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Eduardo Garcia-del-Rey and Juan Antonio Rodriguez-Lorenzo
Avian mortality due to power lines in the Canary Islands with special
reference to the steppe-land birds
589916
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Journal of Natural History
Vol. 00, No. 00, Xxxx 2011, 1–11
Avian mortality due to power lines in the Canary Islands with special
reference to the steppe-land birds
Eduardo Garcia-del-Reya * and Juan Antonio Rodriguez-Lorenzob
a
Macaronesian Institute of Field Ornithology, C/Enrique Wolfson 11-3, 38004 Santa Cruz de
Tenerife; b Fundacion Global Nature, Edif. Olympo, Pza. Candelaria 28, 3◦ , Of. 304-A, 38003
Santa Cruz de Tenerife, Canary Islands, Spain
5
(Received 9 August 2010; final version received 17 May 2011)
Biodiversity is being lost worldwide at an increased rate particularly as the result of
human activities and infrastructure. Avian mortality through collision with power
lines has been an important topic in animal ecology research but studies of this
kind have never been undertaken in the Canary Islands, a volcanic archipelago
located near the northwest African coast that has important seabird colonies, several endemic bird species and endemic races of steppe-land birds of conservation
concern. During two contrasting periods in 2008 (breeding vs post-breeding), a
total of 366 km of power lines were surveyed on this archipelago covering the
entire distributional range of the most important steppe-land bird species (i.e.
232 km, Fuerteventura; 134 km, Lanzarote). In all, 310 carcasses representing
23 families and 26 species were detected. We estimated with DISTANCE Sampling
that 25.5% and 6.3% of individuals of the total population of Houbara bustards,
Chlamydotis undulata fuertaventurae, and Eurasian stone curlews, Burhinus oedicnemus insularum, respectively, were killed in a year. We encourage the Canary
Islands authorities (Consejería de Medio Ambiente del Gobierno de Canarias) to
try to minimize the Houbara bustard collision rate, particularly in the northern
plains of Lanzarote (i.e. Jables de Famara), as a means to reduce mortality of this
emblematic species in this insular environment.
Keywords: Chlamydotis undulata; Canary Islands; power lines; mortality;
TANCE ; collision
ISSN 0022-2933 print/ISSN 1464-5262 online
© 2011 Taylor & Francis
DOI: 10.1080/00222933.2011.589916
http://www.informaworld.com
15
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DIS -
Introduction
Biodiversity is being lost at an increased rate as a result of human activities and infrastructure. How bird species vary in response to infrastructure has been a major topic in
avian ecological research (Newton 1998) and the impact of power lines has been intensively studied worldwide (Bevanger 1995, Norway; Garrido and Fernandez-Cruz 2003,
southern Spain; Harness et al. 2008, Mongolia; Lehman et al. 2010, western USA;
Shaw, Jenkins, Ryan et al. 2010; Shaw, Jenkins, Smallie et al. 2010, South Africa). Two
types of impacts to power lines have been described (Lehman et al. 2007), i.e. electrocution vs collision, and mortality has sometimes been found to differ significantly
among pylons of different designs, habitats and species (Ferrer et al. 1991). It has been
suggested that several factors determine avian collision risk including location, structural attributes and height of pylons, weather conditions, and bird morphology and
*Corresponding author. Email: [email protected]
10
30
AQ1
35
2 E. Garcia-del-Rey and J. A. Rodriguez-Lorenzo
behaviour (Drewitt and Langston 2008); avian mortality caused by power lines has
been suggested to be species-specific with collision victims being fast and low flyers
(i.e. species that are not very manoeuvrable) and electrocution victims being mainly
large wing-span birds that frequently try to perch on artificial structures (Janss 2000).
The archipelago of the Canary Islands lies near the northwestern African coast
and is considered an important biodiversity hotspot (Stattersfield et al. 1998) with
endemic bird species, important seabird colonies and endemic steppe-land birds that
are subspecies of conservation concern (BirdLife International 2004). Important populations of Houbara bustard (Chlamydotis undulata fuertaventurae), black-bellied
sandgrouse (Pterocles orientalis) cream-coloured courser (Cursorius cursor bannermani) and Eurasian stone curlew (Burhinus oedicnemus insularum) occur on the
semi-arid islands of Fuerteventura and Lanzarote and their associated offshore islets
(Garcia-del-Rey 2010). The Canaries experience massive tourism, which demands
more energy each year and as a result new power lines are still being built to satisfy this increasing demand (Fernandez-Palacios et al. 2004). It is a priority, therefore,
to assess the impact of power lines on the avifauna in general but with special reference to the steppe-land birds, because of their high collision risk (Janss 2000) and
conservation concern. The aims of this study are: (1) to present a first evaluation of
the families and different bird species affected by power lines on the semi-arid islands
of this archipelago, (2) to evaluate annual avian mortality rate during the breeding
(spring) and post-breeding (autumn) periods, and (3) to identify sites of high avian
mortality and risk of collision.
Material and methods
Study area
This study was conducted in Fuerteventura (28◦ 25 N, 13◦ 59 W) and Lanzarote
(29◦ 1 N, 13◦ 35 W), eastern islands of the the Canary Islands (28◦ 34 N, 16◦ 2 W).
Fuerteventura is the closest island to the African mainland (c. 100 km) and the oldest of the Canaries (20 million years old); it occupies a total area of 1659 km2 and is
the second largest island in the archipelago. Lanzarote is smaller, occupying a total
surface of 846 km2 , and is 15 million years old. Both islands are similar in relief with
extended flat areas interspersed with low massifs (i.e. peaks of 807 m above sea level
on Fuerteventura and 670 m above sea level on Lanzarote). The landscape of these
volcanic islands is dominated by semi-arid steppes with variable shrub and soil cover
and is characterized by a semi-desert climate with dry summers and heavy torrential
rains in winter (143 mm annually) (Marzol-Jaén 1984). The vegetation is dominated
by a handful of steppe-shrub plant species such as Launaea arborescens, Euphorbia
regis-jubae, Lycium intricatum, Salsola vermiculata and Suaeda spp. (Rodriguez et al.
2000).
40
45
50
AQ2
55
60
65
70
75
Steppe-land birds
Four species of steppe-land birds, of EU conservation concern (BirdLife 2004), occur
as resident breeders in the Canary Islands (Garcia-del-Rey 2011). The Houbara bustard, Chlamydotis undulata, has a predominantly North African distribution, which
just extends into Europe in the Canary Islands, southernmost Russia and Azerbaijan.
80
Journal of Natural History 3
Its European breeding population is very small and no information is available on
population trends, but the population size is suspected to have declined in recent
decades. The resident subspecies endemic to the Canary Islands, Chlamydotis undulata
85
fuertaventurae, is clearly susceptible to the risks affecting isolated and small populations and is today considered as ‘Vulnerable’ in Europe (BirdLife 2004). Black-bellied
sandgrouse, Pterocles orientalis, breeds in Iberia, the Canary Islands and parts of
southeast Europe, which together account for less than a quarter of its global breeding range. Its European breeding population is small and has suffered a large decline 90
between 1970 and 1990. Its current status is ‘moderate continuing decline’ (BirdLife
2004). The cream-coloured courser, Cursorius cursor, has a predominantly African
breeding distribution, which just extends into Europe in the Canary Islands and southeastern Turkey. Its European breeding population is extremely small (as few as 100
pairs) and declined between 1970 and 1990. Although the trend in its Canary Islands
95
stronghold during 1990–2000 is not known, these small island populations are susceptible to the risks affecting small populations and it is today considered as ‘Endangered’
(Cursorius cursor bannermani) under the International Union for the Conservation of
Nature criteria. The Eurasian stone curlew, Burhinus oedicnemus, is a widespread but
patchily distributed breeder in the southern half of Europe and today it is considered 100
vulnerable in both Spain and the Canary Islands (Burhinus oedicnemus insularum).
All except the stone curlew are restricted to the islands of Fuerteventura and
Lanzarote and their offshore islands and islets (La Graciosa, Montaña Clara,
Alegranza, Lobos) but no power lines occur on the offshore islands and islets.
According to official estimates (i.e. Viceconsejería del Gobierno de Canarias, Canarian 105
Government, unpublished report) the total population size (size of breeding population) of these steppe-land birds has been estimated as follows: Houbara bustard,
1002 birds (577 birds, Fuerteventura; 425 birds, Lanzarote); black-bellied sandgrouse, 2256 birds; cream-coloured courser, 1159 birds (917 birds, Fuerteventura;
242 birds, Lanzarote); stone curlew, 3023 birds (841 birds, Fuerteventura; 2182 birds, 110
Lanzarote).
Bird survey
During 2008 all power lines in the Canary Islands (which are all big transmission
lines with a low probability of electrocution) within the steppe-land bird habitat (a
total of 366 km) were surveyed along their entire length (232 km in Fuerteventura; 115
134 km in Lanzarote) (Lorenzo 2007) (see Figure 1). Three observers (one at the centre and two on each side separated by 25 m) walked the power lines during the spring
(2–16 March, Fuerteventura; 3–13 April, Lanzarote) and the following autumn (1–
15 November, Fuerteventura; 5–15 October, Lanzarote). Observers were trained so as
to maximize detection of carcasses in this habitat type. This period coincides with the 120
breeding and post-breeding periods of all bird species sampled. Every carcass detected
was removed and its location was georefenced with the aid of a GPS. Carcasses were
very easy to spot in this habitat type. For the purpose of this study every carcass found
was assumed to have died as the result of collisions (i.e. few carcasses were found
near poles) because the real causes of death are difficult to determine. Mortality esti- 125
mates from most studies of this kind are biased in their estimates because they do not
consider the effects of scavengers and long sampling intervals (3 months or longer)
4 E. Garcia-del-Rey and J. A. Rodriguez-Lorenzo
Figure 1. Location of study sites and distribution of power lines and steppe habitat on the
Canary Islands of Fuerteventura and Lanzarote.
(Janss and Ferrer 2000; Lehman et al. 2007, 2010). Mammalian scavengers are scarce
on these islands, however, we did not address any of these effects, so our data should
be considered as minimum annual collision mortalities. Search and habitat biases may 130
be considered negligible in this study.
Journal of Natural History 5
Statistical analysis
We used SPSS (SPSS 1986) for basic descriptive statistics and ARCVIEW 3.2. to georeference the power lines and prepare the maps. DISTANCE 4.1 (Thomas et al. 2004)
was used to obtain density and abundance of carcasses (with confidence intervals) 135
within the surveyed area (Buckland et al. 1993, 2001) and only for those bird species
with reasonable sample sizes (i.e. > 60 carcasses). A series of model distributions were
compared with the observed distribution using the default settings of DISTANCE. The
model that provided the best overall fit with the fewest parameters was determined
using Akaike’s Information Criterion, after accounting for detectability.
140
Results
Carcasses belonging to 23 families and 26 bird species (Table 1) were found in the
area surveyed below the power lines. Figure 2 suggests that Otididae and Burhinidae
are the families more affected by collisions. The Houbara bustard (Chlamydotis undulata fuertaventurae) and the Eurasian stone curlew (Burhinus oedicnemus insularum)
are the steppe-land birds most affected by this infrastructure on Fuerteventura and
Lanzarote, with 66 and 63 carcasses found during the year of study, respectively
(Tables 1, 2).
The computer software DISTANCE 4.1 (Thomas et al., 2004) was used to calculate
the effective strip width for each stratum (=island) and the detection probability in
relation to the exact distance of the carcass to the observer at the centre of the transect
line (figures not presented). Buckland et al. (2001) suggest that a minimum of 60–
80 observations are required for DISTANCE to model detection functions successfully
and hence produce reliable density and abundance estimates. We only obtained enough
carcasses for the Houbara bustard and the stone curlew (Table 1, Figures 3, 4). The
analysis with DISTANCE (data from both periods combined because of small sample
sizes) suggests that 92 (95% CI 33–255) Houbara bustards died as the result of power
line collision during 2008 on Lanzarote, higher than on Fuerteventura (23, 95% CI
9–54). Mortality was also found to be higher for the stone curlew on Lanzarote (68,
95% CI 21–222) (Table 2).
If we assume a total population size of 577 houbara bustards for Fuerteventura
and 425 for Lanzarote, the mortality rates are 4.0% and 21.6% respectively (i.e. total
of 11.5%). The population sizes for stone curlew on Fuerteventura and Lanzarote are
840 and 2182, respectively, giving mortality rates of 3.3% to 3.1% (i.e. a total of 3.2%).
145
150
155
160
Discussion
165
Our study highlights the fact that representatives of 26 bird species, belonging to 23
different families, died because of power lines in the Canary Islands of Fuerteventura
and Lanzarote during the year of study. These species ranged from large summer visiting seabirds (Bulwer’s petrel, Cory’s shearwater) to small passage migrants
(European bee-eater, barn swallow) and very small endemic passerines (Berthelot’s 170
pipit). However, all of these could be considered as anecdotal as the number of carcasses found is generally small or very small. Both common pigeons and yellow-legged
gulls suffered medium mortality rates because of this infrastructure and this could be
6 E. Garcia-del-Rey and J. A. Rodriguez-Lorenzo
Table 1. Number of dead carcasses found per species during the two periods of study (spring vs
autumn) on the islands of Fuerteventura (F) and Lanzarote (L).
Common name
Bulwer´s petrel
Cory´s shearwater
Western cattle egret
White stork
Egyptian vulture
Montagu´s harrier
Common kestrel
Barbary partridge
Houbara bustard
Eurasian stone
curlew
Cream-coloured
courser
Eurasian curlew
Yellow-legged gull
Gull
Black-bellied
sandgrouse
Common pigeon
Pigeon
Eurasian collared
dove
Western barn owl
European bee-eater
Eurasian hoopoe
Lesser short-toed
lark
Barn swallow
Berthelot´s pipit
European pied
flycatcher
Southern grey
shrike
Northern raven
Trumpeter finch
Unidentified
species
Total
Scientific name
Spring 2008
Autumn 2008
F
L
F
0
1
0
1
1
0
2
2
0
0
0
1
1
0
0
2
1
1
0
0
0
0
2
10
0
0
0
28
0
0
2
10
1
2
18
7
24
12
2−0
0
0
10
1
Numenius arquata
Larus michahellis atlantis
Larus sp.
Pterocles orientalis orientalis
0
6
1
1
0
5
2
0
0
10
0
0
1
6
1
0
Columba livia
Columba sp.
Streptopelia decaocto
decaocto
Tyto alba gracilirostris
Merops apiaster
Upupa epops epops
Calandrella rufescens
rufescens
Hirundo rustica
Anthus berthelotii berthelotii
Ficedula hypoleuca
5
3
1
11
7
0
0
0
1
8
0
1
0
0
1
0
1
1
0
0
0
0
0
0
0
0
1
1
0
0
0
0
2
0
0
0
0
2
2
1
Lanius (meridionalis) koenigi
0
1
0
0
Corvus (corax) canariensis
Bucanetes githagineus
amantum
–
5
1
1
0
3
0
0
0
5
28
8
15
51
115
58
86
Bulweria bulwerii
Calonectris diomedea borealis
Bubulcus ibis ibis
Ciconia ciconia
Neophron percnopterus
majorensis
Circus pygargus
Falco tinnunculus dacotiae
Alectoris barbara koenigi
Chlamydotis undulata
(fuertaventurae)
Burhinus oedicnemus
insularum
Cursorius cursor bannermani
L
Note: total number of unidentified species at the end of the list and total number detected.
Journal of Natural History 7
70
60
Dead bird
50
40
30
20
10
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Family
Figure 2. Distribution of number of dead birds (carcasses) found per family. 1, Otididae;
2, Burhinidae; 3, Unidentified; 4, Columbidae; 5, Laridae; 6, Glareolidae; 7, Corvidae; 8,
Procellariidae; 9, Ardeidae; 10, Phasianidae; 11, Motacillidae; 12, Ciconiidae; 13, Accipitridae;
14, Falconidae; 15, Upupidae; 16, Hirundinidae; 17, Scolopacidae; 18, Pteroclididae; 19,
Tytonidae; 20, Meropidae; 21, Alaudidae; 22, Muscicapidae; 23, Laniidae; 24, Fringillidae.
Table 2. Density (D) of carcasses per square kilometre by species and island for Houbara
bustard (Chlamydotis undulata) and Eurasian stone curlew (Burhinus oedicnemus).
Species
Is. n
D (bird/km2 )
95% CI
A
95% CI
ESW
AIC
M (%)
Chlamydotis
undulata
Chlamydotis
undulata
Burhinus
oedicnemus
Burhinus
oedicnemus
F 20
0.98
0.41–2.33
23
9–54
42
162.0
4.0
L 46
6.84
2.45–19.05
92
33–255
24
341.4
21.6
F 19
1.21
0.15–10.0
28
3–232
30
144.7
3.3
L 44
5.10
1.57–16.5
68
21–222
26
279.4
3.1
Results from both periods were combined because of small sample sizes. Note in Table 1 the
raw data are per season.
Number of carcasses (n), 95% confidence intervals (95% CI), total abundance (A), effective
stripe width (ESW), Akaike´s information criterion (AIC) and mortality rate (M) are also
included.
related to the increase of feral populations of pigeons and the movement of gulls to
rubbish dumps.
175
We also calculated some important minimum annual collision mortality rates for
some of the resident endemic steppe-land birds of the Canary Islands, as has been
found elsewhere for other steppe-land bird species (Janss and Ferrer 1998, 2000).
Surprisingly, only one black-bellied sandgrouse was found dead on Fuerteventura
(this species is not found on Lanzarote; BWPi 2008) where the total population size 180
has been estimated at 2256 birds. This could be attributed to the flying behaviour of
this species (BWPi 2008), always extremely high and possibly not near power lines.
8 E. Garcia-del-Rey and J. A. Rodriguez-Lorenzo
Figure 3. Distribution of power lines, steppe habitat and carcasses of houbara bustard,
Chlamydotis undulata fuertaventurae, on the Canary Islands of Fuerteventura and Lanzarote.
Cream-coloured coursers were not detected during the spring survey but some carcasses were found in the autumn particularly on Fuerteventura where this species is
more abundant (see Table 1). This species is a fast flyer and might be avoiding power 185
lines with quick turns (BWPi 2008) but there is also the possibility that young birds
tend to die as the result of collisions at this time when the breeding season is over.
However, the results of the present study suggest that special attention should be paid
to the Eurasian stone curlew and houbara bustard, for which we estimated minimum
mortality rates of 3.2% and 11.5%, respectively, the losses in spring being more sig- 190
nificant because these are more likely to be breeding adults. For the stone curlew it
is clear that the numbers found could be related to abundance on these islands (i.e.
more casualties in higher abundance areas) but the opposite is found for the houbara
Journal of Natural History 9
Figure 4. Distribution of power lines, steppe habitat and carcasses of stone curlew, Burhinus
oedicnemus insularum, on the Canary Islands of Fuerteventura and Lanzarote.
bustard. Mortality rates for this species were 21.6% on Lanzarote (425 birds) versus
a small 4.0% on Fuerteventura (577 birds) (see Figures 3, 4). This may be explained 195
by distributional differences, because in the north of Lanzarote there is a high concentration of houbaras (e.g. Jable de Famara) in areas with power line, as compared
with the larger island of Fuerteventura. Our results support those of studies reported
elsewhere for other similar bird species (e.g. Denham’s bustard in South Africa) where
large terrestrial birds are the most numerous victims found (Shaw, Jenkins, Ryan et al. 200 AQ3
2010).
10 E. Garcia-del-Rey and J. A. Rodriguez-Lorenzo
Based on our results we recommend that the Canarian Government (Consejería
de Medio Ambiente del Gobierno de Canarias) tries to reduce the high collision rate
of houbara bustards in the northern plains of Lanzarote by marking the wires to make
them more visible, as a means to reduce mortality as the result of power line collision 205
and so improve this protected area. Future research should try to minimize sampling
intervals and evaluate mortality among pylons of different designs.
Acknowledgements
We would like to thank Consejería de Medio Ambiente del Gobierno de Canarias (Canarian
Government) and particularly Dr José Luis Martín Esquivel for fully financing this project and
Excmo. Cabildo Insular de Fuerteventura, D. Antonio Gallardo, for full collaboration during
our stay on that island. We thank both Cabildo de Fuerteventura and Cabildo de Lanzarote
(Área de Juventud) for allowing free accommodation to our team of volunteers. Special thanks
go to all of them for their effort during the hot days on these islands and to Juan José Ramos
and Chus Guitian for coordinating them. We thank Tristan Norton for improving the English of
this paper. We thank Sociedad Ornitológica Canaria (SOC) for providing the means to analyse
the data.
210
215
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