SHORT COMMUNICATIONS J. Raptor Res. 54(2):166–171 Ó 2020 The Raptor Research Foundation, Inc. ELECTROCUTION ON POWER LINES IS AN IMPORTANT THREAT FOR THE ENDANGERED CHACO EAGLE (BUTEOGALLUS CORONATUS) IN ARGENTINA 1 JOSE´ H. SARASOLA Centro para el Estudio y Conservacio´n de Aves Rapaces en Argentina (CECARA). Universidad Nacional de La Pampa, Avda Uruguay 151, 6300 Santa Rosa, Argentina and Instituto de las Ciencias Ambientales y de la Tierra de La Pampa (INCITAP-CONICET), Avda Uruguay 151, 6300 Santa Rosa, La Pampa, Argentina MAXIMILIANO A. GALMES Centro para el Estudio y Conservacio´n de Aves Rapaces en Argentina (CECARA), Universidad Nacional de La Pampa, Avda Uruguay 151, 6300 Santa Rosa, Argentina and The Peregrine Fund, Boise, ID 83709 USA BRYAN D. WATTS Center for Conservation Biology, College of William & Mary, Williamsburg, VA 23187 USA and Virginia Commonwealth University, Williamsburg, VA 23284 USA ABSTRACT.—Electrocution is a widespread conservation problem for birds of prey that has received little attention in the Neotropics. Here we present electrocution records involving the endangered Chaco Eagle (Buteogallus coronatus) in central Argentina, and we provide information on the power pole structural characteristics associated with electrocutions. Nine Chaco Eagles were recorded electrocuted during the period 2012–2019 over an area of 9000 km2. Chaco Eagles were found electrocuted in association with five types of power poles, but more than half the electrocutions (55%) were on poles made of steel-reinforced concrete and with jumper wires above the crossarms. With the addition of four previous electrocution reports in this region during the same time period, the annual rate of Chaco Eagle electrocutions was similar to the rate of mortality by other human-related factors such as direct persecution. Future conservation actions and research should focus on retrofitting the small fraction of poles that pose the highest electrocution risks for Chaco Eagles, and on assessing the demographic effects of electrocution mortality for this species and other endangered raptors in Argentina. KEY WORDS: Chaco Eagle; Buteogallus coronatus; conservation; electrocution; endangered species; mortality. LA ELECTROCUCION´ EN LINEAS´ ELECTRICAS´ ES UNA AMENAZA IMPORTANTE PARA BUTEO- GALLUS CORONATUS, UNA ESPECIE EN PELIGRO DE EXTINCION´ EN ARGENTINA RESUMEN.—La electrocucio´n es un problema de conservacio´n muy extendido para las aves de presa que ha recibido poca atencio´n en el Neotro´pico. Aqu´ı presentamos registros de electrocucio´n que involucran a la especie Buteogallus coronatus, considerada en peligro de extincio´n en el centro de Argentina, y proporcionamos informacio´n sobre las caracter´ısticas estructurales de los postes ele´ctricos asociados con 1 Email address: [email protected] 166 JUNE 2020 SHORT COMMUNICATIONS 167 las electrocuciones. Nueve individuos de B. coronatus fueron registrados electrocutados durante el per´ıodo 2012–2019 en un a´rea de 9000 km2. Los individuos fueron hallados electrocutados en asociacio´n a cinco tipos de postes ele´ctricos, pero ma´s de la mitad de las electrocuciones (55%) fueron en postes de hormigo´n armado y con cables puente sobre las crucetas. Con la adicio´n de cuatro registros previos de electrocucio´n en esta regio´n durante el mismo per´ıodo de tiempo, la tasa anual de electrocucio´n de B. coronatus fue similar a la tasa de mortalidad de otros factores antropoge´nicos como la persecucio´ndirecta. Las futuras acciones de conservacio´n e investigacio´n deber´ıan enfocarse en reacondicionar la pequena˜ fraccio´n de postes que plantean los mayores riesgos de electrocucio´n para B. coronatus, y en evaluar los efectos demogra´ficos de la mortalidad por electrocucio´n para esta especie y otras rapaces en peligro en Argentina. [Traduccio´n del equipo editorial] Electrocution is an important threat for many birds of Here we present new electrocution records involving prey worldwide. This mortality source is responsible for Chaco Eagles in central Argentina and discuss the relative declines in raptor populations on most continents (Eccles- effect this source of mortality has on their populations in ton and Harness 2018, Slater et al. 2020). However, this comparison with previously identified threats. We also threat from human infrastructure has received little provide information on the structural characteristics of attention in the Neotropics despite the high raptor species the poles associated with the electrocutions as a way to diversity in the region (but see Ibarra and De Lucca 2015, identify poles posing a high risk of electrocution for Galmes et al. 2018a), and the critical conservation status of Chaco Eagles. many of those species (Sarasola et al. 2018). Compared to other regions, systematic studies of raptor electrocution are lacking (Lehman et al. 2007). METHODS Most avian electrocution is associated with electrical distribution lines of low- to medium-voltage (i.e., 1–60 kV; We documented electrocutions involving Chaco Eagles Lehman et al. 2007) due to narrow clearances between across an area of ca. 90,000 km2 in the southernmost energized and grounded components. Contributing fac- extreme of the species’ range in central Argentina (Fig. 1). tors associated with higher avian electrocution risks include This region is characterized by a semiarid landscape and species-specific traits such as body size and behavior (Ferrer includes two habitat types, the Espinal and the Monte and Hiraldo 1992, Ledger and Hobbs 1999), and environ- desert biomes, that appear critical to the Chaco Eagle. mental factors such as the proximity of lines to activity areas We gathered information on electrocutions of Chaco (Watts et al. 2015), local prey abundance (Dixon et al. Eagles from 2012 to 2019 from two main sources. First, 2017), nest sites (Dwyer and Mannan 2007), and the Chaco Eagles equipped with transmitters as nestlings were availability of non-power-pole perching sites (Dona´zar et al. discovered electrocuted after transmission ceased. Second, 2002, Lehman et al. 2010). However, the risk of avian we investigated reports of Chaco Eagle mortalities made by electrocution is mainly the result of the combination of two local farmers and conservation nongovernmental organi- crucial features of power poles in the lines: the design of zations. For each carcass found under a power pole, we the poles and the materials with which they are built (Avian established the cause of death by external examination of Power Line Interaction Committee [APLIC] 2006). Poles built with conductive materials such as steel-reinforced the body and we diagnosed electrocution based on and the concrete may significantly increase avian electrocution risk presence of burns on the feathers and skin (Kagan 2016). relative to poles made of nonconductive material such as When possible, we classified electrocuted birds based on wood. plumage as juvenile (,1 yr old), immature (1–4 yr old), or The Chaco Eagle (Buteogallus coronatus) is one of the adult (.4 yr old); and as male or female based on largest and most endangered raptor species in the Neotrop- molecular determination or morphometric characteristics ics, with an estimated global population of fewer than 1000 (females are larger; Galmes et al. 2018b). reproducing individuals and a decreasing population trend For every electrocution, we identified the pole respon- (BirdLife International 2016). The most important threats sible and we classified poles based on their structural documented for the species are human-related, including characteristics, including the design and material of the habitat loss (Fandino˜ and Pautasso 2013) and direct pole. Poles were classified according to the number of persecution (Sarasola and Maceda 2006, Sarasola et al. phases (i.e., one or three long wires between poles) on the 2010, Barbar et al. 2016). Recently, Galmes et al. (2018a) line, the presence of jumper wires (short wires connecting documented four Chaco Eagle electrocutions in central equipment on poles) above the crossarms, and the material Argentina, and asserted that the observed level of mortality with which the pole was built (steel-reinforced concrete or is important given the small population of the species. wood) following Galmes et al. (2018a). 168 SHORT COMMUNICATIONS VOL. 54, NO.2 Figure 1. Locations of the electrocutions of Chaco Eagles across semiarid biomes in central Argentina from 2012 to 2019. Filled circles indicate the nine electrocutions reported in this study. Open circles indicate four electrocutions reported by Galmes et al. (2018). JUNE 2020 SHORT COMMUNICATIONS 169 Table 1. Number of electrocuted Chaco Eagles in considering that information was gathered opportunisti- association with power pole features (material of the pole, cally, it appeared that mortality of Chaco Eagles by number of phases, and presence/absence of suspended electrocution was similar to mortality attributed to other jumper wires). human-related factors previously identified for the species and assessed in a similar way. For example, the mortality of POWER POLE FEATURES Chaco Eagles by electrocution in our study area was 1.2 NUMBER OF eagles/yr but increased to 1.6 eagles/yr when four CHACO EAGLES POLE NUMBER OF JUMPER additional reports for the same area and time period are ELECTROCUTED MATERIAL PHASES WIRES included. These values are slightly lower than the annual 1 Wood 3 Present rate of persecution for the period 2010–2014 of two eagles/ 1 Wood 1 Present yr (Barbar et al. 2016). However, this last value was derived 2 Concrete 3 Absent from both field data and reports from rehabilitation 2 Concrete 3 Present centers in seven provinces all over the country, whereas 3 Concrete 1 Present the electrocution reports involving Chaco Eagles come from a comparatively small area comprising three provinces in central Argentina (Fig. 1). In addition, electrocution was RESULTS responsible for a third of the deaths of Chaco Eagles tagged with satellite transmitters during the period 2012–2016 (J. We recovered nine electrocuted Chaco Eagles from Sarasola unpubl. data). Other than direct persecution, 2012 to 2019.