especially needed on subjects outside typically studied topics such as breeding and feeding ecology. Also important to expanding knowledge of this group will be collaboration with researchers studying other avian scavengers such as condors and vultures, focusing on common threats, and coordination among researchers in countries inhabited by multiple caracara species.

Prevalence of Pathogens in Free-Living Adult Chimango Caracaras (Milvago chimango) in Three Areas with Different Levels of Urbanization in the Pampas Ecoregion, Argentina

ABSTRACT Urbanization can adversely impact animal populations through factors such as loss of natural habitat, introduction of nonnative competitors and predators, pollution, and increased exposure to pathogens. Because they are top predators, raptors are considered good indicators of ecosystem health. However, there is limited information about how environmental factors associated with urbanization can alter raptors’ susceptibility to pathogens. We evaluated exposure to selected pathogens of the Chimango Caracara (Milvago chimango), a generalist and opportunistic species endemic to South America. This species is distributed over a wide range of environments, including urban areas, and often takes advantage of human-generated resources such as domestic waste, urban garbage, and carrion, potentially increasing its exposure to pathogens. We captured adult Chimango Caracaras in three areas that varied in level of urbanization, in the southeastern region of the Buenos Aires Province, Argentina. Captured individuals were tested for exposure to Bacillus anthracis, Salmonella spp., and Trichomonas spp. All individuals tested were negative for these pathogens. Whether this represents a true lack of exposure to these microorganisms, the ability of this raptor to effectively inhibit the colonization of the gastrointestinal tract by these microorganisms, or an inability of the pathogen to colonize the Chimango Caracara’s gastrointestinal tract remains to be determined. This is the first study to assess the prevalence of selected pathogens in Chimango Caracaras inhabiting areas with different levels of urbanization.

Vocal Repertoire of Chimango Caracaras in Rural and Urban Habitats

ABSTRACT Acoustic communication, such as bird song, is vital in animal ecology, facilitating reproduction, feeding, defense, and more. Variation in bird song may result from adaptation to environmental features such as anthropogenic noise. The vocal repertoire of raptors is essentially unstudied, particularly in urban environments. The aim of this work was to describe and quantify the acoustic repertoire of Chimango Caracaras (Milvago chimango) in rural and urban areas in La Pampa Province, Argentina. I recorded 26 1-min sound samples at each of four breeding colonies (one rural and three urban) during the austral reproductive season of 2021–2022. I recorded 241 vocalizations corresponding to nine clearly distinct call types. Two types of calls made up 50.6% and 19.5% of the vocalizations and seven others made up <10.0% each. Three call types had trills (fast repetitive notes). Average percentage of call types differed significantly between the two habitats (P < 0.01), with more trills produced in rural habitats. Average calling rate was 6.6 ± 5.1 calls/min at rural colonies and 10.7 ± 10.7 at urban colonies. The number of different call types produced was 2.1 ± 1.6 types/min at rural colonies and 2.7 ± 1.8 at urban colonies. The greater calling rate of Chimango Caracaras in urban areas may represent an attempt to improve signal effectiveness among the anthropogenic acoustic clutter.

Biparental Care in a Generalist Raptor, the Chimango Caracara in Central Argentina

ABSTRACT The allocation of parental care behaviors between the sexes may be influenced by the species’ mating system, degree of sexual size dimorphism, and predictability of food resources. Biparental care (i.e., both parents contributing to raising young) has been documented in raptors, including those with minimal sexual size dimorphism and/or whose food resources are unpredictable in time (e.g., scavengers). The Chimango Caracara (Milvago chimango) is a common raptor with slight sexual size dimorphism and a scavenging lifestyle. During two breeding seasons, we performed focal observations at nests in a Chimango Caracara colony in central Argentina to assess the division of labor between the sexes. For males and females separately, we measured the time spent incubating and brooding, and the food delivery rate to nestlings; then we used GLMMs to assess various factors that may influence these behaviors, including parental sex, time of day, clutch or brood size, and nestlings’ age. We used GLMMs to test the influence of time spent brooding and food delivery rate (both parents combined for these variables) on nest success and productivity. Although both sexes contributed to all parental care activities, females spent more time incubating and brooding than males. Brooding time decreased as nestlings aged. Food delivery rate did not differ between the sexes. Food delivery rate was higher during the middle of nestlings’ development but declined thereafter. Nest success and productivity were higher at nests with higher food delivery rates. Adults spent more time incubating and brooding during morning and midday, and food delivery rate was higher during the afternoon.

Cognitive flexibility in a generalist raptor: a comparative analysis along an urbanization gradient

Abstract In this study, we analyzed the variation in cognitive flexibility in the Chimango Caracara (Milvago chimango), across areas with different levels of urbanization. To assess this, we utilized the reversal learning assay which measures the ability to adapt behavior in response to changes in environmental contingencies. We also investigated the impact of neophobia on this variation. All chimangos studied succeeded in acquiring a color-reward association and reverting this learned association when the contingencies changed. Urban chimangos were faster than their rural and suburban counterparts during the initial discrimination and reversal phases. The reversal phase proved to be the most challenging task. The analysis of the errors made during this phase revealed that acquiring a new association (i.e. regressive errors) was challenging for the individuals studied, in comparison to inhibiting a previously learned one (i.e. perseverative errors). Neophobia was found to be lower in urban individuals compared to suburban and rural raptors. Moreover, neophobia showed a correlation with regressive errors during the reversal phase among rural and suburban chimangos, while no such correlation was observed among city-dwelling chimangos. We suggest that neophobia acted as a regulating factor of cognitive flexibility, mainly for individuals expressing relatively high levels of this personality trait.

Chimango Caracaras (Milvago chimango) Nesting in Natural and Anthropogenic Cavities in Argentina

Chimango Caracaras (Milvago chimango) Nesting in Natural and Anthropogenic Cavities in Argentina

Urban Parks Are Related to Functional and Phylogenetic Filtering of Raptor Assemblages in the Austral Pampas, Argentina

Urban parks are hot spots of bird diversity in cities. However, their role as urban filters for raptor species has not been assessed yet. This study aimed to compare the functional and phylogenetic traits of raptor assemblages in urban parks with the regional species pool of raptors in east–central Argentina. Diurnal raptors were surveyed in 51 urban parks in six cities during breeding and nonbreeding seasons. The regional species pool was assessed through raptor surveys and published maps surrounding the cities. The observed functional and phylogenetic relatedness of urban raptors was compared with 999 simulated raptor assemblages from the regional species pool. A total of five species were recorded in urban parks. The Chimango Caracara (Milvago chimango) was the numerically dominant species, comprising 95% of the 172 individuals recorded. The regional species pool was composed of 20 diurnal species. The functional and phylogenetic relatedness of urban raptors was higher than expected by chance, suggesting filtering induced by urban parks. Urban raptors were, in general, generalist species with small body sizes. Moreover, species tended to be part of the Falconidae family. Based on the results obtained here and in other published work, a model of raptor assembling in urban parks is proposed. The design of urban parks needs to be more heterogeneous, promoting the occurrence of specialist raptors.

Comunidades de aves en barrios residenciales y en bosques implantados en médanos costeros de la localidad de Cariló, Argentina

Coastal areas have the largest human population, causing significant urbanization impacts on biodiversity. The coast of Buenos Aires province (Argentina) has touristic cities, which have shown significant growth during the last decades. Therefore, it is fundamental to analyze the effect of urbanization on bird communities. The aim of this study is to analyze the bird communities present in residential areas and implanted forests on coastal dunes in Cariló. Eight fixed radius point counts were carried out in each habitat between spring 2021 and summer 2022. Both habitat types had similar values of species richness, Shannon and Simpson diversity, and functional diversity. However, residential habitat showed higher abundance than the forest. Significant changes between habitats in species composition were found. The Tropical Parula (Setophaga pitiayumi) and the Rufous-collared Sparrow (Zonotrichia capensis) were more abundant in the forest, while the Chimango Caracara (Phalcoboenus chimango), the Monk Parakeet (Myiopsitta monacha) and the Picazuró Pigeon (Patagioenas picazuro) were more abundant in the residential habitat. The residential area had a greater abundance of birds feeding on the ground, the canopy and the air. The results obtained suggest that the urban expansion on implanted forests promotes bird compositional changes, favoring species typical of semi-open habitats and impairing species associated with high tree cover and unmanaged herbaceous vegetation.

HEMATOLOGY AND PLASMA BIOCHEMISTRY REFERENCE INTERVALS FOR FREE-LIVING ADULT CHIMANGO CARACARA (MILVAGO CHIMANGO) DURING THE NONBREEDING SEASON.

Hematological and blood biochemistry values are useful in assessing the physiological, nutritional, and overall health status of captive and free-living wildlife. For the chimango caracara (Milvago chimango), the most common raptor species in Argentina, reference intervals (RIs) for hematology and blood biochemistry are lacking. For this study, 86 chimango caracaras were captured and studied in Mar del Plata and neighboring areas (Buenos Aires, Argentina) during winter (April-July) in 2018 and 2019. This is the first study to present RIs for 33 blood parameters in a large number of free-living chimango caracaras during the nonbreeding season. In addition, the variability of blood parameters according to sex and calendar year was analyzed. Overall, values for the studied parameters were similar to those described for other raptor species. There were significant differences between years for absolute monocyte counts, relative eosinophils, monocyte counts, glucose, phosphorus, and alanine aminotransferase. Only the relative count of eosinophils, aspartate aminotransferase, and calcium showed significant differences between the sexes. The values of absolute monocyte counts and the relative count of eosinophils and monocytes, glucose, phosphorus, and alanine aminotransferase were higher in 2019 than in 2018, whereas mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration were higher in 2018. Relative eosinophil counts were higher for males than for females, and aspartate aminotransferase activity and calcium concentration were significantly higher for females than for males. The RIs for hematology and plasma biochemistry from this large number of chimango caracaras is of clinical relevance not only for chimango caracaras under medical care in rehabilitation centers but also in ecological studies aimed to investigate the physiological responses of this species to natural and anthropogenic changes.

What makes an urban raptor?

Raptor communities are negatively impacted by urbanization. However, some species can thrive in urban areas. Raptor species traits that favour their presence in urban areas have been scarcely studied. Moreover, phylogenetic relatedness may be a factor promoting raptor occurrence in urban areas. In this study, we use data gathered through citizen science in Argentina to analyse the phylogenetic signal and the drivers that correlate with raptor presence in urban settings. The mean percentage urban cover for the records of each species was considered as an index of raptor occurrence in urban areas. A total of 55 species were analysed, which accounted for 90% of the diurnal raptors of Argentina. Harris’s Hawk Parabuteo unicinctus, Pearl Kite Gampsonyx swainsonii and Chimango Caracara Milvago chimango had the highest urban index. Raptor occurrence in urban areas had a marginal phylogenetic signal, indicating a tendency for more closely related species to have similar tolerances to urbanization. The index of raptor occurrence in urban areas was highest for the most common species of non‐urban areas, and was not related to traits such as body mass, diet, nesting site and migratory behaviour. Our results highlight the importance of citizen science projects in data gathering at large geographical scales.

NIDIFICACIÓN DENTRO DE CAVIDADES INÉDITA ENTRE FALCÓNIDOS: UNA POBLACIÓN DE CHIMANGOS (MILVAGO CHIMANGO) APROVECHANDO NIDOS DE LOROS BARRANQUEROS (CYANOLISEUES PATAGONUS) EN PATAGONIA ARGENTINA

Abstract. Unprecedented cavity nesting among falconids: a Chimango Caracaras (Milvago chimango) population using Borruwing Parrots (Cyanoliseus patagonus) nests in Patagonia Argentina. The Chimango Caracara (Milvago chimango) is the most abundant member of raptor assemblages from Paraguay and Bolivia to the southern tip of Argentina. In Argentinian Patagonia we studied nesting and other biological aspects of a Chimango Caracaras population that exploits cavities built by marine psittacines, in a unique ornithological assemblage: 12 km of sea cliffs with 37,000 active nests of Burrowing Parrots (Cyanoliseus patagonus). During 56 days we assessed a total of 18 active Chimango Caracaras nests (11 in 2014 and 7 in 2015). All nests contained plant material inside and had some structure to facilitate landing and perching. Most were located in the upper third of the cliff and had a single entrance mouth. The average distance to the nearest nest in the same breeding season was 108.9 m ± SD 90.90 m. We document in detail for the first time the construction of Chimango Caracaras nests inside cavities. Our results document a new breeding substrate for this species and a nesting behaviour unique among falconids, which could be interpreted as evidence of adaptability and plasticity of Chimango Caracaras.

Behavioural factors underlying innovative problem-solving differences in an avian predator from two contrasting habitats.

Innovative behavior is considered one of the main factors facilitating the adaptation of animals to urban life. However, the relationship between urbanization and innovativeness is equivocal, perhaps reflecting aspects of urban environments that influence differently the behavioural traits underlying the occurrence of an innovation. In this work, we analysed the variation in innovative problem-solving performance between urban and rural individuals of the Caracara Chimango (Milvago chimango), with the goal of determining which behavioural trait (or combination) most explained such variation. We found that urban raptors outperformed rural ones in their solving speed and solving level (number of solutions) with a multiaccess box. They also showed more persistence, motor flexibility and diversity, as well as higher effectiveness in their solving attempts than rural chimangos. Sex was not an important factor. Urban chimangos showed less neophobia and spent more time exploring the box than rural birds during the initial habituation period, which probably determined the amount of information about the system that each individual had at the beginning of first problem solving trial. This difference in novelty response both directly and indirectly, through its relationship with persistence, motor flexibility and proportion of effective attempts, explained variability in solving performance. All individuals showed a decrease in solving latency, and an increase in solving level with experience, indicating that learning occurred in both raptor groups. This improvement occurred in parallel with changes in the afore-mentioned traits, though the pattern of improvement differed between urban and rural chimangos. We suggest that the characteristics of urban areas modulate the novelty response of chimangos, along with other correlated non-cognitive behavioural traits, which act in combination to increase the chances that novel problems could be quickly solved, and the resulting new behaviours established in city populations of this species.

UNEXPECTED LACK OF EFFECT OF THE INVASIVE AMERICAN MINK ON NESTING SURVIVAL OF FOREST BIRDS

Nest predation by invasive mammalian predators can cause major impacts on native bird populations. The American mink (Neovison vison) was recently introduced on Navarino Island in southern Chile. The mink established as a new terrestrial mesopredator on the island with documented impacts on waterfowl breeding success. However, little is known about mink effects on forest bird’s reproduction. Here, we investigated nest-predation rate by native predators and the invasive mink on open-cup nesting forest birds by using artificial and natural nests. In six different plots, we deployed a grid (7 x 2) of 14 artificial nests spaced by 50 m and at random heights from the ground. We used camera traps in each nest to identify predators. At each plot, we estimated predator relative abundance using camera traps, Sherman traps, and bird point counts. We estimated nest survival probability as a function of nest age, concealment, distance to the river, and nest height. Additionally, we monitored 43 natural nests of five open-cup nesting bird species. Contrary to expected, mink was not a main predator of nests, depredating only one natural nest. The native raptor Chimango Caracara (Milvago chimango) was the main nest predator, preying on 39.8% artificial nests and 27.0% natural nests. We also found evidence that Chimango Caracara learned to associate the artificial nests with the egg reward. We argue that the lower abundance of mink in the forest and a mismatch between mink peak activity patterns and bird breeding phenology can result in low depredation. Mink impacts, however, may be more pervasive in summer months and on fledglings when mink activity peaks, and more research should be conducted to assess these questions. Our results are valuable to better understand mink impacts on biodiversity and to prioritize conservation actions on species more severely affected.

Nest-site selection and breeding success of passerines in the world's southernmost forests.

BackgroundBirds can maximize their reproductive success through careful selection of nest-sites. The ‘total-foliage’ hypothesis predicts that nests concealed in vegetation should have higher survival. We propose an additional hypothesis, the ‘predator proximity’ hypothesis, which states that nests placed farther from predators would have higher survival. We examined these hypotheses in the world’s southernmost forests of Navarino Island, in the Cape Horn Biosphere reserve, Chile (55°S). This island has been free of mammalian ground predators until recently, and forest passerines have been subject to depredation only by diurnal and nocturnal raptors.MethodsDuring three breeding seasons (2014–2017), we monitored 104 nests for the five most abundant open-cup forest-dwelling passerines (Elaenia albiceps, Zonotrichia capensis, Phrygilus patagonicus, Turdus falcklandii, and Anairetes parulus). We identified nest predators using camera traps and assessed whether habitat characteristics affected nest-site selection and survival.ResultsNest predation was the main cause of nest failure (71% of failed nests). Milvago chimango was the most common predator, depredating 13 (87%) of the 15 nests where we could identify a predator. By contrast, the recently introduced mammal Neovison vison, the only ground predator, depredated one nest (7%). Species selected nest-sites with more understory cover and taller understory, which according to the total-foliage hypothesis would provide more concealment against both avian and mammal predators. However, these variables negatively influenced nest survival. The apparent disconnect between selecting nest-sites to avoid predation and the actual risk of predation could be due to recent changes in the predator assemblage driven by an increased abundance of native M. chimango associated with urban development, and/or the introduction of exotic mammalian ground predators to this island. These predator assemblage changes could have resulted in an ecological trap. Further research will be needed to assess hypotheses that could explain this mismatch between nest-site selection and nest survival.

Comparación de la dieta del tiuque (Milvago chimango) y el pequén (Athene cunicularia) en un sitio peri-urbano de Chile central

La diferenciación trófica entre rapaces cumple un rol esencial para su coexistencia, situación que se hace especialmente relevante cuando existe transformación del hábitat, lo que lleva a modificaciones en la disponibilidad de recursos. En diciembre de 2018 examinamos la dieta de Milvago chimango y Athene cunicularia en Chile Central, en una zona próxima a un relleno sanitario en la localidad de Montenegro. Colectamos 226 egagrópilas de M. chimango y 68 egagrópilas de A. cunicularia, y observamos que ambas especies concentraron una alta proporción de presas en torno a artrópodos (principalmente de la clase Insecta, con un 54% y un 64% para M. chimango y A. cunicularia, respectivamente), con variaciones en el consumo de los distintos órdenes y familias en cada caso. A pesar de que tuvieron diferencias en torno al consumo de aves (5.36% para M. chimango y 1.42% para A. cunicularia) y mamíferos (2.53% para M. chimango y 7.13% para A. cunicularia), ambas especies presentaron una alta sobreposición dietaria (S = 0.94), donde las diferencias espaciales y de caza de cada especie serían los mecanismos que explicarían su coexistencia en el área de estudio.

Urban Ecology. Bird Diversity in Cities in Southern Chile

Urbanisation is a dominant demographic trend and an important component of the earth’s global transformation. It has unprecedented socioeconomic, cultural and environmental implications, and poses a threat to the conservation of biodiversity, as it can provoke alterations in ecological systems and lead to poor functioning of urban systems as they are currently structured. From the ecological point of view, the city is a fragmented, heterogeneous, complex mosaic of habitats, including ecosystems with different degrees of alteration. Urban systems contain only small areas of fragments of original vegetation and/or artificial green spaces, leading to a drastic decrease from their original abundance and diversity. However, green spaces, including original fragments, can help to conserve bird diversity, improving the functioning of these artificial systems in the medium term. This study looks at the characteristics and benefits of urban ecology in the framework of sustainable development, and carries out a meta-analysis of research into bird diversity in four cities in southern Chile, using ecological indices (Shannon-Wiener, β diversity between cities). The results reveal that there is low evenness in the four cities and that the city with the highest evenness is Valdivia (J = 0.78). There is clear dominance by a few bird species (e.g. the exotic species house sparrow Passer domesticus and rock pigeon Columba livia, and the native species rufous-collared sparrow Zonotricia capensis, austral thrush Turdus falklandii, southern lapwing Vanellus chilensis, and chimango caracara Milvago chimango). β diversity is low as the four cities show similarity greater than 50%. Birds reject paved surfaces in squares and prefer areas with native bushes and trees, with nearby bodies of water and large spaces (parks rather than squares). The study proposes technical recommendations and suggests further research.

PUNTOS CALIENTES Y FACTORES ASOCIADOS AL ATROPELLO DE AVES RAPACES EN UNA RUTA COSTERA DE LA ZONA SEMIÁRIDA DE CHILE CENTRAL

The pressures of road infrastructure on wildlife are among the eleven main threats to biodiversity conservation. Birds are one of the most threatened groups, mainly through direct collisions with road traffic and the fragmentation of their habitats. We characterized the assem- blage of raptors that were impacted on a coastal highway in central Chile and analyzed the possible relationship between areas with high impact density and some landscape variables. Between April 2016 and June 2017 we registered 86 raptor carcasses, nine species belonging to five different families, among which Tyto alba, Milvago chimango, and Bubo virginianus were the birds with a higher frequency of road- kills. These impacts were concentrated between February and April 2017. In the sections studied, we detected eight hot spots that included 37% of the impacts and found at least five variables related to these road kill hot spots: i) A larger surface covered with trees, ii) a small number of lighting poles, iii) sites closer to creeks, iv) road sections without curves, and v) double tracks would favor roadkills for these birds in the studied site. Additionally, collisions for the different species of raptors recorded in this study could be due to the availability of prey on the edges of the road, their foraging strategies, and the ecology of these birds, especially during breeding season.

Variation in boldness and novelty response between rural and urban predatory birds: The Chimango Caracara, Milvago chimango as study case

The study of traits that enable species to thrive in urban habitats is critical to a better understanding the evolution of urban ecosystems. Here, we examined variation in boldness, neophobia, and exploratory behavior in a generalist raptor, the Chimango Caracara, Milvago chimango, occurring in areas with different urbanization level. We also focused on the relationship between object exploration and neophobia in rural and urban population of this species. The results showed that birds from more urbanized habitats showed more tolerance to humans than rural raptors, without any effect of age and sex in this trait. Rural birds were also more neophobic and were slower to explore than urban raptors, though they dedicated a similar amount of time to exploring novel objects, indicating a non-correspondence between the speed to approach and contact these objects and the amount of exploration performed. Finally, we found a correlation between exploration speed and neophobia in rural birds, whereas for urban raptors this correlation was not observed. Our results show that urbanization not only influences the expression of risk-taking behaviors and novelty responses in the chimango, but can also modify the relationship between exploration and neophobia.

Exposure of Raptors in Central Argentina to St. Louis Encephalitis and West Nile Viruses

Arthropod-borne viruses represent the most important emerging viruses worldwide. Saint Louis encephalitis (SLEV) and West Nile (WNV) viruses are vectored by Culex spp. mosquitoes and amplified by several bird species. We carried out an extensive retrospective serosurvey study to analyze the exposure of free-ranging raptors to SLEV and WNV in central Argentina. We collected samples from eight species of raptors between 2008 and 2015. We used Plaque Reduction Neutralization Tests (PRNT) to analyze 523 plasma samples for both viruses. Of the individuals tested for WNV, 85.2% of the Swainson's Hawks (Buteo swainsoni) were positive. Fewer birds presented neutralizing antibodies against SLEV: 20.8% of the Black Vultures (Coragyps atratus), 25% of the Southern Caracaras (Caracara plancus), and 0.3% of the American Kestrels (Falco sparverius). One Swainson's Hawk was positive for both viruses. We found no neutralizing antibodies in samples from Turkey Vultures (Cathartes aura), Chimango Caracaras (Phalcoboenus chimango), Burrowing Owls (Athene cunicularia), and a Ferruginous Pygmy-Owl (Glaucidium brasilianum). Although seroprevalence varied among species, our results confirmed SLEV and WNV circulation in resident and migratory populations of raptors in central Argentina. These findings suggest the need for further studies regarding circulation and ecological characterization of these viruses in bird communities in Argentina.