PUBLICATIONS
Academic- and conservation-related contributions to advance our knowledge in conserving species around developments.
Protecting Black Harriers: Threats and solutions
Black Harrier Project page of the website of The Overberg Renosterveld Conservation Trust.
ORCT has partnered with harrier guru Dr Rob Simmons of the University of Cape Town, as well as with BirdLife South Africa and the Endangered Wildlife Trust to better understand Black Harriers, how they move and forage, and the greatest threats facing them. A total of 15 Black Harriers have been tagged with GPS trackers since 2020, which have led to a number of eye-opening discoveries regarding this Endangered species. Chief among these is just how reliant Black Harriers are on Renosterveld, but also how many threats they face every time they take to the skies.
ORCT has partnered with harrier guru Dr Rob Simmons of the University of Cape Town, as well as with BirdLife South Africa and the Endangered Wildlife Trust to better understand Black Harriers, how they move and forage, and the greatest threats facing them. A total of 15 Black Harriers have been tagged with GPS trackers since 2020, which have led to a number of eye-opening discoveries regarding this Endangered species. Chief among these is just how reliant Black Harriers are on Renosterveld, but also how many threats they face every time they take to the skies.
Lack of evasive behaviour by a Martial Eagle on impact with a turbine blade at a South African wind farm: causes and mitigations
SIMMONS RE, MARTINS M. 2024. Lack of evasive behaviour by a Martial Eagle Polemaetus bellicosus on impact with a turbine blade at a South African wind farm: causes and mitigations, Ostrich, 1–4.
We describe a collision of Africa’s largest raptor, the Martial Eagle Polemaetus bellicosus with a spinning blade at a South African wind farm in the Eastern Cape in July 2016, and the abandonment of the territory following a second fatal collision of an adult Martial Eagle at the same farm. Most evidence suggests that the eagle took no evasive action because she did not detect the blade due to the poor contrast abilities among raptors in general. Increasing blade visibility with black or “Signal Red” stripes is a simple and promising cost-effective mitigation action that should be further tested in South African wind farms.
We describe a collision of Africa’s largest raptor, the Martial Eagle Polemaetus bellicosus with a spinning blade at a South African wind farm in the Eastern Cape in July 2016, and the abandonment of the territory following a second fatal collision of an adult Martial Eagle at the same farm. Most evidence suggests that the eagle took no evasive action because she did not detect the blade due to the poor contrast abilities among raptors in general. Increasing blade visibility with black or “Signal Red” stripes is a simple and promising cost-effective mitigation action that should be further tested in South African wind farms.
Considerations for Blade Patterning as a mitigation measure to reduce avifaunal collisions with wind turbines in South Africa
MORKEL D, CERVANTES F, CLARKE C, RALSTON-PATON S, SCOTT-SHAW L, SIMMONS RE, TAYLOR S. 2023. Considerations for Blade Patterning as a Mitigation Measure to Reduce Avifaunal Collisions with Wind Turbines in South Africa. SAWEA and Birdlife South Africa
The vision of birds, particularly those that hunt from the air, such as birds of prey, has not evolved to perceive large, moving structures in their environment, such as wind turbines. This is largely due to birds’ physiological limitations, such as low colour contrast detection abilities, combined with motion smear created by moving, un-patterned turbine blades. This makes these species vulnerable to blade collisions, which is particularly concerning for threatened species.
The vision of birds, particularly those that hunt from the air, such as birds of prey, has not evolved to perceive large, moving structures in their environment, such as wind turbines. This is largely due to birds’ physiological limitations, such as low colour contrast detection abilities, combined with motion smear created by moving, un-patterned turbine blades. This makes these species vulnerable to blade collisions, which is particularly concerning for threatened species.
Population viability assessment of an Endangered raptor using detection/non-detection data reveals susceptibility to wind farm impacts
CERVANTES PERALTA F, MARTINS M, SIMMONS RE 2022. Population viability assessment of an Endangered raptor using detection/non-detection data reveals susceptibility to wind farm impacts. Royal Society Open Science 9: 220043
As the demand for carbon-neutral energy sources increases, so does the need to understand the impacts that thesetechnologies have on the environment. Here, we assess the potential consequences of additional mortality on an Endangered raptor recently exposed to wind farms for the first time, the Black Harrier Circus maurus, one of the world’s rarest harriers. We conduct a population viability assessment using a Bayesian model integrating life-history information and annual reporting rates from detection/non-detection surveys from the South African Bird Atlas Project. Our model estimates a global population of approximately 1300birds currently declining at 2.3% per year, and one that could collapse in under 100 years, if an average of three to five adult birds are killed annually. This level of mortality may soon exist, given the current rate of fatalities and the number of wind farms planned within the species’ distribution. Inaddition, we find that the population is sensitive to changes in climate. Our results highlight the critical need for appropriate placement, and adaptive management of windfarms and other infrastructure causing harrier mortality. We also show how detection/non-detection data may be used to infer population dynamics and viability, when population counts are unavailable.
As the demand for carbon-neutral energy sources increases, so does the need to understand the impacts that thesetechnologies have on the environment. Here, we assess the potential consequences of additional mortality on an Endangered raptor recently exposed to wind farms for the first time, the Black Harrier Circus maurus, one of the world’s rarest harriers. We conduct a population viability assessment using a Bayesian model integrating life-history information and annual reporting rates from detection/non-detection surveys from the South African Bird Atlas Project. Our model estimates a global population of approximately 1300birds currently declining at 2.3% per year, and one that could collapse in under 100 years, if an average of three to five adult birds are killed annually. This level of mortality may soon exist, given the current rate of fatalities and the number of wind farms planned within the species’ distribution. Inaddition, we find that the population is sensitive to changes in climate. Our results highlight the critical need for appropriate placement, and adaptive management of windfarms and other infrastructure causing harrier mortality. We also show how detection/non-detection data may be used to infer population dynamics and viability, when population counts are unavailable.
Staggered towers on parallel transmission lines: a new mitigation to reduce collisions of birds, especially bustards
PALLET J, SIMMONS RE, BROWN CJ. 2022. Staggered towers on parallel transmission lines: a new mitigation to reduce collisions of birds, especially bustards. Namibian Journal of Environment 6: 14-21
Significant numbers of birds are killed annually by flying into power lines across Africa, and numerous attempts have been made to mark lines to make them more conspicuous, to reduce these collisions. Results from surveys reported in this paper and many others indicate that bustards (family Otidae) are most susceptible. Bustard fatalities are not greatly reduced by adding bird diverters to earth wires. Here we propose a new mitigation measure that may reduce the number of mortalities by two-thirds where two power lines run in parallel: staggered towers. Power line surveys in Namibia and South Africa indicate that 87% of 134 bird collisions occurred in and near the middle sections of a span, while only 13% of collisions occurred near the towers themselves. Despite the skull morphology of bustards creating a blind spot immediately ahead of them, it appears that the towers are big enough to be seen (or heard) and avoided. Thus, by aligning power lines of similar size in parallel and as close as technically feasible and staggering the towers such that each tower is aligned with the mid-span of the neighbouring line, the lines may become more visible. This should allow collision-prone birds to gain altitude and fly over the lines. Theoretically, this method is expected to reduce power line fatalities by 67% for each new line. We call for experimental validation of this novel mitigation measure.
Significant numbers of birds are killed annually by flying into power lines across Africa, and numerous attempts have been made to mark lines to make them more conspicuous, to reduce these collisions. Results from surveys reported in this paper and many others indicate that bustards (family Otidae) are most susceptible. Bustard fatalities are not greatly reduced by adding bird diverters to earth wires. Here we propose a new mitigation measure that may reduce the number of mortalities by two-thirds where two power lines run in parallel: staggered towers. Power line surveys in Namibia and South Africa indicate that 87% of 134 bird collisions occurred in and near the middle sections of a span, while only 13% of collisions occurred near the towers themselves. Despite the skull morphology of bustards creating a blind spot immediately ahead of them, it appears that the towers are big enough to be seen (or heard) and avoided. Thus, by aligning power lines of similar size in parallel and as close as technically feasible and staggering the towers such that each tower is aligned with the mid-span of the neighbouring line, the lines may become more visible. This should allow collision-prone birds to gain altitude and fly over the lines. Theoretically, this method is expected to reduce power line fatalities by 67% for each new line. We call for experimental validation of this novel mitigation measure.
Black Harriers and wind energy: guidelines for impact assessment, monitoring and mitigation
SIMMONS RE, RALSTON-PATON S, COLYN R, GARCIA-HERAS MS. 2020. Black Harriers and wind energy: guidelines for impact assessment, monitoring and mitigation. Birdlife South Africa
As an Endangered species, with a very small global population and low genetic diversity, Black Harriers require concerted protection from all anthropogenic impacts. While collisions with wind turbines may be rare, harriers are not immune to this risk. Displaying, migrating and breeding harriers often fly at blade heights and therefore may collide with turbines. Black Harriers, especially breeding birds may also be negatively affected by disturbance associated with the construction, operation and maintenance of wind energy facilities (WEFs). These guidelines present the most up to date research findings on Black Harriers, combined with contemporary overseas research on other harrier species and WEFs. Where data are limited, recommendations have been supplemented with expert opinion.
As an Endangered species, with a very small global population and low genetic diversity, Black Harriers require concerted protection from all anthropogenic impacts. While collisions with wind turbines may be rare, harriers are not immune to this risk. Displaying, migrating and breeding harriers often fly at blade heights and therefore may collide with turbines. Black Harriers, especially breeding birds may also be negatively affected by disturbance associated with the construction, operation and maintenance of wind energy facilities (WEFs). These guidelines present the most up to date research findings on Black Harriers, combined with contemporary overseas research on other harrier species and WEFs. Where data are limited, recommendations have been supplemented with expert opinion.
Migratory patterns and settlement areas revealed by remote sensing in an endangered intra-African migrant, the Black Harrier
GARCIA-HERAS M-S, MOUGEOT F, ARROYO B, BILDSTEIN KL, THERRIEN J-F, SIMMONS RE. 2019. Migratory patterns and settlement areas revealed by remote sensing in an endangered intra-African migrant, the Black Harrier (Circus maurus). PLOS ONE 14(1): e0210756
Annual movements have been widely described for birds migrating across the Americas and between Eurasia and Africa, yet relatively little information exists for intra-African migrants. Identifying the areas used throughout a species annual cycle by understanding migratory patterns and settlement areas during breeding and non-breeding seasons is essential for conservation initiatives. Here, we describe for the first time, the migratory patterns and settlement areas of an endangered raptor endemic to Southern Africa, the Black Harrier (Circus maurus). From 2008 to 2015, thirteen breeding adult Black Harriers were trapped in south-western South Africa and fitted either with a GPS-GSM or with a PTT tracker device. Adults were monitored for 365 ± 198 days (range: 56–819 days) revealing great individual variability in annual movements. Most Black Harriers performed an unusual West-East migration from their breeding areas, but routes of all migrating individuals covered the entire southern land area of South Africa and Lesotho. The distance travelled averaged 814 ± 324 km, but unlike many other species, migrants travelled faster during post-breeding (i.e. austral summer) (207.8 ± 113.2 km.day-1) than during pre-breeding (i.e. austral winter/spring) migrations (143.8 ± 32.2 km.day-1). Although most marked individuals displayed movements similar to those that bred following pre-breeding migrations, only two of thirteen were confirmed as breeders the year after being tagged. This suggests that individuals may sometimes take a sabbatical year in reproduction, although this requires confirmation. Most tagged birds died on migration or during the non-breeding season. Adults frequently returned to the same non-breeding settlement areas, and often used up to 3 different locations an average of about 200 km apart. On the other hand, there was wide variation in distance between subsequent reproductive events. We discuss the implications of our study for the conservation of Black Harriers and more broadly for intra-African bird migrants.
Annual movements have been widely described for birds migrating across the Americas and between Eurasia and Africa, yet relatively little information exists for intra-African migrants. Identifying the areas used throughout a species annual cycle by understanding migratory patterns and settlement areas during breeding and non-breeding seasons is essential for conservation initiatives. Here, we describe for the first time, the migratory patterns and settlement areas of an endangered raptor endemic to Southern Africa, the Black Harrier (Circus maurus). From 2008 to 2015, thirteen breeding adult Black Harriers were trapped in south-western South Africa and fitted either with a GPS-GSM or with a PTT tracker device. Adults were monitored for 365 ± 198 days (range: 56–819 days) revealing great individual variability in annual movements. Most Black Harriers performed an unusual West-East migration from their breeding areas, but routes of all migrating individuals covered the entire southern land area of South Africa and Lesotho. The distance travelled averaged 814 ± 324 km, but unlike many other species, migrants travelled faster during post-breeding (i.e. austral summer) (207.8 ± 113.2 km.day-1) than during pre-breeding (i.e. austral winter/spring) migrations (143.8 ± 32.2 km.day-1). Although most marked individuals displayed movements similar to those that bred following pre-breeding migrations, only two of thirteen were confirmed as breeders the year after being tagged. This suggests that individuals may sometimes take a sabbatical year in reproduction, although this requires confirmation. Most tagged birds died on migration or during the non-breeding season. Adults frequently returned to the same non-breeding settlement areas, and often used up to 3 different locations an average of about 200 km apart. On the other hand, there was wide variation in distance between subsequent reproductive events. We discuss the implications of our study for the conservation of Black Harriers and more broadly for intra-African bird migrants.
Photographic record of a Martial Eagle killed at Jeffreys Bay wind farm
This short note describes an eye-witness and photographic account of the death of a juvenile Martial Eagle at the Jeffreys Bay Wind farm in winter 2016. The bird’s behaviour prior to, and after, being struck by a turbine blade and a post-mortem X-ray are described. This is the first record of a Martial Eagle killed at an operational wind farm and may be the first witnessed death of a collision-prone bird at a wind farm in South Africa.
A molecular phylogeny of the harriers (Circus, Accipitridae) indicate the role of long distance dispersal and migration in diversification
OATLEY G. SIMMONS RE, FUCHS J. 2015. A molecular phylogeny of the harriers (Circus, Accipitridae) indicate the role of long distance dispersal and migration in diversification. Molecular Phylogenetics and Evolution 85: 150–160.
The monophyly of the raptorial Circus genus (harriers) has never been in question, but the specific status of many, often vulnerable island endemic, taxa remains uncertain. Here we utilise one mitochondrial and three nuclear loci from all currently recognised Circus taxa (species and subspecies) to infer a robust phylogeny, to estimate the divergence date and to reconstruct the biogeographic origins of the Circus group. Our phylogeny supports both the monophyly of Circus and polyphyly of the genus Accipiter. Depending on the rate of molecular clock used, the emergence of the harrier clade took place between 4.9 and 12.2 mya which coincides with the worldwide formation of open habitats which extant harriers now exploit. The sister relationship of the Northern Harrier C. cyaneus hudsonius and the Cinereous Harrier C. cinereus contradicts previous classifications that treated the former as conspecific with the Hen Harrier C. cyaneus cyaneus. Thus both should be elevated to species status: C. hudsonius and C. cyaneus. Further, the African Marsh C. ranivorus and the European Marsh C. aeruginosus Harriers emerge as sister species. The remaining marsh harriers exhibit very little genetic diversity, and are all recently diverged taxa that exhibit allopatric distributions. Considering their sister relationship and geographic proximity, we recommend treating C. approximans and C. spilonotus spilothorax as subspecies of C. approximans. For C. spilonotus spilonotus C. maillardi maillardi and C. maillardi macrosceles, their plumage and morphometric differences, phylogenetic relationship and geographic distributions make lumping of these taxa as a single species complicated. We thus propose to recognise as separate, recently evolved species: C. spilonotus, C. maillardi and C. macrosceles. Biogeographic inferences on the ancestral origin of harriers are uncertain, indicating that the harriers emerged in either the Neotropics, Palearctic or Australasia. We are, however, able to show that speciation within the harriers was driven by long range dispersal and migration events.
The monophyly of the raptorial Circus genus (harriers) has never been in question, but the specific status of many, often vulnerable island endemic, taxa remains uncertain. Here we utilise one mitochondrial and three nuclear loci from all currently recognised Circus taxa (species and subspecies) to infer a robust phylogeny, to estimate the divergence date and to reconstruct the biogeographic origins of the Circus group. Our phylogeny supports both the monophyly of Circus and polyphyly of the genus Accipiter. Depending on the rate of molecular clock used, the emergence of the harrier clade took place between 4.9 and 12.2 mya which coincides with the worldwide formation of open habitats which extant harriers now exploit. The sister relationship of the Northern Harrier C. cyaneus hudsonius and the Cinereous Harrier C. cinereus contradicts previous classifications that treated the former as conspecific with the Hen Harrier C. cyaneus cyaneus. Thus both should be elevated to species status: C. hudsonius and C. cyaneus. Further, the African Marsh C. ranivorus and the European Marsh C. aeruginosus Harriers emerge as sister species. The remaining marsh harriers exhibit very little genetic diversity, and are all recently diverged taxa that exhibit allopatric distributions. Considering their sister relationship and geographic proximity, we recommend treating C. approximans and C. spilonotus spilothorax as subspecies of C. approximans. For C. spilonotus spilonotus C. maillardi maillardi and C. maillardi macrosceles, their plumage and morphometric differences, phylogenetic relationship and geographic distributions make lumping of these taxa as a single species complicated. We thus propose to recognise as separate, recently evolved species: C. spilonotus, C. maillardi and C. macrosceles. Biogeographic inferences on the ancestral origin of harriers are uncertain, indicating that the harriers emerged in either the Neotropics, Palearctic or Australasia. We are, however, able to show that speciation within the harriers was driven by long range dispersal and migration events.
Lack of mtDNA genetic diversity in the Black Harrier Circus maurus, a Southern African endemic
FUCHS J, SIMMONS RE, MINDELL DP, BOWIE RCK, OATLEY G. 2014. Lack of mtDNA genetic diversity in the Black Harrier Circus maurus, a southern African endemic. Ibis 156: 227-230
The Black Harrier Circus maurus is one of the three rarest endemic avian species in South Africa (Curtis et al. 2004, Simmons et al. 2005), and certainly the rarest endemic raptor. Global populations of breeding Black Harriers are currently estimated at under 1000 mature individuals, mostly in the Northern and Western Cape (especially the south western corner: Curtis et al. 2004) provinces of South Africa, and sighted less frequently in the Eastern Cape and Kwazulu-Natal (Simmons et al. 2005). They nest primarily in protected areas and remnant patches of renosterveld in the Overberg, which has been highly fragmented by agriculture (Curtis et al. 2004), further reducing the suitable habitat for this species. Recent satellite-tagging studies have revealed that the birds in the Western Cape move freely to the east of the country and may spend the summer in Lesotho and the Free State. This suggests that the Eastern Cape and Free State population is not independent of the Western Cape core of the species' distribution and that the world population may be smaller than assumed (1000 adults). These factors have led to the species' recent reclassification as Endangered in South Africa's revised red data book (M. Taylor in litt. 2012). With a small population size, its increasingly degraded and fragmented habitat, and satellite data suggesting that the core Western Cape population may be smaller than estimated, it has become imperative to determine the species' genetic structure, to help ensure that divergent lineages are protected. Here, we assess the mitochondrial DNA (mtDNA) genetic diversity for breeding adults sampled throughout the species' range and screened two nuclear introns for a subset of the individuals.
The Black Harrier Circus maurus is one of the three rarest endemic avian species in South Africa (Curtis et al. 2004, Simmons et al. 2005), and certainly the rarest endemic raptor. Global populations of breeding Black Harriers are currently estimated at under 1000 mature individuals, mostly in the Northern and Western Cape (especially the south western corner: Curtis et al. 2004) provinces of South Africa, and sighted less frequently in the Eastern Cape and Kwazulu-Natal (Simmons et al. 2005). They nest primarily in protected areas and remnant patches of renosterveld in the Overberg, which has been highly fragmented by agriculture (Curtis et al. 2004), further reducing the suitable habitat for this species. Recent satellite-tagging studies have revealed that the birds in the Western Cape move freely to the east of the country and may spend the summer in Lesotho and the Free State. This suggests that the Eastern Cape and Free State population is not independent of the Western Cape core of the species' distribution and that the world population may be smaller than assumed (1000 adults). These factors have led to the species' recent reclassification as Endangered in South Africa's revised red data book (M. Taylor in litt. 2012). With a small population size, its increasingly degraded and fragmented habitat, and satellite data suggesting that the core Western Cape population may be smaller than estimated, it has become imperative to determine the species' genetic structure, to help ensure that divergent lineages are protected. Here, we assess the mitochondrial DNA (mtDNA) genetic diversity for breeding adults sampled throughout the species' range and screened two nuclear introns for a subset of the individuals.
The value of the Black Harrier as a predictor of biodiversity in the plant-rich Cape Floral Kingdom, South Africa
JENKINS J, SIMMONS RE, CURTIS O, ATYEO, M, RAIMONDO D, JENKINS AR. 2013. The value of the Black Harrier (Circus maurus) as a predictor of biodiversity in the plant-rich Cape Floral Kingdom, South Africa. Bird Conservation International 23:66-77.
Determining the efficacy of using indicator species to predict the spatial location of biodiversity hotspots is one way of maximising the conservation of biodiversity in already threatened habitats. Recent evidence from Europe suggests raptors can play such an indicator role, so we tested this approach with a globally threatened southern hemisphere species, the Black Harrier Circus maurus. We asked if this species, found in South Africa’s mega-diverse Cape Floral Kingdom, breeds in habitat fragments that were more diverse in terms of small mammals, birds and plants than unoccupied fragments of similar size. Renosterveld is a highly fragmented habitat that has lost > 90% of its original extent and remains only on privately-owned lands. Surveys of small mammals, birds and plants undertaken in 20 fragments in the Overberg region, South Africa, revealed nine with breeding harriers and 11 without harriers. Harrier-occupied fragments were associated with a 3.5 fold higher number of bird species and higher small mammal species richness than unoccupied ones. There was a lower abundance of most plants in occupied patches, except for red grass Themeda triandra which is an indicator of pristine renosterveld. Vegetation structure was significantly different, with harriers nesting on patches with taller, more open vegetation. While the diversity trends were not statistically significant, a positive trend between the presence of harriers and higher abundance of red grass – as an indicator of the more pristine state of the patch, suggests that harriers might allow biodiversity managers a heuristic approach for selecting the remaining patches of pristine renosterveld. The need for intensive sampling of several taxa leads to small samples and a lack of clear-cut trends for these top predators as indicators of plant diversity.
Determining the efficacy of using indicator species to predict the spatial location of biodiversity hotspots is one way of maximising the conservation of biodiversity in already threatened habitats. Recent evidence from Europe suggests raptors can play such an indicator role, so we tested this approach with a globally threatened southern hemisphere species, the Black Harrier Circus maurus. We asked if this species, found in South Africa’s mega-diverse Cape Floral Kingdom, breeds in habitat fragments that were more diverse in terms of small mammals, birds and plants than unoccupied fragments of similar size. Renosterveld is a highly fragmented habitat that has lost > 90% of its original extent and remains only on privately-owned lands. Surveys of small mammals, birds and plants undertaken in 20 fragments in the Overberg region, South Africa, revealed nine with breeding harriers and 11 without harriers. Harrier-occupied fragments were associated with a 3.5 fold higher number of bird species and higher small mammal species richness than unoccupied ones. There was a lower abundance of most plants in occupied patches, except for red grass Themeda triandra which is an indicator of pristine renosterveld. Vegetation structure was significantly different, with harriers nesting on patches with taller, more open vegetation. While the diversity trends were not statistically significant, a positive trend between the presence of harriers and higher abundance of red grass – as an indicator of the more pristine state of the patch, suggests that harriers might allow biodiversity managers a heuristic approach for selecting the remaining patches of pristine renosterveld. The need for intensive sampling of several taxa leads to small samples and a lack of clear-cut trends for these top predators as indicators of plant diversity.
Greater Kestrel survives impact with power line
SIMMONS RE, 2011 Greater Kestrel survives impact with power line. Ostrich 81: 75 -76
Here I describe the circumstances in which a Greater Kestrel Falco rupicoloides struck a power line and apparently survived.
Here I describe the circumstances in which a Greater Kestrel Falco rupicoloides struck a power line and apparently survived.
Protecting Black Harriers: Threats and solutions
Black Harrier Project page of the website of The Overberg Renosterveld Conservation Trust.
ORCT has partnered with harrier guru Dr Rob Simmons of the University of Cape Town, as well as with BirdLife South Africa and the Endangered Wildlife Trust to better understand Black Harriers, how they move and forage, and the greatest threats facing them. A total of 15 Black Harriers have been tagged with GPS trackers since 2020, which have led to a number of eye-opening discoveries regarding this Endangered species. Chief among these is just how reliant Black Harriers are on Renosterveld, but also how many threats they face every time they take to the skies.
ORCT has partnered with harrier guru Dr Rob Simmons of the University of Cape Town, as well as with BirdLife South Africa and the Endangered Wildlife Trust to better understand Black Harriers, how they move and forage, and the greatest threats facing them. A total of 15 Black Harriers have been tagged with GPS trackers since 2020, which have led to a number of eye-opening discoveries regarding this Endangered species. Chief among these is just how reliant Black Harriers are on Renosterveld, but also how many threats they face every time they take to the skies.
Lack of evasive behaviour by a Martial Eagle on impact with a turbine blade at a South African wind farm: causes and mitigations
SIMMONS RE, MARTINS M. 2024. Lack of evasive behaviour by a Martial Eagle Polemaetus bellicosus on impact with a turbine blade at a South African wind farm: causes and mitigations, Ostrich, 1–4.
We describe a collision of Africa’s largest raptor, the Martial Eagle Polemaetus bellicosus with a spinning blade at a South African wind farm in the Eastern Cape in July 2016, and the abandonment of the territory following a second fatal collision of an adult Martial Eagle at the same farm. Most evidence suggests that the eagle took no evasive action because she did not detect the blade due to the poor contrast abilities among raptors in general. Increasing blade visibility with black or “Signal Red” stripes is a simple and promising cost-effective mitigation action that should be further tested in South African wind farms.
We describe a collision of Africa’s largest raptor, the Martial Eagle Polemaetus bellicosus with a spinning blade at a South African wind farm in the Eastern Cape in July 2016, and the abandonment of the territory following a second fatal collision of an adult Martial Eagle at the same farm. Most evidence suggests that the eagle took no evasive action because she did not detect the blade due to the poor contrast abilities among raptors in general. Increasing blade visibility with black or “Signal Red” stripes is a simple and promising cost-effective mitigation action that should be further tested in South African wind farms.
Considerations for Blade Patterning as a mitigation measure to reduce avifaunal collisions with wind turbines in South Africa
MORKEL D, CERVANTES F, CLARKE C, RALSTON-PATON S, SCOTT-SHAW L, SIMMONS RE, TAYLOR S. 2023. Considerations for Blade Patterning as a Mitigation Measure to Reduce Avifaunal Collisions with Wind Turbines in South Africa. SAWEA and Birdlife South Africa
The vision of birds, particularly those that hunt from the air, such as birds of prey, has not evolved to perceive large, moving structures in their environment, such as wind turbines. This is largely due to birds’ physiological limitations, such as low colour contrast detection abilities, combined with motion smear created by moving, un-patterned turbine blades. This makes these species vulnerable to blade collisions, which is particularly concerning for threatened species.
The vision of birds, particularly those that hunt from the air, such as birds of prey, has not evolved to perceive large, moving structures in their environment, such as wind turbines. This is largely due to birds’ physiological limitations, such as low colour contrast detection abilities, combined with motion smear created by moving, un-patterned turbine blades. This makes these species vulnerable to blade collisions, which is particularly concerning for threatened species.
Population viability assessment of an Endangered raptor using detection/non-detection data reveals susceptibility to wind farm impacts
CERVANTES PERALTA F, MARTINS M, SIMMONS RE 2022. Population viability assessment of an Endangered raptor using detection/non-detection data reveals susceptibility to wind farm impacts. Royal Society Open Science 9: 220043
As the demand for carbon-neutral energy sources increases, so does the need to understand the impacts that thesetechnologies have on the environment. Here, we assess the potential consequences of additional mortality on an Endangered raptor recently exposed to wind farms for the first time, the Black Harrier Circus maurus, one of the world’s rarest harriers. We conduct a population viability assessment using a Bayesian model integrating life-history information and annual reporting rates from detection/non-detection surveys from the South African Bird Atlas Project. Our model estimates a global population of approximately 1300birds currently declining at 2.3% per year, and one that could collapse in under 100 years, if an average of three to five adult birds are killed annually. This level of mortality may soon exist, given the current rate of fatalities and the number of wind farms planned within the species’ distribution. Inaddition, we find that the population is sensitive to changes in climate. Our results highlight the critical need for appropriate placement, and adaptive management of windfarms and other infrastructure causing harrier mortality. We also show how detection/non-detection data may be used to infer population dynamics and viability, when population counts are unavailable.
As the demand for carbon-neutral energy sources increases, so does the need to understand the impacts that thesetechnologies have on the environment. Here, we assess the potential consequences of additional mortality on an Endangered raptor recently exposed to wind farms for the first time, the Black Harrier Circus maurus, one of the world’s rarest harriers. We conduct a population viability assessment using a Bayesian model integrating life-history information and annual reporting rates from detection/non-detection surveys from the South African Bird Atlas Project. Our model estimates a global population of approximately 1300birds currently declining at 2.3% per year, and one that could collapse in under 100 years, if an average of three to five adult birds are killed annually. This level of mortality may soon exist, given the current rate of fatalities and the number of wind farms planned within the species’ distribution. Inaddition, we find that the population is sensitive to changes in climate. Our results highlight the critical need for appropriate placement, and adaptive management of windfarms and other infrastructure causing harrier mortality. We also show how detection/non-detection data may be used to infer population dynamics and viability, when population counts are unavailable.
Staggered towers on parallel transmission lines: a new mitigation to reduce collisions of birds, especially bustards
PALLET J, SIMMONS RE, BROWN CJ. 2022. Staggered towers on parallel transmission lines: a new mitigation to reduce collisions of birds, especially bustards. Namibian Journal of Environment 6: 14-21
Significant numbers of birds are killed annually by flying into power lines across Africa, and numerous attempts have been made to mark lines to make them more conspicuous, to reduce these collisions. Results from surveys reported in this paper and many others indicate that bustards (family Otidae) are most susceptible. Bustard fatalities are not greatly reduced by adding bird diverters to earth wires. Here we propose a new mitigation measure that may reduce the number of mortalities by two-thirds where two power lines run in parallel: staggered towers. Power line surveys in Namibia and South Africa indicate that 87% of 134 bird collisions occurred in and near the middle sections of a span, while only 13% of collisions occurred near the towers themselves. Despite the skull morphology of bustards creating a blind spot immediately ahead of them, it appears that the towers are big enough to be seen (or heard) and avoided. Thus, by aligning power lines of similar size in parallel and as close as technically feasible and staggering the towers such that each tower is aligned with the mid-span of the neighbouring line, the lines may become more visible. This should allow collision-prone birds to gain altitude and fly over the lines. Theoretically, this method is expected to reduce power line fatalities by 67% for each new line. We call for experimental validation of this novel mitigation measure.
Significant numbers of birds are killed annually by flying into power lines across Africa, and numerous attempts have been made to mark lines to make them more conspicuous, to reduce these collisions. Results from surveys reported in this paper and many others indicate that bustards (family Otidae) are most susceptible. Bustard fatalities are not greatly reduced by adding bird diverters to earth wires. Here we propose a new mitigation measure that may reduce the number of mortalities by two-thirds where two power lines run in parallel: staggered towers. Power line surveys in Namibia and South Africa indicate that 87% of 134 bird collisions occurred in and near the middle sections of a span, while only 13% of collisions occurred near the towers themselves. Despite the skull morphology of bustards creating a blind spot immediately ahead of them, it appears that the towers are big enough to be seen (or heard) and avoided. Thus, by aligning power lines of similar size in parallel and as close as technically feasible and staggering the towers such that each tower is aligned with the mid-span of the neighbouring line, the lines may become more visible. This should allow collision-prone birds to gain altitude and fly over the lines. Theoretically, this method is expected to reduce power line fatalities by 67% for each new line. We call for experimental validation of this novel mitigation measure.
Black Harriers and wind energy: guidelines for impact assessment, monitoring and mitigation
SIMMONS RE, RALSTON-PATON S, COLYN R, GARCIA-HERAS MS. 2020. Black Harriers and wind energy: guidelines for impact assessment, monitoring and mitigation. Birdlife South Africa
As an Endangered species, with a very small global population and low genetic diversity, Black Harriers require concerted protection from all anthropogenic impacts. While collisions with wind turbines may be rare, harriers are not immune to this risk. Displaying, migrating and breeding harriers often fly at blade heights and therefore may collide with turbines. Black Harriers, especially breeding birds may also be negatively affected by disturbance associated with the construction, operation and maintenance of wind energy facilities (WEFs). These guidelines present the most up to date research findings on Black Harriers, combined with contemporary overseas research on other harrier species and WEFs. Where data are limited, recommendations have been supplemented with expert opinion.
As an Endangered species, with a very small global population and low genetic diversity, Black Harriers require concerted protection from all anthropogenic impacts. While collisions with wind turbines may be rare, harriers are not immune to this risk. Displaying, migrating and breeding harriers often fly at blade heights and therefore may collide with turbines. Black Harriers, especially breeding birds may also be negatively affected by disturbance associated with the construction, operation and maintenance of wind energy facilities (WEFs). These guidelines present the most up to date research findings on Black Harriers, combined with contemporary overseas research on other harrier species and WEFs. Where data are limited, recommendations have been supplemented with expert opinion.
Migratory patterns and settlement areas revealed by remote sensing in an endangered intra-African migrant, the Black Harrier
GARCIA-HERAS M-S, MOUGEOT F, ARROYO B, BILDSTEIN KL, THERRIEN J-F, SIMMONS RE. 2019. Migratory patterns and settlement areas revealed by remote sensing in an endangered intra-African migrant, the Black Harrier (Circus maurus). PLOS ONE 14(1): e0210756
Annual movements have been widely described for birds migrating across the Americas and between Eurasia and Africa, yet relatively little information exists for intra-African migrants. Identifying the areas used throughout a species annual cycle by understanding migratory patterns and settlement areas during breeding and non-breeding seasons is essential for conservation initiatives. Here, we describe for the first time, the migratory patterns and settlement areas of an endangered raptor endemic to Southern Africa, the Black Harrier (Circus maurus). From 2008 to 2015, thirteen breeding adult Black Harriers were trapped in south-western South Africa and fitted either with a GPS-GSM or with a PTT tracker device. Adults were monitored for 365 ± 198 days (range: 56–819 days) revealing great individual variability in annual movements. Most Black Harriers performed an unusual West-East migration from their breeding areas, but routes of all migrating individuals covered the entire southern land area of South Africa and Lesotho. The distance travelled averaged 814 ± 324 km, but unlike many other species, migrants travelled faster during post-breeding (i.e. austral summer) (207.8 ± 113.2 km.day-1) than during pre-breeding (i.e. austral winter/spring) migrations (143.8 ± 32.2 km.day-1). Although most marked individuals displayed movements similar to those that bred following pre-breeding migrations, only two of thirteen were confirmed as breeders the year after being tagged. This suggests that individuals may sometimes take a sabbatical year in reproduction, although this requires confirmation. Most tagged birds died on migration or during the non-breeding season. Adults frequently returned to the same non-breeding settlement areas, and often used up to 3 different locations an average of about 200 km apart. On the other hand, there was wide variation in distance between subsequent reproductive events. We discuss the implications of our study for the conservation of Black Harriers and more broadly for intra-African bird migrants.
Annual movements have been widely described for birds migrating across the Americas and between Eurasia and Africa, yet relatively little information exists for intra-African migrants. Identifying the areas used throughout a species annual cycle by understanding migratory patterns and settlement areas during breeding and non-breeding seasons is essential for conservation initiatives. Here, we describe for the first time, the migratory patterns and settlement areas of an endangered raptor endemic to Southern Africa, the Black Harrier (Circus maurus). From 2008 to 2015, thirteen breeding adult Black Harriers were trapped in south-western South Africa and fitted either with a GPS-GSM or with a PTT tracker device. Adults were monitored for 365 ± 198 days (range: 56–819 days) revealing great individual variability in annual movements. Most Black Harriers performed an unusual West-East migration from their breeding areas, but routes of all migrating individuals covered the entire southern land area of South Africa and Lesotho. The distance travelled averaged 814 ± 324 km, but unlike many other species, migrants travelled faster during post-breeding (i.e. austral summer) (207.8 ± 113.2 km.day-1) than during pre-breeding (i.e. austral winter/spring) migrations (143.8 ± 32.2 km.day-1). Although most marked individuals displayed movements similar to those that bred following pre-breeding migrations, only two of thirteen were confirmed as breeders the year after being tagged. This suggests that individuals may sometimes take a sabbatical year in reproduction, although this requires confirmation. Most tagged birds died on migration or during the non-breeding season. Adults frequently returned to the same non-breeding settlement areas, and often used up to 3 different locations an average of about 200 km apart. On the other hand, there was wide variation in distance between subsequent reproductive events. We discuss the implications of our study for the conservation of Black Harriers and more broadly for intra-African bird migrants.
Photographic record of a Martial Eagle killed at Jeffreys Bay wind farm
This short note describes an eye-witness and photographic account of the death of a juvenile Martial Eagle at the Jeffreys Bay Wind farm in winter 2016. The bird’s behaviour prior to, and after, being struck by a turbine blade and a post-mortem X-ray are described. This is the first record of a Martial Eagle killed at an operational wind farm and may be the first witnessed death of a collision-prone bird at a wind farm in South Africa.
A molecular phylogeny of the harriers (Circus, Accipitridae) indicate the role of long distance dispersal and migration in diversification
OATLEY G. SIMMONS RE, FUCHS J. 2015. A molecular phylogeny of the harriers (Circus, Accipitridae) indicate the role of long distance dispersal and migration in diversification. Molecular Phylogenetics and Evolution 85: 150–160.
The monophyly of the raptorial Circus genus (harriers) has never been in question, but the specific status of many, often vulnerable island endemic, taxa remains uncertain. Here we utilise one mitochondrial and three nuclear loci from all currently recognised Circus taxa (species and subspecies) to infer a robust phylogeny, to estimate the divergence date and to reconstruct the biogeographic origins of the Circus group. Our phylogeny supports both the monophyly of Circus and polyphyly of the genus Accipiter. Depending on the rate of molecular clock used, the emergence of the harrier clade took place between 4.9 and 12.2 mya which coincides with the worldwide formation of open habitats which extant harriers now exploit. The sister relationship of the Northern Harrier C. cyaneus hudsonius and the Cinereous Harrier C. cinereus contradicts previous classifications that treated the former as conspecific with the Hen Harrier C. cyaneus cyaneus. Thus both should be elevated to species status: C. hudsonius and C. cyaneus. Further, the African Marsh C. ranivorus and the European Marsh C. aeruginosus Harriers emerge as sister species. The remaining marsh harriers exhibit very little genetic diversity, and are all recently diverged taxa that exhibit allopatric distributions. Considering their sister relationship and geographic proximity, we recommend treating C. approximans and C. spilonotus spilothorax as subspecies of C. approximans. For C. spilonotus spilonotus C. maillardi maillardi and C. maillardi macrosceles, their plumage and morphometric differences, phylogenetic relationship and geographic distributions make lumping of these taxa as a single species complicated. We thus propose to recognise as separate, recently evolved species: C. spilonotus, C. maillardi and C. macrosceles. Biogeographic inferences on the ancestral origin of harriers are uncertain, indicating that the harriers emerged in either the Neotropics, Palearctic or Australasia. We are, however, able to show that speciation within the harriers was driven by long range dispersal and migration events.
The monophyly of the raptorial Circus genus (harriers) has never been in question, but the specific status of many, often vulnerable island endemic, taxa remains uncertain. Here we utilise one mitochondrial and three nuclear loci from all currently recognised Circus taxa (species and subspecies) to infer a robust phylogeny, to estimate the divergence date and to reconstruct the biogeographic origins of the Circus group. Our phylogeny supports both the monophyly of Circus and polyphyly of the genus Accipiter. Depending on the rate of molecular clock used, the emergence of the harrier clade took place between 4.9 and 12.2 mya which coincides with the worldwide formation of open habitats which extant harriers now exploit. The sister relationship of the Northern Harrier C. cyaneus hudsonius and the Cinereous Harrier C. cinereus contradicts previous classifications that treated the former as conspecific with the Hen Harrier C. cyaneus cyaneus. Thus both should be elevated to species status: C. hudsonius and C. cyaneus. Further, the African Marsh C. ranivorus and the European Marsh C. aeruginosus Harriers emerge as sister species. The remaining marsh harriers exhibit very little genetic diversity, and are all recently diverged taxa that exhibit allopatric distributions. Considering their sister relationship and geographic proximity, we recommend treating C. approximans and C. spilonotus spilothorax as subspecies of C. approximans. For C. spilonotus spilonotus C. maillardi maillardi and C. maillardi macrosceles, their plumage and morphometric differences, phylogenetic relationship and geographic distributions make lumping of these taxa as a single species complicated. We thus propose to recognise as separate, recently evolved species: C. spilonotus, C. maillardi and C. macrosceles. Biogeographic inferences on the ancestral origin of harriers are uncertain, indicating that the harriers emerged in either the Neotropics, Palearctic or Australasia. We are, however, able to show that speciation within the harriers was driven by long range dispersal and migration events.
Lack of mtDNA genetic diversity in the Black Harrier Circus maurus, a Southern African endemic
FUCHS J, SIMMONS RE, MINDELL DP, BOWIE RCK, OATLEY G. 2014. Lack of mtDNA genetic diversity in the Black Harrier Circus maurus, a southern African endemic. Ibis 156: 227-230
The Black Harrier Circus maurus is one of the three rarest endemic avian species in South Africa (Curtis et al. 2004, Simmons et al. 2005), and certainly the rarest endemic raptor. Global populations of breeding Black Harriers are currently estimated at under 1000 mature individuals, mostly in the Northern and Western Cape (especially the south western corner: Curtis et al. 2004) provinces of South Africa, and sighted less frequently in the Eastern Cape and Kwazulu-Natal (Simmons et al. 2005). They nest primarily in protected areas and remnant patches of renosterveld in the Overberg, which has been highly fragmented by agriculture (Curtis et al. 2004), further reducing the suitable habitat for this species. Recent satellite-tagging studies have revealed that the birds in the Western Cape move freely to the east of the country and may spend the summer in Lesotho and the Free State. This suggests that the Eastern Cape and Free State population is not independent of the Western Cape core of the species' distribution and that the world population may be smaller than assumed (1000 adults). These factors have led to the species' recent reclassification as Endangered in South Africa's revised red data book (M. Taylor in litt. 2012). With a small population size, its increasingly degraded and fragmented habitat, and satellite data suggesting that the core Western Cape population may be smaller than estimated, it has become imperative to determine the species' genetic structure, to help ensure that divergent lineages are protected. Here, we assess the mitochondrial DNA (mtDNA) genetic diversity for breeding adults sampled throughout the species' range and screened two nuclear introns for a subset of the individuals.
The Black Harrier Circus maurus is one of the three rarest endemic avian species in South Africa (Curtis et al. 2004, Simmons et al. 2005), and certainly the rarest endemic raptor. Global populations of breeding Black Harriers are currently estimated at under 1000 mature individuals, mostly in the Northern and Western Cape (especially the south western corner: Curtis et al. 2004) provinces of South Africa, and sighted less frequently in the Eastern Cape and Kwazulu-Natal (Simmons et al. 2005). They nest primarily in protected areas and remnant patches of renosterveld in the Overberg, which has been highly fragmented by agriculture (Curtis et al. 2004), further reducing the suitable habitat for this species. Recent satellite-tagging studies have revealed that the birds in the Western Cape move freely to the east of the country and may spend the summer in Lesotho and the Free State. This suggests that the Eastern Cape and Free State population is not independent of the Western Cape core of the species' distribution and that the world population may be smaller than assumed (1000 adults). These factors have led to the species' recent reclassification as Endangered in South Africa's revised red data book (M. Taylor in litt. 2012). With a small population size, its increasingly degraded and fragmented habitat, and satellite data suggesting that the core Western Cape population may be smaller than estimated, it has become imperative to determine the species' genetic structure, to help ensure that divergent lineages are protected. Here, we assess the mitochondrial DNA (mtDNA) genetic diversity for breeding adults sampled throughout the species' range and screened two nuclear introns for a subset of the individuals.
The value of the Black Harrier as a predictor of biodiversity in the plant-rich Cape Floral Kingdom, South Africa
JENKINS J, SIMMONS RE, CURTIS O, ATYEO, M, RAIMONDO D, JENKINS AR. 2013. The value of the Black Harrier (Circus maurus) as a predictor of biodiversity in the plant-rich Cape Floral Kingdom, South Africa. Bird Conservation International 23:66-77.
Determining the efficacy of using indicator species to predict the spatial location of biodiversity hotspots is one way of maximising the conservation of biodiversity in already threatened habitats. Recent evidence from Europe suggests raptors can play such an indicator role, so we tested this approach with a globally threatened southern hemisphere species, the Black Harrier Circus maurus. We asked if this species, found in South Africa’s mega-diverse Cape Floral Kingdom, breeds in habitat fragments that were more diverse in terms of small mammals, birds and plants than unoccupied fragments of similar size. Renosterveld is a highly fragmented habitat that has lost > 90% of its original extent and remains only on privately-owned lands. Surveys of small mammals, birds and plants undertaken in 20 fragments in the Overberg region, South Africa, revealed nine with breeding harriers and 11 without harriers. Harrier-occupied fragments were associated with a 3.5 fold higher number of bird species and higher small mammal species richness than unoccupied ones. There was a lower abundance of most plants in occupied patches, except for red grass Themeda triandra which is an indicator of pristine renosterveld. Vegetation structure was significantly different, with harriers nesting on patches with taller, more open vegetation. While the diversity trends were not statistically significant, a positive trend between the presence of harriers and higher abundance of red grass – as an indicator of the more pristine state of the patch, suggests that harriers might allow biodiversity managers a heuristic approach for selecting the remaining patches of pristine renosterveld. The need for intensive sampling of several taxa leads to small samples and a lack of clear-cut trends for these top predators as indicators of plant diversity.
Determining the efficacy of using indicator species to predict the spatial location of biodiversity hotspots is one way of maximising the conservation of biodiversity in already threatened habitats. Recent evidence from Europe suggests raptors can play such an indicator role, so we tested this approach with a globally threatened southern hemisphere species, the Black Harrier Circus maurus. We asked if this species, found in South Africa’s mega-diverse Cape Floral Kingdom, breeds in habitat fragments that were more diverse in terms of small mammals, birds and plants than unoccupied fragments of similar size. Renosterveld is a highly fragmented habitat that has lost > 90% of its original extent and remains only on privately-owned lands. Surveys of small mammals, birds and plants undertaken in 20 fragments in the Overberg region, South Africa, revealed nine with breeding harriers and 11 without harriers. Harrier-occupied fragments were associated with a 3.5 fold higher number of bird species and higher small mammal species richness than unoccupied ones. There was a lower abundance of most plants in occupied patches, except for red grass Themeda triandra which is an indicator of pristine renosterveld. Vegetation structure was significantly different, with harriers nesting on patches with taller, more open vegetation. While the diversity trends were not statistically significant, a positive trend between the presence of harriers and higher abundance of red grass – as an indicator of the more pristine state of the patch, suggests that harriers might allow biodiversity managers a heuristic approach for selecting the remaining patches of pristine renosterveld. The need for intensive sampling of several taxa leads to small samples and a lack of clear-cut trends for these top predators as indicators of plant diversity.
Greater Kestrel survives impact with power line
SIMMONS RE, 2011 Greater Kestrel survives impact with power line. Ostrich 81: 75 -76
Here I describe the circumstances in which a Greater Kestrel Falco rupicoloides struck a power line and apparently survived.
Here I describe the circumstances in which a Greater Kestrel Falco rupicoloides struck a power line and apparently survived.