Multi-dimensional niche differentiation of two sympatric breeding secondary cave-nesting birds in Northeast China using DNA metabarcoding.

Niche theory predicts that ecologically similar sympatric species should show differentiation in at least one of the main niche dimensions (time, space, and/or food). Here, we combined observations of breeding timing, nest site selection, and diet (the latter determined using DNA metabarcoding) to analyze the niche overlap and differentiation between two sympatric secondary cavity-nesting birds, the Japanese Tit Parus minor and the Yellow-rumped Flycatcher Ficedula zanthopygia. The results showed that (1) there were significant differences in the first egg laying date, length of the egg laying period, incubation date, and hatching date between tits and flycatchers, and the breeding time of flycatchers peaked later (about 30 days) than that of tits; (2) the two species had a large overlap in nest site selection, although the canopy coverage and shrub density of flycatchers were significantly higher than those of tits; and (3) the niche overlap in diet was minimal, with both species heavily relying on Lepidoptera (39.6% and 63.7% for tits and flycatchers, respectively), but with flycatchers consuming significantly higher percentages of Lepidoptera, Diptera, and Coleoptera than tits. The results indicate that these two sympatric secondary cavity-nesting species have significant niche differentiation in breeding time and diet, but little differentiation in nest site selection.

Distribution of brood of the acorn ant Temnothorax crassispinus in artificial nests after forced migration.

Nest sites are important for social insects, as they provide refuge against enemies and ensure optimal conditions for the brood development. In large nests, the different chambers can be used for different reasons; for example, for food storage or as a brood chamber. Acorn ants from the genus Temnothorax dwell in small cavities in acorns and wood; however, even such small chambers can have a high degree of spatial heterogeneity. During this study, the distribution of brood items of the acorn ant Temnothorax crassispinus inside artificial nest cavities composed of three chambers in a linear system was analysed. 29 ant colonies were photographed 13 times during a period of approximately one month: during three consecutive days, and after forced migrations. I found that the distribution of the brood inside the nest cavity was similar during the consecutive days; however, after the forced migration, the distribution typically changed. Almost all the brood items were kept farther from the entrance. Keeping the brood farther from the entrance could be explained as a safer option.

Null models confirm nest site fidelity by male smallmouth bass, Micropterus dolomieu.

BACKGROUND: Many animals appear to preferentially renest in proximity to a site they previously occupied. Evidence of nest fidelity is often inferred from a right skewed distribution of distances between the nests of individuals that breed in two consecutive reproduction episodes, where many individuals nest some arbitrarily close distance to their prior nest and others, in the extended right tail of the distribution, nest far from the nest they previously occupied. Because right skewed distributions of inter-nest distances can arise even when individuals choose nest locations randomly, however, such inferences are prone to error. The importance of null models-used to generate patterns of individual inter-nest distances by processes that do not involve site attachment-for inferences about site fidelity has been known for decades but is still often unappreciated or ignored. METHODS: The right skewed distributions of inter-nest distances observed in two earlier studies of male smallmouth bass (Micropterus dolomieu) suggest prima facie that males exhibit nest site fidelity between annual reproduction episodes, but patterns of inter-nest distances have yet to be compared to an adequate null model. Here, we evaluate the nest site fidelity of marked male M. dolomieu in a decade-long dataset, where we apply a randomization procedure based on the rencontre probability problem to generate null models. Eight observed distributions of individual, annual inter-nest distances are compared to a year-specific null model to determine whether random processes are sufficient to explain the observed distributions of inter-nest distances. RESULTS: Through contrasts between observed annual inter-nest distances and results derived from null models that imposed realistic constraints on behavior, we show that some males were undoubtedly nest-site faithful. To reinforce the utility of null models and to make these kinds of models more accessible, we also provide a supplemental tutorial. The tutorial illustrates how random site choices, subject to common ecological and behavioral constraints, and even how distance is measured, can produce patterns of inter-nest distances that falsely imply nest site fidelity, or a lack of fidelity. The R code needed to reproduce these null models is included. The inference errors evident in our examples generalize to other forms of site fidelity, such as the apparent patch fidelity of certain sea bird foragers. CONCLUSIONS: The comparisons of observed distributions of inter-nest distances with those generated by null models imply that, as suggested in prior studies, male M. dolomieu indeed exhibit annual nest site fidelity. Procedures like those we apply are necessary first steps in analyses when distributions of distances between the nests of individuals in consecutive reproduction episodes are used to infer nest-site fidelity. Why male M. dolomieu are site faithful is a question yet to be answered.

Comparison of Reproductive Strategies between Two Sympatric Copsychus Passerines.

Reproduction plays a crucial role in determining the development, fate, and dynamics of bird populations. However, reproductive strategies vary among species and populations. In this study, we investigated the reproductive strategies of the Oriental Magpie Robin (Copsychus saularis) and White-rumped Shama (C. malabarica), which are closely related passerines that reproduce in sympatric areas. We found that although these two species were both cavity nesting, their nest-site selection differed; the Shama preferred nesting close to trees and forests, whereas the Magpie Robin nested close to human residential areas. Furthermore, their egg incubation patterns differed; the Shama increased daily incubation frequency with incubation time, but the Magpie Robin maintained its daily incubation time regardless of changes in incubation frequency. However, the nestling heating patterns of these two species were similar, indicating a critical demand for regulating hatchling body temperature during this crucial stage. The feeding frequencies of male parents were strongly correlated with those of females in both species, suggesting equal contribution and good synchronization between the sexes. Nestling feeding frequency was also correlated with nest cleaning frequency, implying coordination between feeding and defecation by parents and offspring, respectively. This research explored the divergence and convergence of reproductive strategies between these two sympatric species, providing valuable insights into the niche differentiation theory.

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.

Age effects in Darwin's finches: older males build more concealed nests in areas with more heterospecific singing neighbors.

Nesting success tends to increase with age in birds, in part because older birds select more concealed nest sites based on experience and/or an assessment of prevailing predation risk. In general, greater plant diversity is associated with more biodiversity and more vegetation cover. Here, we ask if older Darwin's finch males nest in areas with greater vegetation cover and if these nest sites also have greater avian species diversity assessed using song. We compared patterns in Darwin's Small Tree Finch (Camarhynchus parvulus) and Darwin's Small Ground Finch (Geospiza fuliginosa) as males build the nest in both systems. We measured vegetation cover, nesting height, and con- vs. heterospecific songs per minute at 55 nests (22 C. parvulus, 33 G. fuliginosa). As expected, in both species, older males built nests in areas with more vegetation cover and these nests had less predation. A novel finding is that nests of older males also had more heterospecific singing neighbors. Future research could test whether older males outcompete younger males for access to preferred nest sites that are more concealed and sustain a greater local biodiversity. The findings also raise questions about the ontogenetic and fitness consequences of different acoustical experiences for developing nestlings inside the nest. Supplementary Information: The online version contains supplementary material available at 10.1007/s10336-023-02093-5.

Can nesting behaviour allow reptiles to adapt to climate change?

A range of abiotic parameters within a reptile nest influence the viability and attributes (including sex, behaviour and body size) of hatchlings that emerge from that nest. As a result of that sensitivity, a reproducing female can manipulate the phenotypic attributes of her offspring by laying her eggs at times and in places that provide specific conditions. Nesting reptiles shift their behaviour in terms of timing of oviposition, nest location and depth of eggs beneath the soil surface across spatial and temporal gradients. Those maternal manipulations affect mean values and variances of both temperature and soil moisture, and may modify the vulnerability of embryos to threats such as predation and parasitism. By altering thermal and hydric conditions in reptile nests, climate change has the potential to dramatically modify the developmental trajectories and survival rates of embryos, and the phenotypes of hatchlings. Reproducing females buffer such effects by modifying the timing, location and structure of nests in ways that enhance offspring viability. Nonetheless, our understanding of nesting behaviours in response to climate change remains limited in reptiles. Priority topics for future studies include documenting climate-induced changes in the nest environment, the degree to which maternal behavioural shifts can mitigate climate-related deleterious impacts on offspring development, and ecological and evolutionary consequences of maternal nesting responses to climate change. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'.

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'.

Brood parasitism risk drives birds to breed near humans.

Urbanization is transforming ecosystems at a global scale and at an increasing rate,1,2 and its profound consequences for wildlife have been well documented.3,4,5,6 Understanding how animals thrive in the urban environment and how this environment affects (co-)evolutionary processes remains an important challenge.7 Urban environments can provide resources such as food or nest sites (e.g., cavities)10,8,9 and also reduce exposure to predators.11,12 For some species, urban environments may also affect susceptibility to brood parasitism,13,14 but this has never been tested experimentally. Here, we use a combination of field observations and experimental manipulations to show that Daurian redstarts, Phoenicurus auroreus, a common host of the common cuckoo, Cuculus canorus, nest in proximity to humans to avoid brood parasitism. First, redstarts were more likely to be parasitized with increasing distance to the nearest building. Second, redstarts adjusted their nesting location in response to a seasonally predictable change in the risk of brood parasitism. Third, experimentally simulating the presence of cuckoos during a period when they are naturally absent increased the likelihood that redstarts nested indoors or closer to human settlements. These findings suggest that redstarts actively choose to place their nest in the vicinity of a human residence as a defense against cuckoos. Our study exemplifies how animals take advantage of the urban environment by using it as a novel line of defense against detrimental interspecific interactions.

Predation risk regulates prey assortative mating by reducing the expected reproductive value of mates.

Many animals exhibit size assortative mating (SAM), but how predation affects it remains largely unknown. We hypothesized that predation risk may turn prey less choosy, disrupting SAM, or reduce the expected reproductive value of mates, maintaining SAM but with different size ratio between mates. Using a manipulative field experiment, we found that desert isopods under risk of scorpion predation maintained SAM, but that males that choose and fight over females were on average smaller for a given female size. Less pairs were formed in risky sites, but there were no differences in female sizes and progeny number, size and age near and away from scorpion burrows. Our complementary behavioral experiments revealed that bigger males stayed longer near safe burrows, and won more male-male contests than smaller conspecifics. Our findings highlight that prey can anticipate future costs of predation and use this information to assess the expected reproductive value of mates.

The Importance of Nest Box Placement for Barn Owls (Tyto alba).

Nest boxes have been used for years to increase breeding bird numbers for conservation and also in biological pest control projects. Barn owls (Tyto alba) have been used as biological pest control agents for rodents for years, and since nest boxes are costly for growers there is a need to determine whether nest box placement can increase the occupation of nest boxes and breeding success. We studied whether barn owl breeding in agricultural areas varied in nest boxes located on trees, poles located in the shade, and poles in the sun. The occupation of nest boxes was highest in nest boxes located on trees, followed by poles in the shade, and finally poles in the sun. In comparison, the number of fledglings was highest for nest boxes on poles in the sun followed by poles in the shade in the first half of the breeding season, whereas more nestlings were fledged in nest boxes on trees in the second part of the breeding season, which is most likely due to the higher internal temperatures in the nest boxes located in the sun. Interestingly, all the nest boxes' internal temperatures were lower than the ambient temperatures but were much lower on trees than those on poles, most likely due to the trees providing better protection from the heat. It is therefore important to not only consider the placement of nest boxes, but how occupation and breeding success may vary seasonally.

Effects of grazing strategy on facultative grassland bird nesting on native grassland pastures of the Mid-South USA.

Understanding how livestock grazing strategies of native warm season grasses (NWSG) can impact facultative grassland bird nesting can provide insight for conservation efforts. We compared pre and post treatment effects of rotational grazing (ROT) and patch-burn grazing (PBG) for facultative grassland bird species nest success and nest-site selection on NWSG pastures at three Mid-South research sites. We established 14, 9.7 ha NWSG pastures and randomly assigned each to either ROT or PBG and monitored avian nest-site selection and nest success, 2014-2016. We collected nesting and vegetation data in 2014, before treatment implementation, as an experimental pre-treatment. We implemented treatments across all research sites in spring 2015. We used a step-wise model selection framework to estimate treatment effect for ROT or PBG on avian nest daily survival rate (DSR) and resource selection function (RSF) at the temporal scale and within-field variables. Daily survival rates were 0.93% (SE = 0.006) for field sparrow (Spizella pusilla), 0.96% (SE = 0.008) for red-winged blackbird (Agelaius phoeniceus), and 0.92% (SE = 0.01) for indigo bunting (Passerina cyanea). Model support for PBG treatment and vegetation height were indicated as negative and positive influences for field sparrow DSR, respectively. Red-winged blackbirds' DSR were negatively influenced by ROT while vegetation height positively affected DSR, and DSR for indigo bunting did not differ among treatments. Combined RSF models indicated nest-site selection for all species was positively related to vegetation height and only weakly associated with other within-field variables. We provide evidence that ROT and/or PBG effects vary by species for DSR for these three facultative grassland birds, and vegetation characteristics affected their nest-site selection in the Mid-South USA. A lack of disturbance in Mid-South grasslands can lead to higher successional stages (i.e., mix shrub-grassland), but some combination of ROT, PBG, and unburned/ungrazed areas can provide adequate nesting habitat on small pasture lands (∼1.8 -7.8 ha) for various facultative grassland birds and potentially offer the opportunity to simultaneously maintain livestock production and grassland bird nesting habitat.

Consequences of Oviposition Site Choice for Geckos 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.

Breeding near heterospecifics as a defence against brood parasites: can redstarts lower probability of cuckoo parasitism using neighbours?

Breeding habitat choice based on the attraction to other species can provide valuable social information and protection benefits. In birds, species with overlapping resources can be a cue of good quality habitats; species with shared predators and/or brood parasites can increase joint vigilance or cooperative mobbing, while raptors may provide a protective umbrella against these threats. We tested whether the migratory common redstart (Phoenicurus phoenicurus) is attracted to breed near active nests of the great tit (Parus major), a keystone-information source for migrant passerine birds, or a top predator, the northern goshawk (Accipiter gentilis). This system is unique to test these questions because the redstart is a regular host for the common cuckoo (Cuculus canorus). Therefore, we also evaluated other possible benefits coming from the heterospecific attraction, especially in terms of reducing brood parasitism risk. We monitored redstart occupancy rates, onset of breeding, reproductive investment, and followed nest outcomes in terms of brood parasitism, nest predation risk and overall reproductive success. Redstarts avoided breeding near goshawks, but showed neither attraction nor avoidance to breed next to great tits. Both neighbours neither reduced brood parasitism risk nor affected overall nesting success in redstarts. Redstarts may not use heterospecific attraction for settlement decisions, as associations with other species can only exist when some benefits are gained. Thus, environmental cues may be more important than social information for redstarts when breeding habitat choice. Other front-line defence strategies may have a better impact reducing breeding negative interactions, such brood parasitism.

Population demography of feral honeybee colonies in central European forests.

European honeybee populations are considered to consist only of managed colonies, but recent censuses have revealed that wild/feral colonies still occur in various countries. To gauge the ecological and evolutionary relevance of wild-living honeybees, information is needed on their population demography. We monitored feral honeybee colonies in German forests for up to 4 years through regular inspections of woodpecker cavity trees and microsatellite genotyping. Each summer, about 10% of the trees were occupied, corresponding to average densities of 0.23 feral colonies km-2 (an estimated 5% of the regional honeybee populations). Populations decreased moderately until autumn but dropped massively during winter, so that their densities were only about 0.02 colonies km-2 in early spring. During the reproductive (swarming) season, in May and June, populations recovered, with new swarms preferring nest sites that had been occupied in the previous year. The annual survival rate and the estimated lifespan of feral colonies (n = 112) were 10.6% and 0.6 years, respectively. We conclude that managed forests in Germany do not harbour self-sustaining feral honeybee populations, but they are recolonized every year by swarms escaping from apiaries.

Functional connections between bird eggshell stiffness and nest characteristics through risk of egg collision in nests.

Eggs and nests are two critical traits for the ecological success of birds. Their functional interactions, however, remain unclear. Here, we examined the functional connections between egg stiffness and nest attachment, site and structure for 1350 avian species. We revealed high eggshell stiffness for eggs in nests with a pensile attachment, located on non-tree vegetation or having a domed shape, suggesting that birds produce stiffer eggs in response to higher egg-collision risk in unstable or enclosed nests. Interdependence models suggested that the evolution of eggshell stiffness was more likely to be driven by than drive that of nest characters. Our results implied a trade-off between investment in competing for established nesting niches and producing stiff eggs to explore novel niches with high collision risk, possibly mediated by predation or thermoregulation. This study highlights an overlooked connection between nests and eggshells that may have broadened the ecological niches of birds.

Developing fine-grained nationwide predictions of valuable forests using biodiversity indicator bird species.

The use of indicator species in forest conservation and management planning can facilitate enhanced preservation of biodiversity from the negative effects of forestry and other uses of land. However, this requires detailed and spatially comprehensive knowledge of the habitat preferences and distributions of selected focal indicator species. Unfortunately, due to limited resources for field surveys, only a small proportion of the occurrences of focal species is usually known. This shortcoming can be circumvented by using modeling techniques to predict the spatial distribution of suitable sites for the target species. Airborne laser scanning (ALS) and other remote sensing (RS) techniques have the potential to provide useful environmental data covering systematically large areas for these purposes. Here, we focused on six bird of prey and woodpecker species known to be good indicators of boreal forest biodiversity values. We used known nest sites of the six indicator species based on nestling ringing records. Thus, the most suitable nesting sites of these species provide important information for biodiversity-friendly forest management and conservation planning. We developed fine-grained, that is, 96 × 96 m grid cell resolution, predictive maps across the whole of Finland of the suitable nesting habitats based on ALS and other RS data and spatial information on the distribution of important forest stands for the six studied biodiversity indicator bird species based on nesting-habitat suitability modeling, that is, the MaxEnt model. Habitat preferences of the study species, as determined by MaxEnt, were in line with the previous knowledge of species-habitat relations. The proportion of suitable habitats of these species in protected areas (PAs) was considerable, but our analysis also revealed many potentially high-quality forest stands outside PAs. However, many of these sites are increasingly threatened by logging because of increased pressures for using forests for bioeconomy and forest industry based on National Forest Strategy. Predicting habitat suitability based on information on the nest sites of indicator species provides a new tool for systematic conservation planning over large areas in boreal forests in Europe, and a corresponding approach would also be feasible and recommendable elsewhere where similar data are available.

Woodpeckers and other excavators maintain the diversity of cavity-nesting vertebrates.

Woodpeckers and other excavators create most of the holes used by secondary cavity nesters (SCNs) in North American temperate mixedwood forests, but the degree to which excavators release SCNs from nest-site limitation is debated. Our goal was to quantify how excavators maintain the diversity and abundance of secondary cavity nesters in a temperate forest through the creation of tree cavities. We examined the short- and long-term (legacy) effects of excavators (principally woodpeckers, but also red-breasted nuthatches and black-capped chickadees) on forest biodiversity using longitudinal monitoring data (1,732 nest cavities, 25 sites, 16 years) in British Columbia, Canada. Sites with higher densities of excavator nests had more cavities available, higher species richness of SCNs and higher nest density of SCNs, indicating the importance of a standing stock of cavities. Years with higher nesting densities of excavators were followed by years with higher SCN diversity, indicating that the creation of nesting opportunities through fresh excavation releases SCNs from community-wide nest-site limitation. We also show that excavators leave a 'legacy' of biodiversity (species richness and abundance) at a site by accumulating cavities at rates faster than they become unusable by decay or destruction. By quantifying site-level effects of cavity excavation on the SCN community, our study highlights the key role of excavators as ecosystem engineers that maintain forest wildlife biodiversity.

Si, dans la forêt mixte tempérée d'Amérique du Nord, les pics et autres excavateurs créent la plupart des cavités utilisées par les cavernicoles secondaires (SCN), la question de savoir s'ils augmentent la disponibilité des sites de nidification des SCN reste ouverte. Notre objectif était d'évaluer et quantifier l'impact qu'ont les excavateurs lorsqu'ils creusent des cavités dans les arbres, sur la diversité et l'abondance de cavernicoles secondaires dans une forêt mixte tempérée. Nous avons examiné les effets des excavateurs (principalement les pics, mais aussi la sittelle à poitrine rousse et la mésange à tête noire) à court et à long terme (survivance), sur la biodiversité de la forêt en Colombie-Britannique, au Canada, en utilisant des données longitudinales de surveillance (1,732 cavités ressource, 25 sites, 16 ans). Les sites à plus fortes densités de nids d'excavateurs avaient une plus grande abondance en cavités disponibles, une richesse en espèce SCN plus élevée, et une plus forte densité de nids de SCN, ce qui montre l'importance des arbres à cavités utilisables, vivants ou morts sur pied. Les années à plus fortes densités de nids d'excavateurs étaient suivies par des années à plus fortes diversités d'espèces SCN, ce qui signifie que la disponibilité de sites de nidification à partir de nouveaux creusements augmente le potentiel de nidification des espèces SCN pour l'ensemble de la communauté qui en dépend. Nous démontrons aussi que, sur un site donné, les excavateurs laissent une 'survivance' de biodiversité (richesse en espèce et abondance) en formant des cavités à un taux plus élevé que le taux avec lequel ces dernières deviennent inutilisables suite à leur décomposition ou destruction. En quantifiant les effets du creusement de cavités au niveau de chaque site par rapport à la communauté des SCN, notre étude met en évidence le rôle clé des excavateurs comme ingénieurs de l'écosystème favorisant la diversité de la faune forestière.

Natural nest substrates influence squamate embryo physiology but have little effect on hatchling phenotypes.

Vertebrate embryos require access to water; however, many species nest in terrestrial habitats that vary considerably in moisture content. Oviparous, non-avian reptiles have served as models to understand how environmental factors, like moisture availability, influence development because eggs are often exposed to prevailing environments in the absence of parental care. Though much research demonstrates the importance of water absorption by eggs, many ecological factors that influence moisture availability in natural nests have received little attention. For example, the type of substrate in which nests are constructed is understudied. We experimentally incubated eggs of the brown anole lizard (Anolis sagrei) in 2 naturally occurring nest substrates that were treated with varying amounts of water to determine how natural substrates influence development at different moisture concentrations. One substrate consisted of sand and crushed seashells and the other was mostly organic material (i.e. decayed plant material). Both are common nesting substrates at our field site. When controlling for water uptake by eggs, we found that egg survival and hatchling phenotypes were similar between substrates; however, embryos developed more quickly in the sand/shell substrate than the organic substrate, indicating substrate-specific effects on embryo physiology. These results demonstrate that different natural substrates can result in similar developmental outcomes if the water available to eggs is comparable; however, some aspects of development, like developmental rate, are affected by the type of substrate, independent of water availability. Further study is required to determine how natural substrates influence embryo physiology independent of water content.

Nest site selection in a southern and northern population of the velvet gecko (Amalosia lesueurii).

In many oviparous reptiles, thermal conditions inside nests influence phenotypic traits of hatchlings that are linked to survival. Maternal nest-site selection can therefore have long-term implications for offspring and maternal fitness. We studied nest-site selection in a nocturnal lizard (Amalosia lesueurii) from south eastern Australia. Females of this species lay their eggs communally inside rock crevices, and previous studies have shown that maximum daily nest temperatures are positively correlated with maximum daily air temperatures. The incubation period extends for up to 100 d, so during hot summers, embryos may be exposed to stressful thermal conditions. Potentially, mothers could buffer their eggs from thermal extremes via careful selection of nest sites. To evaluate this, we studied nest site selection in a southern population (Morton) and a northern population (Yengo) that experience mild and hot summers respectively. In the field, we measured the physical characteristics, orientation, canopy cover and incident radiation load, and thermal regimes of nest sites and randomly available crevices during one of the hottest Australian summers on record (2018-2019). We found strong inter population differences in the degree of canopy cover and solar radiation loads above nest sites. Nest sites from Morton were more open, and received higher radiation loads, than nest sites from Yengo. Mean nest temperatures were similar in Morton and Yengo, but nests from Yengo experienced higher daily temperatures than those from Morton. During heatwaves, temperatures in some nests exceeded the species critical thermal maximum (39.9 °C) for several hours each day. Our results show that females can adjust nest-site choice to match local environments, but future research is necessary to clarify whether exposure to high temperatures influences hatching success or offspring phenotypes in this species.