Nest Failure Research Articles

Managing Native Predators: Evidence from a Partial Removal of Raccoons (Procyon lotor) on the Outer Banks of North Carolina, USA

Raccoons (Procyon lotor) are important predators of ground-nesting species in coastal systems. They have been identified as a primary cause of nest failure for the American Oystercatcher (Haematopus palliatus) throughout its range. Concerns over the long-term effects of raccoon predation and increased nest success following a hurricane inspired a mark-resight study of the raccoon population on a barrier island off North Carolina, USA. Approximately half of the raccoons were experimentally removed in 2008. Nests (n = 700) were monitored on two adjacent barrier islands during 2004–2013. Daily nest survival estimates were highest for 2004 (0.974 ± 0.005) and lowest for 2007 and 2008 (0.925 ± 0.009 and 0.925 ± 0.010, respectively). The only model in our candidate set that received any support included island and time of season, along with a diminishing effect of the hurricane and a constant, 5-year effect of the raccoon removal. For both hurricane and raccoon removal, however, the support for island-specific effects was weak (β = -0.204 ± 0.116 and 0.146 ± 0.349, respectively). We conclude that either the raccoon reduction was inadequate, or factors other than predation cause more variation in nest success than previously recognized. A multi-faceted approach to management aimed at reducing nest losses to storm overwash, predation, and human disturbance is likely to yield the largest population level benefits.

Coyote Diets on the Rolling Plains Quail Research Ranch, Texas

Predation is a major cause of mortality and nest failure for the northern bobwhite (Colinus virginianus) across its range. Coyotes (Canis latrans) are a potential predator of bobwhites and typically the most common mesocarnivore on bobwhite range in Texas. Few data exist regarding the importance of bobwhites in the coyote’s diet in the Rolling Plains of Texas. We describe the seasonal and annual diets of coyotes on the Rolling Plains Quail Research Ranch (RPQRR), Fisher County, Texas. The RPQRR encompasses 1,902 ha of rolling terrain consisting of ridges and mesquite (Prosopis glandulosa) dominated rangeland; other common shrubs include netleaf hackberry (Celtis laevigata), littleleaf sumac (Rhus microphylla), lotebush (Ziziphus obtusifolia), wolfberry (Lycium berlandieri), chittam (Bumrlia lanuginosa), catclaws (Acacia spp., Mimosa spp.), and agarito (Mahonia trifoliolata). Prickly pear (Opuntia spp.) is abundant on most sites. The study area received 58 and 64 cm of rainfall, respectively during 2009 and 2010, below the 30-year average of 76 cm for Fisher County, Texas. We collected, and examined 720 coyote scats from December 2008 to December 2010. Each scat was prepared for analysis by placing it inside a nylon mesh bag and washing it for 2 cycles in an automatic washing machine. We analyzed scat contents macroscopically and any guard hairs were analyzed microscopically to identify prey to genus. We also collected estimates of abundance for a range of potential food sources including bobwhites, small mammals, and insects. Preliminary analyses suggest coyotes were minor predators of quail and their diets mainly consisted of seasonally-available mast (e.g., tunas of prickly pear) and rodents. Variation in timing and amount of rainfall during our study allowed us to document how coyotes adjusted their diets to the resulting fluctuations in food availability (especially mast).

Parental care and breeding strategies of the Jacky Winter and its life-history traits compared with other Australasian robins, and northern temperate and tropical songbirds

We studied parental care in the Jacky Winter Microeca fascinans at Gluepot Reserve, South Australia, for one breeding season from 16 August to 9 November 2001, supplemented by observations on breeding and social behaviour in September 2012. We monitored ten nests in 2001, nine of which were attended by pairs and one by three adults, and watched three nests for a total of c. 117 hours. Female incubation constancy was 69%, duration of incubation sessions averaged 4.58 minutes and absences from the nest 2.07 minutes. Mean number of nest visits per hour by two pairs during the incubation period was 10.6 and for a group of three adults (two males, one female) was 15.8. Female care included brooding, feeding of nestlings, and nest-hygiene. Male care included delivering food to the sitting female, feeding the nestlings, nest-hygiene, nest-defence, and territoriality. Mean female brooding constancy was 55%. Mean number of feeding trips per hour by male and female combined for the entire nestling period was 14.6. Older young, 12, 13 and 14 days of age, received 21, 20, and 29 feeds/h respectively or one feed about every 2 minutes. Mean number of visits per hour by male and female combined to a nest with two young was 16.5 for Days 1–10 and 20.4 for Days 11–18 of the nestling period. High nest-predation is discussed in relation to nest placement and concealment, high nest visitation during incubation and nestling stages, anti-predator behaviour, nest-defence and types of predators, and re-nesting capacity, and compared with other Australasian robins and northern temperate and tropical songbirds. The small nest, small clutch-size, high nest failure, and anti-predator posture and mottled plumage of nestlings suggest that nest-predation is a strong selective pressure in the Jacky Winter. However, the moderately long nestling period, brood-size reduction, high rates of feeding young and nest visits by both male and female, and short and frequent incubation and brooding bouts on and off the nest relative to other robins are not consistent with nest-predation theory, and suggest behavioural responses to food availability and an ultimate response to food limitation. Incubation behaviour on and off the nest, parental care of young, nest visitation and other life-history traits that influence reproductive effort are discussed to elucidate the breeding strategy compared with other Australasian robins.

Multi-state, multi-stage modeling of nest-success suggests interaction between weather and land-use.

Many factors may affect daily nest survival. We present a novel multi-state, multi-stage model to estimate daily survival for each nest stage, daily hatching probability and probability that a failed nest died during a specific stage when stage of failure is unknown. The model does not require that hatching date be known. We used data from a large citizen science dataset to demonstrate the application of this approach, exploring the impact of laying dates, weather conditions, conserved soil moisture, soil carbon, habitat type and urbanization on failure rates of common blackbird (Turdus merula) nests. Models selected and estimates of nest success were similar to those of the simpler logistic exposure method, but accounted for additional uncertainty. Simulations suggest the multi-state approach performs better when incubation mortality is affected by nest age, but not when incubation mortality is assumed constant. Both approaches worked best when date of incubation initiation was known for all nests first visited during the incubation stage. Daily blackbird survival probabilities were higher in human rural habitat than in urban or countryside habitats supporting the hypothesis that these intermediate habitats offer a better balance between low food availability in urban areas and high predation rates in the wider countryside. Nest success was influenced more by recent precipitation in urban habitats, but by a longer-term measure of water availability, soil moisture, in non-human dominated habitats, indicating that climatic change is likely to alter relationships between habitat and breeding success (and their temporal scale) by influencing the trade-off between food availability and predation rates. The multi-state, multi-stage model developed here may be helpful to other researchers modelling ecological processes in which transition probabilities between multiple stages are of interest.

Summer Survival of Translocated Northern Bobwhite in the New Jersey Pine Barrens: Preliminary Results

Northern bobwhite (Colinus virginianus) have declined precipitously since the 1960s, largely due to habitat deterioration and changes in land use; some of the highest declines have been observed in the Mid-Atlantic States. In other regions, attempts to augment bobwhite populations have been relatively successful using translocation. As part of a long-term restocking program, focal areas for translocation in the mid-Atlantic region were identified by biologists at a National Bobwhite Conservation Initiative (NBCI) workshop. The objective of this project is to evaluate translocation to restore bobwhite populations in the New Jersey Pine Barrens, a focal area designated with a high ranking for potential bobwhite recovery. The study site, Pine Island Cranberry Co., is the largest privately owned land tract (>6,000 hectares) in New Jersey, with a mix of shortleaf pine (Pinus echinata), pitch pine (P. rigida), scrub oak (Quercus ilicifolia), and early successional forbes and grasses. For three consecutive years (2015—2017) prior to breeding season, we are translocating eighty radio-collared bobwhite (40 male, 40 female) from wild populations in southwest Georgia. These individuals are radio-located 3-5 times per week, year round. We are collecting microhabitat measurements (e.g., groundcover, understory, and canopy closure) and monitoring nests to characterize habitat use, nest site selection, and nest fate. Survival is estimated using staggered-entry Kaplan-Meier analyses and a Cox proportional hazard model in R to determine covariates of daily mortality. Six of 14 nests were successful in summer 2015 (66 known hatches), and 0 of 12 nests were successful in summer 2016. Snake depredation was the cause of 41.7% of failed nests in 2016. Preliminary analyses produce a five-month adult survival rate of 0.455 (SE = 0.138) for summer 2015 and 0.270 (SE = 0.0516) for 2016. Our planned third summer (2017) of data collection will increase our understanding of these disparate survival estimates.

Behavioral plasticity in response to perceived predation risk in breeding house wrens.

Predation is a significant cause of nest failure in passerine birds, and, thus, natural selection is expected to favor behavioral plasticity to allow birds to respond to perceived changes in predation risk. However, behavioral plasticity in response to perceived predation risk, and its potential fitness-related costs, are understudied. In a wild population of breeding house wrens (Troglodytes aedon), we tested the hypotheses that (1) birds show behavioral plasticity in response to perceived nest-predation risk to reduce self-risk or risk to offspring, but (2) this plasticity incurs fitness-related costs. We experimentally increased the perceived risk of nest predation by enlarging the diameter of the nestbox entrance from the standard 3.2 cm to 5.0 cm once incubation began. Unexpectedly, large-hole females spent significantly less time being vigilant than small-hole (control) females during late incubation. Both males and females also exhibited plasticity in their provisioning behavior. Large-hole males increased and large-hole females decreased provisioning visits with increasing brood size, whereas small-hole males and females behaved similarly and were unaffected by brood size. Females did not show plasticity in their incubation or brooding behavior. Notwithstanding this behavioral plasticity in response to increased perceived predation risk, treatment had no effect on hatching success or early hatchling survival, nor did it affect nestling body condition or fledging success. We conclude, therefore, that house wrens show behavioral plasticity in response to perceived nest-predation risk, but that any short-term fitness-related costs associated with this flexibility appear negligible.

Experimentally induced alloparental care in a solitary carpenter bee

Alloparenting, in which adults help to raise nondescendent offspring, is the hallmark of both cooperatively breeding and eusocial animal groups. Previous studies of the small carpenter bee, Ceratina calcarata, showed that mothers sometimes produce very small daughters, reminiscent of eusocial workers, suggesting retention of a complex social trait, alloparenting, in this secondarily solitary bee species. We tested the hypothesis that small daughters can act as alloparents by removing mothers from nests just prior to brood emergence, creating conditions under which small daughters should behave as alloparents. In 25 of 43 orphaned nests, a daughter took over the mother's role, foraging for pollen to feed her siblings. Alloparenting never occurred in control nests with surviving mothers. Alloparenting also did not occur when mothers disappeared before brood emerged as adults, as this invariably resulted in complete brood mortality. A second experiment demonstrated that post-eclosion feeding is necessary for overwintering survival. The expression of alloparenting in experimental nests suggests that alloparents could represent maternal insurance to ensure that adult offspring are fed before winter, and that alloparents could achieve indirect fitness from sibling care through assured fitness returns. However, complete nest failure in orphaned control nests demonstrates that brood only survive if their mother survives as well, which obviates the need for alloparenting. Therefore, alloparenting behaviour appears to represents the retention of an ancestral social trait that appears to have no current adaptive benefit in circumstances that highly favour solitary nesting and maternal brood care.

Post-Predation Parental Behavior of Boreal Songbirds

ABSTRACT Songbirds have a high nest failure rate, with most failed nest attempts caused by predation. While songbird behavior before and during predation events has been documented, post-predation behavior has not. We observed post-predation behavior from 36 complete predation events (all fledglings or eggs taken by predator resulting in an empty nest) of nine songbird species by using video monitoring. We examined the time for the parent to abandon the empty nest and the number of return visits the parent made before abandoning the empty nest. Increased nestling age at the time of predation resulted in parents abandoning the nest sooner and making fewer return visits to the nest post-predation. There was weak evidence that parental behavior after predation differed based on the species of predator that destroyed the nest. Other post-predation behaviors included parents returning to eat eggshells, incubation of empty nests, and food provisioning. The extended time required to leave a nest after it has fai...

When the neighbourhood goes bad: can endangered black robins adjust nest‐site selection in response to the risk of an invasive predator?

AbstractThe introduction of exotic predators into new areas has had significant impacts on naïve prey species, which initially lack behavioural mechanisms to avoid predation. Understanding a species’ ability to respond appropriately to novel threats may inform in situ management options for threatened island populations. In the presence of nest predators, physical characteristics of the nest site can influence the likelihood that eggs or chicks are lost to predation. Some birds that evolved under high nest predation pressure show predictable changes in nest‐site selection following nest predation, but the ability of naïve island birds to alter nest‐site decisions based on experience with novel nest predators has not been well studied. We examined nest‐site choices of re‐nesting Chatham Island black robins Petroica traversi following nest predation by invasive European starlings Sturnus vulgaris. Robins whose first nests were depredated re‐nested in a new location that was significantly lower to the ground than pairs whose first nests were lost through other causes. As predation risk increases with nest height, the lower placement of re‐nests is consistent with a movement towards safer nest sites. The cause of nest failure did not influence the choice of substrate for a replacement nest, nor did individual pairs re‐nest further away from depredated nests. Changes in nest‐site selection did not carry over into subsequent nesting seasons. Our results suggest that some evolutionarily naïve species may be capable of assessing immediate risk through individual experience with novel predators, and modifying their nest‐site decisions accordingly.

Nest predators, nest-site selection and nest success of the Emei Shan Liocichla (Liocichla omeiensis), a vulnerable babbler endemic to southwestern China

The Emei Shan Liocichla (Liocichla omeiensis) is a globally vulnerable babbler, endemic to southwestern China. We investigated its nest predators, nest-site selection and nest success at the Laojunshan National Nature Reserve in Sichuan, China in order to identify the precise nesting-habitat requirements of the species, and to test whether the nest-site-selection cues, preferred by the Emei Shan Liocichla, are positively associated with nest success. We used infrared cameras to determine nest predators. We compared the microhabitat attributes between nest and random sites, as well as successful and failed nests. We used Binary Logistic Regression to determine the most important variables affecting nest-site selection of the Emei Shan Liocichla. We used the nest survival analysis in Program MARK to estimate daily nest survival rates (DSR). Nest success was calculated using the Mayfield method. In total 56 nests were found. The DSR for all nests that contained at least one egg was 0.9564 ± 0.0091 (95 % CI 0.9346–0.9711) (n = 40), while the total nest success was 27.5 %. We identified four categories of predators in 10 nest predation events, i.e. squirrels (n = 5), snakes (n = 3), raptors (n = 1) and wasps (n = 1). We found that: (1) nest predation was the primary reason for nest failure of the Emei Shan Liocichla, (2) tree cover, bamboo cover, liana abundance and distance to forest edge or gap were the most important variables affecting nest-site selection of this species, and (3) the nest-site-selection variables we measured appeared not to be positively associated with nest success. Our findings suggest that the Emei Shan Liocichla tended to select nest sites near forest edges or gaps with good concealment and that nest-site selection by this species was nonrandom but not necessarily adaptive. Reducing forest-edge development and protecting bamboo stands should be effective for conservation of this species.

Interactive effects between nest microclimate and nest vegetation structure confirm microclimate thresholds for Lesser Prairie-Chicken nest survival

AbstractThe range of Lesser Prairie-Chickens (Tympanuchus pallidicinctus) spans 4 unique ecoregions along 2 distinct environmental gradients. The Sand Shinnery Oak Prairie ecoregion of the Southern High Plains of New Mexico and Texas is environmentally isolated, warmer, and more arid than the Short-Grass, Sand Sagebrush, and Mixed-Grass Prairie ecoregions in Colorado, Kansas, Oklahoma, and the northeast panhandle of Texas. Weather is known to influence Lesser Prairie-Chicken nest survival in the Sand Shinnery Oak Prairie ecoregion; regional variation may also influence nest microclimate and, ultimately, survival during incubation. To address this question, we placed data loggers adjacent to nests during incubation to quantify temperature and humidity distribution functions in 3 ecoregions. We developed a suite of a priori nest survival models that incorporated derived microclimate parameters and visual obstruction as covariates in Program MARK. We monitored 49 nests in Mixed-Grass, 22 nests in Sand Shinnery Oak, and 30 nests in Short-Grass ecoregions from 2010 to 2014. Our findings indicated that (1) the Sand Shinnery Oak Prairie ecoregion was hotter and drier during incubation than the Mixed- and Short-Grass ecoregions; (2) nest microclimate varied among years within ecoregions; (3) visual obstruction was positively associated with nest survival; but (4) daily nest survival probability decreased by 10% every half-hour when temperature was greater than 34°C and vapor pressure deficit was less than −23 mmHg during the day (about 0600–2100 hours). Our major finding confirmed microclimate thresholds for nest survival under natural conditions across the species' distribution, although Lesser Prairie-Chickens are more likely to experience microclimate conditions that result in nest failures in the Sand Shinnery Oak Prairie ecoregion. The species would benefit from identification of thermal landscapes and management actions that promote cooler, more humid nest microclimates.

To exclose nests or not: structured decision making for the conservation of a threatened species

AbstractDecisions regarding endangered species recovery often face sparse data and multiple sources of uncertainty about the effects of management. Structured decision making (SDM) provides a framework for assembling knowledge and expert opinion and evaluating the tradeoffs between different objectives while formally incorporating uncertainty. The Atlantic Coast piping plover provides an illustrative case for the utility of SDM in endangered species management because its population growth is simple to model, most populations are monitored, decision alternatives are well defined, and many managers are open to recovery recommendations. We built a model to evaluate the decision to use nest exclosures to protect piping plover eggs from predators, where the objective was to maximize λ and the tradeoff was between nest survival and adult survival. The latter can be reduced by exclosures. We used a novel mixed multinomial logistic exposure model to predict daily nest fates and incorporated the results into a stochastic projection matrix that included renesting after nest failure, and adult mortality associated with abandonment. In our test data set (n = 329 nests from 28 sites over four years), the mean nest survival over 34 days was markedly higher for exclosed nests (0.76 ± 0.03 SE) than for unexclosed nests (0.37 ± 0.07). Abandonment rates were also higher for exclosed nests (0.092 ± 0.017) than for unexclosed nests (0.045 ± 0.017), but the difference was not statistically significant and the loss rate to “other sources” (mostly predators) was much lower for exclosed nests (0.15 ± 0.03) than for unexclosed nests (0.58 ± 0.07). Population growth rate (λ) was clearly improved by exclosure use at the sites with high background nest loss rates, but λ was still <1 with exclosure use. Where the background nest loss rates were low, the decision to use exclosures was ambiguous, and λ could benefit from reducing uncertainty in vital rates. Our process demonstrated that geographic and temporal variation in nest mortality determines whether exclosures will be useful in attaining positive population growth rates and that other management options must be considered where the background nest mortality rates are high.

Threat predictability influences seaside sparrow nest site selection when facing trade-offs from predation and flooding

Habitat selection trade-offs between avoiding predation and gaining energy are well studied, but similar trade-offs resulting from multiple threats to survival remain poorly understood. We studied how seaside sparrows, Ammodramus maritimus , approach nest site selection decisions to avoid threats to nesting success from predation and tidal flooding. Along a nest height gradient, nest site selection to avoid tidal flooding (i.e. placing nests higher) may make seaside sparrow nests more vulnerable to predation, and selection to avoid predation may make nests susceptible to flooding. We monitored nesting success rates and nest site selection decisions of breeding seaside sparrow pairs at five sites near Brunswick, Georgia in April–July of 2013–2015. We found that seaside sparrows encountered a nest site selection trade-off along a gradient of nest height. Nest height had an effect on survival probability during each of our study years, with positive effects of nest height on predation probability and negative effects of nest height on flooding probability observed in some years. Sparrows dealt with this trade-off by altering their nest site selection in relation to a threat's predictability; low within-season variability in predation risk and high information about predator presence in open marshes make predation risk more predictable than the magnitude of tidal flooding, which is governed by unpredictable and variable winds. Sparrows responded to predictable predation threats by nesting at lower nest heights in years with higher predation risk, but sparrows responded to unpredictable flooding threats by placing nests higher off the ground but only following nest failure from flooding. Understanding decision making through a lens of threat predictability could provide a useful approach for studies of other animals' habitat selection trade-offs.

Daily survival rate of nests is lower in fruiting than non-fruiting tree species for a Hawaiian forest bird, the Kaua̒i ̒elepaio (Chasiempis sclateri)

ABSTRACT Nest-site characteristics are important drivers of nest success in birds, and are particularly important to understand in systems where anthropogenic factors may exacerbate their negative effects on population demographics. In Hawaii, it is suggested that forest bird nests in fruiting tree species may have higher rates of nest predation than in non-fruiting tree species, because fruit is an important dietary component of introduced rats. I assessed the differential daily survival rate (DSR) of nests of Kauai Elepaio (Chasiempis sclateri) on Kauai Island, Hawaii, in fruiting versus non-fruiting tree species using generalized linear models in program MARK. Nests were located in six fruiting tree species (n = 19) and one non-fruiting species (n = 25). Nest-tree reproductive strategy was a driver of DSR (β = −1.15 ± 0.55 SE, 95% CI = −2.23–-0.07) and DSR was lower in fruiting tree species compared to the non-fruiting species (0.975 vs. 0.992, respectively). Most nest failures were attributed to ...

A helping hand: artificial nest site provisioning increases breeding success of a tropical seabird

Common white terns Gygis alba lay a single egg balanced on rocks or branches and consequently are at risk of low nesting success. A novel technique of hollowing out coconut husks and providing artificial nest sites was developed on Cousine Island, Seychelles. Our study aimed to critically assess whether common white tern nesting success differed between artificial and natural nest sites. For natural nest sites, nesting success and the stage of nest failure were also compared between seasons, nest heights, and tree species. Finally, we compared results from our study to those of a study conducted 10 years ago on the same island. Nesting success differed significantly between artificial nests and natural nests, with the success of artificial nests nearly double that of natural nests. Hatching success was similar for artificial and natural nests (65% and 52% respectively), suggesting coconut husks do not reduce egg losses, but rather provide secure perches for young chicks. Most natural nest failures occurred during the egg phase (70%), followed by the youngest chick phase (21%). Of the eggs that hatched in natural nests, 61% fledged successfully. Tree species and season significantly influenced nesting success for natural nests and nest height varied significantly between tree species. Higher nesting success was observed during the mixed seasonal period (50%) followed by the cooler, windier and drier South-East Monsoon season (33%). The hotter and more humid North-West Monsoon period had the lowest nesting success (20%). Comparisons of nesting success at natural and artificial nest sites with the earlier study did not differ significantly, despite a smaller population of common white terns being present on the island at that stage. Our results support the use of artificial nest sites to improve nesting success for this species and serve as a model for similar species currently under threat.

Microhabitat Conditions in Wyoming's Sage-Grouse Core Areas: Effects on Nest Site Selection and Success.

The purpose of our study was to identify microhabitat characteristics of greater sage-grouse (Centrocercus urophasianus) nest site selection and survival to determine the quality of sage-grouse habitat in 5 regions of central and southwest Wyoming associated with Wyoming’s Core Area Policy. Wyoming’s Core Area Policy was enacted in 2008 to reduce human disturbance near the greatest densities of sage-grouse. Our analyses aimed to assess sage-grouse nest selection and success at multiple micro-spatial scales. We obtained microhabitat data from 928 sage-grouse nest locations and 819 random microhabitat locations from 2008–2014. Nest success was estimated from 924 nests with survival data. Sage-grouse selected nests with greater sagebrush cover and height, visual obstruction, and number of small gaps between shrubs (gap size ≥0.5 m and <1.0 m), while selecting for less bare ground and rock. With the exception of more small gaps between shrubs, we did not find any differences in availability of these microhabitat characteristics between locations within and outside of Core Areas. In addition, we found little supporting evidence that sage-grouse were selecting different nest sites in Core Areas relative to areas outside of Core. The Kaplan-Meier nest success estimate for a 27-day incubation period was 42.0% (95% CI: 38.4–45.9%). Risk of nest failure was negatively associated with greater rock and more medium-sized gaps between shrubs (gap size ≥2.0 m and <3.0 m). Within our study areas, Wyoming’s Core Areas did not have differing microhabitat quality compared to outside of Core Areas. The close proximity of our locations within and outside of Core Areas likely explained our lack of finding differences in microhabitat quality among locations within these landscapes. However, the Core Area Policy is most likely to conserve high quality habitat at larger spatial scales, which over decades may have cascading effects on microhabitat quality available between areas within and outside of Core Areas.

Video Surveillance of Painted Bunting Nests to Determine the Effect of Parental Behavior on Nest Success

Declines in populations of Passerina ciris (Painted Buntings) have led to their recent classification as a species of conservation concern. As part of a larger study investigating factors associated with nest success in south-central Louisiana during 2010–2011, we monitored a subsample of nests (n = 14) with video cameras in 2011 to identify nest predators and parasitism events. In addition, we quantified parental activity at the nest to determine if nest attendance and visitation rate during the incubation and nestling stages affected nest success. On average, successful nests were visited less frequently (0.74 ± 0.07 visits/hr) than failed nests (1.04 ± 0.07 visits/hr) during incubation. During the nestling stage, mean nest attendance of successful nests was lower (11.51 ± 1.96 min/hr) compared to failed nests (30.95 ± 3.23 min/hr), and contrary to predictions, mean visitation rate of successful nests (5.46 ± 0.46 visits/hr) was greater than that of failed nests (2.50 ± 0.50 visits/hr). Visitation was positively associated with greater nest concealment, which may have helped mitigate the risk of attracting predators and brood-parasites through increased parental activity.

Breeding habitat characteristics and nest survival of yellow-rumped flycatcher (Ficedula zanthopygia) in natural tree-cavities

Studies of nest-site selection and reproduction are essential for bird species assessment and conservation. We compared breeding habitats and random sites within a secondary cavity-nesting bird, Yellowrumped Flycatcher (Ficedula zanthopygia), in a 5-year studying period in northeast China. We also modeled the effects of factors on daily nest survival rates. The flycatcher nest cavities were mostly located in tree trunks, with only 15% found in limbs. They often located their nests in east and south direction (45°–180°) with dense canopy cover surrounding the nest trees. Yellow-rumped Flycatcher nest-site selection appears to be nonrandom, such that they select nest sites with higher tree density and higher canopy closure. Yellowrumped Flycatcher daily nest survival rate was 0.9731 ± 0.007. Daily nest survival increased with increasing percent cover of canopy closure and decreased with the distance closing to the edges. The causes for nest failure were mainly nest usurpation by other secondary cavity-nesters. Predation rate and the competition for cavities with other secondary cavity-nesters may constrain the ability of Yellow-rumped Flycatchers to optimize nest nest-site selection.

Predators of bird nests in the Atlantic forest of Argentina and Paraguay

ABSTRACT Predation is the major cause of avian nest failure, and an important source of natural selection on life history traits and reproductive behavior. However, little is known about the identity of nest predators in much of the world, including the Neotropics. To identify some of the nest predators exerting selection pressure on birds of the subtropical Atlantic forest, we present observations of animals depredating bird nests in Argentina and Paraguay. We recorded depredations (destruction or removal of eggs or nestlings) at 33 nests of 25 species of birds, confirming as predators ten species of birds (Squirrel Cuckoo Piaya cayana, White-eared Puffbird Nystalus chacuru, Toco Toucan Ramphastos toco, Red-breasted Toucan Ramphastos dicolorus, Saffron Toucanet Pteroglossus baillonii, Chestnut-eared Aracari Pteroglossus castanotis, Planalto Woodcreeper Dendrocolaptes platyrostris, White-throated Woodcreeper Xiphocolaptes albicollis, Buff-browed Foliage-gleaner Syndactyla rufosuperciliata, and Plush-crest...

Do seasonal patterns of rat snake (Pantherophis obsoletus) and black racer (Coluber constrictor) activity predict avian nest predation?

Avian nest success often varies seasonally and because predation is the primary cause of nest failure, seasonal variation in predator activity has been hypothesized to explain seasonal variation in nest success. Despite the fact that nest predator communities are often diverse, recent evidence from studies of snakes that are nest predators has lent some support to the link between snake activity and nest predation. However, the strength of the relationship has varied among studies. Explaining this variation is difficult, because none of these studies directly identified nest predators, the link between predator activity and nest survival was inferred. To address this knowledge gap, we examined seasonal variation in daily survival rates of 463 bird nests (of 17 bird species) and used cameras to document predator identity at 137 nests. We simultaneously quantified seasonal activity patterns of two local snake species (N = 30 individuals) using manual (2136 snake locations) and automated (89,165 movements detected) radiotelemetry. Rat snakes (Pantherophis obsoletus), the dominant snake predator at the site (~28% of observed nest predations), were most active in late May and early June, a pattern reported elsewhere for this species. When analyzing all monitored nests, we found no link between nest predation and seasonal activity of rat snakes. When analyzing only nests with known predator identities (filmed nests), however, we found that rat snakes were more likely to prey on nests during periods when they were moving the greatest distances. Similarly, analyses of all monitored nests indicated that nest survival was not linked to racer activity patterns, but racer‐specific predation (N = 17 nests) of filmed nests was higher when racers were moving the greatest distances. Our results suggest that the activity of predators may be associated with higher predation rates by those predators, but that those effects can be difficult to detect when nest predator communities are diverse and predator identities are not known. Additionally, our results suggest that hand‐tracking of snakes provides a reliable indicator of predator activity that may be more indicative of foraging behavior than movement frequency provided by automated telemetry systems.