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The United Nations Sustainable Development Goals aim to improve livelihoods and maintain functioning ecosystems, and include the provision of electricity and the prevention of desertification. We show that the pursuit of those two goals can lead to developments that put critical ecosystem functions at risk. Vultures are scavengers that provide sanitary ecosystem services, but their populations across Africa are declining due to poisoning, electrocution, and collision with power infrastructure. The extent to which the pursuit of sustainable development threatens vultures in Africa is unclear. We surveyed 227 km of powerlines in Ethiopia, which revealed bird mortality (0.15 vulture carcasses / km) at power infrastructure constructed under a National Electrification Programme to provide universal electricity access by 2025. We also interviewed 190 local pastoralists in 10 areas about livelihood challenges, which revealed that the bush Prosopis juliflora, which was originally introduced to prevent desertification but then invaded north-eastern Ethiopia, increased livestock predation and motivated the use of poison to control predators. Actions to increase universal access to electricity and to reduce desertification therefore have undesired side-effects that increase vulture mortality through electrocution and poisoning. To avoid negatively affecting local vulture populations and the services they provide, we urge governments to use infrastructure designs that minimise the risk of electrocution and assist pastoralists to protect their livestock and reduce the risk of poisoning to vultures and other wildlife.
Saudi Arabia is the fastest growing electricity consumer in the Middle East, with a rapidly expanding network of powerlines. Bird mortality through electrocution and collision has been recorded in the country, but so far there is little information as to how much the electricity infrastructure affects globally threatened raptor populations that migrate to Saudi Arabia. In 2019, the world’s largest wintering congregation of Steppe Eagles Aquila nipalensis was discovered near a rubbish dump in central Saudi Arabia. We evaluated whether powerlines in the vicinity of this, and another congregation site, caused mortality of large birds. In November 2019, we surveyed powerlines within 6 km of two focal rubbish dumps at Al Qunfudhah (12.4 km) and Ushaiqer (2 km). We found 52 carcasses of five species, of which 85% were Steppe Eagles. Based on the age of these carcasses, we coarsely extrapolate that 14.4 km of powerlines near these two congregation sites may kill 94–240 Steppe Eagles per winter, representing up to 0.3% of their global population. We call for the urgent safeguarding of powerlines that cause mortality near known Steppe Eagle congregation sites, and the adoption and implementation of regulations that ensure that future infrastructure is constructed with designs that are safe for birds.
Invasive rodents detrimentally affect native bird species on many islands worldwide, and rodent eradication is a useful tool to safeguard endemic and threatened species. However, especially on tropical islands, rodent eradications can fail for various reasons, and it is unclear whether the temporary reduction of a rodent population during an unsuccessful eradication operation has beneficial effects on native birds. Here we examine the response of four endemic land bird species on subtropical Henderson Island in the Pitcairn Island Group, South Pacific Ocean, following an unsuccessful rodent eradication in 2011. We conducted point counts at 25 sampling locations in 14 survey periods between 2011 and 2015, and modelled the abundance trends of all species using binomial mixture models accounting for observer and environmental variation in detection probability. Henderson Reed Warbler Acrocephalus taiti more than doubled in abundance (2015 population estimate: 7,194-28,776), and Henderson Fruit Dove Ptilinopus insularis increased slightly between 2011 and 2015 (2015 population estimate: 4,476–10,072), while we detected no change in abundance of the Henderson Lorikeet Vini stepheni (2015 population estimate: 554–3014). Henderson Crake Zapornia atra increased to pre-eradication levels following anticipated mortality during the operation (2015 population estimate: 4,960–20,783). A temporary reduction of rat predation pressure and rat competition for fruit may have benefitted the reed warbler and the fruit dove, respectively. However, a long drought may have naturally suppressed bird populations prior to the rat eradication operation in 2011, potentially confounding the effects of temporary rat reduction and natural recovery. We therefore cannot unequivocally ascribe the population recovery to the temporary reduction of the rat population. We encourage robust monitoring of island biodiversity both before and after any management operation to better understand responses of endemic species to failed or successful operations.
Changes in food availability that lead to lower reproductive output or lower survival probability are important drivers of the widespread declines in vulture populations. Permanent feeding stations for scavengers, such as vulture restaurants or rubbish dumps, may have both positive and negative effects on reproductive parameters. Here we examine the effects of the closure of a large communal rubbish dump on breeding success and fledging rate of a dense population of the ’Endangered’ Egyptian Vulture Neophron percnopterus in central Turkey to assess whether the closure may have affected the population. We monitored territories from 2011 to 2016, and tested whether the closure of the rubbish dump in early 2015 coincided with changes in reproductive parameters while accounting for confounding variables such as weather and the availability of other predictable foraging opportunities. We found an average productivity of 0.78 fledglings per territorial pair before the dump closed and 0.82 after the closure, an average breeding success of 0.64 before and 0.71 after the closure, and an average fledging rate of 1.17 fledglings per successful pair before and 1.26 after the closure of the rubbish dump. Once confounding variables were accounted for, the closure of the rubbish dump did not have a significant effect on reproductive parameters (P = 0.426 for nest survival and P = 0.786 for fledging rate). We speculate that the Egyptian Vulture population in central Turkey may have sufficient alternative food sources and high levels of intra-specific competition due to its density, so that the closure of the rubbish dump may not have resulted in detectable positive or negative effects. We recommend the maintenance of small traditional animal husbandry farms and disposal practices that mimic the spatio-temporally unpredictable supply of food sources that appears to be most beneficial for avian scavengers.
Safeguarding threatened species in captivity is a promising management approach, but evaluating the performance of captive programmes is essential to assess reintroduction potential. The eastern population of the Northern Bald Ibis, Geronticus eremita, used to be a locally common migratory bird species, but catastrophic population declines throughout the past century have resulted in a single population in southern Turkey that forages freely during summer but only survives in captivity during winter. We examined whether breeding success of this semi-wild colony was comparable to breeding success of previous wild populations, and to what extent breeding success was influenced by supplementary feeding and wild foraging in habitats near the breeding station. Average productivity from 2009 to 2015 was 1.12 fledglings per nesting pair (range 0.96–1.19). In 2013 and 2014, there was no correlation between attendance at supplementary feeding events and productivity, and breeding birds attended on average only 35% of supplementary feeding events. Birds that were frequently observed at a local tree nursery raised fewer offspring, while birds observed more frequently in poldered cultivation, and in particular in mint crops or in fields covered with manure, raised on average more offspring. Foraging success was highest in meadows and cropland, particularly in mint crops and fields covered in manure, and lowest at the tree nursery. We speculate that selection of highly suitable wild foraging habitat such as mint crops or fields covered in manure allows the Northern Bald Ibis to raise more fledglings than exclusive reliance on supplementary food provided at the breeding station. Establishing a second breeding colony of this species in Turkey will therefore require a careful assessment of the suitability of wild foraging habitat in the vicinity of suitable nesting opportunities.
A prominent threat to European vultures has been sanitary regulations that banned the disposal of livestock carcasses. Changes in food abundance following these regulations have been associated with changes in vulture behaviour and demographic parameters, but to what extent diet changes are responsible for population declines is poorly understood. The Egyptian Vulture Neophron percnopterus is the smallest and most threatened European vulture species and has an opportunistic and diverse diet. In Eastern Europe, the Egyptian Vulture population is declining more rapidly than elsewhere but there is little information on diet composition and the relationship between diet and demographic parameters to inform conservation management. We examined whether Egyptian Vulture population declines in Bulgaria and Greece may have been associated with diet changes that affected breeding productivity by monitoring breeding success and collecting diet remains from 143 Egyptian Vulture breeding attempts between 2006 and 2013. We found no relationship between diet diversity or composition and productivity. However, there was a significant relationship between occupancy rate of territories and diet diversity, indicating that occupancy rate decreased with a very diverse or a very narrow diet and a higher proportion of wild animals or a lower proportion of livestock in the diet. There was no temporal change in diet diversity in Bulgaria after admission to the EU in 2007. We conclude that it is unlikely that diet limitations on reproductive output are a critical threat to Egyptian Vultures on the Balkan Peninsula. The relationship between diet diversity and territory occupancy rate may indicate that adult birds with a very narrow or a very broad diet may be more susceptible to consuming poisoned carcasses, and more information on the effect of diet availability on adult and juvenile survival would be useful to inform and improve conservation management actions.
Habitat loss, the primary driver for loss of biodiversity worldwide, is of special concern for species that have a small area of occurrence, such as those restricted to islands. The Forest Thrush Turdus lherminieri is a ‘Vulnerable’ (VU) species endemic to four islands in the Caribbean, and its population has declined dramatically over the past 15 years. Because this decline is poorly understood, we studied its habitat associations on Montserrat. We conducted three repeat point count surveys and measured forest structure and habitat at each of 88 randomly placed locations in the largest forest area remaining on the island. We related Forest Thrush abundance to habitat using binomial mixture models that account for imperfect detection. Detection probability was a function of survey time, survey date, location of the survey point, and wind. Local habitat structure had the greatest influence on Forest Thrush abundance, with birds being more abundant at mid-elevations under closed canopies. We conclude that the Forest Thrush prefers mature mesic and wet forests on Montserrat. Assuming similar habitat selection in the rest of its range, the species’s long-term future depends on good protection of these natural forests on all four islands where it occurs.
The Egyptian Vulture has been classified as ‘Endangered’ due to a rapid population decline in India and long term declines in Europe and Africa. Although the species has been reported to be declining in Eastern Europe, no quantitative assessment of the magnitude or the causes for population declines are available. We used monitoring data from the Balkan Peninsula to estimate changes in population size and extent of occurrence of Egyptian Vultures between 1980 and 2013. We quantified population trends in three countries (Bulgaria, Greece and the former Yugoslav Republic [FYR] of Macedonia) to assess whether population declines are similar within the Balkan range states. We found a rapid and consistent decline of the Egyptian Vulture population that was largely similar among the three countries (λ = 0.940 in FYR of Macedonia, 0.951 in Bulgaria, 0.920 in Greece). As a consequence of population declines, the breeding range of Egyptian Vultures has contracted and the population in the Balkan Peninsula has fragmented into six subpopulations separated by more than 80 km. Population declines may be driven by factors such as poisoning, electrocution, direct persecution and changes in food availability which operate at large spatial scales and affect birds both on breeding grounds as well as during migration and wintering. Because the relative importance of threats to the survival of Egyptian Vultures are poorly understood, there is a critical need for research into causes of mortality and potential conservation actions that may halt and reverse population declines.
Many island endemics are of great conservation concern due to small range and population sizes. The Montserrat Oriole Icterus oberi is a forest passerine endemic to the Caribbean island of Montserrat, where recent volcanic activity has destroyed a large proportion of suitable forest habitat. From 1997 to 2000 the Montserrat Oriole population declined dramatically even in the remaining forest habitat, leading to its classification as ‘Critically Endangered’. We present trend estimates of the Montserrat Oriole population from 2000 to 2013, and estimate the world population size in 2012 based on repeat point counts and beta-binomial mixture models. Montserrat Orioles recovered between 2003 and 2005, and we found no evidence for a continuing population decline. However, there was large uncertainty around trend estimates, and the power to detect a shallow negative trend was very low. Based on the comparison of count data at 42 points, the Montserrat Oriole population in 2013 was less than half as large as in 1998. To improve future trend estimates a new monitoring design was introduced in 2011, and applied to all subpopulations of the species in 2012. The world population in 2012 was estimated to hold between 307 (95% credible interval 212–503) and 690 birds (476–1131) birds in the two forest fragments on Montserrat, depending on whether the sampling area around each point count was assumed to encompass 100 m or 150 m. Based on these estimates, the Montserrat Oriole currently does not meet the IUCN criteria for ‘Critically Endangered’, and we recommend a revision of the species’ conservation status.
The Aquatic Warbler Acrocephalus paludicola is a globally threatened habitat specialist that breeds in open fens in Central and Eastern Europe. Because bush and reed encroachment threaten many suitable breeding areas, habitat management is necessary to maintain the open wetlands that Aquatic Warblers require for nesting. The effectiveness of mowing as habitat management has so far only been assessed by counting the number of singing males. To assess whether mowing also affected vital reproduction parameters, we analysed Aquatic Warbler productivity in the Biebrza National Park, Poland, on plots in four different successional stages after mowing. Our study showed that productivity was lowest in the first year after mowing, but increased to the highest levels in the second year after mowing. The productivity differences between areas at different stages after mowing resulted from differences in nest density, since we found little evidence for an effect of mowing on nest survival or the number of fledglings produced per successful nest. Nest survival was highly variable between years and varied mostly with nest age and nest initiation date. The density of singing males was positively correlated with both the nest density and the number of fledglings produced in an area, suggesting that this simple indicator could be used to rank the quality of Aquatic Warbler habitats. We recommend that in mesotrophic fen mires, such as the Biebrza valley, mowing as habitat management is applied less frequently than every second year.
Electrocution on poorly designed power poles is increasingly shown to pose a threat for the populations of many large raptors. Here we document that a power line in Sudan continues to cause mortality of Egyptian Vultures Neophron percnopterus, a problem that was first identified in 1984. We suggest that this power line may have caused the death of sufficient Egyptian Vultures to partially explain population declines in the Middle East, from where the electrocuted birds may originate. This report highlights the urgent need to plan and retro-fit power lines in Africa with non-lethal support structures.
Pale-headed Brush-finch Atlapetes pallidiceps is a restricted-range species that is threatened with extinction due to habitat loss. The total population of 60–80 individuals achieved a reproductive output of only 0.74 young per breeding pair in 2002. Brood parasitism by Shiny Cowbird Molothrus bonariensis was a major factor reducing breeding success, affecting 38.5% of broods. Parasitism rates reached 50% in an ungrazed reserve, but only 14% on an adjacent grazed plot. The resulting difference in breeding success was not, however, attributable to vegetation parameters used to describe microhabitat use. Cowbird parasitism rates therefore seem to be influenced largely by factors operating at the landscape level. These may include grazing scheme, topography, humidity and host availability. It is suggested that lower species diversity and bird abundance rendered the grazed site less attractive to cowbirds. Current parasitism rates are of great conservation concern due to the low population size of Pale-headed Brush-finch, and the initiation of controlling measures is pressing. Management options described from intensive cowbird control programmes in North America are reviewed and evaluated for their applicability here. To combine the possibility of further data collection with commencement of immediate conservation action, we consider two alternative approaches. Nest monitoring and cowbird egg removal would enable the study of the distribution of parasitism in relation to landscape and vegetation variables, whereas cowbird shooting and nest monitoring might provide a larger short-term benefit to reproductive output. Habitat management, resumption of some grazing in the reserve and cowbird removal should be considered for the intermediate future.
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