Nest Survival Research Articles

Ineffectiveness of plastic mesh for protecting artificial freshwater turtle nests from red fox (Vulpes vulpes) predation

AbstractInvasive mammalian predators are efficient at driving native animal declines. The red fox (Vulpes vulpes) kills millions of endemic reptiles in Australia each year. In areas of south‐eastern Australia, the eastern long‐necked turtle (Chelodina longicollis) and Murray River turtle (Emydura macquarii) have declined by more than 50%. High rates of nest predation by foxes limit the recruitment of young turtles in these populations, but previous methods of fox control have been ineffective at protecting turtle nests. Here, we tested the effectiveness of plastic mesh for protecting artificial turtle nests from predation by foxes, in the mid‐Murray catchment, Victoria. We also tested whether protecting a large number of artificial nests in a given area encourages foxes to give up foraging following predictions from giving‐up density theory. We made a series of plots, each containing 32 artificial turtle nests. In each plot, we covered a percentage (0%, 25%, 50%, 81% or 100%) of the nests with either 1 or 2 sheets of plastic mesh. We used remote cameras to photograph and identify any predator that attacked nests in the plots. The cameras also allowed us to estimate the amount of time a fox was visible on each plot, as a metric of how much effort foxes expended on protected nests. Nest survival rate was not increased by either 1 or 2 sheets of mesh, and increasing the number of protected nests on a plot did not reveal a giving‐up density (GUD) value for fox foraging behaviour. Our study demonstrates that plastic mesh is not effective for protecting artificial turtle nests from foxes in this region.

Waterfowl distribution and productivity in the Prairie Pothole Region of Canada: tools for conservation planning

AbstractSpecies conservation requires an understanding of the factors and interactions affecting species distribution and behavior, habitat availability and use, and corresponding vital rates at multiple temporal and spatial scales. Opportunities to investigate these relationships across broad geographic regions are rare. We combined long‐term waterfowl population surveys, and studies of habitat use and breeding success, to develop models that identify and incorporate these interactions for upland‐nesting waterfowl in the Prairie Pothole Region (PPR) of Canada. Specifically, we used data from the annual Waterfowl Breeding Population and Habitat Survey (1961–2009) at the survey segment level and associated habitat covariates to model and map the long‐term average duck density across the Canadian PPR. We analyzed nest location and fate data from approximately 25,000 duck nests found during 3 multi‐year nesting studies (1994–2011) to model factors associated with nest survival and habitat selection through the nesting season for the 5 most common upland nesting duck species: mallard (Anas platyrhynchos), gadwall (Mareca strepera), blue‐winged teal (Spatula discors), northern shoveler (Spatula clypeata), and northern pintail (Anas acuta). Duck density was highly variable across the Canadian PPR, reflecting positive responses to local wetland area and count, and amounts of cropland and grassland, a regional positive response to latitude, and a negative response to local amounts of tree cover. Nest survival was affected by temporal and spatial variables at multiple scales. Specifically, nest survival demonstrated interactive effects among species, nest initiation date, and nesting cover type and was influenced by relative annual wetness, population density, and surrounding landscape composition at landscape scales, and broad geographic gradients (east‐west and north‐south). Likewise, species‐specific probability of nest habitat selection was influenced by timing of nest initiation, population density, relative annual wetness, herbaceous cover, and tree cover in the surrounding landscape, and location within the Canadian PPR. We combined these models, with estimates of breeding effort (nesting, renesting, and nest attempts) from existing literature, in a stochastic conservation planning model that estimates nest distribution and success given spatiotemporal variation in duck density, habitat availability, and influential covariates. We demonstrate the use of this model by examining various conservation planning scenarios. These models allow estimation of local, landscape, and regional influence of conservation investments and other landscape changes on the productivity of breeding duck populations across the PPR of Canada. These models lay the groundwork for the incorporation of conservation delivery costs for full return‐on‐investment analyses and scenario analyses of climate, habitat, and land use change in regional and continental population models.

Conspecific density and habitat quality affect breeding habitat selection: Support for the social attraction hypothesis

AbstractBreeding habitat selection is a critical component of the annual cycle because of its effect on fitness. Multiple theories of habitat selection can be differentiated by their responses to the quantity of habitat, conspecific density, and habitat quality. Here, we use network analysis to understand the characteristics of fine‐scale breeding habitat selected by both immigrant and returning adult piping plovers (Charadrius melodus) to test five hypotheses of habitat selection. Between 2014 and 2019, we recorded 2034 uniquely marked adults breeding at 326 breeding locations with 1240 successive breeding events. Among adults, immigration events (i.e., individuals that moved to a new breeding location) were detected as often as fidelity to the same breeding location. We found support for the social attraction hypothesis for both immigrants and returners, indicating that adult plovers use social cues for settlement decisions. Adult plovers selected habitats with intermediate levels of conspecific density and high habitat quality, as assessed by con‐ and heterospecific nest survival, with no effect from the amount of available habitat. We also simulated the loss of breeding habitat and identified highly connected breeding locations, which occurred mostly on the riverine habitat type, which have important implications for habitat conservation for this listed species. Our results highlight the role of conspecifics at identifying high‐quality breeding habitat regardless of whether individuals return to the same breeding site or immigrate to new areas.

Patterns in avian reproduction in the Prudhoe Bay Oilfield, Alaska, 2003–2019

The Arctic Coastal Plain is one of the most important avian breeding grounds in the world; however, many species are in decline. Arctic‐breeding birds contend with short breeding seasons, harsh climatic conditions, and now, rapidly changing, variable, and unpredictable environmental conditions caused by climate change. Additionally, those breeding in industrial areas may be impacted by human activities. It is difficult to separate the impacts of industrial development and climate change; however, long‐term datasets can help show patterns over time. We evaluated factors influencing reproductive parameters of breeding birds at Prudhoe Bay, Alaska, 2003–2019, by monitoring 1265 shorebird nests, 378 passerine nests, and 231 waterfowl nests. We found that nest survival decreased significantly nearer high‐use infrastructure for all guilds. Temporally, passerine nest survival declined across the 17 years of the study, while there was no significant evidence of change in their nest density. Shorebird nest survival did not vary significantly across years, nor did nest density. Waterfowl nest density increased over the course of the study, but we could not estimate nest survival in all years. Egg predator populations varied across time; numbers of gulls and ravens increased in the oilfields 2003–2019, while Arctic fox decreased, and jaeger numbers did not vary significantly. Long‐term datasets are rare in the Arctic, but they are crucial for understanding impacts to breeding birds from both climate change and increasing anthropogenic activities. We show that nest survival was lower for birds nesting closer to high‐use infrastructure in Arctic Alaska, which was not detected in earlier, shorter‐term studies. Additionally, we show that Lapland longspur nest survival decreased across time, in concert with continent‐wide declines in many passerine species. The urgency to understand these relationships cannot be expressed strongly enough, given change is continuing to happen and the potential impacts are large.

Causes and consequences of nest-site fidelity in a tropical lekking bird: Win-stay-lose-shift tactics are unrelated to subsequent success, but site-faithful females nest earlier

Abstract Nest-site selection influences the survival of care-giving parents and their offspring, but search costs and site availability may limit site choices. Returning to previous nest sites may reduce costs and allow parents to better avoid local predators or access familiar resources. We investigated nest-site fidelity in the Lance-tailed Manakin (Chiroxiphia lanceolata), in which long-lived females raise offspring without male assistance, and found that site choices are responsive to past success but do not predict future outcomes. We compared georeferenced nest locations for the same females detected in consecutive years (245 comparisons for 138 females) and females nesting repeatedly within a year (137 comparisons for 97 females). Females were faithful to nesting sites in 13.9% of comparisons across years and 10.2% within years, and were more likely to nest again in the same site if their offspring fledged. When switching sites, females moved farther if their previous nest failed. Nest-site fidelity was unrelated to mate fidelity or female age. We then assessed whether site choice related to subsequent female survival, nest timing, or nest survival. Contrary to the hypothesis that win-stay-lose-shift tactics improve subsequent nesting outcomes, we found females were no more likely to fledge chicks or survive to a later year after they reused nest sites. However, across years, site-faithful females nested earlier on average than females that switched sites. Early nests were more likely to fledge chicks, and early-nesting females were more likely to renest when their first nesting effort was complete. Win-stay-lose-shift tactics may allow females to avoid areas where predation is likely, but new nest sites are not safer. Females that reuse nest sites benefit from early nest initiation, which both correlates with immediate success and creates potential for longer-term benefits of fidelity through increased opportunities to renest throughout the breeding season.

A simple trail camera modification reveals red-bellied woodpeckers as important egg predators of box-nesting wood ducks

Artificial nesting structures have been used to aid the recovery and maintenance of certain avian populations such as the wood duck (Aix sponsa). The success of nest boxes for wood ducks relies on excluding common nest predators such as raccoons (Procyon lotor) and rat snakes (Pantherophis spp.) via the use of predator guards; however, woodpeckers cannot be excluded. Red-bellied woodpeckers (Melanerpes carolinus) are foraging generalists and have been anecdotally observed preying on wood duck eggs where documenting predation events is difficult to accomplish through traditional nest box monitoring. Here, we used custom-modified trail cameras to document egg depredations and foraging events by red-bellied woodpeckers and the removal of damaged eggs by wood ducks during the laying and incubation periods. We captured 35,686 videos and documented 1173 different events consisting of 608 (51.8%) videos of red-bellied woodpeckers and 565 (48.2%) of wood ducks. We determined 38 (30.6%) eggs were depredated during the laying period and 14 (11.3%) during incubation. Wood ducks removed 23 (60.5%) eggs depredated during the laying period and 13 (92.9%) depredated during incubation. We found no difference in the daily number of times red-bellied woodpeckers visited boxes with nests in the laying or incubation period (t = −0.967, df = 14.699, P = 0.349). Red-bellied woodpeckers depredated 1.0 ± 0.2 eggs during each event and returned to forage on previously depredated eggs 5.3 ± 4.4 times each day spending 2.1 ± 1.1 min during each return. Our results suggest that red-bellied woodpeckers forage on eggs when nests are unguarded, and they have previously been under-recognized in the literature as predators of wood duck eggs. Future nest box programs should consider the impact red-bellied woodpeckers have on wood duck egg loss and nest survival.

Factors influencing incubation behavior and nesting success of yellow‐billed loons in Arctic Alaska

AbstractReductions in nest attendance can increase predation risk and, therefore, reduce nesting success of ground‐nesting birds. We recorded the incubation behavior, nest predators, and nesting success of yellow‐billed loons (Gavia adamsii) at 2 adjacent study areas with differing amounts of industrial activity on the Arctic Coastal Plain of Alaska, USA, during 2008–2015 and 2019. Successful pairs had higher incubation constancies (97.3 ± 1.7% [SE], n = 96 nests) than failed pairs (91.6 ± 3.1%, n = 79 nests) and took fewer and shorter recesses than failed pairs. The intrusion of conspecifics into territories significantly lowered the daily incubation constancy of nesting pairs. Daily incubation constancy also declined as the daily maximum temperature increased, especially during periods with little wind. Both conditions contributed to nest failure. Predation was the primary cause of nest failure, with glaucous gulls (Larus hyperboreus) and parasitic jaegers (Stercorarius parasiticus) accounting for 41% of the nest failures. These avian predators took advantage of unattended nests, underscoring the consequence of disrupting incubation behavior. In both study areas, nest survival decreased as recess frequency increased. In the Colville Delta study area, loons with territories composed of separate nesting and brood‐rearing lakes had lower nest survival than loons that used 1 lake for both activities. In the National Petroleum Reserve‐Alaska study area (NPR‐A), loons nesting on shorelines and peninsulas had lower nest survival than those nesting on islands and nest survival decreased as the proportion of days with intruders increased. The overall probability of a nest hatching ≥1 egg in the Colville Delta study area was 0.40 (95% CI = 0.26–0.54) and was 0.68 (95% CI = 0.40–0.91) in the NPR‐A study area. Our results demonstrate the importance of nest attendance by yellow‐billed loons in warding off nest predators on the Arctic Coastal Plain of Alaska and provide a mechanism that shows how a warming Arctic climate could negatively affect yellow‐billed loons.

Detecting ecological traps in human-altered landscapes: A case study of the thick-billed longspur nesting in croplands.

Conversion of the North American prairies to cropland remains a prominent threat to grassland bird populations. Yet, a few species nest in these vastly modified systems. Thick-billed longspurs historically nested in recently disturbed or sparsely vegetated patches within native mixed-grass prairie, but observations of longspurs in spring cereal and pulse crop fields during the breeding season in northeastern Montana, USA, suggest such fields also provide cues for habitat selection. Maladaptive selection for poor-quality habitat may contribute to ongoing declines in longspur populations, but information on thick-billed longspur breeding ecology in crop fields is lacking. We hypothesized that crop fields may function as ecological traps; specifically, we expected that crop fields may provide cues for territory selection, but frequent human disturbance would result in reduced reproduction. To address this hypothesis, we compared measures of habitat selection (settlement patterns and trends in abundance) and productivity (nest density, nest survival, and number of young fledged) between crop fields and native grassland sites during 2020-2021. Across both years, settlement patterns were similar between site types and occupancy ranged from 0.52 ± 0.17 SE to 0.99 ± 0.01 on April 7 and 30, respectively. Early season abundance differed by year, and changes in abundance during the breeding season appeared to be associated with precipitation-driven vegetation conditions rather than habitat type. While an index of nest density was lower in crop than native sites, the number of young fledged per successful nest (2.9 ± 0.18 SE) and nest survival (0.24 ± 0.03 SE; n = 222 nests) were similar for crop and native sites. Collectively, the data did not support our ecological trap hypothesis: longspurs did not exhibit a clear preference for crop sites and reproductive output was not significantly reduced. Our results indicate that croplands may provide alternative breeding habitat within a human-dominated landscape.

The effectiveness and cost efficiency of different predator exclosure designs to increase piping plover (Charadrius melodus) nest success and fledging rate in Alberta, Canada

AbstractAn estimated 30% of the North American piping plover (Charadrius melodus) breeding population occurs in Canada, where it is Endangered. Predator exclosures are a common management tool across the species' range to increase nest success. Using data from 1998 to 2010 on 820 nests, collected as part of an ongoing management program in Alberta, we compare daily nest survival (DNS), numbers of chicks hatched and fledglings produced, and cost/chick among three treatments (large, medium, small exclosures) and natural nests. During the early period (1998–2001), when all three types of exclosures were applied, there were no significant differences in DNS between exclosed nests and natural nests. During the late period (2002–2010), when only small exclosures were applied, nests with small exclosures had a significantly higher DNS rate ( = 0.994, n = 594) compared with natural nests ( = 0.984, n = 88). Nests with small exclosures also hatched more chicks ( = 3.21, n = 598) and produced more fledglings ( = 1.17, n = 337) than natural nests ( = 1.73 chicks, n = 31; = 0.59 fledglings, n = 21) during the late period. However, considering only successful nests, the differences were not significant for either period, indicating no added benefit of exclosures beyond protecting the nest. The cost/chick rate was lowest using small exclosures (cylindrical, 40 by 60 cm), and this portable design is well‐suited for widespread application in the field. We demonstrate increased DNS for nests with small exclosures and a mean fledging rate close to the goal of 1.25 chicks/nest/year, although this did not increase Alberta's piping plover population beyond the timeframe of systematic exclosure application. Long‐term, cost‐efficient management tools that increase nest success and fledging rates should continue.

Estimating direct and indirect effects of habitat structure on nesting field sparrows (Spizella pusilla) using structural equation models

Due to consistent population declines across the continent, grassland birds have become a guild of high conservation and management interest. Despite a large number of studies investigating grassland bird habitat associations, we know relatively little about the mechanisms through which habitat characteristics may impact grassland birds, as these mechanisms are often assumed rather than directly tested. For this study, we estimated whether the effects of habitat structure on breeding Field Sparrows are mediated through changes in predator (snake and raccoon) abundance, alternative prey availability, or arthropod biomass using structural equation models. We found no evidence of nest survival or nest density of Field Sparrows being directly influenced by nest predator abundance, alternative prey, or arthropod biomass, although habitat characteristics associated with increased nest survival were also associated with greater arthropod biomass and reduced predator abundance. We suggest that habitat structure in our study area primarily impacts breeding Field Sparrows through direct means, such as influencing nest concealment or foraging efficiency. Our results also suggest that nest success and nest density are decoupled in our study area, so Field Sparrows may be preferentially selecting nest sites with structural characteristics that do not increase nest survival. Ultimately, our findings from this study indicate that while predator avoidance and food provisioning likely play an important role in determining nest survival for grassland birds, predator abundance and arthropod biomass may not necessarily predict predation risk and foraging efficiency to the extent that is often assumed.

A potential consequence for urban birds’ fitness: Exposed anthropogenic nest materials reduce nest survival in the clay-colored thrush

Urban bird dwellers survive and reproduce in highly urbanized ecosystems. Some individuals adjust to these novel conditions by changing natural nesting materials for artificial materials, thus making nests more conspicuous in the environment. The consequences of using artificial materials for nesting remain poorly understood, especially from a nest-predator perspective. We studied if exposed artificial materials on bird nests affect the daily survival rate in a common dweller species, the clay-colored thrush (Turdus grayi). We used previously collected nests with a different area of exposed artificial materials and placed them with clay eggs on the main campus of the Universidad de Costa Rica. During 12 days of the reproductive season, we monitored the nests using trap cameras located in front of each nest. We found that nest survival decreased as the proportion of exposed artificial materials increased in the nest and, unexpectedly, that the principal predators were conspecifics. Thus, artificial materials used in the outer layer of nests make them more susceptible to predation. The use of artificial materials likely reduce reproductive success and population size in urban clay-colored thrush, but further field experiments measuring the effect of waste in birds' nests on the reproductive success of urban birds are needed.

Lead exposure is correlated with reduced nesting success of an urban songbird

Lead exposure is a concern in urban ecosystems, with physiological and behavioral effects well documented in humans. Wildlife inhabiting urban ecosystems are also exposed to lead, yet little work has documented the sublethal effects of lead exposure in urban wildlife. We studied northern mockingbirds (Mimus polyglottos) in three neighborhoods of New Orleans, Louisiana, two with high soil lead and one with low soil lead, to better understand how lead exposure may influence mockingbirds' reproductive biology. We monitored nesting attempts, measured lead concentrations in blood and feathers of nestling mockingbirds, documented egg hatching and nesting success, and assessed rates of sexual promiscuity in relation to neighborhood soil lead levels. We found that nestling mockingbirds’ blood and feather lead levels reflected the soil lead levels of their neighborhoods and nestling blood lead levels were similar to those of adult mockingbirds in the same neighborhoods. Nest success, as evaluated by daily nest survival rates, was higher in the lower lead neighborhood. Clutch sizes varied substantially across neighborhoods, but rates of unhatched eggs did not covary with neighborhood lead levels, suggesting that other drivers are influencing variation in clutch sizes and hatching success in urban habitats. At least one-third of nestling mockingbirds were sired by an extra-pair male, and there was no relationship between extra-pair paternity rates and neighborhood lead levels. This study provides insight on how lead contamination may influence reproduction in urban-dwelling wildlife and suggests that nestling birds could serve as useful bioindicators of lead levels in urban neighborhoods.

Is green the new black? Black-backed Woodpecker vital rates do not differ between unburned and burned forests within a pyrodiverse landscape

AbstractWoodpeckers often reflect rapid changes to forest health and serve as indicator species to help guide forest management decisions. The Black-backed Woodpecker (Picoides arcticus) is known for its strong association with recently burned forests and is a species of conservation concern due to habitat loss stemming from post-fire management of burned forest. Several studies have found the Black-backed Woodpecker occupying extensive areas of unburned (i.e., green) forests in the western part of its range during the breeding season, raising questions about whether green forests can support viable nesting populations in this region. We studied breeding Black-backed Woodpeckers in southern Oregon, USA to evaluate whether 2 vital rates critical to population recruitment—nest survival and post-fledging survival—differed between green and burned forests. During 2018, 2019, and 2021, we monitored 91 Black-backed Woodpecker nests (n = 34 in green forest, n = 57 in burned forest) and found that neither daily nest survival rate nor reproductive output (i.e., the number of fledglings per successful nest) differed between nests located in green and burned forest; however, nestling body condition was slightly enhanced in green forest. We also quantified survival of recently fledged individuals using VHF radio telemetry and found that the survival rate of birds in green forest was nearly identical to those in burned forest, with most mortalities occurring within 4 weeks of fledging. Our results indicate that Black-backed Woodpeckers in green forests were equally successful at breeding as conspecifics in recently burned forest, although densities of nesting pairs in green forest were lower than those in burned forest. Our findings indicate certain types of green forest, particularly mature lodgepole pine, can support viable populations of the Black-backed Woodpecker in the western portion of its range. This finding has conservation implications given that green forest occupies much of the forested landscape in this region and is often juxtaposed to areas subjected to high severity fire. Therefore, practices that promote pyrodiversity—landscape-level spatial and temporal variability in fire effects—as well as connectivity between green and burned forest within fire-prone landscapes are likely to provide the greatest conservation benefit for this species.

Nest‐site features influence nest survival of the Hellmayr's pipit in extensive cattle‐grazed grasslands

AbstractThe Pampas Grasslands in South America have been almost completely transformed by urbanization and agriculture. Many grassland birds persist only in extensive natural pasturelands, which are under constant pressure from fragmentation, cattle‐grazing, and exotic plant species. Identifying which habitat features affect bird breeding success is important for their conservation in altered habitats, although few studies have been conducted in the Pampas Grasslands. We analyzed the influence of habitat features on the daily nest survival rates (DSR) of the Hellmayr's pipit (Anthus hellmayri), a grassland passerine endemic to South America, in a cattle‐grazed grassland. We evaluated the effects of vegetation features at a nest‐site scale, proximity to habitat edges, cattle density, and temporal factors. During 3 breeding seasons (2017–2020), we confirmed the fate of 90 nests, 25 of which were successful (27.8%). Predation was the most common cause of failure (80%), followed by weather‐induced abandonment (10.8%). Average DSR was 0.9106, with a cumulative survival probability of only 7.4%. The best model indicated that DSR was higher in nests adjacent to grass clumps than in those placed in depressions and followed a quadratic trend with nest age. Clump nests may be better protected from aerial predators and rainfall; hence pipits could be more successful in areas with more grass clumps. The very low nest success raises concern regarding the value of these grazing fields as breeding habitats; we urge authorities and landowners to increase conservation efforts in the remaining natural grasslands in the Pampas.

Nest traits and major flooding events influence nest survival of Emperor Geese while regional environmental variation linked to climate does not

Abstract The reproductive ecology of geese that breed in the Arctic and subarctic is likely susceptible to the effects of climate change, which is projected to alter the environmental conditions of northern latitudes. Nest survival is an important component of productivity in geese; however, the effects of regional environmental conditions on nest survival are not well understood for some species, including the Emperor Goose (Anser canagicus), a species of conservation concern that is endemic to the Bering Sea region. We estimated nest survival and examined how indices of regional environmental conditions, nest traits (nest age, initiation date, and maximum number of eggs in the nest), and researcher disturbance influenced daily survival probability (DSP) of Emperor Goose nests using hierarchical models and 24 years of nest monitoring data (1994–2017) from the Yukon–Kuskokwim Delta (Y–K Delta) in western Alaska. Our results indicate that overall nest survival was generally high (µ = 0.766, 95% CRI: 0.655–0.849) and ranged from 0.327 (95% CRI: 0.176–0.482) in 2013 to 0.905 (95% CRI: 0.839–0.953) in 1995. We found that DSPs of nests were influenced by nest traits, negatively influenced by major tidal flooding events and by researcher disturbance, but were not influenced by regional indices of spring timing, temperature and precipitation during nesting, or fox and vole abundance on the Y–K Delta. However, the number of nests found each year was negatively related to our index of fox abundance, suggesting nests that failed as a result of fox predation may have never been discovered due to our limited nest-searching efforts during egg laying. Our results suggest that regional environmental variation had minimal influence on the nest survival of Emperor Geese, although major flooding events were important. Nevertheless, we suspect that within-year variation in local weather conditions and local abundance of predators and alternative prey may be important and should be considered in future studies.

Mammalian predators and vegetated nesting habitat drive reduced protected area nesting success of Kentish plovers, Yellow Sea region, China.

Protected areas provide essential habitats for wildlife by conserving natural and semi-natural habitats and reducing human disturbance. However, whether breeding birds vulnerable to nest predation can benefit from strict land management in the protected area is unclear. Here, we compare the nesting performance of two groups of a ground-nesting shorebird, the Kentish plover (Charadrius alexandrinus), in the protected area (Liaohekou Natural Reserve, hereinafter PA), and the control non-protected area (non-PA) around the Liaohekou Natural Reserve, in the north of the Yellow Sea, China, and identify which environmental factors, such as nesting habitat and nest materials, influence the daily nest survival rate (DSR). We found similar nesting habitats in both study areas, dominated by bare land or Suaeda salsa grassland. However, DSR was lower in PA (0.91 ± 0.01) than in non-PA (0.97 ± 0.01). Kentish plovers nesting in areas with vegetation cover experienced lower DSR than in bare lands in both areas, and nests built with materials of S.salsa sticks had the lowest DSR in the bare land. Data from infrared cameras confirmed relatively higher predator abundances and nest predation rates by nocturnal mammals, such as Eurasian badgers (Meles meles), in PA than in non-PA, and this pattern was especially evident for plover nests located in S.salsa grassland. Our results suggest that Liaohekou Natural Reserve protected area may not necessarily provide safe nesting sites for Kentish plovers due to the abundance of generalist mammal nest predators. However, the PA includes about 80% of the nests from both locations. This means the contribution of the total number of successful nests continues to be much higher within PA, with the benefit for the species that this brings in terms of conservation. The variation and mechanisms underlying differences in the nest predator communities of PA and non-PA deserve further study.

Geothermal energy production adversely affects a sensitive indicator species within sagebrush ecosystems in western North America

Growing demand for renewable energy has resulted in expansion of energy infrastructure across sagebrush ecosystems of western North America. Geothermal power is an increasingly popular renewable energy source, especially within remote areas, but little is known about the impacts it may have on local wildlife populations. Investigations are warranted given similarities to more conventional surface disturbance activities with well-documented impacts. Using a novel 2-pronged analytical approach, we estimated effects of geothermal energy production activities (hereafter, geothermal) on populations of greater sage-grouse (Centrocercus urophasianus; hereafter, sage-grouse), a species of high conservation concern. First, we applied a before-after-control-impact paired series design at two geothermal sites in Nevada, USA, to estimate absence rates of male sage-grouse from lek sites (breeding grounds) and changes in predicted apparent abundance (λ̂) in relation to geothermal energy infrastructure. We then estimated effects of geothermal energy infrastructure and other environmental covariates on demographic rates. We found λ̂ declined ∼24 % within 5 km of geothermal sites, while lek absence rates (e.g., indicating local extirpation) increased by ∼730 % within 2 km. Our demographic models revealed decreased nest survival in association with proximity to geothermal infrastructure, reduced topographic impedance surface (TIS; a proxy for sound and light dispersion emanating from geothermal infrastructure), and increased density of common ravens (Corvus corax), an effective nest predator. Models also estimated decreases in adult survival in relation to TIS. Finally, we applied population matrix models within a quantitative decision support framework to help guide locations for future geothermal development that balance the need for domestic energy production while minimizing adverse effects on wildlife populations.

The basics of peer review

The basics of peer review

Comparability and Repeatability of Candling and Floating Methods for Estimating Embryo Age of Waterbird Eggs

Determining embryo age is important for predicting hatch dates, planning nest visitation schedules, and as a model covariate examining factors affecting nest survival and behavior. Two common methods of estimating embryo age are egg candling and egg flotation (floating). Despite the reliance on these methods, there is little information regarding the repeatability of these techniques between multiple observers, or whether these techniques produce equivalent estimates. To determine how these methods compare and if precision of each method is biased by individual observers, paired observers candled and floated the same Common Eider (Somateria mollissima) eggs. We compared differences in embryo-age estimates across incubation between (1) candling and floating, (2) paired observers candling eggs, and (3) paired observers floating eggs. Floating and candling produced different embryo-age estimates during some periods of incubation. Although most estimates deviated by a few days, inconsistencies could impact results and statistical power when methods are interchanged between projects or across years. Observers derived different embryo-age estimates for candling, but not for floating, suggesting flotation may be more reliable. Our results suggest caution when combining candling and floating-derived data when collected across incubation stages. Investigators should consider how data collected by multiple observers may affect their research question.

Integrative assessment of immunity, health-state, growth and survival of Magellanic penguin chicks in a colony exposed to ecotourism

Accumulating reports of negative impacts of tourist activities on wildlife emphasize the importance of closely monitoring focal populations. Although some effects are readily noticed, more subtle ones such as changes in physiological functions of individuals might go overlooked. Based on evidence of altered physiology associated with ecotourism on Magellanic penguins Spheniscus magellanicus, here we performed an integrated assessment using a diverse physiological toolkit together with more traditional fitness-related measures to better understand mechanisms and potential consequences. Chicks exposed to tourism showed altered immune parameters and elevated flea prevalence, reinforcing previous findings. Tourism-exposed female, but not male, chicks also showed relatively lower hematocrit and plasma protein levels, providing evidence consistent with a sex-specific response to tourist visitation. Physiological alterations detected in tourism-exposed young chicks (week 1–2) were maintained and the effect on flea infestation increased during the study period (week 4–5 of post-hatch). Despite the effects on physiology, these did not seem to translate into immediate fitness costs. No detectable tourism effects were found on brood sex ratios, chick growth and body condition, and survival until week 5–6 post-hatch. We detected no effects on reproductive output and only a marginal effect on nest survival during incubation despite previous reports of tourism-associated alterations in stress indices of adults. This disconnection could result if the physiological changes are not strong enough to impact fitness, if effects balance each other out, or if changes are part of a copying strategy. Alternatively, the physiological alterations might only show impacts later in the brooding cycle or even after chick emancipation from their parents. Our results suggest that integrative monitoring of potential anthropogenic impacts on wildlife should include evaluation of physiological mechanisms and individual-level responses in populations exposed to human activities.