Vultures and Electric Power Lines

Electric power lines are also dangerous for vultures, either through electrocution or collisions. Bird electrocutions were first documented in the 1970s, when thousands of raptors were killed in North America (APLIC 2006). In the following years, research on this topic has been conducted in North America, Western Europe and South Africa (Lehman et al. 2007; Manville 2005). Electric power lines (both collisions and electrocutions) contribute to the deaths of millions of birds in the African-Eurasian region (Haas et al. 2005). It is estimated that up to 10,000 electrocutions and hundreds of thousands of collisions occur in most countries in the African- Eurasian region annually (Prinsen et al. 2011). Millions are estimated in Germany (Hoerschelman et al. 1988). In some countries in Northwest Europe, the electrocution problem is lower, as many voltage lines have been placed underground. This is the case in Germany, Belgium, the United Kingdom, Denmark and Austria (Tucker et al. 2008). Collisions are more common when the power lines bisect vulture foraging or nesting habitats (Hunting 2002). Features necessary for vulture presence may include alternative perch availability, vegetation form and carcass presence. Power lines and towers may be utilized as replacements for nesting or roosting trees, especially deserts, open plains and intermontane basins (APLIC 2006).

Lehman et al. (2007) conducted a literature review of raptor electrocution research, mitigation and monitoring, and also evaluated the results of 30 years of efforts to reduce deaths due to electrocution and collisions. Most studies focused on North America, Western Europe, and South Africa.

Many early studies from the 1970s focussed on the United States from the 1970s onwards, where there has been 'extensive research, product testing, design standards development, and mitigation' (Lehman et al. 2007; see also Boeker and Nickerson 1975; Nelson and Nelson 1976; Olendorff et al. 1981). There is evidence that these efforts have not stopped the killing of birds, at least in the United States (Franson et al. 1995; Melcher and Suazo 1999; Harness and Wilson 2001). In addition to bird deaths, there was 'negative media attention, increased scrutiny by regulatory agencies, and a landmark court conviction' (Lehman et al. 2007; see also Melcher and Suazo 1999; Williams 2000; Suazo 2000). The electrocution problems also cost the energy suppliers billions of dollars each year due to power interruptions, necessary equipment repairs, revenue losses and statutory compliance issues (Hunting 2002).

A 2001 review of 30 years of responses and projections in the United States that bird deaths would be eliminated found overly optimistic projections and no real results (Lehman 2001; see also Nelson and Nelson 1976; Wildlife Management Institute 1982; Phillips 1986; Gauthereaux 1993; Avian Power Line Interaction Committee [APLIC] 1996). More than 185 million wood distribution poles were operating in North America in 2005, with at least some threats to birds (Lehman 2001; American Iron and Steel Institute 2005). Actions to reduce deaths are mostly modifications of the poles after the event, rather than examination and elimination of the issues that contribute to the mortalities and ameliorating or eliminating them where possible (Lehman 2001).

Factors for the electrocution risk depend on ecological, physical, and landscape factors, i.e., vegetation structure and composition, which are also related to the species, time, location, or environmental conditions (Hunting 2002; Lehman et al. 2007).

Electrocution of the bird occurs when the bird bridges the gap between two energized components or an energized and an earthed (also called 'grounded') component of the pole structure. Electricity then flows through the bird and kills it. Low to medium voltage lines are usually the most dangerous, as the structures are more closely spaced. The conductors and ground/earth wires or earthed devices are usually too far apart for smaller birds to touch simultaneously (APLIC 1996; Janss and Ferrer 1998, 1999a, 2000; Janss et al. 1999). Therefore, most incidents involve large raptors and storks during the breeding season (Boeker and Nickerson 1975; Benson 1981; Olendorff et al. 1981; APLIC 1996; Kruger 1999; Harness and Wilson 2001; Prinsen et al. 2011). In South Africa vultures are the risk birds (Ledger and Annegarn 1981; Ledger 1984; Kruger 1999). Bird size is less relevant in Europe, as most poles are constructed of steel or steel-reinforced concrete, which can make all birds of any size vulnerable (Bayle 1999; Negro 1999).

Birds are more likely to perch on the power lines if there are no other perches, natural or artificial nearby (Olendorff et al. 1981; Janss and Ferrer 1999a). In forests with many natural perches, very few birds are killed by electrocution (Switzer 1977; O'Neil 1988; Harness and Wilson 2001). The same applies for ground-nesting species that may hunt in flight but perch on or near the ground (Pendleton 1978; Benson 1981). Other factors are relative pole height, pole-top configuration and clearances among electrical components (Lehman et al. 2007).

In the United States there are reported to be 50 regularly breeding species of birds of prey (thirty-one of diurnal raptors and 19 of owls) (Johnsgard 1988, 1990). Twenty six of these species have been recorded as victims of electrocution. Golden Eagles comprised between 50-93% of bird deaths in some reports (Smith and Murphy 1972; Boeker and Nickerson 1975; Ansell and Smith 1980; O'Neil 1988; Harness and Wilson 2001). Golden eagles in the United States are commonest in the shrub-steppe regions in the Western inter-montane region, where there are few natural perches (Harlow and Bloom 1989). The similarly sized Bald eagle inhabits forested areas with abundant perches (Stalmaster 1987). Vultures in the open African plains, such as the gregarious Cape and African white-backed vultures also crowd onto powerlines.

The design of the power lines and the associated hardware is also important for electrocution risk. Most electrocutions in the United States occur on low-voltage distribution lines (<69 kV) for mostly individual residential use, because prior to 1971, most of these lines were built with little or no insulation and narrow clearances between the energized components. Most poles are made of wood, which is nonconductive. Electrocution is more likely to occur when there is more possibility of links between energized components, e.g., with transformers or other auxiliary equipment (fused cutouts, capacitors, reclosers, jumper wires) (Olendorff et al. 1981; APLIC 1996; Harness and Wilson 2001).

The design in Europe is composed of steel or steel-reinforced concrete, which are conductive and grounded (Bayle 1999; Janss 2000). Therefore, unlike in the American model, a bird on a crossarm may be electrocuted on contact with a conductor (Janss and Ferrer 1999b). This results in much higher mortality levels, such as the 10,000 losses in the Slovak Republic (Adamec 2004). This is one reason for the transfer of power lines in Europe underground, which has been done in the Netherlands, and is being undertaken in Germany, The United Kingdom and Belgium (Bayle 1999). As the structures in Europe are usually steel or steel reinforced concrete, which are conductive, size is less important than in other continents (Bayle 1999; Janss 2000). Collision with cable lines also occurs, in which the bird may be killed by the impact or later through injuries. Collisions are common on multiple vertical layered, high voltage lines.

Another factor for electrocution is topography. Studies in the United States have shown that, as raptors use poles for surveying food possibilities, poles located on raised topography are perched more often and therefore have greater numbers of electrocutions (Benton and Dickinson 1966; Boeker and Nickerson 1975; Nelson and Nelson 1976; Benson 1981; APLIC 1996). The daily weather and seasonal changes also affect bird usage of poles and powerlines. For Golden Eagles in some western states, 80 percent of the deaths occurred during the winter (Benson 1981). Most other species recorded losses during the nesting period (Harness and Wilson 2001). Wet feathers increase the electrocution risk ten-fold and skin-to-skin contacts are also very conductive (Nelson 1979, 1980). Wind direction relative to the crossarms, may also be a factor for electrocutions. When the wind is diagonal or parallel to the crossarms, there may be more accidents than when the wind is perpendicular to the crossarm, because landings and takeoffs are more difficult in the former situation (Nelson and Nelson 1976; Benson 1981).

Bird behavior is also important. During fledging, the population increase may increase accidents (Harness and Wilson 2001). Physical contact between birds during nest defence or mating may link conductive components (Dickerman 2003). Nesting behavior and material lying across conductors have killed young birds (Hardy 1970; Gillard 1977; Switzer 1977; Vanderburgh 1993). Young, inexperienced birds are more likely to be electrocuted; for example at least 90% of Golden eagles killed in North America were immature or subadult (Boeker and Nickerson 1975; Benson 1981), with only slightly lower figures for young Spanish Imperial eagles (females also had more accidents due to their greater size) (Ferrer and Hiraldo 1992). Age has also been cited for smaller raptors (Fitzner 1978; Dawson and Mannan 1994).

In European countries, other than those mentioned above, accidents are common; the affected birds are mainly raptors and storks. Vultures are less affected, arguably because they were already rare in central Europe. In Eastern Europe, Bulgaria has been well studied for this topic. Forty- five thousand kilometres of power lines were a risk to birds (Stoychev and Karafeizov (2003). Twenty-two species were recorded dead, more than half being diurnal raptors, storks and crows (Demerdzhiev et al. 2009; Gerdzhikov and Demerdzhiev 2009; Demerdzhiev 2010). Studies are conducted on the effects the Cinereous vulture in Bulgaria by the Green Balkans Federation of Non-Governmental Organizations (Prinsen et al. 2008). In Hungary, 877 electrocuted birds of 46 species were found under one percent of the medium voltage electric poles in the country (6,500 poles) (Kovacs et al. 2008). The annual dead bird count has been estimated at over 30,000 (Demeter 2004). Affected species between 2003 and 2008, in order of decreasing number were the Golden eagle, Common kestrel (Falco tinnunculus, Linnaeus 1758), Saker falcon (Falco cherrug, Gray, 1834) and European roller (Coracias garrulus Linnaeus, 1758) (Horvath et al. 2008). Other less affected species were the Imperial eagle (Aquila heliaca Savigny, 1809), the Eagle owl (Bubo bubo Dumeril, 1805), White stork (Ciconia ciconia Linnaeus, 1758), Black stork (Ciconia nigra Linnaeus, 1758), Red-footed falcon (Falco vespertinus Linnaeus, 1766), (Buteo buteo Linnaeus, 1758) common buzzard, White-tailed eagle (Haliaeetus albicilla Linnaeus, 1758) and the Peregrine falcon (Falco peregrinus Tunstall, 1771) (Horvath et al. 2008; Horvath et al. 2011). In Central Europe, including Switzerland, White storks and Eagle owls are strongly affected (Lovaszi 1998; Marti 1998; Moritzi et al. 2001; Breuer 2007; Schaub et al. 2010; Schurenberg et al. 2010).

In Southern Europe, storks and raptors are similarly the species most affected by electrocution and to a lesser extent by collisions. In one study in France, the deaths were mostly by electrocution (96.5%) and the rest due to collisions (Seriot and Rocamora 1992 in Bayle 1999; see also Schurenberg et al. 2010). Raptors were seriously affected, e.g., Common buzzard, Common kestrel, Black kite, Bonelli's eagle (Aquila fasciata Vieillot, 1822) the Griffon vulture and the Short-toed eagle (Cheylan et al. 1996; Bayle 1999; Kabouche et al. 2006). In Italy, Common buzzard (Buteo buteo Linnaeus, 1758), Common kestrel, Griffon vulture, Osprey (Pandion haliaetus Linnaeus, 1758) Eurasian Sparrow hawk (Accipiter nisus Linnaeus, 1758), flamingoes, herons and storks were affected (Rubolini et al. 2005). Prinsen et al. (2011) note that the raptors and corvids were mostly affected by electrocution, and herons, flamingos and small passerines were more susceptible to collisions.

In Portugal, in a survey between 2003 and 2005, out of 945 dead birds mostly electrocuted in steppe areas, the most affected were the White stork (137 electrocuted) and common buzzard (146). Vultures included the Griffon vulture (12) and Eurasian black vulture (1) (Infante et al. 2005). In Spain, the Eurasian Black Vulture, the Griffon Vulture and the Egyptian vulture are affected (Martmez 2003; Palacios 2003). In the Donana National Park, in Southern Spain, 233 electrocuted raptors included Griffon vulture (14 individuals) (Ferrer et al. 2001). Another study by Guzman and Castano (1998) in southern Spain for an eight year period (1988-1996) and 69 kilometres of lines and 1,629 poles, among 274 raptors and 14 species found dead were Eurasian Black Vultures (2 ) and Griffon Vultures (1).

In the Canary Islands, electrocution, in addition to poisoning, habitat destruction, reduction of food supplies and use of pesticides in the 1950s-1960s to eradicate locust plagues have been blamed for the decline of Egyptian vultures (Tucker and Heath 1994; Palacios 2000). In Fuerteventura, the second largest Canary Island, after Tenerife, Egyptian vultures roost on power lines, possibly due to the lack of trees in the desert environment (as this is not case in non desert environments) (Donazar et al. 1996; Sigismondi and Politano 1996). They are thus likely to be electrocuted (Janss 2000). In one area, six Egyptian vultures were found dead near 12 km of power lines—two by collision and four by electrocution (Lorenzo 1995). These incidents were important for vulture populations in the area (Ferrer 1993; Ferrer and Janss 1999).

In Asia, the electrocution and collision problems also exist. In the Kazakhstan steppes, larger raptors (including the Cinereous vulture), crows and gulls account for 93% of the dead (Haas and Nipkow 2006; Lasch et al. 2010). It is estimated that about 58,000 raptors are killed annually during spring migration along 9,478 kilometres of power lines (Karyakin 2008). In Kazakhstan, eagles (White-tailed Eagle, Steppe eagle (Aquila nipalensis Hodgson, 1833), Golden Eagle, Greater Spotted eagle (Clanga clanga Pallas, 1811) and the Short-toed Eagle) and falcons were particularly affected (Karyakin et al. 2006; Karyakin and Novikova 2006; Karyakin 2008; Lasch et al. 2010). In Mongolia, more than 60% of the electrocuted birds were raptors, especially near poles with closely spaced electrical equipment (Harness and Gombobaatar 2008; Harness et al. 2008). In the Russian Federation, above ground medium voltage power lines are estimated at 1,500,000 kilometres, with 0.5% equipped with isolated cables or modern facilities for bird protection. It is estimated that 10 million birds belonging to 100 species are killed annually through collisions and electrocutions (Matsyna and Matsyna 2011).

Concerning the Middle East, Prinsen et al. (2011) found no published information except for Israel. In Israel, mostly Griffon vultures were electrocuted (up to 5% of the population killed each year). Other affected species were Black kites, Ospreys storks and pelicans (Bahat 1997). Fewer deaths were recorded between 2007 and 2009, possibly due to pylon insulating near garbage dumps (Prinsen et al. 2011).

In Africa, as in Europe, sparse vegetation and absence of natural perching sites encourages use of power lines by any type of bird (Prinsen et al. 2011). In Egypt, a factor for bird deaths is the large number of low voltage power lines with short insulators and steel lattice towers near bird migration bottlenecks and food attractants such as rubbish dumps. In Sudan, in a 50-year old, 31 km section on the Red Sea coast 50 dead vultures were recorded in 1982 and two in 1983 (Niklaus 1984). Seventeen dead Egyptian vultures were also recorded during September 2010 (Angelov et al. 2011). The pole structures included a steel t-type and concrete staggered vertical type structures. Up to 5,000 vultures are estimated to have been killed in the past 80 years (Angelov et al. 2011). This is a possible factor for the declining population of Egyptian vultures in the Middle East, where many of the Sudanese birds originate.

In Ethiopia, the migratory raptors have been found dead near unsafe poles in areas with little vegetation for perching (Haas 2011). In Kenya, in the Magadi and Naivasha areas most pole designs were found to pose an electrocution risk to medium to large birds (Virani 2006; Smallie and Virani 2010). Species at risk included Egyptian vultures, White-headed vultures, Lappet-faced vultures, African White-backed vultures and Ruppell's vultures and also other species such as the Martial eagle (Polemaetus bellicosus Daudin, 1800), Augur buzzard Buteo augur (Ruppell, 1836) Grey crowned crane (Balearica regulorum Bennett, 1834), Lesser flamingo (Phoenicopterus minor Geoffroy Saint-Hilaire, 1798), White Stork, Secretary bird (Sagittarius serpentarius J.F. Miller, 1779).

In South Africa, there are several types of structures. There are 22-kV wooden T-structures, 88-kV steel kite transmission towers, terminal H-frame wood structures, and Delta suspension structures (Kruger 1999). The largest number of electrocutions of different sized birds occur on the T-structures and terminal H-Frames. Birds are killed from the Genera Gyps, Polemaetus, Aquila, Buteo, Circaetus, Falco, and Bubo spp. The steel kite transmission towers and the Delta suspension structures generally kill larger species such as Cape griffons, African White-backed vultures and Martial eagles (Lehman et al. 2007).

In this country, where vulture habitats are frequently open plains with few trees, the vulture species (e.g., Cape vultures and African White-backed vultures) roost or perch communally on power lines, resulting in multiple electrocutions (Bevanger 1994; APLIC 2006; Lehman et al. 2007; Prinsen et al. 2011). These two species have been strongly affected since the early 1970s (Markus 1972; Ledger and Annegarn 1981; Ledger and Hobbs 1999; Smallie et al. 2009). Kruger et al. (2004) report the electrocution of 46 Lappet faced vultures, 24 African White-backed vultures, 4 Cape griffons and 12 unidentified vultures in South Africa. For example, between August 1996 to May 2011, there were 1,504 electrocuted Cape griffons, White-backed vultures, Lappet faced vultures, and eagles, storks, corvids and other birds. For the Cape vulture, which is endemic to South Africa and a threatened species, it is estimated that about 80 are killed annually in the Eastern Cape (Boshoff et al. 2011).

Collisions are also a leading cause of non-fatal injuries to vultures. Where the birds survive, there are now organizations that attempt to rehabilitate them (Naidoo et al. 2011). Three organizations were involved in the rescue and/or rehabilitation (R&R) of vultures in the Magaliesberg mountain range of South Africa over 10 years; the De Wildt Cheetah and Wildlife Trust, the National Zoological Gardens of South Africa (NZG) and the Vulture Programme of the Rhino and Lion Wildlife Conservation NPO (R&L). The commonest birds in these centres were Cape griffon and African White-backed vultures. The available data identified the cause of injuries as collisions with pylons, resulting in soft tissue and skeletal injuries. The study concluded that 'urbanisation has had a major negative impact on vultures around the Magaliesberg mountain range' (ibid. 24).

Data management on bird deaths on or near power lines in South Africa is conducted by Eskom-EWT Strategic Partnership in a Central Incident Register. The result of these mortalities induced Eskom to stop building vertically configured medium voltage designs that were a particular risk to vultures. Vulture deaths were blamed on the birds' size, gregarious nature, limited alternative natural perching areas and the small size of pole-top perching area. Electrocution occurred when a vulture landed on the pole top, and slipped between the conductors. Insulating the conductors reduced but did not stop such fatal accidents. 'Furthermore, in some instances, the vultures started attacking the insulation by ripping it apart' (Kruger et al. 2004: 439). Vultures were found to be perching on one conductor while touching another. The study recommended the discontinuation of vertically configured medium voltage structures (Kruger et al. 2004).

Considering the problems created by wind turbines and power lines in terms of structures and collisions, the question is why cannot birds see these objects, especially considering most flying birds have good eyesight? Martin et al. (2012) set out to answer this question. The findings of their study are that 'the visual fields of vultures contain a small binocular region and large blind areas above, below and behind the head.' Studies of the visual ability of cranes, ibises, spoonbills and bustards have noted that even a small-amplitude forward pitch (for example when the bird scans the ground) results in inability to detect direction and any object in front of the bird; a reason for powerline and wind turbine collisions (Martin and Shaw 2010; Martin and Portugal 2011; Martin 2011a, 2011b). Martin et al. (2012) also found that the small binocular region and the large blind spot allows coverage of the ground below, protects the eyes from the sun above, and also allows extensive lateral vision during foraging. Vultures therefore have narrow, frontal binocular vision. By 'erecting structures such as wind turbines, which extend into open airspace, humans have provided a perceptual challenge that the vision of foraging vultures cannot overcome' and possible solutions should include attracting vultures away from such areas at the broad, landscape level, due to the wide foraging ranges of vultures (Martin et al. 2012: 5).