Table Of Content/ RaptorRes. 33(l):49-52
© 1999 The Raptor Research Foundation, Inc.
RAPTOR USE AND ABUSE OF POWERLINES IN
SOUTHERN AFRICA
John A. Ledger
Endangered Wildlife Trust, Private Bag x 11, Parkview, 2122 South Africa
Jonathan C.A. Hobbs
Environmental Policy and Strategy Division, Eskom, PO. Box 1091, Johannesburg, 2000 South Africa
Powerlines pose problems to raptors when they some 60 000 km. Africa is home to a large variety
nest, roost, collide with or are electrocuted by elec- of raptors, some of which, like large eagles and
tricity wires and their supporting structures. Rap- vultures (Mundy et al. 1992) are particularly sus-
tors gain advantage from nesting and roosting on ceptible to electrocution on powerlines.
electricity towers, while eagles and vultures are Prior to 1977, there was no systematic recording
killed by flying into wires or being electrocuted on of raptor and powerline interactions on Eskom’s
towers. Collisions are not known to be a problem network. Dean (1975) published the first records
for raptors in southern Africa, but electrocution is of Martial Eagles (Polemaetus bellicosus) nesting on
a serious mortality factor for vultures and eagles. transmission towers, while Markus (1972) had ear-
The problems inevitably arise from the design of lier recorded the mortality of Cape Griffons {Gyps
the electricity structures, and all new powerlines in coprotheres) by electrocution on 88-kV towers. As
Africa should be designed to bird-friendly stan- part of an ongoing research program on the Cape
dards. Various methods are available to retrospec-
Griffon, the problem of electrocution was exam-
tively modify dangerous structures but they are
ined (Ledger and Annegarn 1981) and in 1977, a
both time-consuming and expensive.
mutually beneficial association between the Endan-
gered Wildlife Trust and Eskom was entered into
Raptors and Powerlines
which has endured to the present. Eskom estab-
Although this paper concerns itself with south- lished a bird research committee, now known as
ern Africa, it is noteworthy that only one paper has Eskom’s Wildlife Impacts Advisory Committee
been published about raptor mortality on power-
(EWIAC). This group started collecting data on
lines elsewhere in Africa. Nikolaus (1984) record-
bird-powerline interactions in a systematic way and
ed the electrocution of at least 55 Egyptian Vul-
encouraged outside research workers to undertake
tures {Neophronpercnopterus) and four Lappet-faced
projects of their own.
Vultures (Torgos tracheliotus) in Sudan in 1982 and
1983. There must be countless interactions be- Today, there is a large body ofinformation avail-
able about raptors and powerlines (Allan 1988,
tween raptors and powerlines in Africa, yet they
Boshoff 1993, Hobbs and Ledger 1986a, 1986b,
remain undocumented. There is one report that
includes details of raptors nesting on transmission Hobbs et al. 1990, Ledger 1983, 1984, Ledger and
towers in Namibia (Brown and Lawson 1989) but Hobbs 1985, Ledger et al. 1987). Eskom has pub-
all Other published information on the subject is lished its own Bird Identification Guide (Ledger
from South Africa, where one utility, Eskom, sup- 1988) for maintenance personnel that summarizes
plies 90% of the country’s electricity (as well par- the problems and solutions. EWIAC meets bian-
tial supplies to neighboring states of Botswana, Le- nually but urgent matters are dealt with on an ad
sotho, Mozambique, Namibia, Swaziland and hoc basis byJ.A.Ledger, who serves as a consultant
Zimbabwe). Eskom generates more than 50% of to Eskom. EWIAC was originally a problem-solving
the electricity consumed on the African continent committee, butwith the devolution ofenvironmen-
(Eskom 1991), and operates a vast national grid of tal responsibility to the various operational regions
765, 400, 275, 132, 88 and 66-kV transmission lines, (or business units), the problems are being solved
and a rural distribution system of 22 and 11 kV on at this level and the biannual meetings provide an
woodpole construction, estimated to comprise opportunity for information-sharing.
49
50 Expanded Abstracts VoL. 33, No. 1
Solving Problems of Raptors and Powerlines towers in the Nama-Karoo over a period of 5-10
Prior to the establishment of Eskom’s bird re- yr. This was done by making an annual series of
km
search committee in 1977, it was normal practice flights in fixed-wing aircraft along 420 of pow-
for all nests to be removed from transmission tow- erline. Mean linear density was 1 pair/19 km and
mean minimum territory size was 284 km^. Lack of
ers during annual maintenance, regardless oftheir
marked variation in annual breeding effort indi-
contents. Apart from the costs ofsuch unnecessary
cated that the population was stable. Breeding suc-
work to Eskom, this must have caused widespread
cess was 0.70 (eggs to nestlings) and 0.62 (breed-
raptor mortality. The opportunity for introducing
ing attempts to nestlings) Overall minimum
some biological thinking into an engineering en- .
reproduction rate was 0.52 young/pair/yr. Boshoff
vironment arose through the meetings of the com-
(1993) concluded that Martial Eagles obtain in-
mittee. It was pointed out that problems of birds
creased breeding success on electricity transmis-
nesting on towers normally occur during the early
He
sion towers. suggested that persecution ofbirds
phases of nest building, when long branches and
on towers may be,less than for birds nesting in low
sticks, or even pieces of wire may fall from the
trees or the large boulders and low cliffs found in
crossarm onto the conductor below, causing a
the Nama-Karoo. Safety from predators was also a
flashover. Once nests are constructed and occu-
factor, as towers provide a nesting substrate inac-
pied, raptors will use them for years, and generally
cessible to mammalian predators, including man.
maintain them in good condition.
Boshoff also recounted the case ofa pair ofMartial
The removal of nests from towers by Eskom
Eagles which nested in a highlyvulnerable position
maintenance personnel was subsequently prohib-
in a tree on a low cliff. They built a new nest on
ited, except in those cases where the nest was col-
an Eskom tower within one year of the construc-
lapsing and posed a direct threat to the electricity
tion of the powerline.
supply. Since this new approach to nest conserva-
The only raptors that roost in any numbers on
tion has been adopted, a wide variety of raptors
Eskom towers are vultures, and in certain parts
including Tawny Eagles {Aquila rapax), Black Ea-
quite large numbers of (up to 100) Cape Griffons,
gles (Aquila verrauxii. Ledger et al. 1987), Martial
sometimes with a few White-backed Vultures, roost
Eagles, African Hawk Eagles (Hieraaetusfasciatus). over a number of towers of a transmission line. A
White-backed Vultures Gyps africanus, Ledger and
( few problems arising from the pollution of insula-
Hobbs 1985), Lanner Falcons {Falco biarmicus).
tors with excreta from the birds have been en-
Greater Kestrels {Falco rupicoloides) and Rock Kes- countered. The only solution has been to fit
trels {Falco tinnunculus) are now breeding on trans-
shields above the insulator strings, but the roost
mission towers. The first five species constructtheir may move elsewhere along the line, depending on
own nests, while the three Falco species use nests
the availability of carrion. In a few cases, it proved
originally built by eagles or crows. If long sticks necessary to wash the insulators from a helicopter
project below the nest, the solution is to trim them which was a very expensive undertaking. It has also
away during maintenance work, to prevent the oc- been found that V-string insulators are much more
currence of flashovers in wet weather. Should a susceptible to pollution by vulture excreta than
nest containing young start to collapse because of straight strings, and that a rubber dustbin lid
wind, the whole structure can be secured to a makes a very good shield for the latter.
wooden platform with wire, and the raptors will Some birds will collide with overhead wires all
continue to feed their chicks. This has been done the time. The impact of this depends on the fre-
successfully with a Black Eagle nest in the Karoo. quency of occurrence and the effects of the mor-
Although nesting platforms have been used suc- tality on the particular species of bird. There is no
cessfully in the U.S., we have found that raptors do evidence of any raptor being seriously at risk from
not readily use them in southern Africa and seem collision with overhead wires in southern Africa.
to have very definite preferences for making their Where raptors are consistently at risk, the conduc-
own decisions about which towers they will select. tors can be marked using PLP Bird Flight Deflec-
The value of electricity transmission towers as tors. These are plastic spirals which clip onto the
nesting sites for raptors is highlighted in a recent wires and make them visible to the birds.
paper by Boshoff (1993). He monitored 7-18 pairs Electrocution of Cape Griffons on 88-kV trans-
of Martial Eagles breeding in Eskom transmission mission towers in the western Transvaal was due to
.
March 1999 Expanded Abstracts 51
the incompatibility ofa large birdwith a dangerous and any bird which perches on the crossarm and
design, the so called ‘kite construction.’ Vultures touches one of the jumpers is electrocuted.
were killed by landing on the crossarm ofthe tower The solution to these hazards is relatively simple,
and contacting a conductor with their extended but time-consuming and labor-intensive. Interme-
wings. A 3-yr study identified the specific problem diate structures can be made safe by cutting a 500-
mm
areas, and perches were fitted to several hundred gap in the earth downlead (or removing the
towers. This largely solved the problem but, where earth spike completely and terminating the down-
it persisted due to high densities of roosting vul- lead just below the crossarm braces) , in conjunc-
tures, PVG spirals were fixed to the middle con- tion with insulation of the middle phase conduc-
ductor around the insulator clamp to create a bar- tor. This can be achieved by fitting the locally
rier to wing tips touching conductors at the developed RP 3 Raptor Protector (Ledger 1992),
moment of landing. The ‘kite construction’ has or by fitting a length of split XLPE (cross-linked
been outlawed for use in rural areas. polyethylene) tubing to the middle phase conduc-
A more insidious problem has been the electro- tor.
cution of raptors on 11 and 22-kV lines, of which To make the terminal structures safe for raptors,
an estimated 60 000 km cross rural terrain within split XLPE insulation must be fitted to all the
South Africa, while Botswana, Lesotho, Namibia, jumper leads above the crossarm, and it is also
Swaziland and Zimbabwe also have extensive net- good practice to do the same to the jumpers run-
works of similar design. The m^ority of these lines ning to the transformer. On new structures, insu-
were constructed on wooden poles with a horizon- lated conductors should be used for all jumpers.
Lightning arrestors are now fitted on the trans-
tal crossarm bearing the conductors on pin or post
former rather than the crossarm.
insulators above the crossarm. In many cases, an
Eskom management agreed in 1991 to direct
earth downlead for lightning protection runs up
that only bird-friendly designs should be used in
the pole and terminates in a spike between the
middle and an outer insulator. The potential for rural areas in the future. The design of choice is
the single pole with staggered insulators, as de-
phase to phase, or phase to earth electrocutions
scribed by Hobbs et al. (1990) although an equally
on such structures is clearly great particularly with ,
good design is one where the outer conductors
the information available from the U.S. (Olendorff
hang below the crossarm on suspension insulators.
at al. 1981), yet very little information on raptor Of great concern the ongoing construction of
is
mortality has accumulated over the years that
bird-unfriendly powerlines throughout Africa.
EWIAC has been active.
A recent questionnaire survey conducted in the Literature Cited
Colesberg district of the Eastern Cape Region Allan, D. 1988. Raptors nesting on transmission pylons
(Ledger et al. 1992) elicited the following raptor African Wildl. 42:325-327.
electrocution figures from 55 respondents: 21 Mar- Boshoff, A.F. 1993. Density, breeding performance and
tial Eagles, 20 Black Eagles, 20 vultures (of which stability ofMartial Eagles Polemaetus bellicosushreeding
four were Cape Griffons); 15 ‘eagles,’ 6 ‘hawks,’ 6 on electricity pylons in the Nama-Karoo, SouthAfrica
‘owls,’ and 2 Jackal Buzzards. Proc. VIII Pan-Afr. Orn. Congr. 95-104.
An unexpected finding from the survey was the Brown, C.J. and J. Lawson. 1989. Birds and electricity
transmission lines in south west Africa/Namibia. Ma-
extent to which raptors are electrocuted on ter-
doqua 16:59—67.
minal structures in rural areas. On many farms, Dean, W.R.J. 1975. Martial Eagles nesting on high tension
there may be a number of such structures where pylons. Ostrich 4&:\\%-\\7
the overhead line terminates at a transformer to Eskom. 1991. Eskom in perspective, 1991 Annual Report.
supply a water pump or other equipment. The ter- Eskom, Johannesburg, South Africa.
minal structure is usually a twin-pole design with a Hobbs, J.C.A. and J.A. Ledger. 1986a. The environmen-
horizontal crossarm hearing three strain insulators tal impact oflinear developments; powerlines and avi-
fauna. Third International Conference on Environ-
for the incoming conductors. Jumper leads from
mental Quality and Ecosystem Stability. Eilat, Israel.
these three conductors go downward to connect to
AND 1986b. Powerlines, birdlife and the
.
the transformer, while another three jumper leads
golden mean. Fauna and Flora 44:23-27.
go above the crossarm to connect to the lightning and T. Auditore. 1990. The impacts of
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ca. makierie 37:99—109.
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