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The European Starling (Sturnus vulgaris) has expanded beyond its native Eurasian range, exploiting both natural cavities and human structures for nesting. We hypothesized that starling exposure to enhanced risk of nest predation at nest boxes (surrogates for nest sites in other structures), due to predator access, would negatively affect occupancy (establishment of a nest and ≥1 egg) and subsequent nest success. We also hypothesized that starlings would show no distinction in occupancy between nest boxes relative to the presence/absence of old nest material (i.e., material from the previous season), conditions that can contribute to nest predation risk. We conducted our study from April to June 2021 in Erie County, Ohio, USA, using 120 wooden nest boxes. Our treatments comprised protected/swept (nest boxes protected by a predator guard below the nest box and swept of old nest material), protected/unswept (containing old nest material), and unprotected/unswept nest boxes. To maximize sample size per treatment, we opted to forego use of unprotected/swept nest boxes, thereby preventing assessment of possible, enhanced nest predation (from below the nest box) at unprotected nest boxes due to the presence of old nest material. We used generalized linear models and nonparametric approaches in our comparisons. Starlings occupied and fledged young in unprotected nest boxes and nest boxes containing old nest material through the breeding season, despite possible, elevated perceived predation risk. There was no advantage of protection or disadvantage of presence of old nest material on reproductive metrics in protected/unswept nest boxes, because of predation from raptors (Accipitridae) and arboreal mammals (Sciuridae). The absolute amount of nest predation was, not surprisingly, highest in unprotected/unswept nest boxes across laying, incubation, and brood stages, but occurred primarily during brood rearing for protected boxes. El estornino Sturnus vulgaris se ha expandido más allá de su rango nativo Eurasiático, explotando tanto cavidades naturales como estructuras humanas para anidar. Hipotetizamos que la exposición del estornino a riesgos aumentados de depredación en cajas nido (sustitutos para sitios de anidación en otras estructuras) debido a acceso de depredadores afectaría la ocupación (establecimiento de nido y ≥1 huevo) y éxito de nido sucesivo. También hipotetizamos que los estorninos no mostrarían diferencia en ocupación entre cajas nido relativas a la presencia/ausencia de material viejo de nido (es decir, material de estaciones anteriores), condiciones que pueden contribuir al riesgo de depredación. Condujimos nuestro estudio de abril a junio del 2021 en el condado Erie, Ohio, Estados Unidos, usando 120 cajas nido de madera. Nuestros tratamientos consistieron en cajas nido protegidas/barridas (cajas nido protegidas por guardián de depredadores bajo la caja nido y barrida de material viejo de nido), protegida/sin barrer (que contenía material viejo de nido) y sin proteger/sin barrer. Para maximizar el tamaño de muestra por tratamiento, optamos por no usar cajas nido sin proteger/barridas, previniendo así la medición de un posible aumento de depredación de nido (desde abajo de la caja nido) a cajas nido sin proteger debido a la presencia de material viejo de nido. Usamos modelos lineales generalizados y un acercamiento no paramétrico para nuestras comparaciones. Los estorninos ocuparon y emanciparon crías en cajas nido sin protección y en cajas nido que contenían material viejo de nido durante la estación reproductiva, a pesar del posible elevado riesgo percibido de depredación. No hubo ventaja en protección o desventaja en presencia de material viejo de nido en métricas reproductivas en cajas nido protegidas/sin barrer, debido a la depredación por rapaces (Accipitridae) y mamíferos arbóreos (Sciuridae). La cantidad absoluta de depredación de nidos fue, sin ninguna sorpresa, mayor en cajas nido sin protección/ sin barrer en puesta, incubación y crianza, pero ocurrión mayormente durante la crianza de los polluelos en cajas protegidas. Palabras clave: depredación de nidos, selección de sitio de anidación, reproducción, especies que anidan en cavidades secundarias.

In the Arctic, nest predation risk is higher at lower latitudes, and some shorebirds (Charadriidae) nesting at the southernmost limits of their ranges near Churchill, Manitoba tend to experience lower nest success than those at other Arctic sites. This study investigates whether proximity to human settlement affects predator abundance, predation risk, and shorebird daily nest survival near Churchill by measuring these variables at varying distances from town during two nesting seasons. Active fox dens decreased in number close to town; however, there was no clear trend in avian predator abundance in relation to town. Predation risk on artificial nests decreased as distances from active fox dens and Parasitic Jaeger (Stercorarius parasiticus) nests increased, decreased with proximity to town, and decreased with a camera present. Shorebird daily nest survival tended to be lower near jaeger nests and there was some support for a positive effect of camera presence and proximity to town. Overall, these results suggest that shorebird nest survival in the sub-Arctic can be heavily impacted by proximity to nests of avian predators, but that shorebirds may benefit from proximity to town likely due to reduced fox denning activity.

Nest defense is an adaptive strategy used by adults to increase survival of independent young. However, the risk adults face by defending young from predators represents an important trade-off and parental investment theory predicts adults will modulate nest defense based on the value of offspring. We used a model of a black rat snake, a potential nest predator on our study site, to quantify nest defense in a population of gray catbirds in eastern Pennsylvania during the breeding seasons of 2017 and 2018. Specifically, we evaluated (1) the difference in nest defense between male and female parents, (2) the relationship between nest defense and nest success, and (3) how variation in nest defense was related to factors associated with offspring value. Although male catbirds tend to be larger than females, they did not defend their nests more aggressively than female catbirds. Response to the model predator we used was also not different between individuals whose nests were successful compared with individuals that failed. Although nests that contained more and older young were not defended more aggressively, our analyses did show that adult catbirds defended young that were laid earlier in the season more intensely than those laid later in the breeding season. In birds, earlier clutch initiation is associated with an increased chance of recruitment into the breeding population. Catbirds, therefore, follow predictions of parental investment theory because they defended offspring of higher value more aggressively.

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.

Abstract Many studies have shown that nest predators affect their prey indirectly by inducing changes in the behaviour of the prey. Studies suggest that the type and degree of nest defence strategies depends heavily on species, along with nest type and location. One such strategy, nest vigilance, allows individuals to collect information and make informed decisions based on their surroundings. In this study, we simulated the intrusion of a common avian nest predator (blue jay, Cyanocitta cristata) into the territory of nesting cerulean warblers (Setophaga cerulea) and evaluated eight different behavioural variables to determine their response to the nest predator. Female cerulean warblers were more vigilant on their nest when exposed to a potential predator compared to a nest with lower threat of predation. Females exposed to a nest predator increased incubation bout by 109% and brooding bout by 60%. Our data also suggest that male cerulean warblers reduce their provisioning rate during the early nestling stage (−1 feeding/hour) and late nestling stage (−3 feedings/hour), although more data are needed. Modification of incubation bout length and nestling provisioning rate are common strategies employed by songbirds to reduce activity around the nest, by decreasing detection opportunities of visually-oriented nest predators. Currently, the only understanding we have on how cerulean warblers respond to a nest predator is based on observational data. The results of this study provide the first evidence that cerulean warblers are able to identify species that pose a threat to the safety of their nest, and that they modify their behaviour to reduce nest detection by predators. The results of this study provide a better understanding of a relatively unknown aspect of the breeding behaviour of this species. This study is also first to describe how an open-cup, canopy-nesting species responds to an increase in nest predation threat.

Understanding the mechanisms by which tropical forest fragmentation can affect the persistence of species and populations is of scientific and practical interest. However, nest survival has been one the least addressed of the potentially harmful effects associated with habitat fragmentation, and studies involving nest predator’s identification are still underdeveloped. The Pernambuco Endemism Center (PEC) is the part of the Atlantic Forest located north of the São Francisco River, in northeastern Brazil, where large forest tracts no longer exist and a wave of bird extinctions has occurred recently. Here, we investigated the nest survival of forest understory birds from three PEC fragments (690, 979, and 1036 ha), and we used infra-red camera traps for predators’ identification. Overall, the apparent nest survival was 15.5%, and nest-day-based survival probability for the four more representative species (including two endemic and threatened taxa) were 2.6, 4.4, 6.9, and 18.9%, being 2.7 to 8.5 times smaller than populations or related taxa from the Atlantic Forest of southeastern Brazil. Predators were marmosets (25%), opossums (25%), tegu (19.4%), coati (16.7%), snakes (8.3%), and hawks (5.5%). Jackknife2 model-predicted nest predator’s richness was 20.7 (SD = 1.6). We reinforce the evidence that nest predation associated with fragmentation can affect negatively the bird populations from tropical forests.

Background For cavity-nesting birds, the nest entrance plays an important role in preventing predators from accessing nests. Several species of nuthatches use mud to narrow the entrance of cavities. In theory, the smaller the entrance hole size, the more effective it is against predators; however, few studies have tested whether narrowing the entrance hole size can affect the estimation of threat levels from nest predators in cavity-nesting birds. Methods Using dummy experiments, we tested whether Eurasian Nuthatches (Sitta europaea, narrow the entrance hole of cavities) and Cinereous Tits (Parus cinereus, do not narrow the entrance hole, as a control) perform different nest defence behaviours against Common Chipmunks (Tamias sibiricus, small nest predator) and Red Squirrels (Sciurus vulgaris, larger nest predator). Results Both nuthatches and tits exhibited stronger response behaviours (high dummy response scores) against chipmunks than against squirrels. Compared with tits, nuthatches exhibited more aggressive behaviours to chipmunks, but their responses to squirrels were similar. Conclusions Nest defence behaviours of nuthatches to chipmunks differed from tits, and the results suggested that nuthatches might estimate threat levels of nest predators according to their narrowed entrance-hole size.

We document the first recorded instance of a fish depredating a hatchling bird while in the nest. Some coastal marsh-nesting avian species, such as the Seaside Sparrow (Ammospiza maritima), experience tradeoffs between the threat of nest predation and nest flooding. Nesting too low may result in nest flooding during the twice-daily high tides and increasing nest height increases the risk of nest predation. However, not much is known about how nest height affects exposure to different predators. We observed a mummichog (Fundulus heteroclitus) enter a Seaside Sparrow nest during a nest flooding event and depredate a hatchling. This observation expands our understanding of the predator–prey relationships experienced by coastal marsh-nesting birds, and the potential detriments of intensifying sea level rise on their nesting success.

The primary driver of nest failure for terrestrial birds is depredation, especially for ground-nesting species that are vulnerable to a diverse guild of predators. However, descriptions of how complex predator–prey interactions happen, and ultimately lead to nest failures, are scarce. Herein, we provide observations collected from cameras stationed at nest sites as part of a larger study on Northern Bobwhite (Colinus virginianus) and Scaled Quail (Callipepla squamata) nesting behavior in the Oklahoma Panhandle during 2016. We observed 2 multi-episode (i.e., multiple predator visits) diurnal nest depredation events at a nest of each species. In both instances, repeated nest depredation by hispid cotton rats (Sigmodon hispidus) as well as 2 different snake species resulted in nest abandonment. We observed that cotton rats routinely visited nest sites (up to 11 times in 1 diurnal period), and often entered the nest during off bouts (64% of off bouts) of the incubating females. By detailing interspecific interactions involved in nest depredation, we provide a glimpse into the complexity of the nesting ecology of ground-dwelling birds. These observations further reinforce the potential pitfalls of categorizing nest depredation events without camera data.

1. Nest predation negatively affects most avian populations. Studies of nest predation usually group all nest failures when attempting to determine temporal and parental activities, habitat or landscape predictors of success. Often these studies find few significant predictors and interpret patterns as essentially random. 2. Relatively little is known about the importance of individual predator species or groups on observed patterns of nest success, and how the ecology of these predators may influence patterns of success and failure. 3. In 2006 and 2007, time-lapse, infrared video systems were deployed at nests of Swainson's warblers (Limnothlypis swainsonii Audubon) in east-central Arkansas to identify dominant nest predators and determine whether factors predicting predation differed among these predators. 4. Analysis of pooled data yielded few predictors of predation risk, whereas separate analyses for the three major predator groups revealed clear, but often conflicting, patterns. 5. Predation by ratsnakes (Elaphe obsoleta) and raptors was more common during the nestling period, whereas predation by brown-headed cowbirds (Molothrus ater) occurred more during incubation. Additionally, the risk of predation by raptors and cowbirds decreased throughout the breeding season, whereas ratsnake predation risk increased. 6. Contrary to expectations, predation by ratsnakes and cowbirds was more common far from edges, whereas raptor predation was more common close to agricultural edges. 7. Collectively, our results suggest that associating specific predators with the nests they prey on is necessary to understand underlying mechanisms.