Nest-site Choice Research Articles

Predation of eggs and incubating females in willow ptarmigan Lagopus l. lagopus

Nest predation is a major cause of reproductive loss in many ground-nesting birds. During 15 consecutive years the predation of nests and females throughout the incubation season were recorded in a willow ptarmigan Lagopus l. lagopus population in central Norway. The temporal predation patterns, factors affecting the predation probability and age-specific nesting patterns in this species were studied. There was a large annual variation in predation rate of both nests (0-50%) and incubating females (0-29%) in this area during the study period. The mean annual predation rate of nests (15%) was on average three times higher than the predation of incubating willow ptarmigan females (5%). Predation rate was not constant throughout the incubation season, and the nest predation rate increased with increasing number of available nests. The predation events started after the mean initiation day of incubation, and coincided with the highest number of available nests. None of the parameters we tested in a logistic regression analysis (physical condition, nest cover, experience and date for initiation of egg-laying) could predict the predation probability of nests and incubating females. However, “good” nest cover tended to have some predictive value on the predation probability. Yearling incubating females had significantly lower physical body condition than adults, and also there were differences in choice of nest site in relation to cover between the two age groups. Initiation of egg-laying in adult females tended to be distributed more evenly over the season, whereas yearling females had a more aggregated egg-laying pattern, compared to adults.

Nest site selection and fidelity of European pond turtle (Emys orbicularis) population of Babat Valley (Gödöllő, Hungary)

BackgroundThe conservation of aquatic and semiaquatic turtles requires knowledge of the area and vegetation structure of habitat used for nesting, and nesting migration route. We aimed to survey the effects of habitat features to the nest site selection, nesting success, and test the possibility of nest site fidelity. Our study was carried out at 10 different nesting areas, with special emphasis on data from returning females in a pond system in Hungary between 2014 and 2017.ResultsMost nesting attempts were found in closed sand steppes, uncharacteristic dry and semi-dry grasslands habitat patches. The principal component analysis (PCA) showed that increased sandy soil cover, sunlight and slope were important variables in nest site choice. The increasing PCA first axis score significantly increased the chance of an emergence. The degradation of open steppe vegetation, occurrence of weeds, invasive and disturbance tolerant species have a negative effect on the selection of nest sites. We observed that 96.55% of nests were located within 20 m south of a pine forest at preferred nest site at pond 5, which provided the right incubation temperature through partial shading. The returning females nested significantly closer to the northern pine forest than the single clutch females. Most probably the returning females already has the necessary experience to select the right nesting site. The individually marked females did not choose new nesting areas during the monitored years which suggests nesting area fidelity, but we did not find nest site fidelity.ConclusionThe maintenance of mosaic habitat structure, slowing down the succession process at the nesting area should be basic priorities in European pond turtle conservation programs. We suggested a spatial and temporal scheduling of land management and agricultural work to the local farmers. If the actual nest site is in an agricultural area, all work should be avoided throughout the year. Agricultural machinery should avoid the migration routes of adult turtles and emerged hatchlings during the concerned period. Under strong predation pressure, predator control should be carried out, and use nest protection.

Brain size mediates the choice of breeding strategy in the red-backed shrike Lanius collurio.

The brain size of vertebrates represents a trade-off between natural selection for enhanced cognitive abilities and the energetic constraints of brain tissue production. Processing information efficiently can confer benefits, but it also entails time costs. Breeding strategies, encompassing timing of breeding onset and nest-site selection, may be related to brain size. In this study, we aim to elucidate the relationship between brain size, breeding timing, nest-site choice, and breeding success in the red-backed shrike Lanius collurio. Our findings revealed that the timing of the first egg-laying date was associated with female head size, with larger-headed females tending to lay eggs later in the breeding season. Additionally, we observed that breeding success was positively correlated with increased nest concealment. However, this relationship was stronger in males with smaller heads. In turn, nest concealment was not related to head size but primarily influenced breeding onset. These results suggest that the choice of breeding strategy may be moderated by brain size, with differences between sexes. Larger-headed females may invest more time in selecting nesting sites, leading to delayed breeding onset, while larger-headed males may compensate for suboptimal nest concealment. Our study sheds light on the intricate interplay between brain size, breeding timing, nest-site preferences, and breeding success in passerine birds, underscoring the potential role of cognitive capacity in shaping individual decision-making processes.

Landscape factors influencing bird nest site selection in urban green spaces

IntroductionUnderstanding the birds’ breeding strategies in urban habitats is vital for ensuring their continued existence. Therefore, more research must be conducted on bird breeding and urban adaptation strategies in urban green spaces. This study aimed to address this gap by investigating the influence of landscape factors on the selection of bird nest sites. MethodsData on the presence and absence of magpie (Pica pica) and gray magpie (Cyanopica cyana) nests were collected through field surveys conducted in the campus of Nanjing Forestry University during the 2023 breeding season. Generalized additive models (GAMs) incorporating landscape variables were employed to assess the effects of these predictors on nest occurrence. The model with the lowest Akaike’s information criterion value was selected among the candidate GAMs.ResultsBelow is a summary of the main results. Nest tree height (TH), distance from the central lawn (D), and tree coverage (TC) within the sampled area were identified as the primary landscape factors influencing nest site choice. Conversely, factors such as the shortest distance to the water source, herb coverage, shrub coverage, percentage of buildings, and percentage of hard pavement did not significantly impact on nest site selection. Furthermore, the nesting potential of magpies and grey magpies initially increased with tree height, reaching a maximum at ca. TH=25 meters after which it began to decline. The nesting occurrence rate showed an initial decrease tendency with increasing distance from the central lawn, reaching a minimum at D=400 meters, and then increased with further distance. Additionally, nesting potential decreased initially with increasing of TC in the range of 0–20%, fluctuated evenly between 20–60% TC, and decreased rapidly when TC exceeded 60%.DiscussionThis study provides valuable insights into the selection of nest sites by birds in urban habitats, specifically with respect to landscape factors. The understanding of the impact of urban green spaces on urban birds and the underlying mechanisms of their behavior contributes to the conservation of wild birds and promotes the harmonious development of urban areas.

Mother knows best: nest-site choice homogenizes embryo thermal environments among populations in a widespread ectotherm.

Species with large geographical ranges provide an excellent model for studying how different populations respond to dissimilar local conditions, particularly with respect to variation in climate. Maternal effects, such as nest-site choice greatly affect offspring phenotypes and survival. Thus, maternal behaviour has the potential to mitigate the effects of divergent climatic conditions across a species' range. We delineated natural nesting areas of six populations of painted turtles (Chrysemys picta) that span a broad latitudinal range and quantified spatial and temporal variation in nest characteristics. To quantify microhabitats available for females to choose, we also identified sites within the nesting area of each location that were representative of available thermal microhabitats. Across the range, females nested non-randomly and targeted microhabitats that generally had less canopy cover and thus higher nest temperatures. Nest microhabitats differed among locations but did not predictably vary with latitude or historic mean air temperature during embryonic development. In conjunction with other studies of these populations, our results suggest that nest-site choice is homogenizing nest environments, which buffers embryos from thermally induced selection and could slow embryonic evolution. Thus, although effective at a macroclimatic scale, nest-site choice is unlikely to compensate for novel stressors that rapidly increase local temperatures. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'.

Factors Affecting Nest Site Selection by Freshwater Turtles: A Systematic Review

Nest site selection is an important behavior, particularly in species that lack parental care, as nest microclimate can greatly impact embryos’ survival and offspring phenotype. Understanding which factors influence oviposition decisions is critical to identifying priority areas for conservation. This systematic review aimed to synthesize the factors that affect nest site selection by freshwater turtles. The search was conducted in the Web of Science database. In total, 35 publications met the eligibility criteria. The first study on the topic was published more than three decades ago, but only within the last ten years have studies started to be published annually. More than half of the studies were conducted in the United States and the most studied species was Chrysemys picta. Environmental factors, mainly vegetation characteristics, but also soil properties and beach morphology, are the most studied. Anthropogenic factors have been increasingly studied, especially residential areas and agricultural fields. Some studies suggest that human-altered habitats may act as ecological traps, emphasizing the need for further research on this topic. More studies are also needed on the influence of predation risk, co-species cues, female size, and offspring phenotype on nest site selection by freshwater turtles. We highlight that understanding the factors affecting nest site selection is important for identifying the habitat needs of nesting females, predicting possible ecological implications of nest site choice, assessing the adaptive potential of species to environmental change, and determining the vulnerability of populations to different threats.

Consistent Nest Site Selection by Turtles across Habitats with Varying Levels of Human Disturbance

Human disturbance impacts the breeding behavior of many species, and it is particularly important to understand how these human-caused changes affect vulnerable taxa, such as turtles. Habitat alteration can change the amount and quality of suitable nesting habitat, while human presence during nesting may influence nesting behavior. Consequently, both habitat alteration and human presence can influence the microhabitat that females choose for nesting. In the summer of 2019, we located emydid turtle nests in east-central Alabama, USA, in areas with varying levels of human disturbance (high, intermediate, low). We aimed to determine whether turtles selected nest sites based on a range of microhabitat variables comparing maternally selected natural nests to randomly chosen artificial nests. We also compared nest site choice across areas with different levels of human disturbance. Natural nests had less variance in canopy openness and average daily mean and minimum temperature than artificial nests, but microhabitat variables were similar across differing levels of disturbance. Additionally, we experimentally quantified nest predation across a natural to human-disturbed gradient. Nest predation rates were higher in areas with low and intermediate levels of disturbance than in areas with high human disturbance. Overall, these results show that turtles are not adjusting their choices of nest microhabitat when faced with anthropogenic change, suggesting that preserving certain natural microhabitat features will be critical for populations in human-disturbed areas.

Dead Sea level decline pushed a sensitive ecosystem out of equilibrium, causing the relocation of a colonial bird breeding site

ABSTRACT Capsule Dead Sea Sparrows Passer moabiticus transferred their historical breeding colony location, following geo-ecological and hydrological changes, to a new, less arid zone within a nature reserve. Aims To find biotic and abiotic factors affecting the choice of nest sites by Dead Sea Sparrows, in order to locate potential breeding areas and plan in advance for their protection. Methods Mapping old and new nest sites of Dead Sea Sparrows within Einot Tzukim nature reserve, Dead Sea Valley, and using anthropogenic and geo-ecological GIS layers, we created a map of the potential preferred breeding colony area. Results We found the biotic and abiotic factors affecting nest site preference of Dead Sea Sparrows, which included areas far from human activity, areas close to historic springs, and areas affected by a major fire. New areas in the reserve exposed by the retreating Dead Sea were inhabited by the birds, which gradually transferred their breeding centre to a less arid zone within the reserve. Conclusion When managing colonial breeding sites, it is crucial to understand the role of both natural and anthropogenic influences in order to prioritize sites for conservation and management. Producing a preference map, based on such data, can help managers locate potential breeding areas and plan in advance for their protection.

Does Euphrates softshell turtle nest in unfavourable substratum? Description of nests from Euphrates River, Türkiye

Nest site selection differs among species based on a characteristic crucial to the embryo's survival. The identified nest-site characteristics of the Euphrates softshell turtle highlight that these turtles, like their other soft-shelled relatives, highly prefer the sandy substrate, even pure sand, to nest. However, alteration and loss of natural habitats for many decades limited the suitable oviposition sites along the Euphrates River. This study presents the uncharacteristic nest-site choice and the nesting time of Euphrates softshell turtle for the first time. I discovered four nests, as well as six unhatched eggs in a nest on 20 August 2017. This discovery extends the known nesting season-end from early June to at least mid-August for the Euphrates River. The eggs were spherical, and their size was 28.38 (±0.2, 28.1-28.6) mm on average. The nesting substrate, consisting of only 51.8% sand, was substantially dissimilar to what was previously reported. Apart from the soil texture, the nest and its site characteristics concerning nest dimension, clutch size, egg size, and distance to the shoreline concord with what was formerly reported. I conclude that many anthropogenic alterations, such as sand mining and damming and hence the scarcity of suitable oviposition sites, may have caused location and time shift of breeding and forced the turtles to nest in these uncommon soil textures.

Nest-site choice by loggerhead sea turtles as a risk-management adaptation to offset hatching failure by unpredictable storms and predators

IntroductionAlong the coasts of Florida, United States, the nesting season of the loggerhead sea turtle, Caretta caretta, overlaps with the hurricane season. Nesting loggerhead females do not extend parental protection beyond depositing eggs in sandy, excavated nests in locations that provide a viable range of temperatures, moisture, and respiratory gas exchange. Thereafter, a female’s clutches are subjected to the uncertainties of desiccation, predation, flooding, or beach erosion.MethodsHere, we used data from a 1996-2004 study of 94 tagged loggerhead females nesting on a small barrier island off the Gulf Coast of south Florida, United States. We tested the hypothesis that the distribution of nest sites by loggerhead females was a randomized response to unpredictable hatching failure.ResultsWe show that nest site choice accounted for 19.2% of variation in hatching success whereas breeding year and breeding month accounted for the remaining 81.8% of variation in hatching success. We show that the emergence site along the beach-length axis, nest site choice along the beach-width axis, and distances between nest locations did not fit a uniform-random distribution or a normal distribution. Instead, we show that loggerhead females employed a “Goldilocks” distribution in which nest sites were “neither too clustered nor too dispersed.” Moreover, loggerhead females selected nest sites with limited overlap with nest sites from previous breeding seasons.DiscussionWe propose that nest site choice by this population of loggerhead females constitutes a significant maternal risk-management adaptation that deserves thoughtful consideration as we continue to assess the impacts of climate change on the future of loggerhead sea turtles.

Consequences of Oviposition Site Choice for Geckos in Changing Environments.

Simple SummaryMost lizards lay eggs inside nests where developing embryos experience large temperature fluctuations. As females do not incubate eggs, the embryos can experience lethally high temperatures during heatwaves. Thus, future changes in the frequency and intensity of summer heatwaves may threaten lizard populations. However, variation in female nest site choice might buffer the embryos in some nests from high temperatures. In this study, we incubated eggs of the velvet gecko under two fluctuating temperature regimes to mimic the temperatures experienced inside currently used sun-exposed (“warm”: mean = 25.4 °C; range = 16.5–35.5 °C) and shaded (“cold”: mean = 23.3 °C; 17.5–30.5 °C) communal nest sites. We found that warm-incubated hatchlings hatched 15 days earlier, on average, and were smaller than their cold-incubated clutch mates. We released the hatchlings to the wild, and monitored their survival over six months. Egg incubation treatment did not influence the survival of hatchlings. This result is reassuring, because even if air temperatures increase by 2 °C in future, some currently used shaded nests will provide thermal regimes that are suitable for embryonic development. Variation in female nest site choice may therefore allow some populations of velvet geckos to persist in changing environments.Most lizards lay eggs inside nests where embryos experience daily fluctuations in temperature. As embryos are sensitive to exposure to high temperatures, increases in nest temperatures may pose a risk to lizards. In the velvet gecko Amalosia lesueurii, nest temperatures are positively correlated with air temperatures, so nests may get hotter in future. However, maternal variation in oviposition site choice might buffer populations from future warming. To evaluate the consequences of oviposition site choice, we incubated eggs under two fluctuating temperature regimes that mimicked temperatures experienced inside sun-exposed (“warm”: mean = 25.4 °C; range = 16.5–35.5 °C) and shaded (“cold”: mean = 23.3 °C; 17.5–30.5 °C) communal nests. We measured the phenotypic traits of hatchlings, released them to the wild, and monitored their survival over 6 months. Warm-incubated hatchlings hatched 15 days earlier, on average, and were smaller than their cold-incubated clutch mates. Incubation treatment did not influence the apparent survival of hatchlings. Hence, even if air temperatures increase by 2 °C in future, thermal regimes inside some currently used shaded nests will be suitable for embryo development. Maternal variation in nest site choice may therefore allow southern populations of the velvet gecko to persist in changing environments.

Do soil density and humidity affect nest‐founding in leaf‐cutting ant queens?

AbstractThe habitat choice of nest sites by founding queens of leaf‐cutting ants varies with abiotic factors such as temperature, soil density, and soil humidity. In this study, we tested the hypothesis that soil density and moisture affect excavation effort (i.e., excavation period, excavated soil amount, initial nest depth, initial chamber volume, and mortality) in queens of the leaf‐cutting ant Atta sexdens (L.) (Hymenoptera: Formicidae). Queens were placed in experimental areas in three natural soils in Brazil with varying density and moisture content. The excavated soil was collected, dried, and weighed, and digging period, nest depth, chamber volume, and queen mortality were evaluated after nest establishment. In artificially shaded habitats (less dense and more humid soil), the establishment of queens was greater, the period of nest foundation was shorter, and excavated soil amount, nest depth, and volume of the initial chamber were greater than in forest and pasture habitats (denser and drier soils). Also, queen mortality was lower in less dense, more humid soil. This indicates a trade‐off between maximizing the depth of the nest, to increase protection against inadequate environmental conditions, and minimizing energy expenditure during excavation, affecting their survival.

Effects of nest site selection and nest concealment on nest survival of Gosling's Bunting (Emberiza goslingi)

Selecting nest sites that provide access to resources and reduce predation risk is crucial to maximizing fitness in breeding birds. Therefore, understanding what habitat features influence nest site selection and nest success is a key component of avian conservation because it allows for identification and protection of habitat that will promote population growth. We examined drivers of nest success in Gosling's Bunting (Emberiza goslingi) by evaluating variables that influence nest site choice and nest survival at 23 nests and an equal number of random, paired, non-nesting locations in a tropical savannah landscape in north-central Nigeria. Gosling's Buntings exhibited a nonrandom nest-placement pattern. Nests were either on or in proximity to large rock surfaces with nesting probability increasing when the immediate nesting area (100 m radius around the nest) consisted of 30–60% bare rock. Compared to random non-nesting sites, buntings selected areas that were low in litter cover and/or had short grass height. Daily nest survival probability was high (0.96) and was positively associated with the proportion of bare rock around the nest but negatively with the amount of litter cover. Although hatching success was 56.9%, only 30% of all nesting attempts successfully fledged a chick suggesting that nest failure occurred mostly at advanced stages of nesting (nestling phase) when renesting is less likely. Nest survival was higher at low concealment, but only significantly higher than nest failure within a restricted concealment range of 45–54%. Our findings show that microhabitat features could benefit reproduction and daily nest survival. Furthermore, by linking nest-site attributes with fitness indices, we highlight the potential importance of fitness measures as a key component of habitat quality assessment for these buntings in tropical savannahs.

Can Reptiles Use Nest Site Choice Behavior to Counter Global Warming Effects on Developing Embryos? Potential Climate Responses in a Turtle

Climate warming is forecasted to cause extinctions, but populations could theoretically avoid extinction in a rapidly changing environmentviaadaptive evolution (i.e., evolutionary rescue), precluding the need for intervention. Although strong links between a changing climate and the physiology of an organism are expected, climate effects can be buffered by behavior. Nest site choice behavior, for example, can reduce environmental variation that would be experienced by embryos placed randomly with respect to environmental temperatures. We tested four provisions of this prediction by quantifying nest sites and “potential” nest sites in the Florida softshell turtle (Apalone ferox). First, turtles chose nest sites with mean canopy openness values (32–47%) that were intermediate between the shadiest (14–17%) and the sunniest potential nest sites (36–57%) available. Second, canopy openness, incident radiation intensity, and nest temperatures were generally, positively related to one another, indicating definitive thermal consequences of nest site choice. Third, our study revealed ample, cooler nest sites available to turtle mothers within close proximity to nest sites utilized; by nesting in the most shaded sites, softshell turtle mothers could depress mean nest temperatures by ∼2°C. Fourth, the growth of vegetative cover throughout incubation had negligible effects on canopy openness, incident radiation intensity, and nest temperatures, supporting the potential for mothers to “predict” developmental temperatures using temperature cues during nest site choice. Finally, our data revealed considerable variation in canopy openness chosen by nesting mothers; such behavior could thus, be subject to natural selectionviaembryonic mortality under future warming. Collectively, our study suggests that Florida softshell turtles, and probably other turtle species nesting in relatively open areas, may be able to counter climate change effects on developing embryos by nesting in more shaded microhabitats, assuming nest site choice behavior is heritable and can evolve at a sufficient rate to keep pace with climate warming. The evolutionary and behavioral mechanisms (e.g., assessing substrate temperatures directly vs. indirect choice of canopy cover) in the repertoire of nesting mother turtles for responding to climate warming remain elusive and are required for a more complete understanding of climate responses.

Population and Nesting Site Evidence for Diamondback Terrapins, Malaclemys terrapin, in Northeast Florida

Diamondback terrapins (Malaclemys terrapin)are listed as Vulnerable by the IUCN Red List Index of Threatened Species. Among the challenges terrapins encounter are habitat loss due to coastal development and sea level rise, mortality at all life stages by mammalian and avian predators, road mortality, boat strikes, harvest for the pet trade, and drowning in crab traps. The primary objective of this study was to locate populations and nesting areas of diamondback terrapins in the four northeastern-most counties of Florida (Nassau, Duval, St. Johns, and Flagler). We conducted head counts and performed land surveys of shorelines and high spots for evidence of terrapin presence. During the land surveys we searched for crawls, intact and depredated nests, dead terrapins, and terrapin bones. To evaluate whether woody plant presence affected nest site choices, we recorded the occurrence of 10 common woody plant species during each land survey and compared areas where nesting did and did not occur. We collected 404 records of terrapin activity in 2013 and 2014. Most were from Nassau County (277) and only one was from Flagler County. Most data were in the form of depredated nests (205) and terrapin remains (147). The woody plant data suggest that terrapins were significantly more likely to nest when Christmas berry (Lycium carolinianum) was present, and nesting was less likely when either wax myrtle (Myrica cerifera) or oak (Quercusspp.) were present.

Taming the temperature: Sagebrush songbirds modulate microclimate via nest-site selection

Abstract Understanding species’ responses to temperature via behavior, and the factors affecting the extent of behavioral responses, is a critical and timely endeavor given the rapid pace at which the climate is changing. The young of altricial songbirds are particularly sensitive to temperature, and parents may modulate temperatures at nests via selection of nest sites, albeit to a largely unknown extent. We examined whether sagebrush-obligate songbirds, that reproduce within an open ecosystem with wide temperature fluctuations and span a range of body sizes, selected their nest sites on the basis of temperature. We further investigated whether nest predation risk and ambient conditions modulated temperature-based choices. We placed temperature loggers at nest sites and in unused but available nest niches and nest shrubs along a known predation-risk gradient and used nearby weather stations to determine ambient temperatures. The two smaller-bodied birds, Brewer’s Sparrow (Spizella breweri) and Sagebrush Sparrow (Artemisiospiza nevadensis), selected nest shrubs and niches that were warmer and less variable relative to unused sites whereas the larger bodied species, Sage Thrashers (Oreoscoptes montanus), did not. Brewer’s Sparrows and Sage Thrashers dampened selection for warmer nest sites when temperatures experienced during the nest-site prospecting period were warmer. None of the three species altered nest-site selection with respect to temperature in response to ambient temperature variability or our index of nest predation risk. The microhabitat characteristics that most influenced temperatures at nests varied across species. Our results suggest that songbirds can modulate temperatures at nests to some extent, and such responses can vary depending on the conditions experienced prior to nest initiation. Responses also varied across species, likely reflecting different physiological tolerances. The extent to which breeding birds will be able to continue to proximately influence temperature via nest-site choices likely will depend on the extent and rate of future climatic shifts.

Don’t listen to mom: no maternal influence on consistent nest and latrine site choice by their offspring in meadow voles

Abstract Where does an animal build a nest? At a large scale, habitat preference can be informed by ‘natal habitat preference induction’, where an animal’s early environment impacts what habitat it finds suitable later in life. Other preferences may be present within a chosen habitat. We tracked the location angle of nests and latrines within the home cages of captive meadow voles, Microtus pennsylvanicus. Nests and latrines were separated from each other by an angle of approximately 180°, perhaps to reduce disease transmission. Meadow voles’ nest and latrine site choices were individually consistent across time. Only nest site choices were consistent between siblings, as assessed by a random effect coefficient, and these choices were repeatable. However, nest site choices at maturity were independent of their mother’s nest choice. We posit that the nest and latrine site choice is a socially learned preference developed through the consensus of siblings after weaning.

Thermal and physical characteristics of the nesting habitat of New Zealand’s only endemic oviparous lizard

Nest characteristics and nest-site choice determine fitness outcomes for reptile embryos and resulting hatchlings. Little is known about the nesting of Oligosoma suteri, New Zealand’s only egg-laying lizard. We investigated the physical and thermal environment of nests and available microhabitats, including nest-like sites, with the aim of applying this information to future search efforts and translocation plans. Nests of O.

Macro- and Microhabitat Predictors of Nest Success and Hatchling Survival in Eastern Box Turtles (Terrapene carolina carolina) and Spotted Turtles (Clemmys guttata) in Oak Savanna Landscapes

Differing selection pressures on stationary nest contents compared to mobile offspring mean that the nest-site characteristics resulting in the highest nest success may not be the same characteristics that result in the highest survival of juveniles from those nests. In such cases, maternal nest-site choice may optimize productivity overall by selecting nest sites that balance opposing pressures on nest success and juvenile survival, rather than maximizing survival of either the egg or the juvenile stage. Determining which macro- and microhabitat characteristics best predict overall productivity is critical for ensuring that land management activities increase overall recruitment into a population of interest, rather than benefiting one life stage at the inadvertent expense of another. We characterized nest-site choice at the macro- and microhabitat scale, and then quantified nest success and juvenile survival to overwintering in two declining turtle species, eastern box turtles and spotted turtles, that co-occur in oak savanna landscapes of northwestern Ohio and southern Michigan. Nest success in box turtles was higher in nests farther from macrohabitat edges, constructed later in the year, and at greater total depths. In contrast, survival of juvenile box turtles to overwintering was greater from nests under less shade cover and at shallower total depths. Spotted turtle nest success and juvenile survival were so high that we were unable to detect relationships between nest-site characteristics and the small amount of variation in survival. Our results demonstrate, at least for eastern box turtles, a tradeoff in nest depth between favoring nest success vs. juvenile survival to overwintering. We suggest that heterogeneity in microhabitat structure within nesting areas is important for allowing female turtles to both exercise flexibility in nest-site choice to match nest-site characteristics to prevailing weather conditions, and to place nests in close proximity to habitat that will subsequently be used by hatchlings for overwintering.

Beyond habitat: effects of conspecific and heterospecific aggregation on the spatial structure of a wetland nesting bird community

Nest location is a key factor influencing reproductive success in birds, and habitat choice is considered the main way in which birds select nest sites. Less attention has been devoted to the demand for proximity to other bird nests, which can provide additional profit, namely defense against predators. Here we analyzed the contributions of habitat, and conspecific and heterospecific aggregation to the spatial arrangement of breeding birds in a model bird community. We surveyed a pristine Siberian wetland bird community with the aim to locate all bird territories or nests, in 1993 and 2013. Habitat explained much of the nest site choice, but the nests were aggregated both intra‐ and inter‐specifically more than the spatial pattern of the habitat could explain. In particular, ducks, grebes and some waders bred nearby the most abundant active nest defenders, such as gulls and terns. Heterospecific associations were particularly pronounced in 2013, when the community was impoverished and one common active defender (white‐winged black tern Chlidonias leucopterus) was replaced by a less numerous but aggressive predator (Mongolian gull Larus mongolicus). The results suggest that spatial pattern in bird nests may be influenced by the (dis)appearance of one or a few species, which can play a role as umbrella or predator species. Integration of factors supporting the breeding of umbrella species, such as gulls, may became key targets for comprehensive conservation measures in large wetlands.