Ground-nesting Birds Research Articles

Hedgerows interact with forests to shape the abundance of mesopredators and their predation rate on eggs in farmland landscapes

Nest predation is the main cause of reproductive failure, particularly in ground-nesting birds on farmlands. Understanding the links between nest predation and habitat change can help design effective management schemes to constrain the negative impact of predation pressure on birds. However, the mechanisms underlying the relationships between landscape attributes, predator distribution, and nest predation are still unclear. Here, we use an experimental approach to examine the effects of distance to the hedgerow as well as hedgerow and forest densities on the abundance of major mesopredators of ground nests of our study area (i.e., corvids) and on the predation rate of artificial ground nests (n = 2576). We found evidence that landscape configuration influenced predation patterns differently depending on the predator species. Nest predation by corvids was more likely in homogeneous and open agricultural landscapes with a low density of forest and hedgerows, whereas predation by other predators was more likely close to hedgerows. Nest predation by corvids and the abundance of corvids also tended to be lower in landscapes dominated by grasslands. Other variables such as road density and distance to human settlements had contrasted effects on the likelihood of a nest being depredated by corvids, i.e., no effect with proximity to human settlements and decreasing trend with road density. Altogether, our results suggest that landscape features interact with mesopredator distribution and their predation rates of ground nests. Therefore, from a conservation and management perspective, a heterogeneous agricultural landscape that includes a mixture of crops associated with patches of forests, hedgerows, and grasslands offering alternative food to generalist predators should contribute to reducing ground-nesting bird predation.

Positive responses of breeding waders to targeted conservation advice and habitat management used to enhance existing wader conservation initiatives in Northern Ireland

Ground-nesting birds such as breeding waders are of high conservation concern throughout Europe, experiencing population declines driven by agricultural intensification and low breeding success often caused by predation. One mechanism for encouraging wader recovery outside of nature reserves is Agri-Environment Schemes (AES), where financial incentives encourage farmers to improve their land management practices to promote wildlife and ecosystem services. The effectiveness of such schemes for waders outside of nature reserves is limited however. Methods for improving delivery of conservation action in the wider countryside are therefore urgently needed. Here we evaluate the effectiveness of the Halting Environmental Loss Project (HELP), where site-specific advice, training and practical assistance in conducting breeding wader habitat management were provided at a range of upland and lowland sites across Northern Ireland. HELP did not provide direct financial incentives to landowners, instead, targeted advice and access to specialist machinery and expertise were provided to stimulate habitat management interventions and enhance existing wader conservation measures (AES or reserve funding). Benefits were observed both on and off reserves, although the quality and extent of the habitat management undertaken was generally higher on reserves. Temporal trends in breeding densities were more positive for three wader species during HELP than previously and continued to be positive for a fourth species. Our results demonstrate that targeted advice and practical assistance can lead to improvements in habitat management and subsequent increases in wader breeding densities inside and outside nature reserves. Future wader conservation projects are likely to be most effective when expert advice is deployed in combination with other mechanisms to fund management such as nature reserves or AES payments, and in many situations reductions in predation pressure will also be needed.

Population trends of ground-nesting birds indicate increasing environmental impacts from Eastern to Western Europe: different patterns for open-habitat and woodland species

Introduction: Bird populations reflect the influence of major environmental changes, and the analysis of their long-term population trends concerning species-specific ecological traits can provide insight into biologically relevant impacts of such changes. In this respect, nest site is a particularly informative trait because ground-nesting bird species are more prone, in contrast to species nesting above the ground, to the impacts of nest predation which can be linked to various environmental drivers including the intensification of agriculture or woodland management. Here we hypothesize that a) ground-nesting species present negative trends due to environmental pressures mentioned above, b) such declining trends should be more pronounced in Western than in Eastern Europe because, in Western countries, the environmental threats are likely greater, and c) the interaction between nest site and habitat association will point at the habitat types where the presumed drivers most likely operate.Methods: We used population trends from 1980 to 2016 of 332 bird species in 16 European countries to test this hypothesis.Results: We found that the long-term population trends of ground-nesting birds are more negative than the trends of species nesting above the ground indicating the effect of nest predation, and this difference increased from Eastern to Western European countries, probably due to steeply increasing populations of nest predators in the West. However, the effect of longitude interacted with the habitat association being strong in woodland species and weak in open-habitat species.Discussion: This pattern suggests that the increased nest predation pressure in the West is linked to woodlands, probably due to higher abundances of mammalian herbivores that destroy forest ground and shrub layer, and thus leave the nests exposed to predators. In contrast, only a weak longitudinal pattern in open-habitat species indicates that the negative impacts of agricultural intensification are no longer confined to the Western part of the continent. Although nature conservation activities are generally successful in Europe, as indicated by benefits provided by the Natura 2000 network, our results uncovered substantial gaps in delivering such benefits.

First description of injury feigning behavior in Godlewski's buntings.

Nest defense behavior helps ground-nesting birds improve their breeding success. Among such behaviors, injury feigning behavior (IFB) is one of the better ways to attract predators and protect birds' nests. IFB is generally associated with shorebirds in general and plovers in particular, however, through field observation, it has been found this behavior is also exhibited in bunting species when they facing the risk of predation. We attempt to explore the detailed description of this behavior in buntings and the factors that affect this behavior. Based on video-recordings of the nest defense behavior by the ground-nesting bird Godlewski's bunting (Emberiza godlewskii) against nest invaders, we explored the characteristic of IFB and differences in nest defense behavior during their brooding seasons. The results showed that female buntings had a distinct IFB: the wings of buntings incited within 60°-90° of the body, ran and called rapidly, pretending to be injured and unable to fly. The nest stage had significant and extremely significant effects on IFB and movement distance (MD), respectively. And IFB was more likely to occur in brooding (34.62%) than incubation period (16.42%). This indicates that there are significant differences in the IFB of buntings at different breeding stages.

Varying response of breeding waders to experimental manipulation of their habitat and predators

Many ground-nesting bird species including waders are of conservation concern across Europe. Population declines of Eurasian Curlew Numenius arquata (hereafter Curlew), a globally Near-threatened wader, exemplify this and are driven by low breeding success due to predation, and loss and degradation of breeding habitat. We tested whether the combined delivery of vegetation management and lethal control of Red Foxes Vulpes vulpes and Carrion Crows Corvus corone and Hooded Crows C. cornix improved Curlew nesting success and breeding abundance across UK study sites over five years. On trial sites, vegetation management improved habitat condition and Curlew distributions shifted towards managed areas. However, changes in predator abundances, Curlew nesting success and Curlew breeding abundance did not differ between trial and reference sites. Northern Lapwing Vanellus vanellus numbers increased on trial sites and decreased on reference sites, whilst Common Snipe Gallinago gallinago numbers showed no treatment response. Some of these outcomes were associated with additional environmental variables added to Treatment:Year terms in three-way interactions (changes in fox abundance associated with abundance of non-native gamebirds; changes in Crow abundance associated with gamebirds and woodland area; changes in Curlew nesting success associated with crow abundance), highlighting that outcomes depend on site-specific contexts, and consistent responses to interventions cannot be assumed. The difficulty in increasing Curlew nesting success likely relates to underlying mesopredator densities in the UK, which are known to be high in a European context. Our results suggest that a model of delivery like this study, including management of predators using lethal control, at comparable intensities, is highly unlikely to be effective for Curlew or Snipe within agri-environment schemes, but could be for Northern Lapwing. To make progress on wader recovery it is imperative to understand the underlying drivers of high mesopredator densities and address these through landscape-scale intervention and policy changes.

Corrigendum

IbisEarly View CorrigendumFree Access Corrigendum This article corrects the following: Effects of overhead power-lines on the density of ground-nesting birds in open sub-arctic habitats Aldís Erna Pálsdóttir, Jennifer A. Gill, Snæbjörn Pálsson, José A. Alves, Verónica Méndez, Böðvar Þórisson, Tómas G. Gunnarsson, Volume 164Issue 4Ibis pages: 1257-1264 First Published online: June 14, 2022 First published: 15 February 2023 https://doi.org/10.1111/ibi.13187AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat It has come to the author's attention that a source of funding was missing from the published paper (Pálsdóttir et al. 2022). JAA was supported by CESAM via FCT/MCTES (UIDP/50017/2020 + UIDB/50017/2020 + LA/P/0094/2020), through national funds. REFERENCE Pálsdóttir, A.E., Gill, J.A., Pálsson, S., Alves, J.A., Méndez, V., Þórisson, B. & Gunnarsson, T.G. 2022. Effects of overhead power-lines on the density of ground-nesting birds in open sub-arctic habitats. Ibis 164: 1257– 1264. Early ViewOnline Version of Record before inclusion in an issue ReferencesRelatedInformation

Bioclimatic Preferences of the Great Bustard in a Steppe Region

(1) The intercorrelated effects of climatic processes and anthropogenic land use changes have been shown to govern the population declines in several bird species, which have led to global extinctions. Ground-nesting birds are especially sensitive to modifications in spatial as well as temporal patterns of climatic change. The Great Bustard (Otis tarda) is one of the most endangered species, which has suffered considerable range contractions and population declines in extensive areas of its historical distribution. (2) Here, we aim to (i) identify the key climatic predictors governing the historical distribution of the Great Bustard within the Carpathian Basin during the past three decades, (ii) provide spatial predictions for the historical range of the study species, and (iii) identify areas where species-specific conservation planning initiatives need to focus on by predicting the distribution of the Great Bustard for future time periods. To do so, here we apply bioclimatic niche modeling implemented in the MaxEnt software package, which is fitted on historical occurrence locations as a function of potential bioclimatic predictors. (3) We show that (i) the most important bioclimatic predictors governing the distribution of the Great Bustard are the annual mean temperature, mean temperatures of the wettest and driest quarters, as well as the annual precipitation; (ii) all lowland areas of the Carpathian Basin were suitable for the Great Bustard during historical time periods; (iii) the SDM predictions show the historical suitability of the Muntenia and Dobrodgea regions and the Upper Thracian Plain; and (iv) the future projections show a substantial decrease in the core distribution area, whereas the boundary areas are expected to remain stable. In summary, our study emphasizes that the distribution modeling of endangered taxa using historical records can strongly support species-specific conservation planning initiatives.

Amblyomma americanum (Lone star tick)

Amblyomma americanum, the lone star tick, is an aggressive three-host tick common in eastern North America with intense populations in the southern USA. Lone star ticks are sustained by feeding on white-tailed deer, ground-nesting birds, and a variety of other wild animals. These ticks also readily feed on humans and domestic animals, transmitting several pathogens. In apparent response to changes in habitat and host populations, the geographic distribution of this vector has contracted and expanded over the past century, spreading northward in recent decades, reclaiming its historic range.

Urban Avian Conservation Planning Using Species Functional Traits and Habitat Suitability Mapping

Urbanization adversely impacts biodiversity by reducing the quantity and quality of natural habitat areas. Additionally, the quality of natural habitat depends on its bio-physical characteristics (e.g., natural cover, impervious surfaces, urban tree canopy) as well as the functional traits of species inhabiting them (e.g., breeding/foraging habitat requirements). To better plan conservation of regional biodiversity in urbanized landscapes, it is therefore critical to assess the relationship between the landscape and the response of key Functional Trait Groups (FTGs) of species. To identify different FTGs of 116 avian species in the urbanized landscape of the Toronto region (Canada), we conducted a Functional Trait Analysis (FTA) using RLQ-fourth corner analysis. We focused on four species traits (diet, foraging, nesting, and territoriality) to identify the FTGs and their association with natural cover and landscape characteristics (landcover types, patch quality, habitat connectivity). Then, to predict FTG presence in relation to the landscape characteristics, we performed a Habitat Suitability Analysis (HSA). From this analysis, we found 21 avian FTGs with different habitat suitability values that correspond to forested patches and wetlands. The HSA for tree canopy, forest insectivore, and ground-nesting birds (or FTGs) have higher suitability values within forest patches, while aerial insectivores have higher suitability values in older residential neighborhoods indicating the value of the urban tree canopy. This methodological approach shows that by mapping habitat suitability by FTG one can identify strategic conservation areas that target multiple species, shifting efforts from a single species to a community-based functional focus. Our study highlights the conservation value of remnant and/or restored habitat patches in near urban and urban landscapes that help to maximize the persistence of regional avian biodiversity.

Protecting prey by deceiving predators: A field experiment testing chemical camouflage and conditioned food aversion

Complicated conservation problems may arise if predator numbers increase beyond their natural boundaries due to anthropogenic influence. For example, dramatic declines in ground-nesting birds are linked to increased nest predation by alien or human-subsidized mammals. While predator control can be temporarily effective, it is often laborious and carries ethical issues. Thus, we need alternative, non-lethal methods for reducing predator impact on their prey. We performed a landscape-scale experiment to study whether two non-lethal methods could protect ground-nesting waterfowl from nests predation. We spread either non-rewarding waterfowl odour (chemical camouflage) or eggs containing an aversive agent (conditioned food aversion) in the surroundings of study wetlands located in southern Finland. Predation of artificial waterfowl nests by red foxes decreased in sites with chemical camouflage, while there was no effect on predation by invasive raccoon dogs. Food aversion created less obvious effects than the chemical camouflage, but both methods indicated potential for reducing nest predation. Based on wildlife-camera data mesopredator observations did not, however, decrease near treatment wetlands. This suggests that treatments did not reduce predator activity, but affected foraging behaviour of predators and reduced their ability to find the nests. We conclude that managers considering non-lethal methods should carefully consider the effectiveness of different methods and potential species-specific responses. Nevertheless, our study support calls for wider use of non-lethal methods in reducing predator impacts on prey. These methods offer ethical and potentially effective approaches which keep native predator fauna intact, but create protection for vulnerable prey.

Accounting for predator species identity reveals variable relationships between nest predation rate and habitat in a temperate forest songbird.

Nest predation is the primary cause of nest failure in most ground‐nesting bird species. Investigations of relationships between nest predation rate and habitat usually pool different predator species. However, such relationships likely depend on the specific predator involved, partly because habitat requirements vary among predator species. Pooling may therefore impair our ability to identify conservation‐relevant relationships between nest predation rate and habitat. We investigated predator‐specific nest predation rates in the forest‐dependent, ground‐nesting wood warbler Phylloscopus sibilatrix in relation to forest area and forest edge complexity at two spatial scales and to the composition of the adjacent habitat matrix. We used camera traps at 559 nests to identify nest predators in five study regions across Europe. When analyzing predation data pooled across predator species, nest predation rate was positively related to forest area at the local scale (1000 m around nest), and higher where proportion of grassland in the adjacent habitat matrix was high but arable land low. Analyses by each predator species revealed variable relationships between nest predation rates and habitat. At the local scale, nest predation by most predators was higher where forest area was large. At the landscape scale (10,000 m around nest), nest predation by buzzards Buteo buteo was high where forest area was small. Predation by pine martens Martes martes was high where edge complexity at the landscape scale was high. Predation by badgers Meles meles was high where the matrix had much grassland but little arable land. Our results suggest that relationships between nest predation rates and habitat can depend on the predator species involved and may differ from analyses disregarding predator identity. Predator‐specific nest predation rates, and their relationships to habitat at different spatial scales, should be considered when assessing the impact of habitat change on avian nesting success.

Cages Mitigate Predation on Eggs of Threatened Shorebirds: A Manipulative-Control Study

Beach-nesting birds (plovers; Aves; Charadridae) are impacted by many natural and human-induced threats (e.g., people trampling, dogs, and natural predators). In this regard, the use of anti-predator cages on their nests is effective in order to mitigate some of these pressures (i.e., predation). To evaluate the efficacy of anti-predator cages and the causes of nest failure in a breeding site of two species (Charadrius alexandrinus and C. dubius), we carried out a control-experimental design, comparing false nests (n = 69) in cages (experiment; n = 30) with false nests without cages (control; n = 39). We carried out the study in three seasonal periods (May, June, and July), controlling predations after three periods (three, six, and nine days) since positioning, recording the frequency of eggs still present and evidencing any predation event. The percentage of residual eggs was significantly higher in experimental nests when compared to control nests in all recording periods. Considering 59 predation events on false nests, the most important predators were: in experimental nests (n = 21) the fox, Vulpes vulpes (47.6%), and in control nests (n = 38), the hooded crow, Corvus cornix (50%). Our data suggest that the use of anti-predator cages significantly limits predation on eggs and therefore is likely to increase the hatching success in these ground-nesting birds independently in the seasonal period. However, also in the presence of a cage, the fox is a relevant egg predator.

Weather conditions determine reproductive success of a ground-nesting bird of prey in natural dune grasslands

The Short-eared Owl (Asioflammeus) inhabits open grasslands and belongs to the ground-breeding birds that have experienced the most severe declines during recent decades. Here, we studied nest and fledgling survival of the owl species in relation to (i) habitat composition, (ii) vegetation structure, (iii) weather conditions and (iv) vole abundance. The study was conducted on the East Frisian Island of Spiekeroog (southern North Sea, Lower Saxony, Germany), which harbours one of the last remaining permanent populations of the species in Central Europe. With a mean hatching success of 5.6 young per nest (N = 34) and an average probability of nest survival of 0.9 (N = 28), values ascertained in this study exceeded those reported in previous research. We attribute this to the special environmental conditions on the island, i.e. (i) the absence of mammalian mesopredators such as the Red Fox (Vulpesvulpes), (ii) nearly no disturbance through agricultural measures and (iii) low level of human disturbance due to legal regulations of the National Park. By contrast, the survival of fledglings was lower than survival of nests and varied considerably between the investigated years. Weather conditions were the key driver of fledgling survival. Maximum wind speed and sunshine duration had a negative effect on the probability that chicks successfully fledged. Both lead to reduced hunting success, and the former is also associated with increased costs for thermoregulation. Consequently, increasing frequency of extreme weather events caused by climate change could negatively impact the breeding success of vole-dependent raptors, such as the Short-eared Owl.

Human-wildlife interactions: presence of the ground-nesting Spotted Thick-knee across a South African mosaic urban landscape.

Urbanisation has increasingly encroached on numerous bird species' natural habitats, generally negatively affecting their persistence. Furthermore, increased human-wildlife interactions may benefit or be detrimental to the long term persistence of these species. The Spotted Thick-knee (Burhinus capensis), a ground-nesting species, persists in some mosaic urban landscapes in South Africa. We, therefore, assessed the presence of Spotted Thick-knees and their interactions with humans in the fragmented natural and human-modified landscape of Pietermaritzburg, KwaZulu-Natal. We conducted presence-only surveys at 52 locations between July 2019 and December 2020. ‘Presence’ locations for Spotted Thick-knee were identified via active surveying and public participation. Newspaper articles were distributed in June 2019, requesting information on Spotted Thick-knee sightings. Questionnaires were also sent to respondents to collect qualitative information regarding their perceptions and observations of this species in Pietermaritzburg. We established that the presence of Spotted Thick-knee's at known locations was not random. They were present at 30 out of 52 sites for 75% of this study's duration. Fewer sites had Spotted Thick-knees present during non-breeding months than breeding months. Respondents' feedback highlighted the pressures associated with Spotted Thick-knees persistence in human-modified mosaic landscapes, particularly predation and disturbance by domestic pets. Our study highlights that some ground-nesting birds, such as Spotted Thick-knees, persist in mosaic urban landscapes, despite the anthropogenic pressures. This study highlights the need to address the paucity of studies on ground-nesting birds in mosaic urban landscapes to determine general trends.Supplementary informationThe online version contains supplementary material available at 10.1007/s11252-022-01254-3.

Aggressiveness in a subtropical shorebird's nest defense is adjusted to the predator species and shared by conspecifics.

Aggression is an important component of an animal's defense when protecting offspring from predators. Ground nesting birds use a variety of defense strategies. However, their choice according to situation context is poorly known, especially in nonpasserines and in the subtropics and tropics. The ability to distinguish between differently dangerous predator species and the opportunity to share defense with conspecifics are potentially important but little-studied aspects of nest defense strategy. We experimentally studied the nest defense of Red-Wattled Lapwing in an individually marked population in a desert area near Dubai, UAE. We used three stuffed models representing 1) a predator dangerous both to adults and to nests (a cat), 2) a nest predator (a raven), and 3) a harmless reference model (a moorhen). We confirmed that the lapwings distinguished between predator species (being most aggressive toward the cat, and least aggressive toward the moorhen) and adjusted their defense strategy accordingly. In addition, conspecific visitors play a variety of roles in parents' defense strategy. They can strengthen the parental reaction, or they can assist in distracting a predator. The visitors included not only nesting neighbors but also nonbreeding floaters. Both parents participated in nest defense to a similar extent, regardless of incubation stage and ambient temperature. This study provides new insight into the complexity of the defensive patterns in ground-nesting birds inhabiting a hot environment. Comparative experimental research on a range of environments, with various bird species and predator models, can help us to understand the drivers of these defensive behavioral patterns.

Detectability and predator strategy affect egg depredation rates: Implications for mitigating nest depredation in farmlands

Predation is a major evolutionary force in animal ecology. Mechanisms by which prey coloration provides camouflage has been widely studied. However, predator response to prey camouflage and concealment has received less attention. Understanding vegetation structure effect on depredation success could help managers design strategies to mitigate the depredation of managed species (e.g., threatened or hunted). We aimed to investigate the relationship between depredation rate, nest camouflage and concealment in ground-nesting birds of farmlands, and their predators. We set up an experiment of 2576 artificial ground nests to assess the role of egg coloration (white, light green, and dark green), egg size (small, medium, and large), and vegetation structure (vegetation height and land use) in nest survival rates. We also explored the role of predator searching strategies by analysing clumped depredation and multiple depredation events. Of the nests, 34.0% were depredated, with corvids as the predators 78.5% of the time. Corvid depredation decreased by 40–60% in grasslands and spring crops above a vegetation height of 30 cm. In contrast, vegetation height and land use may be of far less importance in avoiding depredation by other predators. The probability of depredation was spatially clumped, suggesting that predators increase search effort in areas where a nest was previously encountered. Neighboring depredation and depredation repetition were more frequent in corvids than in other predators. Our study indicates that nests in vegetation higher than 30 cm had a drastic reduction in depredation rates by corvids. Management of vegetation structure is a key tool to mitigate depredation risk, and improving the availability of alternative food resources may be a complementary tool.

Nesting habitats of free-ranging Indian peafowl, Pavo cristatus, revealed by sniffer dogs in Okinawa, Japan

The Indian peafowl, Pavo cristatus, is the largest of the pheasants and ground-nesting bird. Because this species was introduced in Okinawa, Japan about 40 years ago and is now increasingly recognized as a pest in the Yaeyama region, and the extermination of this species has been promoted for ecosystem conservation. It was thought that there is need to develop a method to reduce the peafowl population and dogs were trained to detect them. We faced two difficulties in developing sniffer dogs to detect peafowl nests as below; (i) it is difficult to obtain a sufficient number of eggs to train the detection dogs, (ii) another difficulty is that the nesting period of peahens and the preferred vegetation used for nesting in Okinawa have not been reported. At first, we screened and trained two dogs of Welsh Corgi Pembroke and one dog of Brittany Spaniel for peafowl nest detection dogs with peahen feathers instead of peahen eggs. These dogs demonstrated a 100% sensitivity rate and there were no false-positives of their precision test. In second step, display survey of peacock to predict the nesting period of peahen was conducted in Kohama (KHM) and Kuroshima (KRS) islands, and the earliest dates of trail displays were observed in late February between 2014 and 2019 in both Islands. We predicted that the eggs would begin hatching in early April. We surveyed peahen nests for a total of 837 h and 1153 km on 962 transects with sniffer dogs and detected 423 peahen’s nests in KHM and KRS islands between 2014 and 2019. Peahens made her nests mainly in Poaceae or Asteraceae plants in research areas. The peak hatching was between mid-April and early May. In this study, we were able to detect peahen nests in the field by dogs trained with peahen feather, and we also identified the exact nesting season and preferred vegetation in Okinawa to control of Indian peafowl as an invasive species.

Contrasting effects of eucalyptus, pine and oak plantations on nest predation risk in Mediterranean grasslands

Large scale afforestation (i.e., establishment of forests on farmland, grassland and other land not previously forested) is increasingly regarded as a cost-effective option to mitigate climate change by promoting carbon sequestration. However, this strategy can have negative biodiversity impacts, potentially causing the loss and fragmentation of open habitats of conservation value, as well as edge effects that can extend well beyond forest boundaries. Mitigating impacts of afforestation programs thus requires a detailed understanding of the mechanisms whereby they affect biodiversity, particularly where new plantations are established close to areas important for open habitat species. Here, we examined how afforestation with oak, pine or eucalyptus trees, commonly planted in Mediterranean Europe, may have distinct effects on nest predation risk of grassland birds in southern Portugal. We used artificial nests with quail eggs and camera traps to: (i) identify nest predators and estimate predation risk of ground-nesting birds in grasslands adjacent to oak, pine and eucalyptus plantations across a distance gradient (0 m to 300 m) from the plantation edge; and (ii) examine how predation risk was influenced by avian predator abundance, sward height and vegetation clearing for photo-monitoring (nest-site manipulation), and their interactions with plantation type. Carrion crow was by far the main egg predator identified, followed by Montagu’s harrier, raven and magpie. Overall, nest predation risk and predator abundance were higher around eucalyptus plantations, compared to either pine or oak plantations. Predation decreased with increasing sward height, but this effect was less noticeable when vegetation around nests was cleared. In pine and oak plantations, predation risk was slightly higher close to edges, and decreased with distance from the edge. Conversely, in eucalyptus plantations predation was lower close to edges, and increased with distance to edges. Distance effects around eucalyptus plantation were, however, absent in manipulated nests. Overall, results show that afforestation with different tree species has distinct impacts on predation risk of artificial nests in Mediterranean farmland. This is probably a consequence of an increasing structural complexity of the plantations, from oak to eucalyptus, driven by differences in tree growth rates and undergrowth cover. These findings suggest that farmland afforestation should favour agro-forest plantations with slow growing species (oak and pine) to mitigate negative effects on breeding grassland birds in adjacent open habitats.

Genetic Insights Into the Introduction History of Black Rats Into the Eastern Indian Ocean

Islands can be powerful demonstrations of how destructive invasive species can be on endemic faunas and insular ecologies. Oceanic islands in the eastern Indian Ocean have suffered dramatically from the impact of one of the world’s most destructive invasive species, the black rat, causing the loss of endemic terrestrial mammals and ongoing threats to ground-nesting birds. We use molecular genetic methods on both ancient and modern samples to establish the origins and minimum invasion frequencies of black rats on Christmas Island and the Cocos-Keeling Islands. We find that each island group had multiple incursions of black rats from diverse geographic and phylogenetic sources. Furthermore, contemporary black rat populations on these islands are highly admixed to the point of potentially obscuring their geographic sources. These hybridisation events between black rat taxa also pose potential dangers to human populations on the islands from novel disease risks. Threats of ongoing introductions from yet additional geographic sources is highlighted by genetic identifications of black rats found on ships, which provides insight into how recent ship-borne human smuggling activity to Christmas Island can negatively impact its endemic species.

Nest remains are insufficient to identify predators of waterfowl nests

Context Nest predation is a leading cause of nest failure for most ground-nesting birds. Methods that allow for accurate classification of fate and identification of predators are important for understanding productivity and conservation strategies. Past studies have used a visual inspection of nest remains to determine nest fate and predict predator identity. Most formal assessments of these methods have addressed small-bodied birds nesting in trees or shrubs, and have revealed that use of evidence at nests can be relatively accurate for determining nest fate but may lead to incorrect conclusions regarding predator identity. However, few have tested the latter hypothesis for larger ground-nesting birds with precocial young. Aim We aimed to evaluate a classification system developed for determining nest fate and identifying predators of waterfowl nests, at both the scale of individual nests and across the study area. Methods From 2016 to 2020, we located 989 blue-winged teal (Spatula discors), mallard (Anas platyrhynchos) and gadwall (Mareca strepera) nests in central North Dakota. We placed cameras at a subset of 249 nests and recorded evidence of nest remains at depredated nests. Key results The most common predators were American badgers (Taxidea taxus), followed by striped skunks (Mephitis mephitis), raccoons (Procyon lotor) and red foxes (Vulpes vulpes). Using evidence of nest remains, we determined nest fates with high accuracy (98.0%). However, evidence of nest remains was only sufficient for identifying predators at 50% of nests, and the classification system was correct only 69.7% of the time. The predicted proportion of predators across the study area differed between the classification system and our video evidence as well. Conclusions The accuracy of predator identifications based upon the classification system that we evaluated was not supported at any scale. Implications Our results suggest that evidence of nest remains can be used to determine nest fate for large-bodied precocial, ground-nesting birds, but accurate identification of nest predators will require alternative methods such as nest cameras.