Comparison of point and roadside transect methods to evaluate the abundance and richness of diurnal raptors in the arid region of Rajasthan.

Diurnal raptors show a wider distribution compared to other groups of birds including passerines, woodpeckers, and seriemas, but occur at lower-than-expected densities. Estimating the precise abundance is essential to achieve conservation goals but the methods used to estimate the populations of birds need to be appropriate to arrive at meaningful conclusions. We compared the two survey methods: roadside point count and strip transects, for estimating species richness and abundance of raptors in the arid landscape of Rajasthan. Roadside point counts and roadside strip transects were done on 50 transects between December 2019- February 2020 (with an average length of 20 km and a total distance of 3000 km) to assess the species richness and abundance of raptors. A total of 2954 observations of raptors belonging to 35 species were recorded using both methods. Mann Whitney U test result showed no significant difference in species richness and abundance estimates between both methods (p = 0.206). The point count method yielded a higher relative abundance of 2.79 individuals [10 km2]-1h-1 than the 1.90 individuals [10 km2]-1h-1 obtained during the strip transect. Also, the number of unidentified species were less for point counts. Extrapolation values indicated that both the methods do not differ much for the detection of unsampled species. The choice of survey method depends on the objectives of the study, but our results favor the use of point counts rather than strip transects to survey raptors in open habitats. The information generated from this study is expected to provide the most efficient method to study the abundance and distribution of raptors in similar landscapes.

Nest boxes buffer the effects of climate on breeding performance in an African urban raptor.

As the world's human population increases, transformation of natural landscapes into urban habitats continues to increase. In Africa, rates of human population growth and urbanisation are among the highest in the world, but the impacts of these processes on the continent's biodiversity remain largely unexplored. Furthermore, the effects of ongoing anthropogenic climate change are likely to be severe and to interact with urbanisation. Some organisms appear resilient to urbanisation, and even proliferate in human-modified environments. One such species is the peregrine falcon Falco peregrinus in Cape Town, South Africa. Using a long-term data set (1989-2014), we investigate the relationship between breeding attempts, timing of breeding and breeding performance under varying weather conditions. Exploring these issues along an urbanisation gradient, we focus on the role of artificially provided nest boxes, and their capacity to buffer against extreme weather events. Pairs in more urbanised areas, and particularly those in nest boxes, were more likely to breed and to commence breeding earlier. Additionally, pairs using nest boxes were more likely to breed in years with higher rainfall. Warm and dry weather conditions generally advanced the timing of breeding, although this relationship with weather was not seen for urban pairs using nest boxes. Furthermore, weather did not impact breeding performance directly (breeding success and fledged brood size), but timing of breeding did, with earlier breeders producing more fledglings. Our study shows that falcons breeding in specially provided nest boxes were less sensitive to local weather dynamics than pairs using more natural nest sites. This has important implications as it suggests that the managed provision of such nesting sites can help this key urban species to cope with extreme weather events, which are predicted to increase with climate change.

Observações comportamentais do gavião-pato Spizaetus melanoleucus (Accipitriformes, Accipitridae) no estado do Paraná, Brasil / Behavioral observations on the black-and-white hawk-eagle Spizaetus melanoleucus (Accipitriformes, Accipitridae) in the state of Paraná, Brazil / Observaciones de comportamiento del aguila azor blanquinegra Spizaetus melanoleucus (Accipitriformes, Accipitridae) en el estado de Paraná, Brasil

O gavião-pato (Spizaetus melanoleucus) é uma ave de rapina florestal e naturalmente rara em toda sua distribuição. No estado do Paraná conta com registros escassos, especialmente na porção noroeste. Devido a suas baixas densidades populacionais e comportamento inconspícuo, são escassas as informações biológicas da espécie. O presente estudo apresenta alguns registros e observações comportamentais do S. melanoleucus em dois remanescentes florestais do interior do Paraná. As observações sugerem que a espécie pode forragear com certa frequência em áreas abertas a procura de mamíferos e outros pequenos vertebrados. Além disso, a espécie aparenta ser mais detectável em voo próximo ao final da manhã e início da tarde. Informações sobre a biologia, comportamento, estratégias de caça e distribuição da espécie podem ajudar a compreender melhor sua biologia e auxiliar estratégias de conservação.

The black-and-white hawk-eagle (Spizaetus melanoleucus) is a forest raptor and naturally rare throughout its distribution. In the state of Paraná, it has few records, especially in the northwest. Due to low population densities and inconspicuous behavior, there is little biological information available on the species. This study presents some records and behavioral observations on Spizaetus melanoleucus in two forest remnants in the countryside of the state of Paraná. Observations suggest that the species may often forage in open areas, seeking small mammals and other vertebrates. Moreover, the species seems to be more detectable in the late-morning and early afternoon flights. Information on the biology, behavior, hunting strategies and distribution of the species can help to better understand their biology and assist on conservation strategies.

El águila azor blanquinegra (Spizaetus melanoleucus) es un ave de rapiña forestal y naturalmente rara en toda su distribución. En el estado de Paraná cuenta con registros escasos, especialmente en la parte noroeste. Debido a sus bajas densidades poblacionales y comportamiento discreto, son escasas las informaciones biológicas de la especie. Este estudio presenta algunos registros y observaciones de comportamiento del Spizaetus melanoleucus en dos remanentes forestales en el interior de Paraná. Las observaciones sugieren que la especie puede forrajear con poca frecuencia en áreas abiertas en busca de mamíferos y otros pequeños vertebrados. Además, la especie aparenta ser más detectable en vuelo próximo al final de la mañana e inicio de la tarde. Informaciones sobre la biología, comportamiento, estrategias de caza y distribución de las especies pueden ayudar a entender mejor su biología y auxiliar estrategias de conservación.

Voluntary nonmonetary conservation approaches on private land: a review of constraints, risks, and benefits for raptor nest protection.

Biodiversity conservation on private land of the developed world faces several challenges. The costs of land are often high, and the attitudes of landowners towards conservation are variable. Scientists and practitioners need to scan for and adopt cost-effective solutions that allow for the long-term sustainability of conservation measures on private land. In this study, we focus on one of such possible solutions: Working with landowners to implement voluntary nonmonetary conservation. We restrict our focus to protection of raptor nests, but the ideas can be applied to other taxa as well. Through a literature review, we show that a voluntary nonmonetary approach for protecting raptor nests has been so far largely neglected and/or rarely reported in the scientific literature. However, results of a questionnaire sent to BirdLife partners across Europe indicate that this approach is more widely used than it appears from the literature. We show that voluntary nonmonetary approaches may represent useful tools to protect raptor nests on private land. We provide a workflow for implementation of such an approach in raptor nest protection, highlighting benefits, potential risks, and constraints in the application of the strategy. We suggest that a voluntary nonmonetary approach may have great potential for cost-effective conservation, but the risks it may entail should be carefully assessed in each case. There is an urgent need to consider and evaluate novel approaches, such as the one described here, which may constitute missed opportunities for cost-effective conservation.

The occurrence of second generation anticoagulant rodenticides in non-target raptor species in Norway.

Second generation anticoagulant rodenticides (SGARs) are commonly used for rodent pest control in Norway resulting in the potential exposure of non-target raptor species. In this study the occurrence of flocoumafen, difethialone, difenacoum, bromadiolone and brodifacoum was determined in the livers of five species of raptors found dead in Norway between 2009 and 2011. The SGARs brodifacoum, bromadiolone, difenacoum and flocoumafen were detected in golden eagle (Aquila chrysaetos) and eagle owl (Bubo bubo) livers at a total SGAR concentration of between 11 and 255 ng/g in approximately 70% of the golden eagles and 50% of the eagle owls examined in this study. In the absence of specific golden eagle and eagle owl toxicity thresholds for SGARs, a level of >100 ng/g was used as a potential lethal range, accepting that poisoning may occur below this level. Thirty percent (7/24) of the golden eagle and eagle owl livers contained total SGAR residue levels above this threshold. Further estimation of the potential mortality impact on the sampled raptor populations was not possible.

The young, the weak and the sick: evidence of natural selection by predation.

It is assumed that predators mainly prey on substandard individuals, but even though some studies partially support this idea, evidence with large sample sizes, exhaustive analysis of prey and robust analysis is lacking. We gathered data from a culling program of yellow-legged gulls killed by two methods: by the use of raptors or by shooting at random. We compared both data sets to assess whether birds of prey killed randomly or by relying on specific individual features of the prey. We carried out a meticulous post-mortem examination of individuals, and analysing multiple prey characteristics simultaneously we show that raptors did not hunt randomly, but rather preferentially predate on juveniles, sick gulls, and individuals with poor muscle condition. Strikingly, gulls with an unusually good muscle condition were also predated more than expected, supporting the mass-dependent predation risk theory. This article provides a reliable example of how natural selection may operate in the wild and proves that predators mainly prey on substandard individuals.

[Red-breasted goose colonies on the Taimyr Peninsula: factors responsible for the proximity of goose nests to nests of peregrine falcons, rough-legged buzzards, and snowy owls].

Red-breasted goose colonies have been studied near Medusa Bay (73 degrees 21' N, 80 degrees 32' E), on the northwestern Taimyr Peninsula, and along the Agapa River (70 degrees 11' N, 86 degrees 15' E) down to its mouth (70 degrees 26' N, 89 degrees 13' E), in the central Taimyr Peninsula. Red-breasted geese nesting near peregrine falcons are protected by the falcons from arctic foxes; however, they are sometimes attacked by the falcons themselves. In the colonies near peregrine falcon nests, the vast majority of goose nests were situated no farther than 100 m from the falcon nest. When food is abundant, falcons protect a larger area around their nest. The distance between the falcon nest and the surrounding goose nests is inversely related to the falcon's activity. In years of higher falcon activity, falcons prevent red-breasted geese from nesting as close to their nest as in years of lower falcon activity. Additional stimuli are required for red-breasted geese to form colonies near rough-legged buzzard nests. The distance between snowy owl nests and red-breasted goose nests was smaller when arctic foxes were abundant than when they were scarce.

The EU environmental policy context for monitoring for and with raptors in Europe.

This paper outlines the importance of the policy context for monitoring with and for raptors, and, conversely, of the importance of such monitoring for policy. It then outlines two key areas of European Union (EU) environmental policy most relevant to monitoring for and with raptors, namely biodiversity policy and pollution policy. For each of the policy areas, the pertinent objectives and actions of the current EU policy are identified, and their relevance for raptor monitoring is discussed. The potential contribution of raptor monitoring to the further development of these policy areas is also addressed.

The conservation status and trends of raptors and owls in Europe.

To conserve biodiversity efficiently, an international framework is needed to ensure that national priorities take into account regional and global priorities. BirdLife International has published five comprehensive assessments of the global status of the world's birds and two evaluations of the status of Europe's birds at a continental level. This paper analyzes the results of these assessments in relation to Europe's 56 species of raptors and owls, 18% of which are of global conservation concern, and 64% of which have an unfavorable conservation status in Europe. The European Union (EU) holds half of the total estimated European breeding population of raptors and owls, and European Russia supports another third, but every European country has a responsibility for at least two species of European conservation concern. During the 1990s, more raptors increased than decreased in most EU member states, but the opposite was true in eastern Europe, where many of the most threatened species are concentrated. Given the popularity of these species with the public, and the political commitment to halt the loss of biodiversity by 2010, much more action is needed to monitor and conserve birds of prey.

European monitoring for raptors and owls: state of the art and future needs.

Sixty-four percent of the 56 raptor and owl species that occur in Europe have an unfavorable conservation status. As well as requiring conservation measures in their own right, raptors and owls function as useful sentinels of wider environmental "health," because they are widespread top predators, relatively easy to monitor, and sensitive to environmental changes at a range of geographical scales. At a time of global acknowledgment of an increasing speed of biodiversity loss, and new, forward-looking and related European Union biodiversity policy, there is an urgent need to improve coordination at a pan-European scale of national initiatives that seek to monitor raptor populations. Here we describe current initiatives that make a contribution to this aim, particularly the current "MEROS" program, the results of a questionnaire survey on the current state of national raptor monitoring across 22 BirdLife Partners in Europe, the challenges faced by any enhanced pan-European monitoring scheme for raptors, and some suggested pathways for efficiently tapping expertise to contribute to such an initiative.

Monitoring birds of prey in Finland: a summary of methods, trends, and statistical power.

In Finland, Comprehensive Surveys to monitor numbers and productivity of four endangered species of birds of prey were started in the early 1970s. In 1982, the Ringing Center launched the Raptor Grid, a nationwide monitoring program for all other bird-of-prey species based on 10 x 10 km study plots of the Finnish National Grid. The annual total of study plots surveyed by voluntary raptor ringers has averaged 120. Since 1986, additional information on breeding performance has been collected using the Raptor Questionnaire. In 2006, more than 44 262 potential nest sites of birds of prey were inspected, and 12 963 occupied territories, including 8149 active nests, were found and reported by ringers. The population trend during 1982-2006 has been significantly negative in six species and positive or neutral in 18 species. Statistical power of the time series of numbers and productivity has been adequate for all species except the microtine specialists.

Monitoring of raptors and their contamination levels in Norway.

This article summarizes results from raptor monitoring and contamination studies in Norway of the golden eagle, gyrfalcon, white-tailed sea eagle, osprey, peregrine, and merlin. Golden eagle and gyrfalcon populations have been monitored since 1990 as part of the "Monitoring Programme for Terrestrial Ecosystems" (TOV). No long-term trend in the population size or productivity of golden eagle has been shown in any of the 5 study areas. The reproductive output of gyrfalcon is monitored in 3 areas. It is positively correlated with the populations of its main prey species, the rock ptarmigan and the willow ptarmigan. The white-tailed sea eagle population has been monitored since 1974 by the Norwegian Ornithological Society, and the population is increasing. The levels of pesticides and polychlorinated biphenyls are low in the eggs of both the golden eagle and the gyrfalcon, but elevated levels and effects on reproduction have been indicated for a coastal subpopulation of golden eagle. The pollutant levels in white-tailed sea eagle are lower than in the Baltic population of sea eagles, and shell thinning was never severe overall, but individual eggs have contained pollutant concentrations above critical levels. The levels of pollutants in the bird-eating falcons, peregrine, and merlin were higher than in other species. New emerging pollutants, like brominated diphenylethers and perfluorinated organic compounds, could be detected in all species. By incorporating available published and unpublished data, we were able to produce time trends for pollutants and shell thickness over 4 decades.

Raptor ecotoxicology in Spain: a review on persistent environmental contaminants.

Initial studies on the pressure from environmental contaminants on raptor populations in Spain date back to the 1980s, and they have been carried out from a range of viewpoints using a range of sentinel raptor species. However, there is no national monitoring scheme, and therefore the research carried out has been sporadic both spatially and temporally. The exposure to metals has not varied over time, except in the case of lead, whose concentration in eggs and tissues has diminished. In general, the concentrations of metals detected in raptor samples from Spain are generally low and not sufficient to produce toxic effects. Excepting DDT and DDE, most organochlorine-based pesticides in raptors from Spain have diminished over the last 2 decades. The concentrations of DDE found in the eggs of various species could in part explain problems in the reproductive success of raptors in Spain.

The Predatory Bird Monitoring Scheme: identifying chemical risks to top predators in Britain.

The Predatory Bird Monitoring Scheme (PBMS) is a long term (>40 y), UK-wide, exposure monitoring scheme that determines the concentration of selected pesticides and pollutants in the livers and eggs of predatory birds. This paper describes how the PBMS works, and in particular highlights some of the key scientific and policy drivers for monitoring contaminants in predatory birds and describes the specific aims, scope, and methods of the PBMS. We also present previously unpublished data that illustrates how the PBMS has been used to demonstrate the success of mitigation measures in reversing chemical-mediated impacts; identify and evaluate chemical threats to species of high conservation value; and finally to inform and refine monitoring methodologies. In addition, we discuss how such schemes can also address wider conservation needs.

Wood thrush nest success and post-fledging survival across a temporal pulse of small mammal abundance in an oak forest.

1. Synchronized mass production of seed crops, such as acorns, produces a resource pulse that may have far-reaching consequences for songbird populations through its effects on avian predators. Seed production in these forests represents only the first of several pulsed events. Secondary pulses emerge as mast-consuming rodents numerically respond to seed production and tertiary pulses emerge as generalist predators, such as raptors, numerically respond to rodents. In turn, these two groups reduce nest productivity and juvenile survivorship 1 and 2 years, respectively, after the initial pulse in seed production. 2. At our study site in south-eastern New York, USA, autumn acorn abundance (primary pulse) largely determines rodent abundance (secondary pulse) the following spring. We tested the hypotheses that the population dynamics of a shrub-nesting passerine (wood thrush Hylocichla mustelina), is influenced by rodents through the: (a) direct effect of predation by rodents; (b) indirect effect of rodents on the abundance of raptors (tertiary pulse); and (c) indirect effect of rodent abundance on raptor diet. The latter specifically hypothesizes that a crash in the rodent population in the wake of region-wide failure of acorn production leads to an extreme diet shift in raptors that increases post-fledging mortality in birds. 3. We conducted a 3-year study to examine variation in wood thrush nest success and fledgling survival, using radio telemetry, across a pulse of rodent abundance (i.e. low, medium and high). We also updated and reanalysed regional wood thrush population growth rates as a function of the annual variation in rodent abundance. 4. Fledgling survivorship, but not nest success, varied in relation to annual rodent abundance. Raptors and eastern chipmunks Tamias striatus were the most commonly identified predators on fledglings. Fledgling survivorship was greatest at intermediate rodent abundance consistent with a shift in raptor diet. Regional rate of wood thrush population growth showed a unimodal relationship with rodent abundance, peaking during years with intermediate rodent abundance. This unimodal pattern was due to wood thrush population growth rates near or below zero during rodent population crashes. 5. The telemetry study, pattern of regional abundance and synchronized population dynamics of coexisting thrushes suggest a common mechanism of behavioural changes in raptors in response to declines in rodent prey, which in turn affects thrush population dynamics.

Bioaccumulation and biotransformation of 61 polychlorinated biphenyl and four polybrominated diphenyl ether congeners in juvenile American kestrels (Falco sparverius).

This study examined the bioaccumulation and dietary retention of 61 polychlorinated biphenyl (PCB) and four polybrominated diphenyl ether (PBDE) congeners in juvenile American kestrels (Falco sparverius). American kestrels were exposed to contaminants via egg injection and daily gavage dosing over the posthatch-to-fledgling period. Retention factors for PCBs were dependent on chemical hydrophobicity and chlorine substitution patterns and ranged from less than 1 to 16.4% for PCBs having vicinal hydrogen substitutions at meta-, para- carbons on at least one of the phenyl rings and between 13.2 and 81.5% for congeners containing chlorine substitutions at 4,4'-, 3',4,5'-, 3,4',5-, or 3,3',5,5'-positions. These results indicate that juveniles are capable of biotransforming PCBs according to the same structure-activity rules as adults. A toxicokinetic model, initially parameterized using adult toxicokinetic parameters, was used to describe concentration trends in juveniles over time. The adult model overestimated PCB concentrations but provided an adequate fit when elimination rate constants were increased by a factor of 12.7. Retention factors for the PBDE congeners 2,2',4,4'-tetrabromodiphenyl ether (BDE 47), 2,2',4,4',6-pentabromodiphenyl ether (BDE 100), 2,2',4,4',5-pentabromodiphenyl ether (BDE 99), and 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE 153) were from 7.8 to 45.3% of the total dose. The retention of BDE 47 was similar that observed for readily cleared PCBs, whereas the remaining PBDEs exhibited retention factors consistent with those of persistent PCBs. Half-lives for PBDEs in juveniles were estimated to range from 5.6 to 44.7 d. Assuming differences in PBDE toxicokinetics between juveniles and adults similar to those measured for PCBs, adult American kestrel PBDE half-lives are expected to range from 72 to 572 d.

Glycated hemoglobin and albumin reflect nestling growth and condition in American kestrels.

Blood chemistry can be used to assess physiological state and condition. Levels of glycated hemoglobin (GHb), which integrates blood glucose levels over a period of weeks, may provide a way to assess resource intake. I tested whether GHb reflects offspring quality by comparing growth rates of nestling American kestrels (Falco sparverius) with GHb levels at 24 days of age. Nestlings that gained structural size faster had higher levels of GHb than did slower growing nestlings. There was no difference in GHb levels between males and females, although females are larger. In addition, I tested whether albumin levels, a measure of protein storage, were correlated with nestling growth and body condition (reflected in residual body mass). Larger individuals, measured by both absolute body mass and by residual body mass, had larger levels of albumin. This was due in part to females having higher albumin levels. Interestingly, there was no correlation between GHb and albumin, suggesting that both measures are necessary to assess physical condition in nestling kestrels. These results suggest that blood chemistry can reflect offspring condition measures and may provide a way to assess offspring quality that reflects conditions experienced by offspring over longer periods through measurements at a single time point.

Developmental toxicity of in ovo exposure to polychlorinated biphenyls: II. Effects of maternal or paternal exposure on second-generation nestling american kestrels.

The development of second-generation nestling American kestrels (Falco sparverius) was altered by in ovo exposure of only one parent to polychlorinated biphenyls (PCBs). Polychlorinated biphenyls appear to alter nestling development through both maternally and paternally mediated effects. In 1998, F0 parent kestrels consumed approximately 5 to 7 microg total PCBs/g bird/d (Aroclors 1248:1254: 1260) for approximately 100 d prior to eggs hatching; these eggs, containing total PCB concentrations of 34.1 microg/g, produced 13 F1 offspring, which were then paired in 1999 with unexposed kestrels to examine developmental effects of maternal or paternal in ovo PCB exposure. Using a toxicokinetics model, eggs from the maternally exposed group had predicted PCB levels of 0.03 to 0.34 microg/g, with enriched higher chlorinated congeners. Polychlorinated biphenyl concentrations in eggs of all generations have recently been found in eggs and nestlings of free-ranging eagles. Consistent with the first generation, maternally exposed F2 females generally were larger, had altered growth rates, and delayed maximal growth and fledging compared with control females. Maternally exposed F2 males were heavier but had shorter bones, grew more quickly and earlier, and fledged 2 d later than control males. In the maternally exposed group, concentrations of plasma triiodothyronine were elevated in F2 females but suppressed in F2 males. Paternally exposed F2 hatchlings of both sexes were comparable in size to controls with the exception of having longer tarsi bones, but subsequently showed slower, delayed growth (both sexes) and fledging (females) and lower thyroxine concentrations (males). The alterations in thyroid hormones in the F2 generation are discussed in light of the enrichment of higher chlorinated PCB congeners and hydroxylated PCB congeners. The developmental changes in the kestrel nestlings are likely a function of several possible mechanisms involving maternal PCB deposition, parental behavior, and neurobehavioral and endocrine-thyroid function in nestlings.

Bird orientation: compensation for wind drift in migrating raptors is age dependent.

Despite the potentially strong effect of wind on bird orientation, our understanding of how wind drift affects migrating birds is still very limited. Using data from satellite-based radio telemetry, we analysed the effect of changing winds on the variation of the track direction of individual birds. We studied adults and juveniles of two raptor species, osprey Pandion haliaetus and honey buzzard Pernis apivorus, on autumn migration between North Europe and Africa, and demonstrate an important difference between the age categories of both species in the extent of wind drift. For juveniles, side- and following-wind components affected the rates of movement perpendicular to and along the mean direction, respectively, to a similar degree, suggesting full wind drift. By contrast, for adults the rate of crosswind displacement was significantly smaller than the effect of wind on forward movement, showing much reduced wind drift (29%). This indicates that adults have acquired a more sophisticated orientation system, permitting detection of and compensation for wind drift, than juveniles. These drift effects are likely to reduce the ability of juveniles to locate species-specific wintering areas in case of rapid climatic wind change.