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Meta-Analysis of the Effectiveness of Marked Wire in Reducing Avian Collisions with Power Lines

  • Spanish National Research Council (Consejo Superior de Investigaciones Científicas CSIC)

Abstract and Figures

Collisions of birds with power transmission and distribution lines have been documented for many species, and cause millions of casualties worldwide. Attempts to reduce mortality from such collisions include placing bird flight diverters (i.e., wire markers in the form of, e.g., spirals, swivels, plates, or spheres) on static and some electrified wires to increase their visibility. Although studies of the effectiveness of such devices have yielded contradictory results, the implementation of flight diverters is increasing rapidly. We reviewed the results of studies in which transmission or distribution wires were marked and conducted a meta-analysis to examine the effectiveness of flight diverters in reducing bird mortality. We included in our meta-analysis all studies in which researchers searched for carcasses of birds killed by a collision with wires. In those studies that also included data on flight frequency, we examined 8 covariates of effectiveness: source of data, study design, alternate design (if marked and unmarked spans were alternated in the same line), periodicity of searches for carcasses, width of the search transect, and number of species, lines, and stretches of wire searched. The presence of flight diverters was associated with a decrease in bird collisions. At unmarked lines, there were 0.21 deaths/1000 birds (n =339,830) that flew among lines or over lines. At marked lines, the mortality rate was 78% lower (n =1,060,746). Only the number of species studied had a significant influence on effect size; this was larger in studies that addressed more species. When comparing mortality at marked and unmarked lines, we recommend use of the same time intervals and habitats and standardizing the periodicity of carcass searches.
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Meta-Analysis of the Effectiveness of Marked Wire
in Reducing Avian Collisions with Power Lines
Departamento de Ecolog´
ıa Evolutiva, Museo Nacional de Ciencias Naturales (CSIC), Jos´
e Guti´
errez Abascal, 2,
E-28006 Madrid, Spain
Abstract: Collisions of birds with power transmission and distribution lines have been documented for
many species, and cause millions of casualties worldwide. Attempts to reduce mortality from such collisions
include placing bird flight diverters (i.e., wire markers in the form of, e.g., spirals, swivels, plates, or spheres)
on static and some electrified wires to increase their visibility. Although studies of the effectiveness of such
devices have yielded contradictory results, the implementation of flight diverters is increasing rapidly. We
reviewed the results of studies in which transmission or distribution wires were marked and conducted a
meta-analysis to examine the effectiveness of flight diverters in reducing bird mortality. We included in our
meta-analysis all studies in which researchers searched for carcasses of birds killed by a collision with wires.
In those studies that also included data on flight frequency, we examined 8 covariates of effectiveness: source
of data, study design, alternate design (if marked and unmarked spans were alternated in the same line),
periodicity of searches for carcasses, width of the search transect, and number of species, lines, and stretches of
wire searched. The presence of flight diverters was associated with a decrease in bird collisions. At unmarked
lines, there were 0.21 deaths/1000 birds ( n=339,830) that flew among lines or over lines. At marked lines,
the mortality rate was 78% lower ( n=1,060,746). Only the number of species studied had a significant
influence on effect size; this was larger in studies that addressed more species. When comparing mortality at
marked and unmarked lines, we recommend use of the same time intervals and habitats and standardizing
the periodicity of carcass searches.
Keywords: bird collision, bird flight diverter, flight frequency, ground-wire marking, power line
alisis sobre la Eficacia de la Se˜
on de los Cables para Reducir las Colisiones de Aves contra
Tendidos El´
Resumen: La colisi´
on de aves con tendidos el´
ectricos tanto de transmisi´
on como de distribuci´
on ha
sido documentada en numerosas especies y causa millones de muertes en todo el mundo. Los intentos
para reducir la mortalidad causada por dichas colisiones incluyen la colocaci´
on de dispositivos anticolisi´
(i. e., marcadores en cables con forma de espiral, dispositivos giratorios, platillos o esferas) en los cables
de tierra, as´
ı como, a veces, en los conductores, para aumentar su visibilidad. Aunque los estudios llevados
a cabo sobre la efectividad de tales medidas han llegado a conclusiones contradictorias, la instalaci´
on de
dispositivos anticolisi´
on est´
a aumentando r´
apidamente. Revisamos los resultados de los estudios en los que
se se˜
nalizaron cables de transmisi´
on o de distribuci´
on y llevamos a cabo un metan´
alisis para examinar la
eficacia de los dispositivos anticolisi´
on a la hora de reducir la mortalidad. Incluimos en nuestro metan´
todos los trabajos en los que los investigadores realizaron una b´
usqueda de aves muertas tras colisionar
con los cables. En aquellos estudios que adem´
as incluyeron frecuencias de vuelo, examinamos 8 covariables
de la efectividad: origen de los datos, dise˜
no del estudio, dise˜
no alternado (si los vanos se˜
nalizados y no
nalizados se alternaban en el mismo tendido), periodicidad en la b´
usqueda de cad´
averes, ancho de la
banda de b´
usqueda, y n´
umero de especies, tendidos y tramos muestreados. La instalaci´
on de dispositivos
on estuvo ligada a un descenso en el n´
umero de aves colisionadas. En los tendidos sin se˜
Current address: ´
Area de Zoolog´
ıa, Departamento de Ciencias Ambientales, Facultad de Ciencias del Medio Ambiente, Universidad de Castilla-La
Mancha, Avenida Carlos III, s/n, E-45071 Toledo, Spain, email
Paper submitted November 3, 2010; revised manuscript accepted February 21, 2011.
Conservation Biology, Volume 25, No. 5, 893–903
2011 Society for Conservation Biology
DOI: 10.1111/j.1523-1739.2011.01699.x
894 Wire Marking to Reduce Bird Collisions
hubo 0.21 muertes/1,000 aves (n=339,830) que cruzaron los cables. En los tendidos marcados, la mortalidad
fue un 78% inferior (n=1,060,746). S´
olo el n´
umero de especies estudiadas tuvo una influencia significativa
en el tama˜
no del efecto; ´
este fue mayor en aquellos trabajos que estudiaron m´
as especies. Cuando se compare
la mortalidad en tendidos se˜
nalizados y sin se˜
nalizar, recomendamos que se usen los mismos intervalos de
tiempo y h´
abitats y que se estandarice la periodicidad de la b´
usqueda de cad´
Palabras Clave: colisi´
on de aves, dispositivo anticolisi´
on, frecuencia de vuelo, se˜
on del cable de tierra,
tendido el´
Avian collisions with and electrocution by power lines
have been documented since the early 1900s, but it was
not until the 1970s that biologists and engineers began to
realize the extent of these events and to study mitigation
measures (e.g., Bevanger 1998; APLIC 2006; Lehman et al.
2007). The number of power lines is increasing world-
wide at 5% per year (Jenkins et al. 2010). This percentage
applies to both power distribution (generally 2.4 kV to
60 kV) and transmission lines, which carry >69 kV of
electricity (APLIC 2006).
Bird mortality from collisions with power lines and
other electric-utility structures has been documented
for nearly 350 species of birds (Manville 1999). Some
crude estimates of the number of individuals that die
are also available. For instance, bird collisions with
power lines may cause 1 million deaths/year in the
Netherlands (Koops 1994), and in the United States esti-
mates show power lines kill from hundreds to thousands
to >175 million birds per year (Manville 2005, 2009).
Worldwide it is estimated that bird collisions with power
structures, including transmission and distribution lines,
that result in fatalities could approach 1 billion annually
(Hunting 2002).
Until an assessment of the cumulative effects of bird
mortality from power lines is conducted, the magnitude
of such mortalities will remain uncertain (Manville 2009).
Although collisions with power lines are the most im-
portant mortality source for some endangered species
of birds (Manville 2009), few detailed analyses of how
these losses affect trends in population size have been
conducted. Collision-related losses may be equivalent to
9–90%, depending on the species, of the annual number
of individual tetraonids (grouse) harvested by hunting
in Norway (Bevanger 1995). Whereas estimated hunting
harvest of Capercaillies (Tetrao urogallus) was 22,200,
estimated mortality from collisions with power lines was
19,900. In Switzerland ring-recovery data show 25% of
juvenile and 6% of adult White Storks (Ciconia ciconia)
die annually due to collision with and electrocution by
power lines (Schaub & Pradel 2004). Shaw (2009) esti-
mated that in South Africa 30% of Denham’s Bustard (Neo-
tis denhami) are killed annually by collisions with power
lines. Birds with low maneuverability, that is, those
with high wing loading and low aspect (e.g., bustards,
cranes, storks, pelicans, waterfowl, some grouses), are
among the species most likely to collide with power lines
(Bevanger 1998; Janss 2000). Species with narrow visual
fields also have a high probability of colliding with power
lines (Martin & Shaw 2010).
Although efforts to reduce bird collisions are increas-
ing rapidly worldwide, the effectiveness of such measures
has not yet been tested adequately. Results from exami-
nations of the effectiveness of anticollision systems are di-
verse, varying from no reduction of collisions (e.g., Scott
et al. 1972; Janss et al. 1999; Anderson 2002) to a reduc-
tion in collisions (e.g., Alonso et al. 1994; Bevanger &
Brøseth 2001). This heterogeneity may be due to differ-
ences in behavior and morphology of species, habitat
variability, weather, type and number of marking devices
used per length of line, and approaches used to test for
an effect.
The mitigation measures used include placement of
raptor decoys on posts (Janss et al. 1999), marking
static wire to make it more visible, and replacement of
static wire with lighting arrestors at transmission tow-
ers (Beaulaurier 1981; Bevanger & Brøseth 2001). Where
collisions of birds with energized transmission lines are a
problem, lines are sometimes marked with clamp-on de-
vices. However, these devices, which surround the wire
where they are attached, can cause power reductions
and line damage and thus may not be feasible for high-
voltage wires (APLIC 2006). Removing the static wire
would reduce bird mortality, but the wires are needed
to protect conductors from lightning (Beaulaurier 1981).
Because lightning strikes can result in power outages and
line damage and fires, the most common mitigation mea-
sure has been the attachment of spirals, plates, swivels,
or spheres to static wire to increase wire visibility. Collec-
tively, these devices are called bird flight diverters (e.g.,
APLIC 1994; Hebert & Reese 1995; Jenkins et al. 2010).
Despite the general belief that bird flight diverters reduce
bird mortality, results of several studies show they do not
(e.g., Scott et al. 1972; Anderson 2002). However, sev-
eral of these studies had small sample sizes or did not
include statistical tests. Placement of bird flight divert-
ers is expensive (e.g., US$1100–2600/km of marking in
South Africa [Kruger 2001] and 6000 in Spain [Alonso
et al. 2005]), so evidence of their effectiveness is needed.
Narrative reviews of the effectiveness of wire mark-
ing to reduce avian collisions with power lines have
been conducted (APLIC 1994; Bevanger 1994; Jenkins
et al. 2010), mainly through counts of the number of
Conservation Biology
Volume 25, No. 5, 2011
Barrientos et al. 895
studies indicating markers do or do not reduce collisions.
These qualitative reviews do not control for sample size
or variance across studies. They give equal value to pub-
lications with anecdotal data and to those with detailed
experimental designs and large sample sizes and small
variances. Not controlling for sample size can lead to
type II errors (Arnqvist & Wooster 1995), that is under-
estimation of the effects of collisions on population sizes
of birds (Fern´
andez-Duque & Valeggia 1994).
We conducted a meta-analysis of the published
literature and unpublished reports (primarily reports of
private companies) to evaluate whether wire marking
reduces the number of bird collisions with power lines.
A meta-analysis is quantitative and allows for comparison
of results among studies. Meta-analysis weights the value
of different studies on the basis of their sample sizes
and variances and provides a balanced effect for the
studied topic (Arnqvist & Wooster 1995; Gurevitch &
Hedges 2001; Stewart 2010). Meta-analyses have been
used widely in research domains in which available
empirical data provide no clear consensus (Stewart et al.
2005, 2007; Ben´
opez et al. 2010). Meta-analyses are
especially valuable when there is a high probability of
incurring type II errors (Arnqvist & Wooster 1995).
Our meta-analyses included studies that reported on
counts of carcasses associated with marked and un-
marked power lines. We did not include studies that
provided only data on the behavior of birds when ap-
proaching the power lines or only data from marked or
unmarked sections of power lines in space or time. We
did not use data on mortality that was estimated after
correcting for potential biases (e.g., scavenger removal,
estimates of injury, habitat, or observers) because not
all studies correct for such biases. Furthermore, calcula-
tion of mortality after correcting for biases was beyond
the scope of our analyses. Instead, we used the raw data
from carcass counts.
We conducted 2 meta-analyses, the first with data from
all studies that reported carcass counts and the second
with studies that also included counts of birds flying
across the line that were used to calculate collision rates.
In the second meta-analysis, we evaluated the sensitiv-
ity of the results from the first by using data on flight
frequency (Stewart et al. [2007]; Ben´
opez et al.
We searched ISI Web of Science, Scirus, Zoological
Record, and JSTOR for wire-marking studies. We identi-
fied additional studies in the reference lists of pertinent
papers we found in the databases. The number of pub-
lished papers listed on the 4 databases was relatively low,
which may reflect the small sample sizes typical of such
studies. Thus, we searched Google for additional studies
not published in peer-reviewed journals.
For all searches, our search terms were combinations
of the following words or phrases: bird, crane, swan,
raptor, waterfowl, aviation ball, flight diverter, swan di-
verter, ground wire, static wire, marker, power line,
spiral, wire, collision, effectiveness, impact, power-line
marking, and wire marking. We searched for publications
in English, Spanish, German, and French. We contacted
most authors who have worked on this topic over the last
30 years. These authors were our most fruitful source of
data because they provided use with other contacts and
with several unpublished studies that would otherwise
have been inaccessible. We also contacted environmen-
tal departments of electrical companies, managers of state
and federal wildlife agencies, and nongovernmental con-
servation organizations worldwide to obtain unpublished
documents, such as PhD dissertations and public and in-
ternal reports, to increase the number of studies we could
use (Fern´
andez-Duque & Valeggia 1994).
We expected this variety of sources would reduce the
probability of biasing the meta-analysis toward studies
reporting statistically significant results, which are be-
lieved to be published more frequently than those with
results that are not statistically significant (Arnqvist &
Wooster 1995; Stewart 2010). We reveal our sources here
so as to avoid the hidden-publication bias that may be
present in other nonsystematic syntheses (Stewart 2010).
However, we also formally tested potential publication
If more than one publication presented results from
the same study area and period (e.g., Crowder [2000],
Crowder & Rhodes [2001], Shaw [2009], and Shaw et al.
[2010]), we relied on data from the most complete study.
We extracted the raw data from each study in our meta-
analyses. Thus, if the same results were published in an
abbreviated form (typically, a paper) and in a more de-
tailed form (for instance, in a report or dissertation), we
used the latter because we could obtain the raw data
more easily. When a publication included more than
one study, for instance if it assessed the number of colli-
sions associated with more than one marker in different
line segments or lines (e.g., Anderson 2002) or the same
marker at different intervals in different line segments or
lines (e.g., Koops & de Jong 1982), we treated the experi-
ments as independent (Ben´
opez et al. 2010; Gilbert-
Norton et al. 2010). We also treated as independent
studies that tested marker effectiveness with a before-
after-control-impact (BACI) design and with a parallel de-
sign (i.e., marked and unmarked lines studied during the
same time interval). We excluded studies that simulta-
neously tested more than one marker (e.g., bird flight
diverters and strips in the same wire) because their ef-
fects could be cumulative and could have stronger effects
than those experiments in which only a single device was
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Volume 25, No. 5, 2011
896 Wire Marking to Reduce Bird Collisions
Studies of Carcasses
Because our primary data were the means of 2 groups,
we calculated the ratio of the means to obtain the
“response ratio” (hereafter R) as the effect size
(Borenstein et al. 2009). Following Bevanger (1999), we
controlled the number of avian deaths per power line
length and period of time as
R=MML/MUML =[cML/(kmML ×tML)]
/[cUML/(kmUML ×tUML)],(1)
where MML is the mortality associated with the marked
line, MUML is the mortality associated with the un-
marked line, cML is the number of carcasses found under
the marked line, kmML is the length in kilometers of
the marked line, tML is the number of months during
which carcasses were counted under the marked line,
and cUML, kmUML, and tUML are the respective values
for the unmarked line. We analyzed Rafter log trans-
formation to maintain symmetry in the analysis (Hedges
et al. 1999; Borenstein et al. 2009). Negative lnRvalues
(i.e., ln R<0) indicated a decrease in mortality, and
positive values indicated an increase. The response ratio
is a common metric in meta-analyses of ecological stud-
ies (Hedges et al. 1999). However, because authors of
the studies we analyzed reported only the total number
of dead birds per kilometer and month, the sample size
for every study was 1.0 (J. Gurevitch, personal commu-
nication). Thus, we conducted an unweighted analysis
(i.e., all the variances were 1.0) (Rosenberg et al. 2000;
J. Gurevitch, personal communication). An unweighted
analysis does not allow one to investigate the potential
structure of the data because the weight from every study
is required (Neter et al. 1989).
Carcass Counts and Flight Frequencies
We examined the sensitivity of the results from the first
analysis by conducting a second meta-analysis that in-
cluded only those studies in which both carcasses and
flight frequencies were counted (i.e., number of birds
flying across studied power lines, or sample size). We as-
sessed the difference between probabilities of collision
(i.e., the risk difference [RD]) associated with unmarked
and marked lines. The probability of collision associated
with either line was mortality divided by the total number
of birds crossing the line (Borenstein et al. 2009).
RD =(MML/nML) (MUML/nUML),(2)
where nML is the number of birds flying across the
marked line and nUML is the number of birds crossing
the unmarked one.
The sample size we used to calculate the weight for ev-
ery study was the total number of birds observed flying
across the studied power lines. Mortality could have been
overestimated in some cases because studies counted
bird crossings during periods that were shorter than
those in which carcasses were counted. Furthermore,
sampling efforts were not always the same in marked
and unmarked sections because the sections were not
always the same length or sampled during the same time
intervals. Thus, we controlled for sampling effort before
calculating nML and nUML. We divided the sample size of
each study by the sampling effort we assessed, ignoring
the reported number of birds crossing marked and un-
marked sections (unless sampling effort was equal). In 4
studies (Brown & Drewien 1995; Crowder 2000; Brauneis
et al. 2003; Lorenzo & Cabrera 2009) that evaluated more
than one device, but did not clearly indicate the sections
of marked lines where flying birds were counted, we av-
eraged the numbers of birds crossing for the different
markers. We did not use data from studies that assumed
the same crossing rates for stretches with and without
markers because this assumption is incorrect (Alonso
et al. 1994; Calabuig & Ferrer 2009). Negative RD val-
ues indicated a decrease in mortality and positive values
indicated an increase. We calculated the variance of RD
with the following formula (Borenstein et al. 2009):
where AML and AUML are birds that were alive after cross-
ing marked and unmarked lines, respectively. In applying
this sensitivity analysis we had to discard some studies,
but we improved statistical power because we could use
weighted analyses.
Data Analyses
We loaded effect sizes and variances to carry out all
analyses with MetaWin (version 2.0, Sinauer Associates,
Sunderland, MA, USA; Rosenberg et al. 2000). We first
assessed the effect of wire marking for the entire data
set with random-effects modeling, which allows for
the possibility that studies differ in sampling error (as
fixed-effects models do) and in random variation in
effect sizes (Gurevitch & Hedges 2001). Random-effects
models are more appropriate for analysis of ecological
data because numerous complex interactions are likely
to result in heterogeneity among studies (Pullin &
Stewart 2006). We calculated 95% confidence intervals
(CIs) (bias-corrected bootstrap, 999 iterations) for each
effect size (Rosenberg et al. 2000). If the 95% CI did not
overlap zero, then effects were significant at p<0.05.
We calculated the total heterogeneity, QT, to analyze
whether the variance among effect sizes was greater than
expected due to the sampling error (Rosenberg et al.
2000). This variable was a weighted sum of squares, and
we tested it against a χ2distribution with n–1 df. A signif-
icant QTimplies that other explanatory variables should
be investigated (Rosenberg et al. 2000). We estimated the
percentage of variation in effect sizes explained by each
Conservation Biology
Volume 25, No. 5, 2011
Barrientos et al. 897
predictor as QM/QT,whereQMis the variance explained
by the model from every predictor (Rosenberg et al.
In analysis of the subset of studies that included data
on flight frequency, we calculated differences in effect
sizes for the set of variables with random-effects models.
We evaluated the homogeneity of results for the set of
variables. We evaluated the “source” of information, that
is, the differences between studies from peer-reviewed
journals (journal) and other sources (unpublished). We
evaluated the variable “design,” which differentiated be-
tween BACI designs and those in which marked and un-
marked lines (or line sectors) were studied in the same
time interval. We used the variable “alternate” to test
whether studies in which spans were marked in alternat-
ing order (i.e., marked-unmarked-marked) affected effect
size; birds may have flown into unmarked spans to avoid
marked spans (Alonso et al. 1994; Crowder 2000). For
categorical data structure, we tested QMagainst a χ2dis-
tribution with n–1 df. We calculated cumulative effect
sizes for every group; effects were significant at p<0.05
when the 95% CI did not overlap zero. A significant QM
indicated there were differences among cumulative ef-
fects for the designated groups, whereas a significant QE
implied some heterogeneity among effect sizes was not
explained by the model (Rosenberg et al. 2000).
We also selected 5 continuous variables: “periodicity,”
mean number of carcass searches per month; “strip,”
total width searched on both sides of the line in meters;
“species,” number of bird species recorded; “lines,” num-
ber of power lines included in the study; and “stretches,”
number of marked or unmarked stretches of power line,
independent of the number of spans (i.e., the length
of line between 2 consecutive posts) contained in ev-
ery stretch. We determined the relation between effect
size and every continuous variable with weighted least-
squares regression. A significant QM(or regression coef-
ficient) implied the independent variable explained sig-
nificant variation in the effect sizes, and a significant QE
implied some heterogeneity among effect sizes was not
explained by the model (Rosenberg et al. 2000).
We explored the possibility of publication bias with
3 different approaches: construction of a funnel plot of
sample size versus effect size; use of Spearman rank corre-
lation between the standardized effect size and the stan-
dardized variance across studies (statistical significance
indicates large effect sizes are more likely to be published
than small effect sizes); and evaluation of the Rosenthal
(1979) fail-safe number, which is the number of non-
significant, unpublished, or missing studies that would
need to add to the meta-analysis to lose the statistical
significance of the results. If the fail-safe number is >5
times the sample size plus 10 ([sample size +10] ×5), it
is reasonable to conclude the results are robust regarding
publication bias. The 3 methods were used with the meta-
analysis that included flight-frequency data. We used the
fail-safe number in the meta-analysis of studies in which
only carcass counts were used because these studies did
not provide sample sizes, an essential parameter for the
other 2 methods.
Twenty-one studies, including 52 separate wire-marking
experiments, met our selection criteria (Supporting Infor-
mation). Wire marking reduced bird mortality at p<0.05
(i.e., 95% CI did not overlap zero; 1.42 to 0.47). The
test for overall heterogeneity was not significant (QT=
51.00, df =51, p=0.47).
We selected 11 of the 21 studies, including 15 sep-
arate wire-marking experiments because data on flight
frequencies were collected (Supporting Information). Of
these 15 experiments with flight frequencies, results of
7 were published in peer-reviewed journals and 8 were
in unpublished reports, 3 of the experiments had BACI
designs, and 11 had parallel designs. Of these 11, 5 had
alternate designs and 6 had continuous designs (Fig. 1).
Overall collision rates were 0.21/1000 bird crossings at
unmarked lines and 0.05/1000 crossings at marked lines
(Fig. 1). With the exception of the few studies with BACI
designs, wire marking reduced bird mortality by 55–94%
(overall 78%; Fig. 1). The test for overall heterogeneity
was significant (QT=69.27, df =14, p<0.001), which
implies other explanatory variables should be investi-
gated. Among the 8 variables, only number of species
was significant at p<0.05 (Table 1 & Fig. 2), and the
effect size of the studies was larger for those in which
more species were present. All variables showed hetero-
geneity among effect sizes that were not explained by
their respective models (Table 1).
The fail-safe number for the meta-analysis of carcass
counts was 751, which is >5 times the sample size plus
10 (i.e., 310). The scatter plot derived from the sensitiv-
ity analysis did not show publication bias. The plot was
funnel shaped with a large opening at the smallest sam-
ple sizes. The fail-safe number for sensitive analysis was
393, which is 5 times larger than the sample size plus
10 (i.e., 125). Accordingly, Spearman rank correlation
of standardized effect size and the standardized variance
was not significant (Rs=−0.10, p=0.73).
Effectiveness of Wire Marking
Our results suggest that marking static wires reduces the
number of bird casualties at power lines. However, colli-
sion risk was generally low even at unmarked lines. We
did not compare the relative efficiency of various types of
markers (color, shape) or evaluate the density of marking
devices on the wire. Few studies have been conducted on
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Volume 25, No. 5, 2011
898 Wire Marking to Reduce Bird Collisions
Figure 1. Rate of avian collisions with power lines for the studies included in the meta-analysis (overall) and for 3
categorical variables, including studies reporting carcass counts and flight frequencies (black, unmarked power
lines; gray, marked power lines; numbers above bars, number of experiments), and percent reduction in collisions
for every category of study (striped, right axis) (, significant at alpha <0.05; ns, alpha 0.05; significant
values are based on 95% bootstrapped confidence intervals). The categorical variables are (1) source (study
published in a journal or unpublished), (2) BACI study design (before-after-control-impact) or study design in
which marked and unmarked lines (or line sectors) were monitored simultaneously (parallel), and (3) parallel
study designs with spans marked alternately (alternate) or continuously (continuous).
the effectiveness of different markers for different species
or habitats.
That our literature review included unpublished re-
ports, dissertations, and papers published in peer-
reviewed journals allowed us to increase the number
of studies included in the meta-analysis and to compare
results between published and unpublished studies. As-
suming positive results are more likely to be published,
use of all possible data sources reduces the probability
of overestimating positive results (Fern´
andez-Duque &
Valeggia 1994).
On the basis of studies reporting only carcass counts,
we inferred that marked lines are associated with a reduc-
tion in the number of collisions. Fifty-six percent of the
studies we examined included estimates of bird density.
Of these, we included in our second meta-analysis only
those in which flight frequencies in relation to marker ef-
fectiveness were analyzed. Bird densities around power
lines may not be associated with the magnitude of col-
lision risk because species with large home ranges and
species that make daily forays between roosting and feed-
ing habitats often cross power lines more frequently than
species with small home ranges (e.g., most sedentary
passerines), which makes them more likely to collide
with wires.
When marked and unmarked spans are alternated,
birds could fly into unmarked spans more often, presum-
ably to avoid marked ones (Alonso et al. 1994; Crowder
2000). However, we found no evidence of this. The ab-
sence of an effect of alternate marking could be due to
the fact that the most common reaction of birds when
approaching marked spans adjacent to unmarked spans
is to fly higher rather than to change direction (Morkill &
Anderson 1991; Savereno et al. 1996). The effect size
was smaller in studies with one or only a few species,
probably because these (e.g., Morkill & Anderson 1991;
Sudman 2000) studies focused on species that rarely re-
spond to marking and thus are most likely to collide with
wires (i.e., cranes and waterfowl) (Bevanger 1998; Janss
2000). All continuous variables had significant residual
error variances, which implies that not all heterogene-
ity among effect sizes was explained by their respective
models (Rosenberg et al. 2000).
Testing Differences among Marker Traits
Some researchers have statistically tested differences
among marker characteristics. Scott et al. (1972) found
no evidence that 2 types of devices, clipped strips
and tapes, reduce bird casualties. Brown and Drewien
Conservation Biology
Volume 25, No. 5, 2011
Barrientos et al. 899
Table 1. Summary of results of random models used to analyze
differences in effectiveness of markers to prevent bird collisions with
power lines.
Variableadf QMb(p) QEc(p) QM/QTd
Source 1, 13 0.12 63.70 0.00
(0.72) (<0.00)
Design 1, 12 0.04 62.20 0.00
(0.85) (<0.00)
Alternate 1, 9 0.49 27.85 0.02
(0.48) (<0.00)
Periodicity 1, 13 1.79 66.27 0.03
(0.18) (<0.00)
Strip 1, 12 2.62 64.71 0.04
(0.11) (<0.00)
Number of species 1, 12 6.85 70.63 0.09
(<0.01) (<0.00)
Number of lines 1, 13 1.45 64.43 0.02
(0.23) (<0.00)
Number of stretches 1, 13 0.80 62.54 0.01
(0.37) (<0.00)
aKey: source, peer-reviewed journal or unpublished; design, BACI
(before-after-control-impact) design or marked and unmarked lines
(or line sectors) studied simultaneously; alternate, stretches of wire
marked in alternating order or in a continuous form; periodicity,
mean number of carcass searches per month; strip, total width of
search strip; number of species, total recorded per study; number of
lines, power lines included in the study; number of stretches, total
marked and unmarked stretches of power line studied.
bHeterogeneity explained by the model or between-group heterogene-
cResidual error variance or within-group heterogeneity.
dFraction of the total heterogeneity explained by the model.
(1995) found slightly fewer mortalities associated with
damper devices compared with plates, although reduc-
tion in mortality of segments marked with these devices
compared with unmarked segments was significant for
both dampers and plates. Janss and Ferrer (1998) found
that white spirals and flapper flight diverters signifi-
cantly reduce mortality, whereas black stripes do not.
However, habitat differences (crops vs. wetlands) may
have influenced their results. Anderson (2002) found that
flappers are more effective than flight diverters. Stake
(2009) found that small flight diverters and large divert-
ers both reduce the number of bird collisions, but that
large diverters are ineffective at some sites. Calabuig and
Ferrer (2009) found that cross-shaped markers are more
effective than spirals of different colors. Calabuig and Fer-
rer (2009) found that spirals of different colors (white,
orange, and yellow) similarly reduce mortality relative to
unmarked spans. Spirals appear to be more durable than
flapper flight diverters (Calabuig & Ferrer 2009). How-
ever, all these studies have low statistical power, which
could lead to type II errors (Arnqvist & Wooster 1995).
Some researchers have evaluated the effects of marking
at different intervals, but did not statistically analyze their
results (Koops & de Jong 1982; Anderson 2002). Other
researchers have examined the effectiveness of markers
of different sizes, but did not make statistical comparisons
among treatments (Koops & de Jong 1982).
Wire marking with standard flight diverters may not re-
duce the number of collisions of crepuscular or nocturnal
birds. Waterfowl and nocturnal migrants are among the
birds most prone to collisions with wires (reviewed in
Drewitt & Langston 2008). Only a few studies of the ef-
fectiveness of new types of flight diverters (e.g., FireFly di-
verters) have been conducted (Pilo et al. 1994; Yee 2007;
Murphy et al. 2009). Furthermore, many collisions may
occur during the day, when visibility is high (Drewitt &
Langston 2008). Martin and Shaw (2010) suggest that
wire marking may have limited success for bird species
with narrow visual fields, such as bustards, storks, and
cranes. Thus, it is possible that no single type of marker
will be equally effective with all bird species or in all situa-
tions, which suggests investigations of nonvisual devices
are needed.
Guidelines for Marking-Efficiency Experiments
The large differences in wire-marking techniques con-
strained our ability to infer whether this method reduces
bird collisions. We expect that the number of studies
on this topic may increase substantially over time given
the increasing demand for fewer and smaller effects of
human actions on the environment and increasing use of
marking devices on power lines worldwide (APLIC 1994,
2006; Manville 2009).
Four improvements in the design of studies of wire-
marking effectiveness may help determine which mark-
ing techniques are the most effective. First, we recom-
mend collecting data on carcass counts and flight fre-
quency for the same length of time and at the same
time of year at marked and unmarked wire segments.
For instance, some studies with BACI designs moni-
tored marked and unmarked lines for different lengths
of time (e.g., Anderson 2002; de la Zerda & Rosselli
2003). This could produce biases in the data because
flight frequencies are not constant throughout the year;
frequencies differ among and within seasons (e.g., spring
migration). Even when data are collected at the same
time of year, flight frequencies can vary. For example,
Alonso et al. (1994) recorded 2.9 times more flights in
December–April before wires were marked compared
with December–April after wires were marked. Conse-
quently, we recommend recording flight frequencies and
number of carcasses simultaneously.
Second, we suggest studying marked and unmarked
lines in areas with similar vegetation and topography,
the use of similar lengths of time spent searching for
carcasses, and searching transects of equal lengths and
widths (Bevanger 1999). For instance, bird collisions with
power lines are more frequent for lines that cross wet-
lands and where lines are between feeding and roosting
areas (Scott el al. 1972; McNeil et al. 1985; Ferrer & Janss
1999). Monitoring of different lengths of lines in different
land-cover types or bird habitats could drive differences
between marked and unmarked lines or among different
Conservation Biology
Volume 25, No. 5, 2011
900 Wire Marking to Reduce Bird Collisions
Figure 2. In a meta-analysis of
studies of effectiveness of wire
marking in reducing bird
collisions with power lines,
relation between effect size and
(a) mean number of carcass
searches per month (periodicity),
(b) total width of transect
searched on both sides of the
power line (strip), (c) number of
species recorded per study, (d)
number of power lines examined
per study, and (e) number of
marked and unmarked stretches
of power line monitored per
study (stretches). Each point
represents an experimental case.
markers (e.g., Janss & Ferrer 1998) because different bird
species have different habitats and not all species have
the same probability of collision (Bevanger 1998; Janss
2000; Martin & Shaw 2010).
Third, we recommend standardizing the periodicity
of carcass searches and the search strip width, at least
within every study. Although both variables must be
constant to support detailed comparisons among studies
Conservation Biology
Volume 25, No. 5, 2011
Barrientos et al. 901
Figure 2. (continued)
(Bevanger 1999), periodicity in the studies we examined
was sometimes fairly different even between marked
and unmarked lines within a study (e.g., Koops & de
Jong 1982). In general, we think the frequency of car-
cass searches should be determined on the basis of the
species’ body size because body size is correlated with
the removal rate of carcasses by scavengers. Larger car-
casses generally remain in the field longer than smaller
ones and are more easily located (Ponce et al. 2010).
Moreover, the carcass removal rate varies among habitats
and density and type of scavengers (Bevanger 1994), so
the periodicity of carcass searches and the length and
width search strip should be defined according to the
target species. Few researchers analyzed the distance
from the power line at which carcasses were found
(but see Frost 2008; Shaw et al. 2010). Ideally, carcass-
disappearance studies in which similar protocols are ap-
plied should be carried out in each study area prior to
studies of marking efficiency (e.g., Pelayo & Sampietro
1994; Onrubia et al. 1996).
Fourth, we recommend researchers compare the effec-
tiveness of currently available commercial markers used
to reduce bird collision. Due to the heterogeneity of mark-
ers used in the studies in our meta-analysis, we could not
compare effectiveness of different types of devices (e.g.,
flight diverters, aviation balls, flappers) or device color,
differences between categorical or continuous measures
of device size, or differences among spacing of devices
(e.g., every 5, 10, 20 m). Few conclusions about effective-
ness can be drawn from experiments in which the life
expectancy or color fading of different commercial de-
vices was examined (Hunting 2002). The optimal density
of markers or the effectiveness of using specific colors
over others has not been explored (Hunting 2002).
R. Harness, B. Parshalle, M. Rogen, A.M. Manville, J.A.
Lorenzo, L. Spiegel, J. Kreuziger, D. Frost, M. de Lucas,
Conservation Biology
Volume 25, No. 5, 2011
902 Wire Marking to Reduce Bird Collisions
M. Ferrer, J. Smallie, M. Stake, T. Lislevand, J.J. Ramos,
S. Smallwood, J. Shaw, F.J. Purroy, and J.M. ´
provided valuable information for this review. J. Gure-
vitch kindly resolved several doubts on meta-analysis
design, J.D. Ib´
nez helped us with MetaWin use, L.
de Neve provided translations of papers in Dutch, and
S. Young reviewed the English. J. Faaborg, M. McCarthy,
E. Fleishman, A.M. Manville, and an anonymous reviewer
improved a first draft. Financial support for this study
was provided by project CGL2008-02567 of the Direcci´
General de Investigaci´
on, Spanish Ministry of Science and
Supporting Information
Raw data and effect sizes calculated from studies used in
the meta-analysis are available online (Appendixes S1 &
S2). The authors are responsible for the content and func-
tionality of these materials. Queries (other than absence
of the material) should be directed to the corresponding
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Conservation Biology
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... In Great Bustards, mortality is 2.4-3.5 times higher in migrants than in sedentary individuals, mostly as the result of collision with power lines during migratory movements . Marking wires with flight diverters only reduces, but does not remove, collision mortality (Barrientos et al. 2011), so it can be considered only a partial conservation measure. The only way to eliminate collision mortality for migratory bustards in Lanzarote is to bury the lines underground. ...
... En las avutardas, la mortalidad es entre 2.4 y 3.5 veces mayor en los individuos migrantes que en los sedentarios, sobre todo como resultado de la colisión con los tendidos eléctricos durante los movimientos migratorios ). El marcaje de las líneas solo reduce, pero no elimina, la mortalidad por colisión (Barrientos et al. 2011), por lo que solo puede considerarse una medida de conservación parcial. La única manera de eliminar la mortalidad por colisión para las hubaras en Lanzarote es soterrar las líneas. ...
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Comprender los cambios en el uso del espacio y el comportamiento reproductivo de las especies, sobre todo de aquellas que se encuentran amenazadas, es crucial no solo para mejorar el conocimiento sobre las mismas, sino para poder aplicar medidas de conservación que eviten su declive y posible extinción. Esta tesis doctoral tiene como objetivo profundizar en la ecología espacial y el comportamiento reproductivo de la avutarda hubara canaria (Chlamydotis undulata fuertaventurae; en adelante, hubara canaria), subespecie endémica de las islas Canarias, catalogada como amenazada a nivel global por la UICN y en peligro de extinción a nivel nacional. Mediante los datos obtenidos con el marcaje y seguimiento de individuos adultos marcados con emisores GSM/GPRS, se pretende conocer los patrones y procesos biológicos y ecológicos que ayuden a diseñar nuevas estrategias de conservación. Tras la Introducción (Capítulo I) y la Metodología General (Capítulo II), la tesis doctoral está estructurada en 4 capítulos de resultados. El Capítulo III (pendiente de publicar). En el Capítulo IV, se aborda el patrón de migración de la subespecie. Los resultados muestran la existencia de migración parcial en la población de estudio, siendo aproximadamente un tercio los individuos que se mueven a otras zonas una vez concluida la reproducción y mostrando una gran fidelidad, tanto a las zonas reproductivas como no reproductivas. Estos patrones de migración parecen estar producidos por las diferencias en la productividad vegetal entre las zonas reproductivas y las no reproductivas, según estimaciones derivadas de los índices NDVI y SAVI. Estos resultados sugieren que la migración parcial se produce como un mecanismo de adaptación a la distinta abundancia de alimento en verano en las diferentes zonas. Además, se profundiza sobre la cantidad de áreas no reproductivas que son utilizadas, observando que una de las zonas no reproductivas es seleccionada por más de la mitad de los individuos migradores. Esta zona presenta un mosaico de parcelas con vegetación natural, mayoritariamente de aulagas (Launaea arborescens), con barbechos y cultivos en regadío. Un resultado relevante es que la mayoría de los vuelos migratorios se realizaron en horario nocturno. En el Capítulo V, se investigan la selección de recursos y las áreas de campeo de los individuos. Se caracterizan el tamaño y la forma de los territorios utilizados, diferenciando entre individuos reproductores y no reproductores y también entre diferentes periodos del año (estación reproductiva y no reproductiva). El tamaño de las áreas de campeo varió en función de la temporada y el estado reproductivo del individuo. Los resultados mostraron que durante la época reproductiva ambos sexos utilizaron casi exclusivamente terrenos con vegetación natural, seleccionando como hábitats de alimentación matorrales de baja densidad, pastos y barbechos verdes. Sin embargo, durante la época no reproductiva (mayo-octubre), se desplazaron a matorrales de alta densidad, pero también en parte a tierras cultivadas y barbechos verdes, mostrando preferencia por las parcelas de regadío. Esta investigación aporta datos sobre los requerimientos ecológicos de la hubara canaria, que son importantes para el diseño de planes de conservación. En el Capítulo VI, se aborda la actividad nocturna (detectada previamente en el capítulo IV), investigando el tipo y la intensidad de dicha actividad. Los resultados muestran que, a pesar de que la hubara se considera un ave exclusivamente diurna, presenta cierta actividad por la noche. Los machos realizan comportamientos reproductivos, con mayor o menor intensidad en función de la fase lunar. La intensidad de la vocalización es mayor en las noches de luna llena, alcanzando niveles similares a los del amanecer, momento del día en el que hasta la fecha se había registrado la máxima actividad sexual en esta especie. Estos resultados sugieren que la luz de la luna puede ayudar a los machos que se exhiben no solo a detectar a los depredadores, sino a comunicarse visualmente con las hembras que se acercan, pudiendo llegar a lograr cópulas nocturnas sin la interferencia de machos vecinos. Tras los capítulos de resultados, se expone la Discusión General (Capitulo VII) y las Conclusiones (Capítulo VIII). Esta tesis pone de manifiesto la necesidad de comprender el uso del espacio y el comportamiento reproductivo de las aves para poder realizar una gestión adecuada. La hubara canaria se encuentra en un preocupante estado de conservación, debido principalmente a la fragmentación del hábitat, las molestias antropogénicas y la mortalidad no natural causada por choques con tendidos eléctricos y telefónicos y con vehículos. Estos problemas no parece que vayan a resolverse en breve, y por ello, las implicaciones para la conservación que se desprenden de esta tesis deberían tenerse en cuenta y aplicarse en un futuro próximo, para así evitar el declive de un ave endémica de las islas.
... A nemzeti parkok tájképi értékeit, ökológiai folyamatait és veszélyeztetett fajait negatívan érintő vonalas létesítmények másik fő típusát alkotják az elektromos légvezetékek (murPhy et al. 2009, BarrienToS et al. 2011, amit a területbejárásaink során mi is tapasztaltunk. míg a magasfeszültségű vonalak elsősorban tájképromboló hatásúak, addig a középfeszültségű vezetékek a nagytestű madarak (elsősorban ragadozók, gólyaalakúak) állományait veszélyeztetik: ennél a vezetéktípusnál ugyanis az oszlopok alakja olyan, hogy a rászálló nagytestű madarak zárhatják az áramkört, ami pusztulásukhoz vezet. ...
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Világszerte a természetvédelmi oltalom alatt álló területek számos antropogén eredetű veszélyeztető tényező hatásának vannak kitéve, amely hatások következményei elsősorban a határvonalakon vizsgálhatóak. Ez azért különösen fontos, mert a védett területek határzónáiban és pufferterületein jelentkező hatások korai detektálása révén megelőzhető azok jelentősebb térnyerése a belső, érzékenyebb zónák felé. A védett területek határvonalait érintő antropogén hatások vizsgálatára a nagy kiterjedésű, egybefüggő nemzeti parkok különösen alkalmasak, amelyek egyik legreprezentatívabb európai képviselője a Hortobágyi Nemzeti Park (HNP). A terület a kontinens legnagyobb összefüggő szikes pusztája, amely egyben a Kárpát-medence egyik legzavartalanabb ökoszisztéma-típusa a Hortobágy, Debrecen közlegelője – rengeteg emberi hatás (zavarás, bolygatás, átalakítás érte a történelem során, aminek a hatására kialakult olyanná, amilyen most). A nemzeti park határterületén több, a régióra jellemző földhasználati típus váltakozása jellemző, melyeknek negatív hatásai mind intenzitásukat, mind térbeli és időbeli eloszlásukat tekintve eltérőek. A HNP határzónáját érintő antropogén eredetű zavarótényezők(özönnövények, bemosódás, tájképromboló elemek, szemét, fényszennyezés, beszántás) vizsgálatára 2011 áprilisa és októbere között végeztünk heti gyakoriságú terepi bejárásokat a Nemzeti Park bejárható határvonalának 95%-án, összesen 221 km-en. Minden szakaszon georeferálás után rögzítettük a földhasználati módot és a potenciális zavaró faktorokat. Eredményeink alapján a Nemzeti Park határvonalát negatívan érintő hatások közül a legjelentősebbek a földhasználati módok változása, az intenzívebb mezőgazdálkodási technológiák elterjedése a hagyományos gazdálkodási formák rovására és az özönnövények térhódítása. Legfontosabb eredményeink azt mutatták, hogy az özönnövényfajok számát elsősorban a védett területen kívüli legeltetettség illetve a védett területen belüli és kívüli élőhelytípus befolyásolta. A mesterséges élőhelyeken magasabb volt az invazív növényfajok száma, a kívülről legeltetett szakaszokon viszont ez az érték alacsonyabbnak mutatkozott. Ezzel szemben az elmúlt évtizedekben csökkent a vadászati nyomás és a kommunális hulladék lerakása: ezek a mai hatások az évszázadok alatt kialakult és ma védendőnek tekintett helyzetet veszélyeztetik.
... The most eff ective mitigation option would have been to re-route the power line in areas where it would otherwise closely approach the sites where Bengal fl oricans breed (such as the study area). Bird fl ight defl ectors, disks or spirals that make it easier for the birds to see the power line, could have been fi tt ed to the wires prior to erection of the power line to reduce the number of birds that would be killed (Barrientos et al., 2011). However, they were only att ached to the pylons, which are of litt le threat to fl ying birds, not to the wires. ...
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Over the last decade, Cambodia has witnessed a rapid expansion of its power transmission line network. This has been driven by rapid economic development and increasing energy demands for manufacturing and residential areas. Power transmission and distribution lines have been found to kill birds in all countries where their impacts have been studied (e.g., Jenkins et al., 2010). For instance, in the United States, it has been estimated that between 8 million and 57 million birds are killed by power lines annually (Loss et al., 2014). Typically, birds are killed not by electrocution, but because they fly into the wires at high speed, causing trauma and broken bones (Loss et al., 2014). Bird species differ in their susceptibility to collisions with power lines in predictable ways. The risk of collisions is higher for species whose eyes are aligned such that they have a narrow field of view when looking forwards because they cannot see the power lines when they are flying directly toward them until they are very close to the lines (Martin & Shaw, 2010). The risk of collision is higher in fast-flying birds with heavy bodies because they cannot manoeuvre easily to avoid the lines, which is a particular problem if they do not see the power line until they are very close (Bevanger, 1998). Bustards, a family of 26 Eastern Hemisphere bird species, possess a combination of physical characteristics that makes them the most vulnerable group to power line collisions (Martin & Shaw, 2010). Elevated mortality due to collisions with power lines has caused population-level declines in some bustard species (Shaw et al., 2017).
... This difference can be attributed to the greater number of power lines that are crossed per flight, relative to the number of turbine footprints encountered per flight (Figure 21). Our findings highlight the importance of fitting diverters to existing power lines that intersect known flight routes to increase their visibility to birds and hence reduce the numbers of collisions (Barrientos et al., 2011;Taylor et al., 2015). Moreover, the burial of existing sections of overhead power lines could under certain circumstances be a potential means of mitigating the potential effects of new energy infrastructure, including wind turbines, in terms of collision risk for goose species such as the Pinkfooted Goose. ...
Technical Report
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The UK supports globally significant numbers of migratory waterbirds and has a requirement to maintain favourable conservation status for these species in the face of climate change and other threats. The growing number of wind turbines are key to the UK’s power supply and play an important role in the UK’s actions on climate change. However, together with overhead power lines, wind turbines may also represent a collision risk for flying animals such as geese. Therefore, as part of efforts to maintain favourable conservation status of key species and to identify issues with existing or planned infrastructure developments, it is critical to be able to assess the cumulative impacts of collisions with energy infrastructure on wildlife. Here, in a study funded by Ørsted, we developed an individual-based model (IBM) of the UK’s overwintering population of Pink-footed Geese (Anser brachyrhynchus) in order to predict the cumulative mortality each winter due to collisions with onshore and offshore wind turbines and overhead power lines. IBMs are spatially- and temporally-explicit models that simulate the interactions between individuals and their environment, informed by the behaviour of their real-world counterparts. Our model was informed by information on the movements and flight heights of 73 geese fitted with GPS-GSM tags, together with census data on the total numbers and key regions used by the birds, as well as some key parameter values from the extensive literature on collision risk. We tested our model against real-world data on goose distributions across the UK; model fit was improved via calibration. Our calibrated IBM predicted that a mean ± 95% CI of 99 ± 10 Pink-footed Geese would be killed in collisions with all wind turbines (considering onshore and offshore together) and 674 ± 33 geese would be killed in collisions with power lines each winter across the UK. Given the total population size of 479,361 that was considered in our study (mean of the three winter counts from 2016 – 2018), these mean mortality estimates associated with wind turbines and power lines account for just 0.02% and 0.14%, respectively, of the total UK wintering population. Only 1.1% of the total predicted mortality (1 bird) was associated with the offshore wind farms in the NE Irish Sea, an area crossed only during a relatively low number of long-distance flights (and not during the more numerous short-distance daily feeding flights). These mortality estimates for the UK wintering population are lower than suggested previously. For comparison, it is estimated that up to c.50,000 Pink-footed Geese are shot each winter in the UK during the recreational shooting season. The collision mortality estimates were obtained from simulations using an avoidance rate of 99.8%, as recommended by Scottish Natural Heritage for collision risk studies of geese. However, no single avoidance rate estimate is accepted universally by all stakeholders; therefore, we also ran simulations with alternative avoidance rate values, covering the range commonly suggested for collision risk studies, for comparison. As expected, simulations that were run with lower avoidance rates resulted in higher estimates of collision mortality, i.e. for an avoidance rate of 95% our IBM predicted that a mean ± 95% CI of 2,363 ± 63 Pink-footed Geese would be killed in collisions with wind turbines and 16,664 ± 147 geese would be killed in collisions with power lines each winter. However, an important caveat is that the model was parameterized for typical weather conditions, as we do not currently have sufficient information to model collision risk during atypical conditions (e.g. high density fog). Collision risk during such atypical weather events could be higher than indicated by our simulations. Future scenarios (under the 99.8% avoidance rate) in which the numbers of turbines and power lines encountered during flights were increased indicated that even a simultaneous doubling of the numbers of all turbines and power lines encountered during flights (relative to the baseline scenarios informed by the tagged geese), which would represent a substantial expansion of the existing network, would have a relatively small effect on the predicted cumulative mortality. The careful siting of any such new energy infrastructure outside of known flight paths and migration routes would reduce these impacts further.
... Therefore, careful route planning is one of the most effective ways to reduce bird collisions with overhead power lines (D'Amico et al., 2018). We recommend attachment of markers onto the power lines in the form of plates, spirals, flappers, swivels, or spheres to increase their visibility are by far the most common mitigation measure applied to reduce bird collisions with power lines (APLIC, 2012; Barrientos et al., 2011;Prinsen et al., 2012). While the use of avian safe pole designed with sufficient separation between energized phase conductors (also called "phases") and between phases and grounded hardware to accommodate at least the wrist-to-wrist or head-to-foot distance of a bird, insulation of exposed part or wire and installation of perch management techniques will help to reduce the electrocution incidents (Prinsen et al., 2012). ...
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Among the several anthropogenic factors, power lines are increasingly regarded as one of the most significant hazards to bird species, primarily owing to collisions and electrocutions. Nepal has comparatively fewer studies on the impact of power line collisions and electrocution on birds compared with developed nations. From November 2021 to May 2022, we assessed the effect of power line collisions and electrocutions on the mortality of birds in the Putalibazar Municipality of the Syangja district of Nepal. We established 117 circular plots in diverse habitats, including agricultural lands, forests, settlements, and river basins, along a 30.6 km long distribution line. Within 18 plots, we detected 43 fatalities of 11 species (17 individuals of six species due to collision and 26 individuals of eight species due to electrocution). House Swift (Apus nipalensis) and Common Myna (Acridotheres tristis) were the primary victims of the collision, whereas House Crow (Corvus splendens) and Rock Pigeon (Columba livia) were frequently observed electrocuted. We also recorded the electrocution of the critically endangered White-rumped Vulture (Gyps bengalensis). The total rate of bird power line collisions per kilometer was 0.55 birds, while the total electrocution rate per 10 poles was 2.22. The bird abundance, distance to agricultural regions, and proximity to human settlements were found to have a strong relationship with the mortality of birds caused by power lines. In order to reduce power line collisions and electrocution fatalities, we recommend conducting a detailed bird population study prior to determining the route of distribution lines.
... In the past, powerlines may have been routed through prairie wetlands because lands in agricultural production had greater value. Future measures to reduce collision mortalities could include precautions to avoid siting of new infrastructure near wetland habitats where shorebirds may be vulnerable during aerial courtship displays, or by marking of powerlines and wind turbines to increase visibility(Barrientos et al., 2011). In other populations of migratory shorebirds, legal and illegal harvest are also major sources of mortality(Andres et al., 2022;Redmond & Jenni, 1986;Watts et al., 2019).Measures to prevent unsustainable harvest require identification of important harvest zones and implementation of improved regulations (McDuffie et al., 2022). ...
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The Prairie Pothole Region of central Canada supports a diverse community of breeding waterbirds, but many species have declining populations and the demographic mechanisms driving the declines remain unknown. We conducted a 7-year field study during 1995-2001 to investigate the demographic performance of Marbled Godwits (Limosa fedoa) and Willets (Tringa semipalmata) breeding in managed wetlands near Brooks, Alberta. Mark-recapture analyses based on Cormack-Jolly-Seber models revealed that the annual rates of apparent survival for Marbled Godwits ( ϕ ^ = 0.953 ± 0.012SE) and Willets ( ϕ ^ = 0.861 ± 0.015SE) are among the highest rates of survivorship reported for any breeding or nonbreeding population of large-bodied shorebirds. Our estimates of life expectancy for males were comparable to longevity records in godwits (17.3 years ±5.8SE vs. 25-29+ years) and willets (7.7 ± 1.5SE vs. 10+ years). The two species both showed strong breeding site fidelity but differed in rates of mate fidelity. Pairs that reunited and males that switched mates usually nested <300 m from their previous nests, whereas females that switched mates usually moved longer distances >1.1-1.5 km. Returning pairs usually reunited in godwits (85%) but not in willets (28%), possibly because of species differences in adult survival or patterns of migration. Baseline estimates of annual survival for banded-only birds will be useful for evaluating the potential effects of new tracking tags or the environmental changes that have occurred during the past 20 years. Conservation strategies for large-bodied shorebirds should be focused on reduction of exposure to anthropogenic mortality because low rates of natural mortality suggest that losses to collisions at breeding sites or harvest at nonbreeding areas are likely to cause additive mortality.
... Similarly, another group that should receive special attention in future studies is the Nearctic-Neotropical migrants, since their numbers had been reduced considerably over the last three decades (Rosenberg et al., 2016). Data based on scientific studies are essential as a baseline to implement and propose mitigation measures that reduce the number of deaths caused by power lines (Barrientos et al., 2011;Bernardino et al., 2019;Chevallier et al., 2015;Dwyer et al., 2019;Ferrer et al., 2020;Luzenski et al., 2016). Practices such as conducting studies before the establishment of transmission lines can be useful to identify areas of higher risk for the avifauna (D'Amico et al., 2018;Luzenski et al., 2016). ...
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Background and Research Aims Power lines are one of the main anthropogenic causes of bird mortality on a global scale, but research is scarce in some countries with a high diversity of birds, such as Mexico. In this study, we assessed the impact of bird collisions and electrocutions with power lines on avian communities at three wind farms located in three different states in Mexico. Methods Carcass searches were carried out at sites in Tamaulipas (4 months in 2021), Guanajuato (2 months in 2020, 4 months in 2021), and Oaxaca (55 months from 2014 to 2021). Results A total of 579 bird carcasses from 65 different species were recorded. The White-winged Dove ( Zenaida asiatica) was the most frequently found species (282 records) across the three sites. When considering the number of species identified per family, Icteridae had the highest number of species at the Oaxaca site, Columbidae and Passerelidae at the Tamaulipas site, and Anatidae at the Guanajuato site. At the order level, Passeriformes had the highest number of species at the Tamaulipas and Oaxaca sites, and Anseriformes in Guanajuato. Of the total species recorded, 12 are within some category of risk according to Mexican legislation and the IUCN Red List, and 18 are migratory species. Conclusions Our results, together with evidence from previous studies, indicate that power lines represent one of the main causes of anthropogenic mortality in Mexico in terms of the number of affected bird species. Further research is urgently needed to explore the effect of power lines on bird populations in the country, particularly those at risk of extinction, and migratory species. Implications for Conservation The high diversity of species found to be affected in this study highlights the wide-ranging impact of these structures and the need to implement mitigation strategies at the three sites studied, particularly for the most affected species, the White-winged Dove ( Zenaida asiatica).
High mountain habitats are globally important for biodiversity. At least 12% of birds worldwide breed at or above the treeline, many of which are endemic species or species of conservation concern. However, due to the challenges of studying mountain birds in difficult-to-access habitats, little is known about their status and trends. This book provides the first global review of the ecology, evolution, life history and conservation of high mountain birds, including comprehensive coverage of their key habitats across global mountain regions, assessments of diversity patterns along elevation gradients, and adaptations for life in the alpine zone. The main threats to mountain bird populations are also identified, including climate change, human land use and recreational activities. Written for ecologists and naturalists, this book identifies key knowledge gaps and clearly establishes the research priorities needed to increase our understanding of the ecology of mountain birds and to aid in their conservation.
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The energy crisis and global shift toward sustainability drive the need for sustainable technologies that utilize often‐wasted forms of energy. A multipurpose lighting device with a simplistic design that does not need electricity sources or conversions can be one such futuristic device. This study investigates the novel concept of a powerless lighting device driven by stray magnetic fields induced by power infrastructure for obstruction warning light systems. The device consists of mechanoluminescence (ML) composites of a Kirigami‐shaped polydimethylsiloxane (PDMS) elastomer, ZnS:Cu particles, and a magneto–mechano‐vibration (MMV) cantilever beam. Finite element analysis and luminescence characterization of the Kirigami structured ML composites are discussed, including the stress–strain distribution map and comparisons between different Kirigami structures based on stretchability and ML characteristic trade‐offs. By coupling a Kirigami‐structured ML material and an MMV cantilever structure, a device that can generate visible light as luminescence from a magnetic field can be created. Significant factors that contribute to luminescence generation and intensity are identified and optimized. Furthermore, the feasibility of the device is demonstrated by placing it in a practical environment. This further proves the functionality of the device in harvesting weak magnetic fields into luminescence or light, without complicated electrical energy conversion steps.
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Guidelines for preventing and mitigating wildlife mortality associated with electricity distribution networks
Technical Report
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EXECUTIVE SUMMARY Collisions with powerlines cause substantial mortality among many species of birds, but such losses may be reduced by installing devices that make powerline wires conspicuous., we investigated mortality of sandhill cranes (Grus canadensis) stemming from collisions with two 69-kilovolt (kV) powerline arrays at a major night roost of the species on the Platte River in Buffalo County, south central Nebraska. Static wires of each powerline were equipped with FireFly™ bird diverters (FireFly Diverters LLC, Grantsville, Utah). We searched for carcasses of cranes at sandbars, islands, and shallow water areas between riverbanks below each powerline three times weekly and attempted to account for detectability biases. An estimated 50-93 sandhill cranes were killed by the two powerlines in 2008 and 37-70 were killed in 2009. These estimates were one-half to one-third of that reported in a previous study at the site, before FireFlys were installed. Using binoculars and night-vision scopes, we observed 101 and 117 collisions by sandhill cranes at one of the powerlines in 2008 and 2009, as the cranes returned to their roost from about 0.5 hours before sunset until about 2 hours after sunset. Most collisions occurred when flocks of more than 1000 cranes suddenly flushed from their roost within 0.5 km of the powerline after dusk. There appeared to be no relationship between collision incidence and weather or light conditions. About one-half of cranes that collided fell immediately to the ground, either dead or crippled. Another 29% continued to fly after striking wires, but their flight was hampered. About 65% of observed collisions involved static wires. We also observed reactions of 474 flocks of sandhill cranes to the powerline in 2009. Cranes reacted more quickly to avoid the powerline than they did to powerlines not equipped with diverters or to powerlines equipped with 30-cm yellow aviation balls as diverters in a previous study in south central Nebraska, and did so mainly by gradually climbing in flight. Individual wires on the powerline we observed also were instrumented in 2009 with bird strike indicators (BSIs), a new electronic technology to detect bird collisions. Collision incidents we observed and those indicated by BSIs were highly correlated. Diel records from BSIs indicated one-half of collisions by birds occurred during evening; nearly all the rest were distributed across remaining night hours. Our results might suggest FireFlys reduce the likelihood that a sandhill crane will collide with powerlines at Rowe, but more rigorous experimental design incorporating replication is needed to reliably assess and provide broader inferences on effectiveness of FireFlys in decreasing mortality of cranes and other bird species at powerlines. BSIs should be further evaluated and incorporated into such assessments. 2
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La colisión de aves contra el cable de guarda y los conductores de líneas eléctricas de alta tensión puede ser un problema serio en algunos hábitats y para algunas especies de aves. Obtuvimos datos de colisión de aves en una localidad atravesada por los dos circuitos de una línea a 500kV en el norte de Colombia. Después de dos años de estudio, se instalaron dispositivos de mitigación (espirales plásticos amarillos) en uno de los circuitos y se efectuaron observaciones a posteriori para evaluar la efectividad de los espirales. Los dispositivos para desvío de vuelo redujeron la mortalidad de las aves según lo indican los datos de menor número de aves reaccionando cerca de la línea, menor número de aves volando a la altura de los conductores y menor tasa de colisión en el circuito marcado. Este estudio pionero en la región aporta una metodología adaptada al Neotrópico para el estudio de los efectos de líneas de transmisión. Se concluye que el problema de colisión en Colombia puede ser bastante grave sobre algunas poblaciones locales de aves, especialmente de especies crepusculares, de tamaño relativamente grande y con poca capacidad de maniobrar en vuelo. Se da una serie de recomendaciones preventivas para empresas electrificadoras incluyendo la instalación de espirales desviadores de vuelo en los sectores de líneas localizados en áreas críticas. Esta política ya se está aplicando en el país.
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The number of birds killed (per km) by collision with power lines in west-central Spain did not differ between one transmission line and two distribution lines. For all three power lines, we tested the ability of different markers to reduce bird collision by comparing marked spans to unmarked spans along the same power line. A spiral (30 cm × 100 cm) reduced collisions (static wire marking). Black crossed bands (35 cm × 5 cm) were also effective, but not for the vulnerable Great Bustard (Otis tarda) (conductor marking). The third marker, consisting of thin black stripes (70 cm × 0.8 cm), did not reduce mortality (conductor marking). The highest mortality from power-line collision was recorded for the Great and Little Bustard (Otis tarda and Otis tetrax).
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1. Capercaillie, black grouse and willow ptarmigan mortality resulting from collisions with high tension power lines (11-420 kV) was estimated, based on the number of casualties found per kilometre of power line patrolled in three boreal forest and low alpine areas. 2. The length (km) of high tension power lines crossing tetraonid habitats was estimated using Geographical Information Systems and general knowledge about species-specific habitats. Of the entire Norwegian high tension power-line grid system (about 95 000 km), 55% was estimated to cross capercaillie habitats, 56% black grouse habitats and 16% willow ptarmigan habitats. 3. Because of biasing factors related to data-collecting procedures, the number of collision victims found per kilometre of power line patrolled was increased by a factor varying from 6.0 to 14.9. The estimated losses were about 20 000, 26 000 and 50 000 for capercaillie, black grouse and willow ptarmigan, respectively, which are about 90%, 47% and 9% of the annual hunting harvest of these species. 4. It was concluded that this estimating procedure may be useful to wildlife management authorities to assess losses caused by overhead wires in general. Locally, this mortality factor should be carefully recorded and considered together with other mortality factors like hunting, to avoid overexploitation.
Alternating spans on powerline segments in S-central Nebraska were marked with yellow aviation balls 30 cm in diameter. The number of spring migrating Grus canadensis flying over marked and unmarked spans did not differ. More dead cranes were found under unmarked than marked spans. Cranes reacted more often to marked than unmarked spans. Reactions included increase in altitude and change in flight direction. -from Authors
Collisions with power lines are a source of mortality to cranes (Grus americana and Grus canadensis), waterfowl, and other birds. Two power line markers were assessed in the San Luis Valley, Colorado. Collision mortality rates at 8 segments of power lines marked with either yellow spiral vibration dampers or yellow fiberglass swinging plates were compared with 8 adjoining unmarked segments. During 3 spring and 3 fall migration periods (1988-1991), estimated mortality on study segments was 706, including ≥35 species. Waterfowl and cranes constituted >80% of mortality. Both marker types reduced mortality. Factors affecting collisions or marker effectiveness included wind, nocturnal flights and disturbance, and age of sandhill cranes. -from Authors
We compared avian behavior and mortality associated with two 115-kV transmission lines on the central South Carolina coast during 3,392 hours of observation from May 1991 through May 1994. One line was marked with 30-cm-diameter yellow aviation markers. The second line was unmarked, but was similar in most other aspects. We conducted ground searches (n = 445) beneath each line year-round to document avian mortality due to power-line collisions. At marked lines, birds that approached at line height changed behavior more at unmarked lines (P< 0.001), and fewer crossed between static and conductor wires. Collision rate was 53% lower at marked than unmarked lines. Among collisions at both sites, 82% of birds collided with static wires. Based on observed collisions and carcass recoveries, wading birds particularly appeared to be at risk. We concluded that aviation markers were effective at increasing line visibility and reducing collisions and recommend marking static wires of power lines in potentially sensitive areas.