We first assessed available knowledge about bird collision or electrocution with power lines in South America from both a scientific (scientific articles) and media (newspaper reports) perspective. To find scientific information, we performed a bibliographic search in English, Spanish and Portuguese. This search was performed using Google Scholar and Scopus until February 2021. We used different key terms in the mentioned languages (e.g., “power line collisions”, “bird electrocution”, “avian electrocution”, “power line mortality”, “colisión con tendidos eléctricos y aves”, “electrocución de aves”, “colisão com linhas de transmissão e pássaros” combined with the different countries of South America, except for the search in Portuguese that was only combined with Brazil). This information was complemented by searching the references of the articles found and adding personal communications of specialists to include data that did not emerge through the search methods used. To find newspaper reports that complement scientific information, we performed additional searches with the same key terms in Spanish and Portuguese in the web search Google (www.google.com) until February 2021.

From each scientific article or newspaper report found, we extracted the following information: species involved, year of publication, geographical origin of the article, number of individuals affected, type of electrical line (distribution/transmission), and conservation status of species involved according to the IUCN (IUCN, 2021). In addition, we obtained information on the methodology applied in each scientific research papers. We excluded scientific articles that only mentioned power lines as a threat to a species, but did not assess it, and articles showing the positive effects of power lines (e.g., benefits of these structures as nest sites). In the case of newspaper reports, we included the species involved only when the species was mentioned or there was a photo of the birds’ electrocution or collision that allowed its correct identification.

In order to complement the information available about this conservation problem, we gathered new data on bird collisions and electrocutions with power lines from electric companies. For this, we compiled data on power outages caused by bird collisions and electrocutions with distribution and transmission power lines provided by electric companies that recorded these events in Peru, Chile, and Argentina from 2009 to 2021.

Data on power outages associated with birds were obtained either by consulting public available reports from the agencies regulating the service of the electric companies (for Peru and Chile), or by contacting the electric companies directly by e-mail (Argentina). In the case of Argentina, the company “Ente Provincial de Energía del Neuquén” (EPEN) was contacted and we requested the data on power outage events caused by birds in the Neuquén province because this company do not perform public reports about this issue. The power outage data for five Peruvian departments (Arequipa, Iquitos, Lima, Madre de Dios, and Piura) were obtained from public reports provided by the “Organismo Supervisor de la Inversión en Energía y Mineria” (OSINERGMIN). Those reports correspond to interruptions due to different problems of unforeseeable causes of power outages; from these database we selected the ones related to birds. Data from Chile regarding annual power outages were obtained through public reports requested to the “Superintendencia de Electricidad y Combustibles” (SEC). This Chilean public agency receives and compiles reports from electric companies about power outages and their causes; from these reports we extracted the ones related to birds.

We performed a field monitoring of distribution power lines in two regions of Chile (Atacama and Coquimbo) from 2015 to 2017 in search of carcasses of electrocuted birds. In the Atacama region (27.12 °S, 70.85 °W) a total of 83 power pylons in six different distribution power lines were monitored during seven days, five in January 2016 and two in November 2017. While in Coquimbo (29.88 °S, 71.27 °W) a total of 150 power pylons in 14 distribution power lines during two days in December 2015 and three days in December 2017. For each pylon, a 2 m area around the base was checked for carcasses or remains. At each pylon the GPS position, the characteristics of the pylon (i.e. crossarm design, crossarm and pylon material), and if bird remains were found, data such as species, state of decomposition, age, and sex were recorded.

In addition, we also obtained data provided by a citizen science project called “Aves y Tendido Eléctrico” (“Birds and power lines”) from the AvesChile ONG (https://aveschile.cl/), where bird collisions and electrocutions on distribution and transmission power lines in Chile were recorded from 2014 to 2021. Therefore, we collected data on bird collision and electrocution events on power lines recorded by citizens through the iNaturalis Chile webpage (https://inaturalist.mma.gob.cl/projects/aves-y-tendido-electrico).

Scientific information on the impacts of power lines on birds in South America is mainly recent, with most studies (9 of 15) conducted in the last decade (Table 1). This is surprising considering that the knowledge of the wires impacts on bird species (e.g., telegraph cables) has a long history in other regions of the world (Coues, 1876; Emerson, 1904) and even in Argentina (Doering, 1881). There has been an increase of scientific information about the impacts produced by power lines -mainly from North America and Europe- in the last decades of the 20th century (Bernardino et al., 2018; Lehman et al., 2007). However, in South America it has been evaluated relatively recently, with the exception of a pioneering work that evaluated bird collisions with a transmission line in Venezuela (McNeil et al., 1985). We found that both scientific articles and newspaper reports have reported on this issue nearly every year of the last decade, which highlights there is some concern in both scientific and lay people.

We showed that only 6 out of 13 of the countries in South America have addressed some aspects of this conservation problem in a scientific study (Fig. 1, Table 1). However, information provided by newspaper reports shows that the problem is widespread and that in most countries of South America - although probably in all -, bird collisions and electrocutions with power lines represent an important source of avian mortality at present (Fig. 1). Moreover, most scientific and anecdotal information from this sub-continent comes mainly from a few countries such as Argentina, Brazil, Peru and Chile. This is probably driven, among other things, by the higher development of socio-economic indicators of these countries (Guil and Pérez-García, 2022), including the increase of the rural electricity distribution network (Yépez-García et al., 2018), which increase the probability of mortality by electrocution. Further research and efforts should be directed to improve scientific and technical information about this problem in all the countries from South America, but especially in countries or regions where there is no information available or in those where information is only anecdotal (i.e., Paraguay, Uruguay or Bolivia).

The methodological approaches implemented in the scientific papers reviewed were: (1) bird carcass searches under power lines (e.g., Galmes et al., 2017; McNeil et al., 1985); (2) reports from wildlife rehabilitation centers or occasional records of dead or injured individuals due to power lines (e.g., Aguiar et al., 2014; Gusmão et al., 2020, 2016; Hinostroza et al., 2020; Nolazco et al., 2010; Pavez and Estades, 2016; Plaza and Lambertucci, 2020a); and (3) location of tracked individuals (e.g., tagged with telemetry devices) found dead, which were complemented with records provided by farmers or NGOs (e.g., Sarasola et al., 2020). Studies that addressed the effectiveness of mitigation actions to reduce the impacts of power lines on birds and studies that evaluated the impacts produced by this threat at the population level are scarce (but see, Biasotto et al., 2017; De la Zerda and Rosselli, 2003; Galmes et al., 2017). Unfortunately, many studies did not report the type of power line associated with bird electrocutions and collisions (distribution or transmission) nor do they provide the detected mortality rates that allow comparison between areas (Guil and Pérez-García, 2022). Finally, the information present in newspaper reports was mainly based on news about power outages associated with different bird species, with several events reporting high numbers of birds affected at the same time by this problem (Table 2, reports 3, 31, 34).

From the total reported data coming from the different sources addressed (i.e., scientific research, newspaper reports, citizen science, field monitoring and electric company), 85 South American bird species belonging to 34 families have been identified affected by power lines (Fig. 2). Twenty of these species were recorded by at least two of the methods we used, 46 were obtained by scientific research, 11 by the citizen science project and eight by newspaper reports exclusively. Field monitoring included six species, which were also recorded by at least one of the other methods. In the case of the electric company records, most of them did not provide data on the species affected. Two species were identified at the genus level, Fulica sp. and Quiscalus sp., reported by citizen science and newspaper reports respectively. These results are a clear underestimation of what is actually happening, but useful to see that the problem is widespread between taxa.

Of the species affected by power lines, 17 were electrocutions, 56 were collisions and 12 were both impacts. The species reported as most affected were the Grey Gull (Leucophaeus modestus) and the Brown Pelican (Pelecanus occidentalis) with 491 and 468 individuals killed by collisions, respectively. Most of the species (n = 79) reported as affected by power lines are classified as Least Concern species. However, five species are considered of conservation concern: the Near Threatened Blackpoll Warbler (Setophaga striata) and Reddish Egret (Egretta rufescens), both affected by collisions (De la Zerda and Rosselli, 2003; McNeil et al., 1985), the Vulnerable Harpy Eagle (Harpia hapyja), affected by electrocution (Aguiar-Silva et al., 2014; Gusmão et al., 2020, 2016) and Andean Condor (Vultur gryphus), suffering from both electrocutions and collisions in different parts of its distribution (Peru: Hinostroza et al., 2020.; Chile: Pavez and Estades, 2016; Argentina: Plaza and Lambertucci, 2020a; this study); and the Endangered Chaco Eagle (Buteogallus coronatus), for which electrocution was reported as one of the most relevant threats along with human persecution (Galmes et al., 2017; Sarasola et al., 2020, Tables 1,2). Finally, the threat category of the species of the genus Fulica sp. was not determined, as they could be species with different degrees of threat.

The information obtained here does not allow us to estimate the annual bird mortality due to power lines in any country of South America. However, our data indicate that in some regions of Chile for which data are available, in just 5 years, there were 19,121 power outages caused by at least the same number of animals (Table S1). It seems clear that the estimations obtained which are based on anecdotic or disperse data suggest the mortality is several folders more. It is urgent to design specific studies to evaluate how many birds are affected by this threat in the different countries of South America, and the mortality per km of power lines (Galmes et al., 2017). Given the current limited knowledge and the great diversity of environments, species and the growth of current power lines infrastructure to provide an estimate is not possible, but the threat is clear and needs to be considered by governments, companies, conservationists, and other stakeholders.

The information obtained shows that, in general, most of the reported events are related to electrocutions rather than collisions. Most newspaper reports are referred to power outages or accidents produced by bird electrocutions rather than collisions (Table 2). This same pattern is observed in the data from the electric companies and field monitoring of power lines (Table S1). These results are probably explained by electrocutions attracting more media attention than collisions because power outages produce economic losses and may cause significant damage from wildfires (Guil et al., 2018), and probably because they impact society's environmental sensibilities through images of dead birds hanging from poles. Furthermore, given that electrocutions most frequently affect large birds, the probability that they will be found is much higher than if they were small birds, such as passerines. In addition, collisions that do not result in electrocutions may not be fatal in many cases or the bird will die far from the power line, so recording the event would be more unlikely. Therefore, the information of impacts of power lines tend to be biased toward electrocution.