Nest predation in Reed Buntings Emberiza schoeniclus: an experimental study

Predation is a major cause of nest failure in many bird species. High levels of nest loss may be a consequence of habitat fragmentation, leading to increased amounts of edge habitat. Yet the evidence for generally high nest predation rates along edges in fragmented landscapes is ambiguous. Using real nests of Reed Buntings Emberiza schoeniclus in which artificial Reed Bunting and real Japanese Quail Coturnix japonica eggs were placed, we experimentally tested for edge effects on nest predation in highly fragmented reed Phragmites sp. habitats in the Swiss lowlands. We also examined seasonal patterns of predation and the impacts of nest visits by observers. We found evidence for an edge effect at the water-sided reed edge, with nests located closer to the water being more likely to be predated than those further away. Predation probability increased from early to late season, suggesting that nest predation may be density dependent. Probability of nest predation was only weakly influenced by whether or not a nest was visited. Our results suggest that the intensive reed management currently applied in Swiss nature reserves may result in unnaturally high levels of nest losses in the Reed Bunting, because reed bands are not wide enough to allow nest placement at a safe distance from reed edges.     

Fragmentation within and between wetland reserves: the importance of spatial scales for nest predation in reed buntings

Wetlands in many parts of the world are affected by fragmentation at multiple spatial scales. In Switzerland, most wetlands have been destroyed over the past two centuries and management of the remaining wetland reserves has intensified in the recent years leading to increased fragmentation of reed areas within reserves. Using four years of data on the reproductive performance of color-banded reed bunting Emberiza schoeniclus populations, we explored fragmentation effects on nest predation rates at four spatial scales ranging from the nest to the landscape scale. In the egg stage, predation rate was negatively related to vegetation cover, vegetation height and nest height, but positively linked to water cover and depth next to the nest (nest scale). Probability of predation declined with increasing size of reed patches containing the nests and distances of nests to the water and land sided reed edge, as well as with decreasing edge to area ratio (edge scale). There was a weak positive association between degree of fragmentation of reed patches within sites and nest predation rates (site scale). Finally, nest predation probability increased with distance to the nearest wetland (landscape scale). Jointly analyzing variables from different spatial scales revealed that a model combining variables from the nest, edge and landscape scale best explained predation probability in the egg stage. In the nestling stage, the single most important factor influencing nest predation probability was the distance to the nearest wetland (landscape scale), with nest predation decreasing with distance between sites. Our results show that the probability of nest predation in reed buntings is affected by fragmentation within and between wetland reserves and that the effects differ between breeding stages. Future management of wetland reserves should aim at sparing reed patches large and dense enough to provide safe nest sites for birds.     

Contrast in edge vegetation structure modifies the predation risk of natural ground nests in an agricultural landscape

Nest predation risk generally increases nearer forest-field edges in agricultural landscapes. However, few studies test whether differences in edge contrast (i.e. hard versus soft edges based on vegetation structure and height) affect edge-related predation patterns and if such patterns are related to changes in nest conspicuousness between incubation and nestling feeding. Using data on 923 nesting attempts we analyse factors influencing nest predation risk at different edge types in an agricultural landscape of a ground-cavity breeding bird species, the Northern Wheatear (Oenanthe oenanthe). As for many other bird species, nest predation is a major determinant of reproductive success in this migratory passerine. Nest predation risk was higher closer to woodland and crop field edges, but only when these were hard edges in terms of ground vegetation structure (clear contrast between tall vs short ground vegetation). No such edge effect was observed at soft edges where adjacent habitats had tall ground vegetation (crop, ungrazed grassland). This edge effect on nest predation risk was evident during the incubation stage but not the nestling feeding stage. Since wheatear nests are depredated by ground-living animals our results demonstrate: (i) that edge effects depend on edge contrast, (ii) that edge-related nest predation patterns vary across the breeding period probably resulting from changes in parental activity at the nest between the incubation and nestling feeding stage. Edge effects should be put in the context of the nest predator community as illustrated by the elevated nest predation risk at hard but not soft habitat edges when an edge is defined in terms of ground vegetation. These results thus can potentially explain previously observed variations in edge-related nest predation risk.     

Different nest predator faunas and nest predation risk on ground and shrub nests at forest ecotones: an experiment and a review

This study examined predator faunas of artificial ground and shrub nests and whether nest predation risk was influenced by nest site, proximity to forest edge, and habitat structure in 38 grassland plots in south-central Sweden. There was a clear separation of predator faunas between shrub and ground nests as identified from marks in plasticine eggs. Corvids accounted for almost all predation on shrub nests whereas mammals mainly depredated ground nests. Nest predation risk was significantly greater for shrub than for ground nests at all distances (i.e. 0, 15 and 30 m) from the forest edge. However, nest predation risk was not significantly related to distance to forest edge, but significantly increased with decreasing distance to the nearest tree. Different corvid species robbed nests at different distances from the forest edge, with jays robbing nests closest to edges. We conclude that the relationship between the predation risk of grassland bird nests and distance to the forest edge mainly depends on the relative importance of different nest predator species and on the structure of the forest edge zone. A review of published articles on artificial shrub and ground nest predation in the temperate zone corroborated the results of our own study, namely that shrub nests experienced higher rates of depredation in open habitats close to the forest edge and that avian predators predominantly robbed shrub nests. Furthermore, the review results showed that predation rates on nests in general are highest <50 m inside the forest and lower in open as well as forest interior habitats (≥50 m from the edge). Received: 16 March 1998 / Accepted: 30 July 1998     

Edge effect on bird nest predation in the fragmented caldén (<Emphasis Type="Italic">Prosopis caldenia</Emphasis>) forest of central Argentina: an experimental analysis

Clearing of caldén (Prosopis caldenia) forests for agriculture and cattle raising in east-central La Pampa Province, central Argentina, has created a highly fragmented landscape, a condition that has resulted in adverse effects on birds in other forests, mainly through increased predation rates near forest edges. We evaluated bird nest predation rates using artificial nests, assessing the effects of forest fragment size, distance to the edge and nest height. We measured survival rate of 570 artificial nests located in trees, in bushes and on the ground, at different distances from the edge, in six forest fragments ranging in size from 2.1 to 117.6 ha, during two consecutive breeding seasons. Nest predation rates were significantly related with the number of days of exposition of the nest, nest height and distance to the edge, whereas fragment size and year of the experiment were not associated with predation rates. Ground nests were less likely to be predated than those located in bushes and trees. Predation rates decreased with the distance to the edge, showing a pattern consistent with the existence of an edge effect.     

Hatch Success and Recruitment Patterns of the Bog Turtle

Researchers suggest that several bog turtle (Glyptemys muhlenbergii) populations in North Carolina, USA, are in decline and have few remaining individuals and low annual survival probability. Most populations are dominated by older adults with few juveniles encountered; however, the proportion of juveniles encountered in 2 populations is higher. It is unknown why the juvenile:adult ratio varies among populations. We conducted a nest monitoring study in 2016 and 2017 to test the hypothesis that sites with fewer juvenile encounters would be where nest predation was highest. We documented the fate of 272 eggs from 83 nests encountered across 7 sites in North Carolina. On average 28% of eggs hatched across all sites over both years, but we observed large variation in hatch success among sites. Predation by mesopredators and small mammals was the primary cause of nest failure. The probability of nest predation decreased with greater emergent vegetation density and increased with greater distance to the edge of the wetland. Cooler temperatures, which prolonged incubation and thus increased predation risk, may also hinder recruitment at higher elevation sites. Our observations are consistent with the hypothesis that nest predation would be highest at sites with fewer juvenile encounters. Managers concerned about low bog turtle recruitment rates should consider the role of nest predation and the potential benefits of management that increases hatch rates. © 2020 The Wildlife Society.     

Cropland edge,forest succession,and landscape affect shrubland bird nest predation

The effects of habitat edges on nest survival of shrubland birds, many of which have experienced significant declines in the eastern United States, have not been thoroughly studied. In 2007 and 2008, we collected data on nests of 5 shrubland passerine species in 12 early successional forest patches in North Carolina, USA. We used model selection methods to assess the effect of distance to cropland and mature forest edge on nest predation rates and additionally accounted for temporal trends, nest stage, vegetation structure, and landscape context. For nests of all species combined, nest predation decreased with increasing distance to cropland edge, by nearly 50% at 250 m from the cropland edge. Nest predation of all species combined also was higher in patches with taller saplings and less understory vegetation, especially in the second year of our study when trees were 4–6 m tall. Predation of field sparrow (Spizella pusilla) nests was lower in landscapes with higher agricultural landcover. Nest predation risk for shrubland birds appears to be greater near agricultural edges than mature forest edges, and natural forest succession may drive patterns of local extirpation of shrubland birds in early successional forest patches. Thus, we suggest that habitat patches managed for shrubland bird populations should be considerably large or wide (>250 m) when adjacent to crop fields and maintained in structurally diverse early seral stages. © 2011 The Wildlife Society.     

Forest fragmentation relaxes natural nest predation in an Afromontane forest

Nest predation is widely regarded as a major driver underlying the population dynamics of small forest birds. Following forest fragmentation and the subsequent invasion by species from non-forested landscape matrices, shifts in predator communities may increase nest predation near forest edges. However, effects of human-driven habitat change on nest predation have mainly been inferred from studies with artificial nests, despite being regarded as poor surrogates for natural ones. We studied variation in predation rates, and relationships with timing of breeding and characteristics of microhabitats and fragments, on natural white-starred robin Pogonocichla stellata nests during three consecutive breeding seasons (2004–2007) in a Kenyan fragmented cloud forest. More than 70% of all initiated nests were predated during each breeding season. Predation rates nearly quadrupled between the earliest and the latest nests within a single breeding season, increased with distance to the forest edge, and decreased with the edge-to-area ratio of forest fragments. These spatial relationships oppose the traditional perception of edge and fragmentation effects on nest predation, but are in line with results from artificial nest experiments in other East African forests. In case of inverse edge and fragmentation effects on nest predation, such as shown in this study, species that tolerate edges for breeding may be affected positively, rather than negatively, by forest fragmentation, while the opposite can be expected for species restricted to the forest interior. The possibility of inverse edge effects, and its conservation implications, should therefore be taken into account when drafting habitat restoration plans.     

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.     

Nest-predation at the edge: an experimental study contrasting two types of edges in the dry Chaco, Paraguay

Forest fragmentation leads to the creation of isolated forest patches with subsequent impact on forest-interior flora and fauna. Forested corridors have been suggested to alleviate some of the impact by increasing the connectivity between remnant forest patches. However, both fragmentation and corridors increase the ratio of edge to core habitat. We studied nest predation of artificial nests at edges between I) contiguous forests and pastures and 2) forested corridors and pastures, in a forest-dominated landscape in the dry Chaco, Paraguay, The aim was lo determine if nest predation was higher near habitat edges compared to within forests and pastures, with special emphasis on edges at forested corridors. We found that predation rates were similar at edges and in interior habitats. Nest predation was higher for both ground and shrub nests in forested areas than in pastures, Predation rates were also higher for both ground and shrub nests at edges along forested corridors compared to edges neighbouring contiguous forests. Forested corridors connecting contiguous forests may thus act as an ecological sink for some species breeding here. Analysis of predator categories revealed that ground nests in pastures were relatively more depredated by mammals and less by birds, compared to both shrub nests in pastures and ground nests in forests.     

Compounding effects of habitat fragmentation and predation on bird nests

Habitat fragmentation and invasive species are two of the greatest threats to species diversity worldwide. This is particularly relevant for oceanic islands with vulnerable endemics. Here, we examine how habitat fragmentation influences nest predation by Rattus spp. on cup‐nesting birds in Samoan forests. We determined models for predicting predation rates by Rattus on artificial nests at two scales: (i) the position of the bird's nest within the landscape (e.g. proximity to mixed crop plantations, distance to forest edge); and (ii) the microhabitat in the immediate vicinity of the nest (e.g. nest height, ground cover, slope). Nest cameras showed only one mammal predator, the black rat (Rattus rattus), predating artificial nests. The optimal model predicting nest predation rates by black rats included a landscape variable, proximity to plantations and a local nest site variable, the percentage of low (<15 cm) ground cover surrounding the nest tree. Predation rates were 22 ± 13% higher for nests in forest edges near mixed crop plantations than in edges without plantations. In contrast, predation rates did not vary significantly between edge habitat where the matrix did not contain plantations, and interior forest sites (>1 km from the edge). As ground cover reduced, nest predation rates increased. Waxtags containing either coconut or peanut butter were used as a second method for assessing nest predation. The rates at which these were chewed followed patterns similar to the predation of the artificial nests. Rural development in Samoa will increase the proportion of forest edge near plantations. Our results suggest that this will increase the proportion of forest birds that experience nest predation from black rats. Further research is required to determine if rat control is needed to maintain even interior forest sites populations of predator‐sensitive bird species on South Pacific islands.     

An ecological paradox: More woodland predators and less artificial nest predation in landscapes colonized by noisy miners

Many passerine bird populations, particularly those that have open‐cup nests, are in decline in agricultural landscapes. Current theory suggests that an increase in habitat generalist predators in response to landscape change is partially responsible for these declines. However, empirical tests have failed to reach a consensus on how and through what mechanisms landscape change affects nest predation. We tested one hypothesis, the Additive Predation Model, with an artificial nest experiment in fragmented landscapes in southern Queensland, Australia. We employed structural equation modelling of the influence of the relative density of woodland and habitat generalist predators and landscape features at the nest, site, patch and landscape scales on the probability of nest predation. We found little support for the Additive Predation Model, with no significant influence of the density of woodland predators on the probability of nest predation, although landscape features at different spatial scales were important. Within woodlands fragmented by agriculture in eastern Australia, the presence of noisy miner colonies appears to influence ecological processes important for nest predation such that the Additive Predation Model does not hold. In the absence of colonies of the aggressive native bird, the noisy miner, the influence of woodland predators on the risk of artificial nest predation was low compared with that of habitat generalist predators. Outside noisy miner colonies, we found significant edge effects with greater predation rates for artificial nests within woodland patches located closer to the agricultural matrix. Furthermore, the density of habitat generalist predators increased with the extent of irrigated land‐use, suggesting that in the absence of noisy miner colonies, nest predation increases with land‐use intensity at the landscape scale.     

Predation on artificial nests in a forest dominated landscape – the effects of nest type, patch size and edge structure

We studied the effects of forest patch size and forest edge structure on nest predation in a boreal coniferous forest landscape. The following predictions were tested. Nest predation should be higher in small than in large stands, in edges than in interior areas of forest stands, and in barren forest/clear–cut edges created by forestry than in natural forest/open marsh edges. Four types of artificial above ground nests (total of 261) were used; open cup nests with reindeer Rangifer t. tarandus hair, open cup nests with domestic hen Gallus domesticus feathers, and unlined open cup and nest–box nests. Nests were baited with one Japanese quail Coturnix coturnix japonica egg. Nest–boxes were depredated significantly less than open cup nests of all types. No edge- or stand size–related nest predation was found. The predation rate, regardless of the nest type, did not differ relative to the edge type and vegetation characteristics. However, better horizontal visibility of open cup nests due to more open vegetation structure increased predation risk in man–made edges compared to inherent edges. The results suggest that edge–related nest predation is absent or weak in forest dominated landscapes. This may be due to predator types present in the landscape and/or predators habitat use in forest dominated areas. Therefore, it might be that findings documented in other areas, such as in agricultural dominated landscapes, cannot be directly applied to managed forest landscapes.     

Distance from riparian edge reduces brood parasitism of southwestern willow flycatchers,whereas parasitism increases nest predation risk

The southwestern willow flycatcher (Empidonax traillii extimus) is a federally endangered subspecies that breeds in increasingly fragmented and threatened habitat. We examined whether temporal and habitat characteristics were associated with risk of predation and probability of brood parasitism by brown-headed cowbirds (Molothrus ater) on flycatcher nests at 6 sites in southern Nevada and northwestern Arizona, USA. For nest predation, we found the most support for a model that included date and an interaction between parasitism status and nesting stage. Daily nest survival decreased from 0.87 (95% CI = 0.81–0.93) to 0.78 (95% CI = 0.72–0.84) through the season for parasitized nests but remained relatively constant for unparasitized nests (0.93, 95% CI = 0.91–0.95 to 0.92, 95% CI = 0.91–93). Parasitized nests had lower survival than non-parasitized nests during the incubation (0.85, 95% CI = 0.84–0.86 vs. 0.92, CI = 0.91–0.93) and nestling (0.79, 95% CI = 0.77–0.81 vs. 0.91, 95% CI = 0.90–0.92) stages. Of the variables included in our parasitism candidate models, model-averaged coefficients and odds ratios supported only distance to habitat edge; odds of parasitism decreased 1% for every 1 m from the habitat edge. Nests greater than 100 m from an edge were 50% less likely to be parasitized as those on an edge, however, only 52 of 233 nests (22%) were found at this distance. Where management and conservation goals include reducing nest losses due to parasitism, we recommend restoration of habitat patches that minimize edge and maximize breeding habitat further from edges. At sites where cowbirds have been documented as important nest predators, controlling cowbirds may be one option, but further study of the link between parasitism and nest predation and the identification of major nest predators at specific sites is warranted. © 2011 The Wildlife Society.     

Nesting success in Redshank Tringa totanus breeding on coastal meadows and the importance of habitat features used as perches by avian predators

Capsule Nest survival rates could not be explained by distance to habitat edges or other features used by predators.

Aims To investigate if predation on Redshank nests was affected by habitat characteristics at a local scale.

Methods We examined survival rates of Redshank nests on coastal meadows on the Baltic island of Gotland, Sweden, over two breeding seasons. We analysed nest survival rates in relation to several habitat characteristics that may benefit predators searching for nests. We examined existing studies concerning predation rates on wader nests in relation to edges and habitat features potentially used by avian predators.

Results We found no significant effects of distance to habitat edge or to nearest potential lookout for avian predators or to shoreline. Abundance of Lapwings Vanellus vanellus, an aggressive species with active nest-defence, did not have any significant effect on nest survival rate, nor did vegetation concealment of nests. Nest survival rates were significantly different between years and lower later in the season.

Conclusions There is only weak support for general effects on wader nest predation rates of proximity to edges and features used by avian predators. Simple mechanical management actions such as removal of trees and bushes on coastal meadows may not directly, and by itself, result in higher reproductive success of waders. Further understanding is needed of the behaviour of predators and the composition of the predator community in different landscapes in order to increase the efficiency of management actions to remove threats to vulnerable species on coastal meadows.     

Multi-scale turtle dove nest habitat selection in a Mediterranean agroforestry landscape: implications for the conservation of a vulnerable species

Determination of factors affecting nest habitat selection is a major topic in avian ecology, with strong implications for conservation purposes especially for the species with unfavorable status. The turtle dove (Streptopelia turtur) is a vulnerable species that has undergone a rapid and serious decline across its distribution range. I investigated the effect of different variables at two spatial scales (10-m radius, nest site; and 100-m radius, landscape) on the probability of presence of turtle dove nests in an agroforestry system of Central Morocco. Topography, habitat structure, human disturbance, and land use parameters were measured at nests (n?=?70) and random points (n?=?70) at both scales. Generalized linear model analyses showed that, at the nest site scale, tree height best explained occurrence of turtle dove nests (with nest occurring preferentially in smaller trees). At the landscape scale, nest occurrence probability decreased with elevation and distance to the nearest forest edge, and increased with forest cover and distance to the nearest habitation. Comparison of explanatory power of the single-scale models showed that the most relevant scale was the nest site level, followed by landscape scales, but the model including both nest-scale and landscape-scale variables was best. The variation partitioning analysis confirmed this pattern. In study area, the turtle dove nest habitat selection process occurs within a relatively small scale, but the joint effect of variables at the two scales is relevant. From a practical perspective, it would be interesting to reproduce the same experimental approach on other Mediterranean breeding habitats (agricultural and other forest habitats) to find out if this species would adopt the same nest habitat selection pattern.     

Nest site attributes and temporal patterns of northern flicker nest loss: effects of predation and competition

To date, most studies of nest site selection have failed to take into account more than one source of nest loss (or have combined all sources in one analysis) when examining nest site characteristics, leaving us with an incomplete understanding of the potential trade-offs that individuals may face when selecting a nest site. Our objectives were to determine whether northern flickers (Colaptes auratus) may experience a trade-off in nest site selection in response to mammalian nest predation and nest loss to a cavity nest competitor (European starling, Sturnus vulgaris). We also document within-season temporal patterns of these two sources of nest loss with the hypothesis that flickers may also be constrained in the timing of reproduction under both predatory and competitive influence. Mammalian predators frequently depredated flicker nests that were: lower to the ground, less concealed by vegetation around the cavity entrance and at the base of the nest tree, closer to coniferous forest edges and in forest clumps with a high percentage of conifer content. Proximity to coniferous edges or coniferous trees increased the probability of nest predation, but nests near conifers were less likely to be lost to starlings. Flickers may thus face a trade-off in nest site selection with respect to safety from predators or competitors. Models suggested that peaks of nest predation and nest loss to eviction occurred at the same time, although a competing model suggested that the peak of nest loss to starlings occurred 5 days earlier than the peak of mammalian predation. Differences in peaks of mammalian predation and loss to starlings may constrain any adjustment in clutch initiation date by flickers to avoid one source of nest loss.     

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.     

The effect of human observers on the intensity of nest predation

Disused nests containing eggs from aviary birds were used to determine the effect of human observers on the intensity of nest predation. Nest predation was significantly higher for nests visited daily than for nests visited only at the end of a typical incubation period. Care should be taken by nest observers to minimise the number of visits to nests of ground-nesting birds. The average distance of nests from the edge of the supporting plant was greater for unsuccessful than successful nests, implying that the position of nests is an important factor affecting their survival. Predation rates on active nests of White-fronted Chats Ephthianura albifrons visited daily over the same period were similar to those of experimental nests, suggesting that 'artificial' nests may be a useful tool for studying nest predation.     

Density-dependent nest predation in waterfowl: the relative importance of nest density versus nest dispersion

When nest predation levels are very high or very low, the absolute range of observable nest success is constrained (a floor/ceiling effect), and it may be more difficult to detect density-dependent nest predation. Density-dependent nest predation may be more detectable in years with moderate predation rates, simply because there can be a greater absolute difference in nest success between sites. To test this, we replicated a predation experiment 10 years after the original study, using both natural and artificial nests, comparing a year when overall rates of nest predation were high (2000) to a year with moderate nest predation (2010). We found no evidence for density-dependent predation on artificial nests in either year, indicating that nest predation is not density-dependent at the spatial scale of our experimental replicates (1-ha patches). Using nearest-neighbor distances as a measure of nest dispersion, we also found little evidence for "dispersion-dependent" predation on artificial nests. However, when we tested for dispersion-dependent predation using natural nests, we found that nest survival increased with shorter nearest-neighbor distances, and that neighboring nests were more likely to share the same nest fate than non-adjacent nests. Thus, at small spatial scales, density-dependence appears to operate in the opposite direction as predicted: closer nearest neighbors are more likely to be successful. We suggest that local nest dispersion, rather than larger-scale measures of nest density per se, may play a more important role in density-dependent nest predation.