Predation on artificial bird nests in chaparral fragments

Summary The predation rate of artificial bird nests was measured in disturbed chaparral habitat fragments and at an unfragmented site in coastal San Diego County, California USA. Local extinctions of chaparral birds has been previously shown to occur in these fragments. The predation rate was highest at the unfragmented site. Among fragments, predation was higher at moderately disturbed than at highly disturbed sites. These results suggest that nest predator species diversity or density is reduced in disturbed chaparral fragments. Nest predation is probably not the most important cause of the observed loss of chaparral breeding bird diversity in these fragments.     

Predation of Lapwing Vanellus vanellus nests on lowland wet grassland in England and Wales: effects of nest density, habitat and predator abundance

There is concern that predation of Lapwing Vanellus vanellus nests may create additional pressure on declining populations of this species in Europe. At seven sites in England and Wales, daily nest predation rates on 1,390 nests were related to variables using Generalised Linear Mixed Models. The strongest predictor was Lapwing nest density (number of nests within 100 m): predation rates declined as nest density increased. Since nocturnal species, probably mammals, have been identified as the major predators of Lapwing nests at these sites, these results suggest that Lapwings are able to deter mammalian predators or may settle to nest at high densities in areas with low predation pressure. At the site level, there was no relationship between Lapwing nesting density and fox density, and a positive relationship with Carrion Crow Corvus corone nesting density. There was a weaker effect of distance to field boundary: nests closer to boundaries were more likely to be predated. Weak interactive effects between crow density and both nest visibility and distance to vantage point were identified in models using a reduced subset of nests. These were counter-intuitive, did not persist in the larger data set, and do not have obvious explanations. If Lapwings nesting at high density are able to deter predators, there are implications for land management. Smaller areas could be managed within potential breeding habitat to encourage Lapwings to nest in dense colonies. Selection of larger fields for such management, where nests could be located far from the field boundary should improve the value of such measures.     

Predation on wader nests in Europe

The population declines of waders in Europe are widely considered to have resulted from habitat loss and degradation due to agricultural changes. However, recent empirical evidence suggests that levels of predation on wader nests are unsustainably high in many cases, even in some situations where breeding habitat is otherwise favourable. We review the published and 'grey' literature on nest predation on waders in Europe and quantify the relative importance of the major predators. Nest cameras offer the least biased method of identifying and quantifying nest predators. A small number of camera studies, in combination with others utilizing nest temperature loggers, indicate that nocturnal/mammalian predators make the largest contribution to wader nest predation. More than half of site-years or studies reviewed reported clutch failure rates of over 50% attributable to predation alone, a rate that is likely to be associated with declining populations, although parameters such as chick and adult survival will also affect population trends. Correlates of wader nest predation are documented, with time of season, field type and management, distance to habitat/field edge, wader nest density, and abundance of mammalian predators being most consistently identified. Future directions of research into wader productivity are discussed, and we suggest that studies quantify additional life-history parameters such as chick survival, as well as examining the predator community, wherever possible.     

Predation on nests: a case of apparent competition

We describe a field experiment designed to evaluate indirect effects in a prey community sharing common predators. A simple prey community was mimicked with two types of artificial nests. Firstly, it was shown that predation rate increased with nest density when only a single prey was present. Secondly, it was shown that an increase in the density of one nest type increased the predation rate on another type. This is the first experimental evidence for indirect effects in vertebrate communities, which also may help to explain the strong interspecific aggression observed in some communities. In a previous treatment we had shown that there is no observer effect on nest predation in the form of density-dependent scent marking while laying out the artificial nests.     

Predation risk of artificial ground nests in managed floodplain meadows

Nest predation highly determines the reproductive success in birds. In agricultural grasslands, vegetation characteristics and management practices influences the predation risk of ground breeders. Little is known so far on the predation pressure on non-passerine nests in tall swards. Investigations on the interaction of land use with nesting site conditions and the habitat selection of nest predators are crucial to develop effective conservation measures for grassland birds.In this study, we used artificial nests baited with quail and plasticine eggs to identify potential predators of ground nests in floodplain meadows and related predation risk to vegetation structure and grassland management.Mean daily predation rate was 0.01 (±0.012) after an exposure duration of 21 days. 70% of all observed nest predations were caused by mammals (Red Fox and mustelids) and 17.5% by avian predators (corvids). Nest sites close to the meadow edge and those providing low forb cover were faced with a higher daily predation risk. Predation risk also increased later in the season. Land use in the preceding year had a significant effect on predation risk, showing higher predation rates on unmanaged sites than on mown sites. Unused meadows probably attract mammalian predators, because they provide a high abundance of small rodents and a more favourable vegetation structure for foraging, increasing also the risk of incidental nest predations. Although mowing operation is a major threat to ground-nesting birds, our results suggest that an annual removal of vegetation may reduce predation risk in the subsequent year.     

Forest fragmentation and avian nest predation in forested landscapes

Summary The size of forest fragments, the use of land bordering fragments, and the distance of nests from an edge all affect the frequency of predation upon bird nests in Maine (USA), an area where the forest has been fragmented by roads, but not significantly reduced in area. We placed artificial nests containing quail eggs in forests of different sizes and at various distances from the edge to test which of these factors was most important in describing predation. Predation was greatest in small tracts surrounded completely by land. Large areas and those bordered on at least one side by a large water body had lower predation rates. This suggests that influx of predators from nearby habitats may be responsible for much of the nest predation in forest fragments.     

Forest fragmentation and rhinocryptid nest predation in central Chile

Fragmentation of forest landscapes can raise the intensity of nest predation by increasing the abundance and richness of generalist or introduced predators. Understory foraging birds, such as rhinocryptids, can be highly vulnerable to nest predation in fragmented landscapes because they often place their nests on the ground. Temperate deciduous forests in Chile have been intensively fragmented in the last centuries, causing changes in nest predator densities. We tested if predation of artificial nests, mimicking those of rhinocryptids, placed on and above ground was higher in the remnant fragments of central Chile due to an increase in predator abundance. The rate of nest predation in forest remnants was larger than in native continuous forest. Small mammals were the main nest predators. Despite high predation rates, the abundance of rhinocryptids is higher in forest remnants, suggesting that fragments might constitute ecological traps.     

Nest position and type affect predation rates of artificial avian nests in the tropical lowland forest on Mount Cameroon

Nest predation is the leading cause of reproductive failure in birds and thus it shapes their life history strategies. Intensities of nest predation appear to differ among nest locations and types in both temperate and tropical regions. However, there is limited knowledge of factors influencing susceptibility of avian nests to predation in Africa. The aim of our study was to investigate artificial nest predation rates of different ground and shrub nests located at different heights in the rainforest undergrowth. We placed artificial avian nests within a homogeneous lowland forest interior with sparse forest undergrowth in the Mount Cameroon National Park, Cameroon. We exposed three sets of nests: 50 bare-ground, 50 cup-ground and 50 cup-shrub nests, for 10 d. Predation was higher for cup-ground nests compared to cup-shrub nests, and bare-ground nests were more depredated than cup-ground nests. We concluded that the presence of a cup as well as higher nest position significantly increased probability of artificial nest survival. The results of this study suggest a potential selection pressure on nest type and placement in lowland forest birds for a poorly known tropical region.     

Forest vegetation structure has more influence on predation risk of artificial ground nests than human activities

As a major process affecting the reproductive success of birds, nest predation influences population density and dynamics and forces species to adapt to ecological and evolutionary time scales. The disentangling of potential natural and anthropogenic drivers of nest predation is crucial for the conservation of species. Thus, we investigated the effects of elevation, egg characteristics, vegetation structure and human activities on daily nest predation rates of artificial ground nests by baiting 700 artificial nests with quail eggs along an elevational gradient of about 1100 m. After 25 days, we found an overall daily nest predation rate of 0.045. Our generalized linear mixed model revealed increasing daily predation rates with increasing forest management, no impact of recreational activities, and lower daily predation rates in the vicinity of buildings. Furthermore, daily predation rates declined with increasing density of near-ground vegetation and increased with increasing tree cover. Finally, we found no influence of elevation, matching of egg and ground colouration, and dead wood on daily nest predation rates. Our results revealed that the risk of nest predation depends more on vegetation structure than on current levels of recreational activities. Moreover, the negative relation of nest predation risk and near-ground vegetation indicates that the changing forest structure after natural disturbances (e.g. wind throw or bark beetle infestation), which is tolerated within the benign neglect strategy applied by the authorities of protected areas, decreases the predation risk, whereas salvage logging increases this risk.     

营巢类型、巢捕食和窝卵数对高寒草甸雀形目雏鸟生长期的影响

根据1998—2001年高寒草甸10种雀形目鸟类的窝卵数、雏期和巢捕食数据,以Logistic方程拟合雏鸟生长过程,并计算出有关生长率参数;根据营巢类型将10种雀形目鸟划分为开放或半开放类群(GOB)和全封闭穴居类群(HCB)两类,将把雏鸟的生长过程划分为3个生长期(缓增期、快增期和渐增期)。3个生长期占雏期的比例因营巢类型而异,GOB类群快增期>渐增期>缓增期;HCB类群渐增期>快增期>缓增期。分析营巢类型、巢捕食和窝卵数与各生长期之间的关系,结果表明3个生长期的体重积累占离巢时体重的比例因巢型不同而有显著差异;营巢类型和巢捕食显著影响各生长期占雏期的比例和体重积累占离巢时体重的比例;窝卵数影响快增期和渐增期长度,而不影响缓增期长度。快增期体重积累与渐增期的生长率不相关,但与渐增期长度显著相关。因此,前期的能量积累不影响后期生长率,而影响后期生长的长度。该结果进一步印证在晚成鸟中不存在补偿性生长。     

Effect of camera monitoring on survival rates of High-Arctic shorebird nests

ABSTRACT.   Monitoring bird nests with cameras provides an opportunity to identify the cause of nest failure and record the behavior of individuals. However, leaving an object continuously within sight of a nest could have potential negative effects on nesting success. We compared daily survival rates of nests monitored using cameras and human visitation to nests tracked via human visitation only to test for potential additional effects of camera monitoring on predation rates. From 2006 to 2008, experiments were conducted on Bylot Island (Nunavut) using 80 artificial nests and 53 real nests of Baird's Sandpipers ( Calidris bairdii ) and White-rumped Sandpipers ( Calidris fuscicollis ). Rates of predation on real and artificial nests varied considerably among years. However, survival rates of camera-monitored nests did not differ from those of nests monitored without cameras. Predators of artificial nests included Arctic foxes ( Vulpes lagopus ), Glaucous Gulls ( Larus hyperboreus ), and Long-tailed Jaegers ( Stercorarius longicaudus ), whereas Arctic foxes were responsible for all camera-recorded predation events at real nests. Camera monitoring should be promoted as a viable method for monitoring nests of Arctic shorebirds because our results indicate that placing cameras at nests does not bias estimates of nest survival obtained via nest visits.     

Experiments with artificial nests on predation in reed habitats

We performed nest predation experiments with artificial nests in reedbeds investigating whether nest predation pressure is different at the water-reed edge and the grassland-reed edge compared with the reed interior. Furthermore, we tested the effects of vegetation structure (reed density, height and thickness) and the effect of other nest site characteristics (distance from edge, water depth) on the success of artificial nests. The experiments were completed 3 times during the breeding season in 2001 at Lake Neusiedl, Austria. Each artificial nest resembled Great Reed Warbler (Acrocephalus arundinaceus) nests and contained one plasticine and one Quail (Coturnix coturnix) egg and the predators were identified by marks left on the eggs. The potential predators were birds, probably the Marsh Harrier (Circus aeruginosus), gulls (Larus spp.) and reed warblers (Acrocephalus spp.). Nest survival data were analysed using the Mayfield method, and we performed a discriminant analysis for the data of vegetation and nest site characteristics. The nest predation was higher at the edges than in the reed interior, and was most pronounced in April, before the new reed sprouted. The reason for this finding was probably that after May the new reed contributed to greater concealment of the nests through the higher reed density and height.     

Habitat edges affect patterns of artificial nest predation along a wetland-meadow boundary

Wetland habitats are among the most endangered ecosystems in the world. However, little is known about factors affecting the nesting success of birds in pristine grass-dominated wetlands. During three breeding periods we conducted an experiment with artificial ground nests to test two basic mechanisms (the matrix and ecotonal effects) that may result in edge effects on nest predation in grass-dominated wetland habitats. Whereas the matrix effect model supposes that predator penetrate from habitat of higher predator density to habitat of lower predator density, thus causing an edge effect in the latter, according to the ecotonal effect model predators preferentially use edge habitats over habitat interiors. In addition, we tested the edge effect in a wetland habitat using artificial shrub nests that simulated the real nests of small open-cup nesting passerines. In our study area, the lowest predation rates on ground nests were found in wetland interiors and were substantially higher along the edges of both wetland and meadow habitat. However, predation was not significantly different between meadow and wetland interiors, indicating that both mechanisms can be responsible for the edge effect in wetland edges. An increased predation rate along wetland edges was also observed for shrub nests, and resembled the predation pattern of real shrub nests in the same study area. Though we are not able to distinguish between the two mechanisms of the edge effect found, our results demonstrate that species nesting in wetland edges bordering arable land may be exposed to higher predation. Therefore, an increase in the size of wetland patches that would lead to a reduced proportion of edge areas might be a suitable management practice to protect wetland bird species in cultural European landscapes.     

Nest site selection and efficacy of artificial nests for breeding success of Scarlet Macaws Ara macao macao in lowland Peru

Psittacidae (parrots) have the most threatened species of any bird family in the world. Most parrots are obligate secondary cavity nesters, and can be limited in their breeding success by the availability and quality of nest hollows. However, nesting opportunities for parrots can be increased by provision of artificial nest boxes. The Tambopata Macaw Project has been studying the breeding ecology and natural history of the Scarlet Macaw Ara macao macao in the south-eastern Peruvian Amazon for over 20 years by monitoring natural nest hollows and two types of artificial nest (wooden and PVC). We present data for breeding success in natural and artificial nests over 12 consecutive breeding seasons. The aims of this study were to: (a) determine the nesting requirements and reproductive success of breeding macaws; and, (b) compare the efficacy of the two types of artificial nests and natural nest cavities. Our data showed a high rate of reoccupation of successful nests in consecutive years and that nests in artificial and natural nests had very similar reproductive parameters. Our results indicate that artificial nest types can be used by conservation managers seeking to assist A. macao populations where nest hollows are in short supply, and that artificial nests can contribute important data to natural history studies of species where access to natural nests is limited.     

Nest Predation Risk on Ground and Shrub Nests in Forest Margin Areas of Sulawesi, Indonesia

Forest loss and fragmentation in Indonesia may seriously affect the survivorship of forest birds and lead to local extinction of bird populations. We used 786 artificial nests baited with quail eggs to examine the effect of habitat alteration on nest predation in Lore Lindu National Park, Sulawesi. Natural forest and four habitats of forest margin areas: forest edge, forest gardens, coffee plantations, and secondary forest, were studied. Two types of artificial nests, ground and shrub nests were placed in these habitats at two different locations for a period of 8 days. In addition, we used automatic cameras and cage-traps to identify the predators. Nests in shrubs experienced significantly higher predation rates in forest margin areas than in natural forest. Predation on ground nests did not differ significantly between these habitat types, but was significantly higher than that on shrub nests in each habitat except forest edge. Rodents were the most common predators of both nests, but shrub nests were also susceptible to Dwarf cuscus (Strigocuscus celebensis), squirrels, and tree snakes. The nest predation rates we found were among the highest found in tropical rainforests, probably a consequence of the unique predator assemblages of Sulawesi. These results suggest that egg survival is negatively affected by human intervention and that human-induced habitats might have only limited importance for the conservation of Sulawesi's largely endemic understorey avifauna. These considerations might be important since forest margins comprise significant proportions of protected areas on Sulawesi and play an important role in future Park zoning concepts as well as in conservation-oriented land use management.     

Local habitat and landscape influence predation of bird nests on afforested Mediterranean cropland

Afforestation programs such as the one promoted by the EU Common Agrarian Policy have contributed to spread tree plantations on former cropland. Nevertheless these afforestations may cause severe damage to open habitat species, especially birds of high conservation value. We investigated predation of artificial bird nests at young tree plantations and at the open farmland habitat adjacent to the tree plantations in central Spain. Predation rates were very high at both tree plantations (95.6%) and open farmland habitat (94.2%) after two and three week exposure. Plantation edge/area ratio and development of the tree canopy decreased predation rates and plantation area and magpie (Pica pica) abundance increased predation rates within tree plantations, which were also affected by land use types around plantations. The area of nearby tree plantations (positive effect), distance to the tree plantation edge (negative effect), and habitat type (mainly attributable to the location of nests in vineyards) explained predation rates at open farmland habitat. We conclude that predation rates on artificial nests were particularly high and rapid at or nearby large plantations, with high numbers of magpies and low tree development, and located in homogenous landscapes dominated by herbaceous crops and pastures with no remnants of semi-natural woody vegetation. Landscape planning should not favour tree plantations as the ones studied here in Mediterranean agricultural areas that are highly valuable for ground-nesting bird species.     

Tracking day and night provides insights into the relative importance of different wader chick predators

Poor reproductive success driven by nest and chick predation severely limits the population recovery of waders breeding on lowland wet grassland. Managing predation requires knowledge of the predators and because these can be grouped into nocturnal or diurnal hunters, detecting the timing of predation can help assess their relative impacts. Wader nest studies investigating the timing of egg predation have identified nocturnal mammals, primarily Red Foxes Vulpes vulpes, as the most important nest predators, but quantifying predator importance for highly mobile wader chicks is more difficult. Manual radiotelemetry can detect whether chicks are alive but cannot detect the time of predation, and predator identity can be determined only in the few cases where remains are recovered. As an alternative we used automatic radio tracking stations (ARTS) to constantly record the signals and predation timing of 179 radiotagged Lapwing Vanellus vanellus chicks, combining this with manual telemetry, inference about predator identity from predated remains and site‐level Fox, mustelid and avian predator activity monitoring. This approach succeeded in detecting the time of predation for 60% of the 155 chicks that were predated. Diurnal chick predation accounted for a larger number of predation events, but nocturnal predation was more intensive in terms of predation likelihood per hour. Mammalian predation during both day and night had a larger impact on chick survival than did avian predation. Raptors were primarily responsible for predation by birds and Foxes for predation by mammals, with Foxes also having a larger influence on daily chick predation rates than other predators. Chick predation increased seasonally, implying that earlier‐hatching breeding attempts are more likely to be successful. Higher Fox, raptor and mustelid activity resulted in higher proportions of chicks being predated by those predators, so quantifying the activity of those three predator groups on a site could be a quicker alternative to studying chicks when investigating which predator species to target with site‐specific predation management.     

模拟增加潜在巢捕食风险对2种鸟类雏鸟生长发育产生不同影响

捕食风险是影响鸟类生活史对策的重要因素之一。为应对捕食风险,鸟类进化出多样的反捕食策略。为探究北热带石灰岩森林地区鸟类生长发育对高巢捕食风险的适应机制,本研究通过利用蛇类模型模拟巢捕食者,增加潜在巢捕食风险,设置实验组,将未放置蛇类模型的实验设置为对照组。测量育雏期内黄腹山鹪莺（Prinia flaviventris）雏鸟与红耳鹎（Pycnonotus jocosus）雏鸟每日的体重、跗跖长与翼长,分别比较分析黄腹山鹪莺雏鸟与红耳鹎雏鸟上述体型特征在实验组与对照组中的生长发育规律。对符合正态分布的各日龄雏鸟生长参数进行t检验,不符合正态分布的参数进行非参数检验（Wilcox秩和检验）并求均值,使用SPSS 26.0统计软件包对雏鸟各日龄参数均值进行Logistic曲线拟合,比较各雏鸟相同生长参数在实验组和对照组实验的“S”发育曲线。结果显示,黄腹山鹪莺雏鸟在实验组的体重、跗跖长与翼长的渐近线分别占成鸟量度的71.57%、94.10%与55.29%,对照组分别占成鸟量度的78.05%、97.49%与55.67%,在实验组和对照组育雏期分别为11.1 d与10.6 d。实验组和对照组黄腹山...     

Predation on artificial ground nests in relation to forest fragmentation, agricultural land and habitat structure

The impacts of forest fragmentation agricultural land and habitat structure on depredation of artificial ground nests were studied in the cultivated area in central Finland and in the forest dominated area in Finnish Lapland The overall predation rate did not differ between the regions The overall predation rate was also independent of landscape characteristics forest patch size and the distance to patch edge However, nest predation was clearly affected by the agricultural land since the robbing rate in forest edges was higher near farmlands than further away This effect was caused by avian predators which proportional importance in predation was higher in the agricultural landscape than in the forest landscape In both regions, depredation correlated positively with high numbers of pine and spruce This can be mainly explained by the preference of predators over coniferous forest habitat as a living or hunting area