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Enhancing Carcass Removal Trials at Three Wind Energy Facilities in Portugal

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During the last years there has been a significant worldwide increase in the number of wind farms. This kind of energy can have negative impacts, such as the direct mortality or lethal injury of birds and bats caused by collision with wind turbines. In order to evaluate bird (or bat) mortality regarding wind power generation facilities, strict monitoring protocols are required which must take into account the possibility of carcass removal by scavenging animals or decomposition before the monitoring session. For this purpose, carcass removal trials with 180 carcasses representing three size classes (small, medium and large) were conducted in two seasons (Spring and Autumn) at three wind farms located in the central region of Portugal. No significant differences were found between removal rates of different wind farms or size classes contrarily to seasons, which presented an average carcass removal time of 3.9 and 4.6 days, respectively for Spring and Autumn. The results of the present study showed the importance of trials to estimate the carcass removal rates, which influences the survey effort management and consequently the monitoring protocols. The experimental design for future trials in the same region should account for season effect and be conducted using daily checks of the carcasses for, at least, 15 days.
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ORIGINAL PAPER
Wildl. Biol. Pract., 2011 December 7(2): 1-14
doi:10.2461/wbp.2011.7.11
Copyright © 2011 J. Bernardino, R. Bispo, P. Torres, R. Rebelo, M. Mascarenhas & H. Costa.
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distri-
bution, and reproduction in any medium, provided the original work is properly cited. Published by: Portuguese Wildlife Society.
En h a n c i n g ca r c a s s rE m o v a l Tr i a l s a T Th r E E Wi n d En E r g y Fa c i l i T i E s i n
Po r T u g a l
J. Bernardino1,*, R. Bispo2, P. Torres1, R. Rebelo3, M. Mascarenhas1 & H. Costa1
1 Bio3 Estudos e Projectos em Biologia e Valorização de Recursos Naturais, Lda., Rua D. Francisco
Xavier de Noronha, 37B 2800-092 Almada, Portugal.
2 Grupo de Estatística e Matemática, Instituto Superior de Psicologia Aplicada, Rua Jardim do tabaco, 34,
1149-041 Lisboa, Portugal.
3 Departamento de Biologia Animal, Faculdade de Ciências da Universidade de Lisboa, Avenida
Senhora do Cabo, Nº 939, 2750-374 Cascais, Portugal.
* Corresponding author: e-mail: joana.bernardino@bio3.pt; Phone: +351 212-951-588
Keywords
Bird Mortality;
Carcass Removal Trials;
Monitoring;
Survey Effort;
Survival Analysis;
Wind Farm.
Abstract
During the last years there has been a signicant worldwide increase in
the number of wind farms. This kind of energy can have negative impacts,
such as the direct mortality or lethal injury of birds and bats caused by
collision with wind turbines. In order to evaluate bird (or bat) mortality
regarding wind power generation facilities, strict monitoring protocols are
required which must take into account the possibility of carcass removal
by scavenging animals or decomposition before the monitoring session.
For this purpose, carcass removal trials with 180 carcasses representing
three size classes (small, medium and large) were conducted in two seasons
(Spring and Autumn) at three wind farms located in the central region of
Portugal. No signicant differences were found between removal rates of
different wind farms or size classes contrarily to seasons, which presented
an average carcass removal time of 3.9 and 4.6 days, respectively for Spring
and Autumn. The results of the present study showed the importance of trials
to estimate the carcass removal rates, which inuences the survey effort
management and consequently the monitoring protocols. The experimental
design for future trials in the same region should account for season effect
and be conducted using daily checks of the carcasses for, at least, 15 days.
Introduction
Nowadays, wind is considered worldwide as one of the most promising energy
sources found in nature. Despite the obvious benets of wind turbines as a clean
energy source, the construction of wind farms can be responsible of impacts on
ying vertebrates, such as fatality through collision with rotating turbine rotor
blades, habitat modication, barrier effect or disturbance in nesting areas [1-4].
These impacts, especially the birds and bats mortality, became a source of major
concern among a number of stakeholder groups [5-10]. In fact, results obtained
during several monitoring studies indicated that wind farms were responsible for the
2 || J. Bernardino et al. | Enhancing Carcass Removal Trials at Three Wind Energy Facilities in Portugal
decrease in some species’ populations [11-14] although many other studies revealed
that these impacts were not important when compared to those originated by other
infrastructures [15-17]. Nevertheless, the potential for wind farms to affect bird or bat
populations should not be underestimated [11,18].
During the last two decades, the need to properly assess the impacts on ying
vertebrates led to the development of methodologies for evaluating bird and bat
fatalities in existing and planned wind facilities developments. Current post-
construction monitoring protocols require that carcass estimates under turbines are
adjusted taking into consideration the rate at which carcasses decompose or are
removed by scavengers [2,19,20]. Therefore, most recent studies include carcass
removal trials, although few follow the exact same protocols [21,22]. Furthermore,
even fewer studies have been conducted with the specic aim of improving the
protocol design for this kind of trials [23,24]. Thus, it is necessary to develop a single
and robust methodology in order to validate any results or comparisons between wind
farms, allowing at the same time a correct evaluation of the impacts regarding its
construction [17].
Over the years protocols have tended to become more strict and demanding
[19,20,25-27]. However, they often increase the monitoring costs, which is a problem
due to the limited budgets of many monitoring studies. Hence, it is crucial to develop
efcient methodologies that consider cost/benet relationships [28], maximizing
effort reduction without compromising the quality of the results. To achieve this
goal, it is necessary to clarify the inuence of effort reduction in monitoring and
consequently in a correct assessment of the results.
The aim of this study was to evaluate the importance of conducting carcass removal
trials in order to achieve a correct evaluation of bird mortality regarding wind power
generation facilities, and to optimize the survey effort employed in monitoring
protocols. It was conducted with data collected during monitoring studies of bird
mortality at three Portuguese wind farms.
Methods
Study area
The studied wind farms are located at the central region of Portugal (Fig. 1), each
comprising a series of mountain ridges.
Caramulo wind farm is situated at Serra do Caramulo (maximum altitude of
1076.57 m a.s.l.) and comprises 45 wind turbines subdivided along ve smaller units,
each turbine with a power of 2.0 MW. The vegetation consists mainly in shrubs and
scattered trees (Quercus robur and Quercus pyrenaica) on the mountain ridges, and
cereal elds in some areas. Average annual temperature and rainfall vary between 10-
12.5ºC and 2000-2400 mm, respectively. This facility is supported by Generg Ventos
do Caramulo, Lda. (Portuguese Promoter GENERG Group).
Pinhal Interior wind farm also comprises several smaller units along Serra de Alvelos
(1084 m), Cabeço da Rainha (1080 m), Moradal (885 m) and Perdigão (566 m), consisting
in 58 wind turbines, each with a power of 2 MW, with the exception of Alvelos, which
Wi l d l i f e Bi o l o g y in Pr a c t i c e 2011, 7(2) || 3
presents each turbine with a power of 3 MW. In the last decades the autochthonous
vegetation has been replaced by pine (Pinus pinaster) and eucalyptus (Eucalyptus
globulus) trees, however due to forest res most of the area is now occupied by low-
growing shrubs of the genus Erica and related genera. Average annual temperature
ranges from 7.5 to16ºC and rainfall from 800 to1600 mm. This wind farm is supported
by GENERVENTOS do Pinhal Interior – (company also included in Generg Group).
Lousã wind farm, located at Serra da Lousã (maximum altitude 1205 m a.s.l.),
comprises 14 wind turbines, each with a power of 2.5 MW. The vegetation consists
in low shrubs (Erica sp. or Calluna vulgaris), herbaceous vegetation, oak forests
and plantations of coniferous and mixed woods [29]. In this area, average annual
temperature ranges 9-22ºC and rainfall 1000-1800 mm. Parque Eólico do Trevim,
Lda (Iberwind Group) manages this facility.
Fig. 1. Location of each wind farm in Portugal. Black dots represent single wind turbines.
4 || J. Bernardino et al. | Enhancing Carcass Removal Trials at Three Wind Energy Facilities in Portugal
Field methods and analytical approach
The carcass removal trials were conducted in two seasons (Spring - May/June;
Autumn – September/October) since, according to the monitoring protocol design
for all three wind farms, carcass searches are restricted to these periods [30-32].
Specically, Spring trials were performed from the 7th until 27th of May, 14th of
May until 8th of June and from 6th until 30th of June for Lousã, Pinhal Interior and
Caramulo wind farms, respectively. During the second season (Autumn), the trials
were conducted between day 3 and 23 of October, in all sites.
Complete and fresh carcasses of parakeets (Melopsittacus undulates), quails
(Coturnix coturnix) and partridges (Alectoris rufa) were used to represent birds
of three size classes (small – ≤15 cm and ≤50g, medium – 15-25 cm and 50-200g;
large ≥25 cm and ≥200g) and more accurately reect realistic removal rates
[33]. Carcasses were obtained in avian breeding facilities. Handling was always
performed with lab gloves to prevent human odour contamination.
In each farm, 10 carcasses of each size class were placed per season, comprising
a total of 180 corpses. The carcasses were placed near the turbines or associated
infrastructures (range 8- 42 m distance), randomly, independently of the size class,
and at a minimum distance of 500 m from each other. After its placing, all carcasses
were checked daily, every morning, until their removal for a maximum period of 20
days.
Statistical approach
Carcass removal trials involve measuring the time until carcass removal. The
obtained data were examined using Survival Analysis [34]. Standard statistical
approaches were discarded based on the positively skewed removal time distribution
[35] and on the presence of censored observations (carcasses with removal times
beyond 20 days).
The survivor function, that in this context describes the probability of a carcass
being removed beyond a time t (or persist until t), was estimated using the Kaplan-
Meier estimator. The Log-Rank test was used to test the existence of signicant
differences between survival curves of different farms, seasons and size classes
[36].
Also, according to the variety of survey effort methodologies used in the last
decade in monitoring studies, some reduction effort scenarios were selected to
evaluate its inuence in the results obtained, by comparing it to the used eld effort
methodology (daily checks through 20 days). The resulting survivor distributions
were compared using the Wilcoxon test. Four inspection scenarios were tested
against the used methodology, in all wind farms:
- Daily checks for 14 days [37];
- Daily checks for 7 days [38];
- Checks every other day for 20 days;
- Daily checks in the rst 4 days and then in the 7th, 10th, 14th and 20th days [39].
Statistical analysis was performed using R software [40]. Data were analysed
under a 0.05 level of signicance.
Wi l d l i f e Bi o l o g y in Pr a c t i c e 2011, 7(2) || 5
Results
The majority (>80%) of the 180 carcasses used was removed in the rst week after
its placement (Fig. 2). After the 15th day, none of the carcasses were removed until
the end of the sampling period, disappearing eventually by decomposition (n=13).
Fig. 2. Histogram of the removal times of non censored carcasses.
The Log-Rank test (Fig. 3) showed no signicant differences for the carcass removal
times between farms (χ2= 4.5; d.f. = 2; p = 0.107) or size classes (χ2= 1.9; d.f. = 2;
p = 0.384). However, removal times differed signicantly between seasons (χ2= 5.3;
Fig. 3. Survival functions determined with the Kaplan-Meier estimator. A - between seasons; B - between
wind farms; C - between carcass sizes.
6 || J. Bernardino et al. | Enhancing Carcass Removal Trials at Three Wind Energy Facilities in Portugal
d.f. = 1; p = 0.021). The data analysis showed that in Spring the carcasses were removed
faster, with almost 80% disappearing in the rst 5 days (Fig. 4). In Autumn, within
the same period, only 60% of carcasses were removed, reecting a lower carcass
removing probability throughout the sampling period (20 days). Mean carcass removal
time (standard deviation in brackets) in the wind farms was 3.9 (0.34) and 4.4 (0.37),
respectively in Spring and Autumn.
Considering the survey effort comparisons, once no carcasses were removed after
the 15th day, there were no changes in the survivor curves of any wind farm when
the trial length was reduced from 20 to 14 days. However, when the survey effort
was reduced to 7 days (Fig. 4A) the resulting survivor curves differ signicantly
for both seasons (p=0.0346 and p=0.0143, for Spring and Autumn, respectively).
Also, when the survey effort reduced to one check every other day (Fig. 4B) the
curves differed signicantly for both seasons (p=0.022 and p=0.014, for Spring and
Autumn respectively). Considering the last scenario, the survey effort consisted in
daily checks in the rst 4 days followed by surveys conducted only on the 7th, 10th,
14th and 20th days (Fig. 4C), again the survivor curves differed signicantly for both
seasons (p=0.005 and p=0.002, for Spring and Autumn respectively).
Fig. 4. Survival functions determined with the Kaplan-Meier estimator according to the survey effort
performed. A - comparison between daily checks for 20 and 7 days, for both seasons; B - comparison
between daily checks and every 2 days, for a period of 20 days, for both seasons; C - comparison between
daily checks and checks every day until the 4th day and then only in the 7th, 10th, 14th and 20th days, for a
period of 20 days, for both seasons.
Wi l d l i f e Bi o l o g y in Pr a c t i c e 2011, 7(2) || 7
Discussion
In our study we did not found a signicant effect of bird size on carcass removal
times. This may be related with specic biophysical characteristics of the mountain
ridges, since the same result has been observed in other regions of Portugal [41]. In
contrast, studies performed for instance in the north of Portugal, with exactly the same
species, detected signicant differences in removal rates between class sizes [42].
Nevertheless, in this study signicant differences were detected between seasons, with
the corpses disappearing faster in spring/early summer than in autumn. This result is
similar to those described in several other studies performed at Portuguese wind farms
[43-45] possibly due to different scavengers activity between seasons [22].
Although the differences between seasons seem relatively small and some times
negligible, they must be taken into account, since it can produce signicant bias
in the mortality estimates (Table 1). To exemplify the importance of even slightly
different removal rates, let’s consider that the mortality rate (number of corpses per
period of time) can be simply estimated by:
M =
where Ci, is the total number of carcass found at the i-th search; ri the removal
correction factor ( proportion of carcasses that persist unscavenged at the i-th search);
and p the detection rate (in this case, we assume 0.25)[46]. Considering that, during
one of the Spring searches, the carcass of 1 bird, which died 5 days before, is found,
the removal correction factor is 0.23, which would result in a mortality estimate of,
approximately, 17 birds (i.e. M= 1/(0.25×0.23)), for that period of time. However,
if the same situation occurred during Autumn, the mortality estimate would be
considerably lower, 10 birds (i.e. M=1/(0.25×0.40)). Naturally, the estimates differ
even more as the number of observed mortality and the time between the bird´s death
and the i-th search increases (e.g. C=5, found 7 days after death; M=143 and M=91,
respectively, during Spring and Autumn).
Table 1. Mortality estimate (estimated by estimator presented in [46]), considering different removal rates
(r) and a detection rate (p) of 0.25. C- Number of carcass found at the i-th search.
Days since
death
Spring Autunm
Removal
rate (r)
Mortality estimate (M) Removal
rate (r)
Mortality estimate (M)
C=1 C=2 C=5 C=1 C=2 C=5
1 0.81 4.9 9.9 24.7 0.84 4.8 9.5 23.8
2 0.63 6.3 12.7 31.7 0.67 6.0 11.9 29.9
3 0.40 10.0 20.0 50.0 0.56 7.1 14.3 35.7
4 0.29 13.8 27.6 69.0 0.48 8.3 16.7 41.7
5 0.23 17.4 34.8 87.0 0.40 10.0 20.0 50.0
6 0.19 21.1 42.1 105.3 0.31 12.9 25.8 64.5
7 0.14 28.6 57.1 142.9 0.22 18.2 36.4 90.9
Despite the differences between seasons, the high rate at which the carcasses were
removed in the three wind farms was similar to that reported for other studies developed
at North America and Europe, in similar mountain ridges [9,47-51], with more than 80%
8 || J. Bernardino et al. | Enhancing Carcass Removal Trials at Three Wind Energy Facilities in Portugal
of the carcasses removed until the end of the rst week. Strickland et al. [52] reported
the mean carcass removal time between six and seven days for birds and about 10 days
for bats at Buffalo Ridge, Minnesota. Also at this site, Higgins, Dieter, and Usgaard
[9] reported scavenging of 12 from 15 carcasses (80%) after one week (two trials). At
Vansycle wind farm located primarily in wheat elds, small carcasses lasted on average
15 days [39]. At the Buffalo Ridge Wind farm, small carcasses persisted on average 4.7
days, whereas small birds at Foote Creek Rim persisted 12.2 days [48]. Also, Wobeser
& Wobeser [53] reported that nearly 80% (79.2) of the chicks placed in a mixed grazed
pasture were removed within 24 hours. In France, Pain [54] estimated duck carcasses
lasted an average of 1.5 days in open vegetations, whereas those concealed by vegetation
or those in water lasted 3.3–7.6 days. At Tehachapi Pass (EUA) small and large carcasses
endured an average of 3.1 and 2.12 days, respectively [48].
This high decrease of animal corpses in the rst days clearly inuences the survey
effort management and monitoring protocols, mainly regarding the estimation of
removal/decomposition rates and consequently the mortality evaluation in wind farms.
No signicant differences were found in the survivor curves when the trial length was
reduced from 20 to 14 days, which is explained by the absence of carcass removal in
this last ve days. In the scenarios where the survey effort was considerably reduced, the
resulting survivor curves changed signicantly. For example, during Autumn with daily
checks, the carcass persistence probability at the end of 6 days was 30%, while in the
last scenario tested (daily checks in the rst 4 days and then in the 7th, 10th, 14th and 20th
days) this probability increased to 50%, underestimating the wind farm mortality rate.
Therefore, in similar mountain ridges it seems advisable to check carcasses daily, for a
minimum period of time of 15 days.
Although these results cannot be directly extrapolated to others regions, considering
that the majority of studies also presented removal rates specially high during the rst
days of the trails, is legitimate to assume similar results in other wind farms, which
highlights the importance of developing strict monitoring protocols, mainly regarding
survey effort. According to Table 2, within 30 monitoring studies performed in the last
decade with removal trials, 43.3% carried out daily checks for a minimum of 14 days.
Still, the majority of these studies presented monitoring protocols less strict, justied by
nancial and logistical limitations that must be contested facing these results.
In the three wind farms studied, and since the inspection periods were restricted, the
removal trials had to be performed just in two seasons (Spring and Autumn). Thus,
further research should be conducted at several other wind farms located in the same
region, especially during winter and summer, in order to determine if the differences
between the removal times remain. In fact, recent guidelines recommend that removal
trials should be performed at least four times a year [20]. As explained above, small
differences regarding the removal rates can signicantly bias the mortality estimates.
So, if no previous studies have been conducted in the vicinity of a new wind farm,
we propose that the removal trials should be performed throughout a year (to include
seasonal effects), with daily checks. Once these rigorous trails have been conducted
(considering different seasons, carcass sizes, etc.) and similar conclusions have been
achieved for the region, the team responsible for developing the monitoring program
of a new wind farm should be able to evaluate if new removal trails are really needed
or if they can be redesign. Nevertheless, it is clear that further studies are required to
optimize the trials design and achieve the best cost/benet relation.
Wi l d l i f e Bi o l o g y in Pr a c t i c e 2011, 7(2) || 9
Acknowledgments
The authors would like to thank those who took part in the eld work. We also would like to thank Bio3
Lda, for all nancial and logistical support, and Grupo GENERG – Gestão e Projectos, SA and Iberwind
Group that allowed accomplishing this study in Caramulo, Pinhal Interior and Lousã wind facilities.
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... K, number of parameters; DAIC c , difference in value of Akaike's Information Criteria (corrected for small sample size) relative to best supported model; x i , Akaike weight of the model. The observed positive correlation between carcass size and persistence after scavenging matches findings from previous studies of anthropogenic mortality, including birdwindow collisions (Ponce et al. 2010, Smallwood et al. 2010, Santos et al. 2011, Teixeira et al. 2013, Bracey et al. 2016, but see Kostecke et al. 2001, Bernardino et al. 2011, Paula et al. 2015. If carcasses are opportunistically scavenged as encountered, carcass size should only affect time to scavenging (in the sense of our definition, which is independent of whether the carcass is entirely removed) insofar as it affects carcass detectability. ...
... A possible explanation for the similar persistence times across carcass sizes is that the size of our trial carcasses did not vary substantially. The largest trial carcass was~150 g, a size matching the small or medium category for other similar studies that also considered larger carcasses, such as Ring-necked Pheasant (Phasianus colchicus;~1,000 g) and Red-legged Partridge (Alectoris rufa;~500 g; e.g., Ponce et al. 2010, Smallwood et al. 2010, Bernardino et al. 2011, Villegas-Patraca et al. 2012. Regardless of the explanation, this finding further illustrates that a full understanding of how scavengers detect and remove carcasses requires parsing apart the factors influencing the time to scavenging, whether or not any carcass remains persist after scavenging, and the time to complete carcass removal. ...
... Although Hager et al. (2012) separately recorded persistence time beyond initial scavenging, all three studies used the terms removal and scavenging interchangeably in presenting and discussing results. Failing to recognize and/or distinguish the difference between the initial scavenging event and complete carcass removal is also common for other anthropogenic mortality sources (e.g., Kostecke et al. 2001, Flint et al. 2010, Bernardino et al. 2011. Because removal may not coincide with scavenging for a large proportion of carcasses, we recommend that future studies follow the terminology used here and clearly distinguish between scavenging (an event where all or part of the carcass is taken by a scavenger) and removal (the end point of persistence, which may or may not coincide with scavenging). ...
Article
Wildlife collisions with human-built structures are a major source of direct anthropogenic mortality. Understanding and mitigating the impact of anthropogenic collisions on wildlife populations require unbiased mortality estimates. However, counts of collision fatalities are underestimated due to several bias sources, including scavenger removal of carcasses between fatality surveys and imperfect detection of carcasses present during surveys. These biases remain particularly understudied for bird-window collisions, the largest source of avian collision mortality. In Stillwater, Oklahoma, USA, we used bird carcasses collected during window collision monitoring to experimentally assess factors influencing scavenging and observer detection, and we employed trail cameras to characterize the scavenger community and timing of scavenging. We recorded nine scavenger species, but the domestic cat and Virginia opossum were responsible for 73% of known-species scavenging events. The most frequent scavenger species were primarily nocturnal, and 68% of scavenging events occurred at night. Scavenger species best predicted time to first scavenging event, season best predicted carcass persistence time, and both season and carcass size predicted whether any carcass remains persisted after scavenging. Our results also suggest that observer detection was influenced by substrate, with greater detection of carcasses on artificial substrates. Our findings related to scavenging timing have important implications for the unbiased estimation of collision mortality because the timing of peak scavenging relative to timing of peak mortality can substantially influence accuracy of adjusted mortality estimates. Further, the differences in correlates for time to first scavenging and time to carcass removal (i.e., persistence time) illustrate the importance of explicitly measuring these often-independent events that are frequently conflated in the anthropogenic mortality literature.
... Previous studies have demonstrated that carcass removal patterns are frequently modulated by seasonality (e.g. Bernardino et al., 2011;Borner et al., 2017;Prosser et al., 2008). In temperate regions, competition for carrion between vertebrate scavengers, invertebrates and microbes tend to increase during spring and summer (DeVault et al., 2004;Henrich et al., 2017;Turner et al., 2017), which can lead to the rapid disappearance of bird carcasses regardless of their size (at least up to 1-2 Kg). ...
... changes in diet, availability of other sources of food/carrion and competition with invertebrates), weather conditions and/or carcass visibility (due to changes on vegetation density). The transmission projects that bisect forests and shrublands are located mainly in central and northern Portugal, characterized for harsher weather conditions during Fall-Winter periods that can promote slower scavenging processes (Bernardino et al., 2011;Paula et al., 2015). Conversely, agroforestry systems and annual crops are located mainly in south Portugal, where weather conditions are milder and undercover vegetation is less dense in cold seasons (Simionesei et al., 2018), which may facilitate carcass detection and removal both by avian and mammalian scavengers. ...
Article
Environmental impact assessment (EIA) follow-up monitoring in energy projects, such as wind farms, solar facilities and power lines, frequently encompasses bird fatality surveys based on regular carcass searches. Since a large number of bird carcasses are often not found, field experiments to determine carcasses persistence (CP) and searcher efficiency (SE) biases in fatality surveys are typically performed for every single project. These data are, however, rarely used beyond the scope of each original project. We compiled data from CP and SE trials performed under 36 independent monitoring programs aiming to assess bird mortality at transmission lines in Portugal, whose results were until now unavailable or dispersed in grey literature. We used survival analysis and generalized linear mixed-effects models to investigate the ecological and methodological factors influencing CP times and SE rates. Bird carcass size was a key driving factor of both CP times and SE rates of human observers, which were consistently out-performed by scent detection dogs. Season and habitat interactions had also an important role in CP patterns, while variations in SE rates by human observers were largely influenced by ground visibility (i.e., a combination of ground cover and vegetation height). Our results reinforce previous studies indicating that CP and SE biases are site-specific and determined by a wide range of ecological and methodological factors not always accounted in standard trial designs. Overall, our study demonstrates that data routinely collected under bird monitoring programs from multiple projects can be combined to identify broad ecological patterns, limitations of current studies and, ultimately, improve EIA follow-up practice.
... In practice, search conditions tend to be far from this ideal and counts of observed turbine-caused wildlife fatalities will necessarily underestimate total mortality (Huso 2011), because not all turbine-caused fatalities are observed in the search process and each carcass may have a unique probability of detection depending on when or where it falls and its specific characteristics (e.g., size or color). Carcasses can be removed by scavengers very soon after they arrive (Bernardino et al. 2011;Bispo et al. 2013;Flint et al. 2010), and humans and even the best scent-dogs fail to detect some carcasses (Homan et al. 2001;Arnett 2006;Mathews et al. 2013;Beebe et al. 2016;Reyes et al. 2016). Trials designed to estimate the probability that a carcass persists to the next search must be flexible enough to allow for non-constant removal and must account for potential differences due to carcass size, season, vegetation density in which the carcass lands, and other carcass-specific factors (Bernardino et al. 2011;Bispo et al. 2013;Turner et al. 2017). ...
... Carcasses can be removed by scavengers very soon after they arrive (Bernardino et al. 2011;Bispo et al. 2013;Flint et al. 2010), and humans and even the best scent-dogs fail to detect some carcasses (Homan et al. 2001;Arnett 2006;Mathews et al. 2013;Beebe et al. 2016;Reyes et al. 2016). Trials designed to estimate the probability that a carcass persists to the next search must be flexible enough to allow for non-constant removal and must account for potential differences due to carcass size, season, vegetation density in which the carcass lands, and other carcass-specific factors (Bernardino et al. 2011;Bispo et al. 2013;Turner et al. 2017). Likewise, searcher efficiency-the ability of a searcher to find a carcass that is present-may change in time (Wolpert 2013). ...
Article
Full-text available
Estimating bird and bat mortality at wind facilities typically involves searching for carcasses on the ground near turbines. Some fraction of carcasses inevitably lie outside the search plots, and accurate mortality estimation requires accounting for those carcasses using models to extrapolate from searched to unsearched areas. Such models should account for variation in carcass density with distance, and ideally also for variation with direction (anisotropy). We compare five methods of accounting for carcasses that land outside the searched area (ratio, weighted distribution, non-parametric, and two generalized linear models (glm)) by simulating spatial arrival patterns and the detection process to mimic observations which result from surveying only, or primarily, roads and pads (R&P) and applying the five methods. Simulations vary R&P configurations, spatial carcass distributions (isotropic and anisotropic), and per turbine fatality rates. Our results suggest that the ratio method is less accurate with higher variation relative to the other four methods which all perform similarly under isotropy. All methods were biased under anisotropy; however, including direction covariates in the glm method substantially reduced bias. In addition to comparing methods of accounting for unsearched areas, we suggest a semiparametric bootstrap to produce confidence-based bounds for the proportion of carcasses that land in the searched area.
... Some of these studies have used parakeets (Melopsittacus undulates), quails (Coturnix coturnix) and partridges (Alectoris rufa). Bernardino et al. (2011) and others have used chickens and ducks, and in 11 days. Body complete, dry, with partially exposed chest and wing bones and loose primary feathers on left wing. ...
... The results of the current study are confirmed by the findings and field observations of Hull et al. (2015) for a Honey Buzzard carcass, as well as our own observations of 17 Great White Pelican carcasses in spring 2015 within and around the same wind farm (personal observation), which lasted for three months. Assessment of removal times using carcasses of different species rather than species killed within the wind farm has given shorter removal times, ranging from 1 day to a maximum of two weeks (Pain 1991, Anderson et al. 2004, Korner-Nievergelt et al. 2011, Bernardino et al. 2011, which leads to overestimation of the total number of carcasses and thus the mortality rate of birds within the operating wind farm. CONCLUSION Assessment of carcass removal times based on killed carcasses is more accurate and realistic and avoids underestimating the time of persistence of carcasses, as when different species are used. ...
Article
Full-text available
Wind farms developing rapidly in order to meet the high demand for energy from green sources. However, the impact of wind farm operation on the environment still needs to be established. The risk to wild birds is drawing the attention of stakeholders and bird conservation organizations. Carcass search is the main method used to assess the impact of wind farm operation on wild birds of various systematic groups and sizes. Assessment of the overall risk that wind farms pose to birds depends primarily on accurate calculation of carcass removal times and the detection ability of the searcher. Most studies have assessed the carcass removal time using pet bird species, pigeons, or various local birds. In Egypt, all studies conducted in operating wind farms up to 2016 had used chickens to assess the carcass removal time and in this way to the estimate the total number of bird fatalities within wind farms. The use of birds killed by a wind farm in carcass removal trials provides the actual time of carcass disappearance, in contrast with the use of other bird species. The removal times of carcasses of parakeets, quails, partridges and chickens were shorter than those of carcasses of White Stork, White Pelican, Honey Buzzard, Black Kites and eagles used in the current study and in another study in Australia. The results of the present study indicate that carcasses of birds killed within the studied wind farm remain for two to three months, while the carcasses of other in species other localities remain no more than 1 to 15 days, which unquestionably influences the calculation of total fatalities and leads to overestimation of the overall risk that wind farms for birds.
... Correction factors derived from carcass removal studies, designed to augment mortality estimates, can have a major effect on the accuracy of such estimates for wind turbines and other anthropic causes of mortality (Smallwood et al. 2010, Bernardino et al. 2011, Santos et al. 2011, Bispo et al. 2013, Teixeira et al. 2013. Our study suggests the use of surrogate species, particularly the substitution of domestic species for raptors, can bias carcass removal studies and therefore lead to inaccurate mortality estimates. ...
Article
Full-text available
Wind energy development can negatively impact bird populations due to bird–turbine collisions. To accurately estimate bird mortality at wind farms, the number of dead birds found under turbines is commonly corrected for carcass removal by scavengers, which is quantified by measuring persistence of experimental carcasses through time. These studies often use domestic birds as surrogates because carcasses of wild birds (e.g., raptors) are difficult to obtain. We assessed scavenger removal of carcasses from five bird species at simulated turbines to determine whether domestic surrogates are scavenged at a different rate than raptors, species of interest for wind turbine mortality. The percentage of carcasses scavenged during 14-d rounds ranged from 34.6% for American kestrels (Falco sparverius) to 65.4% for chickens (Gallus gallus), and the percentage of carcasses completely removed ranged from 13.5% for red-tailed hawks (Buteo jamaicensis) to 67.3% for northern bobwhites (Colinus virginianus). Carcass type (i.e., species) was the only predictor included in the best-fit logistic regression model of complete carcass removal, and a survival analysis indicated carcass type influenced elapsed time to scavenging events. Our results suggest the use of surrogate species to quantify carcass removal at wind turbines could lead to inaccurate mortality estimates.
... Relative to the period that the carcasses were monitored for removal, studies commonly used four protocols: (i) daily checks for 7 days; (ii) daily checks for 14 days; (iii) daily checks for 20 days; (iv) daily visits in the first days after carcass placement, followed by visits spaced in time Bernardino et al. 2011). In Portugal, authorities recommend a daily check during 15 days (APA 2010; ICNB 2009). ...
Book
This book presents a review of the state-of-the-art knowledge on the interactions between biodiversity and wind energy development, focused on the Portuguese reality. The volume addresses the particularities of the impact assessment procedures in Portugal, contrasting it with the international practices and presenting its main findings by covering the following broader themes: i) evaluation of spatial and temporal dynamics of wildlife affected by wind farms, including birds, bats and terrestrial mammals (in particularly Portuguese wolf population); ii) the methodologies used to assess impacts caused by this type of developments in biodiversity; iii) the best practice methodologies to implement an adaptive management approach to reconcile biodiversity and wind farms. The knowledge presented in this book was gathered through the research and development activities developed by Bioinsight company (former Bio3 company) during the last 13 years and partially funded by a R&D project designated as “Integrated solutions for biodiversity management at wind farms: reduce and compensate bird and bat mortality” (acronym: Wind & Biodiversity), co-funded by the European Regional Development Fund (FEDER), under the Regional Operational Programme of Centre (Mais Centro). This volume fills a void in the literature as a book giving insights on the best practices to install and manage a wind farm from a biodiversity management point of view, while establishing a commitment between economic sustainability and biodiversity conservation.
Article
It is often necessary to estimate the number of wind turbine collision fatalities to assess impacts to birds following construction of wind farms. Detection of bird carcasses at wind turbines in the field is affected by carcass persistence and searcher detection rate. Integrated detection trials, which integrate carcass persistence and searcher detection trials into the periodic fatality search, have been proposed as an effective method for estimating these parameters. The purpose of our study was to test whether and how environmental factors affect integrated detection trial outcomes at multiple wind farms. We conducted this study at 10 wind farms in various environments of Japan. Binary data on trial outcomes in open versus forested areas served as our response variable in a generalized additive mixed model informed by days into trial, carcass body mass, season, whether snow covered the ground, and precipitation. For both ground cover types, days into trial and body mass were included in all the top models, suggesting that these factors most influenced bird carcass detection probability in integrated trials. The best model in open areas included days into trial, body mass, snow, and precipitation, and the best model in forested areas included days into trial, body mass, snow, precipitation, and season. Values of area under the curve indicated high accuracy of the best model for both ground cover types. The survey design needs to be appropriate to the size of the target species and to the environment in which the impacts will occur, such as the site's seasonality, its ground cover, and whether snow will cover the ground. Frequency of post‐construction fatality monitoring should also be set cautiously, especially at wind farms located on small‐bird migration routes, at wind farms in open areas, in areas with snow‐covered ground in winter, or in forested areas during spring and summer because detection probabilities decline fastest under such conditions. The purpose of our study is to clarify whether and how environmental factors affect integrated detection trial outcomes at multiple wind farms in various environments of Japan. Frequency of post‐construction fatality monitoring should also be set cautiously, especially at wind farms located on small‐bird migration routes, at wind farms in open areas, with snow‐covered ground in winter, or in forested areas during spring and summer, because detection probabilities decline fastest under such conditions.
Chapter
Crete has been characterized as an area with a high wind energy capacity due to its mountainous terrain and the strong prevailing winds throughout the year. At the same time, the island constitutes the last stronghold for vulture species in Greece, currently holding the largest insular population of Eurasian griffons (Gyps fulvus) worldwide (ca. 1000 individuals). Given the empirical data on the mortality of large raptors due to collisions with wind turbine blades, the aim of the present study was to predict the potential impact of wind energy installations on the griffon vulture population on the island. The study was developed in two steps, namely, (a) the spatial mapping of the existing and planned wind energy projects up to the year 2012 and the delineation of their risk area and (b) the calculation of the annual collision rate based on the expected number of vulture risk flights and the probability of being killed. Overall, the minimum number of fatalities due to collision of vultures to wind turbines was estimated at 84 individuals per year. However, this figure could drop by over 50% if the European network of the NATURA 2000 sites was set as an exclusion zone for wind energy facilities. The study pinpoints the need for proper siting of wind farms and the prerequisite of sensitivity mapping for vulnerable species prone to collision on wind turbines.
Chapter
In the last decades, there has been a worldwide increase in wind energy. Despite its advantages, wind farms carry negative impacts on bird and bat populations, such as direct mortality due to collision with wind turbines.
Chapter
Wind energy production across the globe has grown over the years and Portugal is no exception. Like other forms of energy production, wind energy causes ecological impacts and these impacts are a matter of major concern. One of the impacts caused by operating wind farms is bird and bat casualties due to collision with the wind turbines. Since real mortality is very difficult to determine, due to the impossibility of detecting all carcasses and the probability of carcass disappearance before being detected, field methods for collecting data and estimating mortality have been implemented. Regular searches around wind turbines are implemented to detect carcasses. The protocol of searches must define the size of the searched area, the search method, the duration and frequency of the searches according to guidelines and the objectives of each study. To correct the observed mortality and estimate real mortality, correction factors, such as the probability of carcass persistence or the carcass detection rate, must be assessed by field trials. For Portugal, a search area of 5 m more than blade length and random walk or zig-zag methods resulted in a cost-effective way to collect carcasses. A frequency of 1–3 days is recommended in order to reduce the bias of mortality estimates. If a considerable number of removal trials had to be carried out, camera-trapping was revealed to be a cost-effective method. Otherwise, a carefully planned traditional method also obtained accurate estimates. For detection trials, the use of models is recommended and the number of models and the design should be adapted to homogeneity or heterogeneity of vegetation cover.
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This report summarizes the results of surveys completed during the period January 1, 1998, through December 31, 1998, at the Ponnequin Wind Energy Project in Weld County, Colorado. The surveys were conducted at two reference sites, and include a pre-construction avian abundance and use survey and raptor nesting, prey, and carcass surveys. The reference sites were situated immediately to the west of the project site in Weld County, Colorado, and 4.8 kilometers to the north of the site in Laramie County, Wyoming. The surveys were conducted along two 800-meter (m) main transects at each site with two 400-m (by 100-m) perpendicular transects. About 30 complete surveys were completed during the year, with a greater frequency of surveys in the late spring and early autumn. The surveys revealed mostly common species, with no endangered or threatened species on the sites. Small numbers of raptors were observed on or near the project and reference areas. During the winter, avian use and abundance was minimal. Prey species consisted primarily of thirteen-lined ground squirrels and northern pocket gophers. Two songbird carcasses were found. The results of these surveys, combined with data from several more months of surveys, will be compared to surveys conducted after construction of the wind farm.
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It has been estimated that from 100 million to well over 1 billion birds are killed annually in the United States due to collisions with human-made structures, including vehicles, buildings and windows, powerlines, communication towers, and wind turbines. Although wind energy is generally considered environmentally friendly (because it generates electricity without emitting air pollutants or greenhouse gases), the potential for avian fatalities has delayed and even significantly contributed to blocking the development of some windplants in the U.S. Given the importance of developing a viable renewable source of energy, the objective of this paper is to put the issue of avian mortality associated with windpower into perspective with other sources of avian collision mortality across the U.S. The purpose of this paper is to provide a detailed summary of the mortality data collected at windplants and put avian collision mortality associated with windpower development into perspective with other significant sources of avian collision mortality across the United States. We provide a summary of data collected at many of the U.S. windplants and provide annual bird fatality estimates and projections for all wind turbines in the U.S. For comparison, we also review studies of avian collision mortality from other major human-made structures and report annual bird fatality estimates for these sources. Other sources also significantly contribute to overall avian mortality. For example, the National Audubon Society estimates avian mortality due to house cats at 100 million birds per year. Pesticide use, oil spills, disease, etc., are other significant sources of unintended avian mortality. Due to funding constraints, the scope of this paper is limited to examining only avian mortality resulting from collisions with human-made obstacles.