Electrocution and collisions on power lines are among the leading causes of non-natural mortality for birds. Power lines are exponentially increasing, particularly in developing countries, but mitigation strategies to prevent bird mortality are questionable. Mongolia combines a recently increased power line network, an abundant raptor population, a dangerous crossarm configuration and a habitat with no natural perches, producing many bird-power line interactions. Our aim is to assess the bird mortality caused by power lines in the Gobi Desert of Mongolia, to determine the factors increasing the risk of bird electrocution, and to evaluate the effectiveness of used retrofitting measures.

Methods

In July 2019 we covered 132.9 km of 15 kV power lines checking 1092 poles. We also conducted bird transects to record raptor and corvid richness and abundance, to assess species vulnerability to electrocution.

Results

We recorded 76 electrocuted birds of 7 species. Electrocution rate was 6.96 birds/100 poles. The most affected species were Common Raven (Corvus corax) and Upland Buzzard (Buteo hemilasius), highlighting the electrocution of 5 endangered Saker Falcons (Falco cherrug). By contrast, we only recorded 8 individuals of 5 species colliding with wires, the most affected being Pallas’s Sandgrouse (Syrrhaptes paradoxus). About 76.1% of sampled poles had some mitigation measure. Of these, 96.6% were brush perch deflectors and 3.4% rotating-mirrors perch deterrents. We found differences in electrocution rates among crossarm configurations, with the strain insulator with one jumper being the most lethal. Additionally, we found no correlation between bird abundance and electrocution rates, suggesting that some species are more sensitive to electrocution. Although no differences in total bird electrocution rates were detected between poles with and without perch deterrents, when bird size is considered, deterrents reduced the mortality rate of small birds, while they were ineffective for medium-sized birds.

Conclusions

Despite the widespread use of perch deterrents in the Mongolian power line network, there is still an alarming electrocution rate. This strategy is ineffective and some mechanisms, such as brush perch deflectors, may increase the electrocution rate for some medium-sized birds. Finally, we propose strategies to minimize the avian electrocution rate in the Gobi Desert.

Background

The development of power line networks is both a consequence and a driver of a country’s economic progress (Chaurey et al. 2004), but it is also an important source of environmental impacts (Sánchez-Zapata et al. 2016). Electrocutions and collisions with power lines are among the leading non-natural causes of bird mortality (Bevanger 1998; Haas 2005), drastically reducing the populations of some endangered species (García-del-Rey and Rodríguez-Lorenzo 2011), especially raptors (Meretsky et al. 2000; Real et al. 2001; López-López et al. 2011; Angelov et al. 2013). Three factors have been linked to the increased risk of accidents between birds and power lines. The first one is related to the pole and crossarm configuration or the wire arrangement (e.g. grounded steel and concrete poles and crossarms, or the increase of jumper wires; Tintó et al. 2010; Guil et al. 2011), the second one is associated with the ecology and biology of birds (e.g. size and wingspan, low maneuverability, narrow visual field, hunting behavior; Janss 2000; Lehman et al. 2007; Martin and Shaw 2010; Guil et al. 2015) and the last one is related to the environment (e.g. absence of natural perches, frequency of fogs, location on migratory routes; Harness et al. 2008; Dixon et al. 2018).

Electrocution occurs when a bird simultaneously contacts two differently energized phases or one energized phase and one grounded area (APLIC 2006). Thus, mitigation strategies (from now on “retrofitting”) used to prevent bird electrocution can be: (i) by “separation” between potential contacts, which is the most recommended strategy since it is permanent and does not require maintenance; (ii) by “insulation”, which requires strategically covering energized or grounded contacts, it is the most used strategy and needs maintenance; and (iii) by “redirection” of birds to perch in safer places, which is the cheapest strategy and also requires maintenance (APLIC 2006). By contrast, bird collisions can be mitigated modifying surrounding habitats, removing overhead shield wires, burying lines, and increasing visibility to birds by marking wires (Eccleston and Harness 2018). Although these mechanisms are considered effective in reducing electrocutions (Tintó et al. 2010) and collisions (Alonso et al. 1994; Barrientos et al. 2011), few studies have evaluated their long-term effectiveness in the field and with different avian populations (Janss and Ferrer 1999).

Asia is undergoing the fastest economic growth and many of its countries are exponentially increasing their power line network (Hammons 2011). In addition to this sharp increase, most power lines have little or no retrofitting (Dixon et al. 2013a), as most Asian countries are limited in their economic resources. However, avian electrocution and collision studies in this continent are scarce (Lehman et al. 2007; Bernardino et al. 2018; Slater et al. 2020), so there is an urgent need to focus efforts on the continent, especially in important bird areas, to understand the magnitude of these impacts. In the last two decades, Mongolia has sharply increased its power line network (Amartuvshin and Gombobaatar 2012). Studies carried out so far show a severe environmental impact as a result of the interaction between rich and abundant raptor populations, an electrical network with hazardous designs (grounded steel and concrete poles and metal crossarm with few or obsolete retrofitting, usually redirection) and habitat conditions without natural perches (Harness et al. 2008; Amartuvshin and Gombobaatar 2012; Dixon et al. 2018). One of the largest concerns is the high mortality rate of the Saker Falcon (Falco cherrug; Dixon et al. 2020), which is globally endangered (BirdLife International 2021) and a large part of its breeding population is in Mongolia (Gombobaatar et al. 2004). Despite previous research about birds and power lines carried out in Mongolia (Harness et al. 2008; Amartuvshin and Gombobaatar 2012; Dixon et al. 2013a), most studies have been located in the central and eastern part of the country (Ganbold et al. 2018). By contrast, large areas in southern Mongolia have remained understudied. The Gobi Desert extends in this area, an extremely arid ecosystem in which many species adapted to these extreme ecosystems survive. Although the abundance of species that are more sensitive to power lines impacts, such as birds of prey, is slightly lower than in other areas previously studied in the country, the presence of potential natural perches is even lower, so the interaction between birds and power lines can be high (Gombobaatar et al. 2004).

In this study, our main goal was to study bird mortality at power lines in the Gobi Desert (southern Mongolia). Specifically, we aimed to: (1) evaluate bird mortality by electrocution and collision with power lines, (2) explore the factors that increase the risk of bird electrocution, such as the crossarm configuration and the size or abundance of the bird species in the area, and (3) evaluate the effectiveness of the retrofitting measures used.

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