Artificial Nest Predation Research Articles

Landscape contexts shape the effects of local factors on the predation of artificial bird nests in cocoa agroforests

ContextNest predation represents the pivotal threat to bird reproduction in disturbed environments. Although some agricultural systems, such as agroforests, are considered biodiversity-friendly, there is still a lack of information on how factors acting at different spatial scales shape nest predation in these environments.ObjectivesWe assessed the effects of landscape (native forest cover and total forest cover) and local factors (number of shade trees, cocoa trees, understory plants, and canopy openness) on the number of predated bird nests in cocoa agroforests.MethodsArtificial nests were placed on the ground and in the understory of 30 agroforests located in the Brazilian Atlantic Forest. The agroforests were embedded in three regions with different amounts of native forest remnants and areas designated for cocoa agroforests and cattle pastures. Using GLMM models and the Akaike information criterion, we identified which environmental predictors can determine nest predation in agroforests.ResultsWe detected that ground nests are more vulnerable to predation than understory nests. We also observed higher nest predation in the region dominated by cocoa agroforestry systems than in the region with high forest cover. Our statistical models evidenced an increase in the number of predated nests in agroforests presenting a high number of understory plants and cocoa trees, particularly when located in deforested landscapes.ConclusionsOur study highlighted that the landscape context in which the cocoa agroforests are situated can modulate the effect of local characteristics on the predation of artificial nests.

Disentangling ground-nest predation rates through an artificial nests experiment in an area with western capercaillie (Tetrao urogallus) presence: martens are the key

The western capercaillie (Tetrao urogallus) is a species of conservation concern that has been experiencing a severe decline in many regions of Europe. The poor breeding success rather than mortality of full-grown birds has been suggested to be responsible for its decline, been the nest loss a potential driver of the low productivity (number of chicks per female and year) of capercaillie. Working in a capercaillie population in the Pyrenees, we aimed to provide further insights into nest predation by monitoring 82 artificial nests (58 of them with camera traps), and estimating the population density of predators using camera traps and applying random encounter model and camera trap distance sampling. Pine/stone martens -Martes foina, Martes martes- were the species with higher nest predation rates (23%) despite being the less abundant (0.49 ind/km2), followed by foxes -Vulpes vulpes- (11%) and a population density of 3.37 ind/km2, and wild boar -Sus scrofa- (4%) and 6.95 ind·km− 2; predators could not be identified at 27% of the events. After fitting statistical models on the nest predation data, we observed that the martens’ encounter rate (i.e. number of martens detected per camera and day) and the altitude had a positive significant effect on the artificial nest predation probability. While caution is recommended in artificial nest experiments, our results are valuable highlighting the importance of martens and red foxes when addressing nest predation to promote the breeding success and population recovery of western capercaillie populations.

Forest habitat loss and human land use alter predation of artificial ground nests

Anthropogenic disturbances including forestry, urbanisation and agricultural expansion are causing significant habitat loss and fragmentation in boreal forests, leading to changes in ecosystem function. Here, we ask whether these anthropogenic disturbances alter predator–prey spatial overlap in the boreal forest landscape, leading to increased nest predation rates on ground-nesting birds such as forest grouse. To study the roles of forest loss and fragmentation on nest survival, we conducted an artificial nest predation experiment in Finland using 370 camera traps across landscapes varying in forest quantity and fragmentation (measured by edge habitat length). Our artificial nests mimicked the early egg-laying stage of forest grouse. Our primary hypotheses were that nest survival is higher in landscapes with more continuous forest habitat and less edge habitat, and that predator communities differ based on the matrix habitat between the forests. Our findings revealed a negative association with forest cover and nest predation risk, but forest fragmentation, measured as edge length, had no detectable relationship with the nest predation risk. Additionally, nest predation risk depended on the matrix habitat types, with agricultural land and urban areas exhibiting higher predation rates than clearcuts exhibited. Furthermore, the number of predator species observed was positively associated with the level of urban area present. We found that the raccoon dog (Nyctereutes procyonoides), a rather novel invasive alien species, was the most common mammalian nest predator, indicating a change in the predator community. Our results highlight the possible impact of both forest loss and the presence of agricultural and urban areas in the landscape on avian nest survival in forest habitats. We conclude that forest loss may be a more important factor affecting nest predation risk than forest fragmentation.

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.

Bird eggs or wheat: Assessing the impact of an overabundant crow species in a landscape mosaic in the Negev desert of Israel

The intensification of land alterations promotes the spread of invasive and overabundant species. Yet, controlling such species is not always derived from extensive impact assessments. We explored the consequences of the Hooded Crow (Corvus cornix) expansion into the arid region of Israel on the local biota. Crow activities and their potential effects were examined in a nature reserve and its surrounding agricultural lands. We used line transect counts and Global Positioning System (GPS) tagging to assess crow habitat utilization patterns. To measure crow impact on the local community, we compared artificial nest predation rates between agrarian and natural land types. Compositional analysis of the GPS-tagged crows' home range indicated a preference for arable lands, with low utilization of natural areas, limited to the vicinity of the nature reserve edges. Accordingly, Hooded Crows were among the dominant nest predators, mainly in agricultural lands or near their borders. These findings suggest that crow impact on natural habitats is low and limited to highly exploratory individuals. As crow abundance is expected to continue increasing, we call for short and long-term management actions, including establishing agri-environmental schemes to boost the local community's resistance to overabundant and invasive species.

Nest density, egg conspicuity, vegetation structure and seasonality affect artificial nest predation in the Brazilian Cerrado

AbstractNest predators use visual, acoustic and chemical cues to locate nests. In the Neotropics, predation is high being the main cause of nest failure. Despite that, it is still not completely clear what kind of information predators are using to find nests or whether predators respond differently according to habitat characteristics. Here, we executed an experimental manipulation to investigate how different ecological factors influence nest predation probability. We hypothesised that egg conspicuousness, nest clustering and a more open vegetation structure would increase nest predation probability, and that nest predation would be higher during the breeding season of most avian species in the region. We used artificial nests baited with plasticine and quail eggs (Coturnix coturnix), manipulated egg coloration and nest density. Artificial nests were distributed over forest and savanna-like vegetations. Overall predation rate was 40.9%. We found that nests baited with conspicuous eggs, located in open habitats, at higher densities and during the dry period were more predated. Results suggest that main predators must be visually orientated, and that egg crypsis is an important trait for open-nest species in the area. Moreover, a higher nest density may affect predator behaviour, favouring an increase in nest searching, which may be facilitated in open habitats.

Visual cues do not increase artificial nest predation in a Brazilian tropical savanna

Visual cues do not increase artificial nest predation in a Brazilian tropical savanna

Does Experimental Non-Reclaimed Sites Differ from Technically Reclaimed Areas in the Risk of Artificial Bird Nest Predation?

Abstract Areas left to natural development have been found to be sites with higher diversity and conservation value of local communities, including bird communities, compared to artificial reclamation of post-industrial areas. Most of the studies conducted so far have focused primarily on bird communities of post-mining areas, in terms of the diversity and richness of species. Our study dealt with bird nest predation on specific case of two experimental sites (20 and 32 ha) with more than a 20-year history of primary spontaneous succession established within the technical reclamation of the Radovesická spoil heap (approx. 1,200 ha, North Bohemia, Czech Republic). In the spring of 2018, we conducted a predation experiment using artificial nests (ground and elevated), installed within both succession areas and beyond, in the adjacent artificially reclaimed areas. We monitored the way of restoration and the distance of the nest placement from the succession-reclamation sites edge. The rate of predation was very high: 92.5 % in reclaimed area and 89.4 % in spontaneous successions. None of the observed factors analysed in the generalised linear model (GLM) have conclusively explained the risk of predation. The two experimental succession sites did not differ from the surrounding reclaimed sites in terms of the risk of predation, nor did they significantly influence predation risk on reclaimed sites. We believe that both relatively small and mutually isolated areas do not provide enough of an inner environment without or with at least a limited effect of predation pressure coming from adjacent reclaimed areas.

Carcasses attract invasive species and increase artificial nest predation in a desert environment

In addition to feeding on animal remains, many scavengers also function as predators. Carcasses may therefore affect local animal communities by attracting facultative scavengers and increasing predation risk for other species in the vicinity of the carcasses. This risk may be elevated in low productivity environments, especially where humans increase carcass production and where facultative scavengers include invasive species. In June and October 2018, we monitored experimentally placed red kangaroo (Osphranter rufus) carcasses and artificial bird nests in two different habitats in the Simpson Desert, Australia, to identify the nest predators attracted to the carcasses, and to determine how carcasses affect overall and predator-specific nest predation. We modelled our nests to approximate those of the ground nesting little buttonquail (Turnix velox) and the endangered night parrot (Pezoporus occidentalis). Native Corvus spp. and then invasive red foxes (Vulpes vulpes) were the top carcass visitors and nest egg predators. Carcass presence and open habitat increased overall nest predation and fewer artificial parrot nest eggs were depredated compared to those of quail. Open habitat and carcass presence only increased predator-specific nest predation by foxes, but corvid nest predation was highest in June 2018, and for the artificial quail nest types. Foxes were the main predator of eggs from night parrot nests. Our study shows that carcass provisioning by humans may have indirect, deleterious effects on ground nesting birds, and indicates that foxes might pose a greater threat to night parrot populations than previously recognised.

A high rate of rodent-mediated predation on artificial nests in hedgerows of an agricultural landscape in southern Chile

ABSTRACT We evaluate, experimentally, the relative rate of artificial nest predation in hedgerows in southern Chile. Predation on artificial eggs was extremely high, with rodents being the main nest predators.

Upland rush management advocated by agri‐environment schemes increases predation of artificial wader nests

AbstractFarmland birds, including breeding waders, have declined across Europe. One frequently advocated strategy to facilitate population recovery is using agri‐environment schemes (AES) to improve vegetation structure. A key example is cutting dense rush Juncus to open the sward which aims to increase the abundance of wading birds, for example by improving foraging conditions. Effects on breeding success are, however, unknown. This is a critical knowledge gap as high nest and chick predation rates are a key driver of wader declines. For wader species that nest across a range of sward structures, for example Eurasian curlew Numenius arquata and common snipe Gallinago gallinago, converting denser swards to more open ones may reduce opportunities for nest concealment and thus increase predation risk. Due to the difficulties of locating large numbers of wader nests, we assess rush management impacts on nest predation risk using artificial wader nests (n = 184) in two upland areas of England, using fields in which rush is managed according to AES prescriptions (treatment; n = 21) or un‐managed (control; n = 22) fields. Daily nest predation rates (DPRs) were twice as high in treatment (0.064 day−1) than control fields (0.027 day−1). Within treatment fields, DPRs were twice as high for nests in cut rush patches (0.108 day−1) than in uncut rush (0.055 day−1). Modelling links higher DPRs associated with rush cutting to the resultant shorter and less dense vegetation. Our results highlight the need to assess how AES prescriptions that alter vegetation structure impact all aspects of the target species’ fitness and thus determine population recovery. Studies using real wader nests should test whether AES rush management inadvertently creates an ecological trap by altering vegetation structure, and identify the sward structure and configuration that optimizes trade‐offs between foraging conditions and nest predation risk.

Conditioned food aversion reduces crow nest predation: An improved framework for CFA trials

The decline of numerous bird species worldwide has been attributed to increased nest predation pressure often associated with anthropogenic factors. Identifying effective management strategies to reduce nest predation is therefore a conservation priority, but tests of management strategies often lack appropriate control treatments. Conditioned Food Aversion (CFA) is a non-lethal method of predator control where distasteful or illness-inducing artificial eggs are used to deliberately deter predators from nests or eggs of vulnerable prey species. Here, we test whether CFA can reduce predation pressure by pied crow on nests using an improved experimental methodology that includes spatial and temporal controls, non-rewarding control egg treatment and concurrent predator monitoring. At the Berg River Estuary, South Africa, we monitored survival of artificial plover-type nests and predator abundance in six sites across three experimental phases (pre-treatment, treatment and post-treatment). During the treatment phase, sites received either illness-inducing (carbachol-treated) or control (water-filled) quail eggs. Our results show that artificial nests survived longer after carbachol treatment in the post-treatment phase, both when compared to the pre-treatment phase and to the control treatment. Nest cameras revealed that pied crow were responsible for nest predation and point counts demonstrated that crow abundance did not change during the study period in control or treatment sites. Together, our results indicate that carbachol treatment induces CFA and reduces artificial nest predation by pied crow, and that mechanistically CFA in crows is likely driven by learning. This study demonstrates the potential for CFA to reduce nest predation and identifies a rigorous methodology for CFA trials.

Camera traps reveal the predation of artificial nests by free‐ranging Azara’s agoutis, Dasyprocta azarae Lichtenstein, 1823, in central Brazil

AbstractAgoutis, Dasyprocta spp., are medium‐sized rodents distributed in Neotropical region. Their diet is usually described as granivorous/frugivorous, and agoutis are recognised as important seed dispersers. Here, we present two spatially and temporally independent records of egg predation by Azara’s agouti, Dasyprocta azarae, in fragments of Cerrado savanna forest. In both cases, the agoutis ingested quail eggs that had been placed in artificial nests at ground level, 100 m from the edge of the forest. As Dasyprocta is a herbivorous rodent, this predatory behaviour is unexpected and may represent an opportunistic foraging strategy. These observations provide important new insights into the feeding biology of agoutis and highlight the value of camera traps as a tool for the collection of data on the behavioural ecology and natural history of vertebrates in general.

Landscape and habitat affect frequency of artificial duck nest predation by native species, but not by an alien predator

Annual Finnish breeding duck surveys over the last 30 years show declining abundance among several species and greater declines on eutrophic waters than oligotrophic lakes. It has been suggested that habitat-related differences in the rate of increase in predation pressure is a potential explanation for contrasting duck population trajectories between habitats. We assessed potential duck nest predation risk and predator presence in various duck breeding habitats in Finland and Denmark by monitoring 333 artificial duck nests with wildlife cameras during 2017–2019. Predation rates differed between landscapes and habitats: nest predation rate and predator diversity were lowest in forested and highest in agricultural landscapes. Forest nests further from water bodies survived better than nests around shorelines of permanent lakes. Of the 16 different predator species detected, the most common were Eurasian magpie (Picapica), hooded crow (Corvus corone) and raccoon dog (Nyctereutes procyonoides). While predation by specific native predator species was typically associated with particular habitats and landscapes, the alien raccoon dog appeared to be a true habitat generalist, ubiquitous and common across all habitats and landscapes. Based on these results, the higher duck nest predation pressure along shorelines, especially in agricultural landscape lakes, due to increased diversity and abundance within the predator community, may contribute to the declining population trends of ducks.

Prescribed Fire Has a Greater Impact on Artificial Nest Predation Than a Recent Bison Re-introduction in Illinois Tallgrass Prairie

Grazing differentially affects both the abundance and breeding success of grassland birds (e.g., due to differences in bird species' preferences for sparse or dense vegetation structure, nest predator response to grazing, and/or trampling of nests). Coupled with prescribed fire, grazing impacts can be compounded by pyric herbivory—the preference of grazers to choose newly-burned sites in which to graze. The purpose of this study was to determine how a recent re-introduction of American bison (Bison bison) coupled with prescribed fire may impact grassland bird nests. Artificial nests were used to determine if grazing and fire impacted nest success, total mammalian depredation, and depredation by the most common nest predator, mice (Peromyscus spp.). Artificial nests were placed in sites with and without bison before (2014) and after bison re-introduction (2015–2018); sites had fire return intervals from 1–2 y. We found the re-introduction of bison had a negligible influence on nest success and total mammalian depredation. However, nest success was lower in burned sites compared to unburned sites. The decrease in nest success correlated with an increase in total proportion of depredation events in burned sites compared to unburned sites. In addition, the proportion of Peromyscus spp. depredation events was marginally higher in burned sites compared to unburned sites. Although predation by Peromyscus increased after bison re-introduction, prescribed fire differences drove this change. Our results suggest prescribed fire may increase nest predation of artificial nests, indicating a possible impact on ground-nesting grassland birds. In contrast, bison had a negligible impact on artificial nest success in the first 4 y following their re-introduction.

Downside in habitat restoration: Predation of artificial nests by invasive rodents in Macaronesian laurel forest

This study assessed black rat predation on artificial nests in relation to restoration undertaken in the Macaronesian laurel forest in São Miguel Island, Azores, evaluating three different points: nest predation rate; rodent relative abundance; and abundance of invertebrates, flowers and fruits. In general, artificial nest predation increased after habitat restoration, and significant differences were found on a successfully restored forest site between year 0 and year 10. Rodent capture rates were significantly higher one decade after habitat restoration, and there were significantly more flowers and fruits available in the area with a higher restoration success than in the area with less restoration success. The results show that habitat restoration leads to an increase of black rat relative abundance, which is consistent with the increasing of artificial nest predation, and with the higher abundance of vegetal food on the successfully restored forest site. It is important to study and analyze these complex interactions which can have an influence on the survival of target species to conserve.

Comparing artificial ground nest predation pressure and predator composition in mongoose-infested and non-mongoose-infested areas of northern Okinawa Island

Comparing artificial ground nest predation pressure and predator composition in mongoose-infested and non-mongoose-infested areas of northern Okinawa Island

Reducing nest predation of ground-nesting birds through conditioned food aversion

Populations of many ground-nesting bird species have declined substantially due to several factors, and predation can be a leading contributor to these declines. As a method for reducing the nest predation on ground-nesting birds, we tested whether conditioned food aversion (CFA) can reduce red-legged partridge (Alectoris rufa) nest predation by red foxes (Vulpes vulpes). With a before-after control-impact design we deployed 1329 artificial nests in two different habitats in Central Spain using thiram as an aversive. Artificial nests were monitored by camera traps to identify the red fox individuals during the predation events. 26 foxes were GPS-tagged to monitor their spatial movements and feeding behavior. Partridge density and productivity were monitored to assess the thiram treatment effect on partridge population. Thiram treatment decreased artificial nest predation by foxes in both study sites by 26.8–50.1%, but this was compensated by an increased predation by other predators, possibly enhanced by the availability of our artificial nests. 78% of identified foxes that ingested thiram-treated eggs, stopped nest predation after treatment. Foxes maintained stable territories during the whole study period. Partridge productivity was 132–677% higher in thiram-treatment areas than in control areas, and partridge density after treatment increased more in thiram-treated areas (193–292%) than in control areas (1.8–99%). Our study shows that CFA reduced ground nest predation by foxes, and had a positive effect on the partridge population despite the compensatory predation. This method could be used as a non-lethal tool for conservation of endangered ground-nesting bird species.

Ground nesting birds in roadside borders of the Argentine Pampas: habitat use and predation risk of artificial nests

Habitat loss and fragmentation have led to grassland bird declines, with ground nesters particularly vulnerable. Roadsides could provide habitat, although their suitability depends on several roadside and field characteristics. Vegetation structure determines foraging and nesting site availability. In addition, road delimits sharp edges where the activity of nest predators is usually higher, whereas herbaceous vegetation determines ground nest concealment. Trees could provide lookouts to predators, and modified habitat and woodlands in surrounding fields could offer additional resources to predators. Our objective was to assess habitat suitability for ground nester birds in roadsides belonging to one modified grassland of the Argentine Pampas. We surveyed birds (90 plots) and monitored artificial nests (60 plots) in different road types: unpaved, paved of one-lane per side, and paved of two-lanes per side. Within each road type, we evaluated the relationship that ground nesters abundance had with vegetation structure of roadsides and surrounding fields. In addition, we related predation of artificial nests with the proximity to the road, roadside vegetation, and modified land and woodlands of surrounding fields. We made 2832 records of 84 species using roadsides, including 1083 records of 13 ground nesting species. Abundance of ground nesters increased with tall grass cover of roadsides and decreased with the number of native trees within roadsides. Roughly half (31/60) of the artificial nests were predated and 82.6% of the identified egg-marks were of mammal teeth. Nest predation decreased with nest proximity to the road. Our results emphasize the importance of tall grass cover of roadsides for the conservation of ground nesting species, and the necessity of monitoring natural nests in order to clarify the effect of trees, proximity to the road, and other environmental variables on nest success.

Changes in grassland bird communities and breeding success after a fire in the Argentinian Pampas

Fire is responsible for the structure and composition of the biological communities in grasslands, despite this, few studies evaluate the effects of fire on bird communities, especially in the southern cone of South America. We compared the structure and composition of vegetation, bird communities, density of nests and predation rates between burnt and unburnt areas in grassland habitats in the Argentine Pampas during two reproductive seasons following a fire. The abundance, richness and diversity of birds were lower in the burnt areas and followed a pattern of interannual recovery associated with the increase in vegetation cover. The density of nests and the number of nesting species was higher in the controls only during the first season. The risk of predation of artificial nests in burnt areas was greater 1 year after the fire in respect to the controls, this difference decreased over time in inverse relationship with the percentage of plant cover surrounding the nests. Our results highlight the importance of a good vegetation structure and cover to support abundant and species-rich bird communities, as well as high values of nest density and reproductive success, and the ability of vegetation and bird communities to recover after the fire. However, this successional and temporary loss of habitats of high nesting value should be analyzed on a larger scale in order to consider the effect of the total reduction, and the fragmentation of the grasslands in a good state of conservation, on the population dynamics of grassland birds.