Breeding Density Research Articles

Acoustic detection rate can outperform traditional survey approaches in estimating relative densities of breeding waders

Passive acoustic devices are increasingly being used to monitor biodiversity. However, few studies have compared the accuracy of acoustic surveys and traditional surveys against ground‐truthed data. Here, we assess whether acoustic recorders used in conjunction with an artificial intelligence (AI) classifier can predict the relative breeding density of four wader species better than traditional fieldworker transect surveys. In a 27‐km2 upland study site, acoustic data were collected at 83 sampling points and analysed using the BirdNet bird‐sound classifier to estimate vocal detection rate at each location; we also carried out concurrent transect bird surveys. To ground‐truth these approaches, intensive field surveys were undertaken to identify each breeding territory of our focal species. With both the acoustic dataset and the transect dataset, we used similar analytical approaches (random forest regression trees) to predict relative territory density across the study site, and then compared these predictions with the territory density obtained from the intensive field surveys. The classifier performed well at identifying the presence of target species' vocalizations within 3‐s periods for Lapwing (accuracy = 0.911), Curlew (0.826) and Oystercatcher (0.841), but less well for Golden Plover (0.699). For Curlew and Oystercatcher, the predictions obtained from the acoustic approach were a better fit to actual territory density than the transect approach. In contrast, for Lapwing and Golden Plover, the transect predictions outperformed the acoustic predictions, with the acoustic model particularly poor for Golden Plover. We attributed these differences to the performance of the classifier, species' ecology and vocal behaviour. Data gathering for the acoustic approach was more time‐efficient than the transect surveys, requiring less than a quarter of the fieldworker days. We conclude that there is high potential for acoustic approaches to augment traditional methods, although species' ecological characteristics should be considered: species that vocalize more frequently, at higher amplitudes and hold larger territories will be better‐suited to sampling‐based acoustic methods.

Interplay of abiotic conditions, density, and body size in shaping demography in a high‐elevation toad population

AbstractIn natural populations, vital rates such as survival and reproduction are influenced by a complex interplay of abiotic conditions (e.g., environment), density dependence, and individual factors (e.g., phenotypic traits). Studies at the extremes of species distributions, particularly high elevations, offer unique insights due to the intensified effects of abiotic stressors, which can amplify both direct and indirect effects on vital rates. In this study, we focus on a high‐elevation population of the common toad (Bufo bufo) located near the upper limit of its elevational range in the Swiss Alps. This setting provides a critical context for examining how extreme abiotic conditions interact with density dependence and individual factors to influence life history traits. Utilizing 28 years of capture–mark–recapture data and individual body size measurements from nearly 2500 toads, we applied in a Bayesian statistical framework a Cormack–Jolly–Seber model for estimating male survival probabilities, and a multistate model for assessing female survival and breeding probabilities, alongside sex‐specific growth curves. Our analysis indicates that survival probabilities are significantly impacted by interactions between abiotic conditions such as the active season length and temperature at emergence from hibernation, density dependence, and individual phenotypic traits such as body size. The breeding patterns of females showed a biennial cycle, with temperature at hibernation emergence influencing the likelihood of skipping breeding events and density affecting the resumption of breeding. These results highlight the role of abiotic conditions and density in shaping physiological and reproductive strategies in a high‐stress ecological niche. Moreover, we uncovered indications of indirect effects, where both abiotic conditions and density potentially affect asymptotic growth and thus survival, mediated through changes in body size. Our findings illustrate the complex dynamics at play in high‐elevation populations and the importance of long‐term, individual‐based data in studying these processes. This study underscores the value of integrating multiple sources of variation to understand population dynamics comprehensively, particularly in understudied, extreme environments where traditional ecological models may not fully capture the nuanced interdependencies of natural systems.

Historical increases of maize leaf area index in the US Corn Belt due primarily to plant density increases

ContextLeaf area index (LAI) and leaf area distribution within the maize plant are important traits used to explain and predict light interception and thus crop productivity. ObjectivesHere we investigate breeding and plant density effects of leaf area traits. Our objectives are to 1) quantify maize breeding impacts on leaf area distribution and determine bell-shape coefficients used in crop modeling, 2) dissect the contribution of breeding from plant density, and 3) explore the relationship between LAI and crop yields. MethodsWe studied 18 hybrids released between 1983 and 2017 at two density treatments: current (8.5 pl m-2) and historical increasing density (from 4.6 to 8.5 pl m-2) in Iowa, USA. ResultsResults indicated that concurrent changes in hybrids and increases in plant density have increased LAI from 3.4 (in 1983) to 5.9 m2 m-2 (in 2017), with the highest LAI increases (>50%) to be realized in the middle canopy. At historical increasing in plant density treatment, the LAI increased by 1.6% year-1, but the individual plant leaf area decreased by 0.33% year-1 from 1983 to 2017. This trade-off indicates that new hybrids are more tolerant to higher plant populations than old hybrids. At current plant density treatment, the year of hybrid release did not affect LAI or individual plant leaf area. New hybrids had 5% narrower leaf area distributions, 23% higher optimum LAI values (5.2 vs 4.2 m2 m-2) and 19% higher grain yields compared to old hybrids. ConclusionsThe main reason for the increase in maize LAI in the US Corn Belt is plant density. However, an increase in LAI does not necessarily translate to higher grain yields as new hybrids had significantly higher grain yields than older hybrids at similar LAI values. Present results contribute to our understanding of maize canopy architecture and allow us to better calibrate crop models to accurately estimate LAI and grain yield.

Yellow mealworm: effects of adults breeding density on adults and larvae performances from an industrial perspective

A key aspect to optimise the Tenebrio molitor (TM) farm productivity is to find an optimal breeding density for adults. To this purpose, this study investigated, from an industrial perspective, the impact of 4 breeding densities (D1, D2, D3 and D4, equal to 0.8, 1.1, 1.3 and 1.6 adults/cm2, respectively) on mortality and reproductive performances of TM adults and larvae. Two weeks after pupae emergence, TM adults were randomly assigned to the four groups and housed in 48 breeding crates (60 x 40 x 14.5 cm; 12 crates/group). The trial consisted in 4 consecutive weeks of adults breeding (each week represented one oviposition), and 8 weeks of larvae growth. From each week of oviposition, a batch of larvae was obtained for a total of 4 batches of larvae (48 crates/batch). Larvae of each batch were grown until 8 weeks of age, corresponding to the period required to reach the selling size. Larvae were kept in the original crates until the 5th weeks of age, after which they were divided into additional crates to ensure a density of 4.2 larvae/cm2 and a final weight of 1500 g of larvae/crate (0.6 g of larvae/cm2). For each oviposition week, TM adult’s mortality, eggs hatchability, BW, feed intake, chemical composition and fatty acids (FAs) profile were evaluated, while ovary weight was measured at weeks 1 and 4. The number of larvae was monitored at week 5 of age while their chemical composition at week 5 and 8. Larvae feed intake and BW were monitored over the 8-weeks growth period. Individual feed intake and BW of adults increased with increasing breeding density (P<0.0001 and P<0.05, respectively). With increasing adults breeding density, the number of larvae per crate increased (P<0.001) while the grams of larvae/gram of adult decreased (R2=0.8856). Larvae from groups D2, D3 and D4 showed higher feed intake per crate and higher individual and total final BW than D1 (P<0.001). However, the feed conversion ratio (FCR) worsened with increasing breeding density (P<0.001). D4 larvae had higher percentages of protein (P<0.001), lipids (P<0.05) and cholesterol (P<0.001) compared to larvae from other groups. Concluding, a breeding density of 0.8 adults/cm2 maximised both grams of larvae produced/grams of adults and larvae FCR. However, breeding densities above 0.8 adults/cm2, resulted in a higher number of produced larvae per crate with a greater final mass weight making a density of 1.6 adults/cm2 the preferable choice from and industrial perspective.

Eurasian Goshawk nesting in relation to prey numbers in Telemark, southern Norway

Cover photo: Eurasian Goshawk Accipiter gentilis eating a Hooded Crow Corvus cornix. Photo: Kjetil Salomonsen. In southern Norway, the breeding density of Eurasian Goshawk Accipiter gentilis has typically ranged between 2–4 pairs per 100 km2. However, not all territorial pairs attempt to nest each year. In a ca. 2000 km2 forest-dominated study area in central parts of Telemark County, the highest number of nesting attempts recorded per year during 1991–2022 was 46, and the highest number of successful nesting attempts was 40. The nesting success of Goshawks increased with age and was 66.7% for juveniles (n = 12), 79.3% for subadults (n = 82) and 89.4% for adult females (n = 736). The annual proportion of young Goshawk females (juveniles and subadults) depended on the annual proportion of recorded replacements of old females and was positively related to mean temperatures in April. The annual proportion of recorded substitutions was positively correlated with population indices of several important prey species, particularly forest grouse, and without a time-lag. In a multiple regression model, the relative change in the recorded number of Goshawk nesting attempts, compared to the previous year, was positively correlated with a population index for thrush spp. and a combined index for Wood Pigeon Columba palumbus and Hooded Crow Corvus cornix, without a time-lag, and with a combined index for Capercaillie Tetrao urogallus and Black Grouse Lyrurus tetrix, with a one-year time-lag. The one-year time-lag with grouse was most evident when only successful nesting attempts were considered. We conclude that the breeding densities of Goshawk in Telemark are rather stable, and we conclude that annual variation in the number of recorded nesting attempts to a large extent reflects the effects of variation in prey density on the body condition of female Goshawks.

Distribution and Density of Common Woodpigeon (Columba palumbus) in Central Northern Bulgaria

The breeding density of the Woodpigeon was determined in square LH75 in the period from March to May 2023. For this purpose, a point counting method was used, and in addition, some characteristics of the habitats were taken into account. The breeding density of Woodpigeon in the present study was 16.42, 12.75 and 14.44 pairs/100ha, in March, April and May 2023 year, respectively. Breeding density decreases from March to May. Anova analysis showed statistically significant differences in the mean number of song pigeons by habitat and cropland types (F=8.11, p=0.005). The number of song Woodpigeons was significantly greater in open habitats with single large trees or small groups of large trees among grassland and meadows than in other breeding habitat types. Their number is relatively high in Silver lime forests, coniferous plantations, and in the fringe strip of all forest habitats. The number of song pigeons is also relatively high in cases where we have a lack of arable land in the fixed radius or in the presence of wheat. Their number in the fixed radius increased with increasing average tree height. The number of singing pigeons is positively correlated with tree height (R=0.49, F=2.132, p&lt;0.0001). The latest data on the breeding density of the Woodpigeon are from the end of the last century in Bulgaria. This study presents first results on the breeding distribution and density of the species in an information-poor area.

Predicting yolk testosterone allocation using ecological contexts and species-specific traits.

The prenatal transfer of testosterone (T) from mother to offspring is an important source of phenotypic plasticity. In birds, exposure to ecologically relevant stimuli, such as social competition or an attractive mate, can cause females to deposit more T into their egg yolks. Exposure to elevated yolk T can modify the expression of several fitness-related traits in offspring (e.g. growth, immune function, secondary sex traits and behaviour). Despite some of these changes being potentially adaptive, not all studies find that yolk T levels change in response to ecologically relevant stimuli. This heterogeneity is currently unexplained, limiting our ability to predict inter-generational responses to ecological change. Here, we performed a systematic literature search and found 119 observations across 39 wild species that measured inter-female variation in yolk T allocation in response to various stimuli. We used boosted regression trees, a form of machine learning, to examine whether species-specific traits or variation in study-level variables could explain variation in yolk T allocation (i.e. statistically significant vs. non-significant responses). We found that both species-specific traits and study-level variables are important predictors of significant changes in yolk T levels. Geographic range (latitude and longitude), evolutionary distinctiveness, longevity, egg mass relative to female mass, sociality, migration status and time to fledge were among the top 10 most influential predictors of the 48 examined. We also found that studies measuring or manipulating social stimuli (e.g. competition and breeding density) or breeding date were more likely to detect changes in yolk T allocation compared with studies examining other ecological contexts. Overall, these data provide several testable hypotheses concerning yolk T allocation and its adaptive value across species and contexts. Additionally, these findings can help us predict how ecological changes will affect hormonal responses in females that can shape future generations.

Uncovering habitat associations and thresholds—insights for managing breeding waterfowl in Eastern Canada

ContextUnderstanding how habitat influences species abundance is crucial in developing ecologically sound wildlife conservation management plans. Exploring habitat associations and ecological thresholds in species’ responses allows for better conservation and management on a landscape-scale.ObjectivesThis work aimed to identify habitat drivers and response thresholds of waterfowl and waterbird species’ densities in eastern Canada to support key landscape-level decisions for habitat conservation and wetland management.MethodsWe developed predictive abundance models for 17 species across eastern Canada from 2001 to 2015 using data from four regional surveys and identified areas where prioritizing enhancement of wetlands would increase the breeding density of five priority waterfowl species.ResultsHabitat associations and spatial abundance patterns varied across species, but most species responded strongly to forest composition, agriculture, and wetland features. Threshold effects occurred and varied among species, yet generally once 14% of a plot was covered in wetlands, positive effects of increased wetland diminished for most species. Our results allow for the targeting of investments in increasing wetland area along portions of eastern Canada that provide the best opportunities to increase breeding densities for priority waterfowl species.ConclusionsUnderstanding species-habitat associations and response thresholds allows for landscape management and planning and prioritization of limited resources. We suggest that management and wetland enhancement efforts for waterfowl in eastern Canada should be guided by predictive models and response thresholds of key habitat attributes to best prioritize actions that will have the biggest positive impact on multiple species.

Trends in greater sage‐grouse lek counts relative to existing wind energy development in Wyoming

AbstractRapid increases in wind energy development globally highlight the need to evaluate how electricity generation may impact wildlife. The greater sage‐grouse (Centrocercus urophasianus; hereafter, sage‐grouse) has experienced range‐wide population declines, primarily due to habitat loss and degradation. Studies have documented a negative association between oil and gas development and sage‐grouse populations. However, potential sage‐grouse population declines associated with wind energy development have not been adequately addressed. We investigated the relationship between wind energy infrastructure and changes in male sage‐grouse counted on leks from 2000–2020 in Wyoming, USA, using Bayesian state‐space models. Our study was conducted in central and southwest Wyoming in the vicinity of 10 wind energy facilities that were in proximity to sage‐grouse leks occurring outside of Wyoming's Core Areas (i.e., areas of high breeding densities of sage‐grouse designated for restricted development by the State of Wyoming) and dominated by big sagebrush (Artemisia spp.) communities. Facilities became operational between 1998 and 2010 and had an average of 67 turbines. Covariates describing wind energy infrastructure included distance to the nearest wind turbine, and the number and distribution (clustering) of turbines within 1.0, 2.0, 4.0, 6.0, 8.0, and 10.0 km. We also explored whether males attending leks exhibited lagged responses of 1–7 years following development. We used counts from 78 leks located within 15 km of the 10 wind energy facilities, consisting of 288 counts before and 845 counts after development. We expected that trends in male lek attendance would experience a delayed negative response following wind energy development like other forms of anthropogenic features. However, we failed to detect a relationship between male sage‐grouse lek attendance and proximity to, density of, or distribution of wind turbines following development in all models. Our findings were based on the average lek in our analysis being 6.5 km from a wind turbine and most turbines were clustered such that undisturbed habitat surrounding leks remained. Therefore, interpretation of our results should be restricted to siting practices of the facilities that we evaluated because direct habitat removal and fragmentation resulting from any form of energy development is unlikely to benefit sage‐grouse populations. Our study evaluated the response of low‐density, peripheral populations of sage‐grouse to wind energy development outside or near the edge of Core Areas. As such, our results should not be extrapolated to higher density sage‐grouse populations occurring in Core Areas.

The evolution of sex roles: The importance of ecology and social environment

Males and females often have different roles in reproduction, although the origin of these differences has remained controversial. Explaining the enigmatic reversed sex roles where males sacrifice their mating potential and provide full parental care is a particularly long-standing challenge in evolutionary biology. While most studies focused on ecological factors as the drivers of sex roles, recent research highlights the significance of social factors such as the adult sex ratio. To disentangle these propositions, here, we investigate the additive and interactive effects of several ecological and social factors on sex role variation using shorebirds (sandpipers, plovers, and allies) as model organisms that provide the full spectrum of sex role variation including some of the best-known examples of sex-role reversal. Our results consistently show that social factors play a prominent role in driving sex roles. Importantly, we show that reversed sex roles are associated with both male-skewed adult sex ratios and high breeding densities. Furthermore, phylogenetic path analyses provide general support for sex ratios driving sex role variations rather than being a consequence of sex roles. Together, these important results open future research directions by showing that different mating opportunities of males and females play a major role in generating the evolutionary diversity of sex roles, mating system, and parental care.

Breeding density affects the movements of gull chicks, the size of their home ranges and their association with neighbours.

Colonies of ground-nesting species often have heterogeneous nest densities and their offspring experience different social conditions depending on the size and location of the breeding territory. For example, unintentional territory crossing by mobile chicks can trigger strong aggression from neighbouring adults, as observed in semi-precocial gulls. This would be expected to shape chicks' movement tendencies, exploratory behaviour and propensity for social contact through aversive feedback learning or pre-natal maternal effects, as mothers may pre-adapt their offspring's behaviour to the expected early life conditions. Therefore, we hypothesize that lesser black-backed gull chicks reared in denser areas of the breeding colony will move less, have smaller home ranges and have fewer social contacts with chicks from neighbouring nests. To test this, we first cross-fostered full clutches between and within high- and low-density parts of the colony, and then used ultra-wideband tags to track free-ranging chicks. In line with our predictions, we found that chicks reared in denser areas had a lower movement activity and smaller home ranges. However, these chicks still had more social contacts, although not necessarily with a higher number of unique individuals. Pre-natal breeding density had no significant effect on any of the parameters. We conclude that parental nest choice strongly affects the early social environment of their chicks, which can shape the development of their (social) phenotype, with potentially long-lasting consequences.

Ecological structure of the avifauna composition as a basis for assessment of its heterogeneity and dynamics

The article describes the methodological approach and the results of classification of breeding bird species in Belarus by their preference for habitat type during the breeding season based on this approach. During the classification process, we took into account the preferences developed in the course of evolution, i. e. those that had been the most characteristic of the species before the domination of altered territories and the escalation of an urbanization rate, as well as before many species started living in urban environments on a large scale.In total, we defined six ornithofaunistic complexes (forest, arboreal-shrub, water-coastal, marsh, dry open spaces and synanthropic) that include all 223 bird species that have been observed breeding in Belarus since 2000. In most cases, the ornithofaunistic complexes were further divided into clusters that reflect a prominent ecological differentiation of species, although less drastic than a difference between the complexes themselves. In controversial or debatable cases, to justify attributing a species to a certain ornithofaunistic complex, we compared and analyzed all available data on the occurrence and breeding density of the species. Most breeding bird species belong to forest and water-coastal ornithofaunistic complexes (80 and 64 species, respectively), while only 12 species belong to the ornithofaunistic complex of dry open spaces. This classification proves to be a convenient tool to estimate the size and nature of the changes in the ecological structure of bird assemblages that have undergone some interference or transformations in time as well as to get comparable ecological characteristics of bird populations in different territories.

A meta-analysis for prevalence of infectious laryngotracheitis in chickens in mainland China in 1981–2022

BackgroundInfectious laryngotracheitis (ILT) is a highly infectious upper respiratory tract disease of chickens caused by infectious laryngotracheitis virus or Gallid herpesvirus 1 (GaHV-1). ILT is an important respiratory disease of chickens and annually causes significant economic losses in the chicken industry. Although numerous relevant studies have been published, the overall prevalence of ILT infection among chicken in mainland China is still unknown, and associated risk factors need to be evaluated to establish preventive measures.ResultsThe present study reviewed the literature on the prevalence of ILT in chickens in China as of December 20, 2022, retrieved from six databases—CNKI, Wanfang, VIP, PubMed, Web of Science, and ScienceDirect—were used to retrieve relevant studies published between January 1, 1981 and December 20, 2022. The literature quality of studies was assessed, and 20 studies with a total of 108,587 samples were included in the meta-analysis. Results of the meta-analysis showed that the overall prevalence of ILT was 10% (95% confidence interval: 8 –12%) through the random-effects model, which showed high heterogeneity, I2 = 99.4%. Further subgroup analyses showed that the prevalence of ILT decreased over time; furthermore, the prevalence in Northwest China was slightly lower than that in North China and South China, and the prevalence estimated using the diagnostic technique AGP was higher than that reported using other diagnostic techniques.ConclusionsILT is prevalent to some extent in mainland China. Given that the ILT attenuated live vaccine has a certain level of virulence and the prevalence differences between regions, we recommend controlling breeding density, improving immunization programs and continuously monitoring viruses and to prevent ILT prevailing in mainland China.

Nesting biology and breeding density of Least Flycatchers (Empidonax minimus) in the Beaverhill Natural Area, Alberta, Canada

Nesting biology and breeding density of Least Flycatchers (Empidonax minimus) in the Beaverhill Natural Area, Alberta, Canada

The development and usability test of an automated fish counting system based on CNN and contrast limited histogram equalization

The aquaculture industry has rapidly grown over the year. One pertinent aspect is the ability of the aquaculture farm management to accurately count the fish populations to provide effective feeding and the control of breeding density. The current practice of counting the fish manually increased the hatchery workers workload and led to inefficiency. The presented work proposed an intelligent, web-based fish counting system to assist hatchery workers in counting fish from images. The methodology consists of two phases. First, an intelligent fish counting engine is developed. The captured image was first enhanced using the contrast limited adaptive histogram equalization. A deep learning architecture in the form of you only look once (YOLO)v5 is used to generate a model to identify and count fish on the image. Second, a web-based application is developed to implement the developed fish counting engine. When applied to the test data, the developed engine recorded a precision of 98.7% and a recall of 65.5%. The system is also evaluated by hatchery workers in the University Malaysia Sabah fish hatchery. The results of the usability and functionality evaluations indicate that the system is acceptable, with some future work suggested based on the feedback received.

Multivariate Analysis of Okra [Abelmoschus esculentus (L.) Moench] Genotypes and Hybrids based on Mineral Content

Background: In 2021, the world production of okra [Abelmoschus esculentus (L.) Moench] was over 10.8 million tonnes which is led by India (about 60%). The objective of this study was to determine mineral content of genotypes and hybrids of okra identified by our in-house heterosis breeding programme. Methods: The samples were digested in a heating block using nitric acid and hydrogen peroxide and analyzed using inductively coupled plasma mass spectrometry (ICP-MS) for mineral profiling of okra samples. Result: The results were evaluated using multivariate analysis. The genotype EC169474 was with the highest concentration of minerals Na (184.91 μg/g), K (14613.52 μg/g) and Fe (268.76 μg/g), while, EC169477 was found to have highest concentration of Mg (6530.76 μg/g) and Ca (273.58 μg/g). Comparatively, in hybrids, EC 169470 x EC169474 contains highest concentration of minerals Na (177.27 μg/g) and Ca (253.01 μg/g), EC169474 x EC169477 contains highest Mg (6301.74 μg/g) and hybrid EC169468 x EC169477 contains highest K (14412.99 μg/g) and Fe (246.51 μg/g). Principal component analysis (PCA) reveals that the element that contributed most for the variability between the genotypes and hybrids was K, moderate contribution by Ca, Fe and Na, while, Mg being the least. Score plot of principal components reveals EC169470 and EC169477 among the most variable genotypes and EC169470 x EC169477 was the most variable hybrid. Hierarchical cluster analysis (HCA) tends to separate all analyzed samples in two major clusters. However, the genotypes EC169474 and EC169477 were grouped in hybrid cluster, while, hybrid EC169470 ´ EC169477 grouped with genotype cluster. The multivariate analysis revealed a systematic difference in the mineral content of okra. The results presented in this study are of great value for nutritionally dense breeding programmes for okra that provides important nutritional diversity by hybrids.

Interactive effects of agricultural landscape heterogeneity and weather conditions on breeding density and reproductive success of a diurnal raptor.

Agricultural intensification and climate change are serious threats toward animal populations worldwide. Agricultural intensification reduces the heterogeneity of agricultural habitats by diminishing crop variation and destroying microhabitats, such as small woody features, whereas the effects of climate change range from the growing frequency of weather extremes to disrupted prey-predator dynamics. We collected long-term ringing data from a population of Eurasian kestrels (Falco tinnunculus) located amidst agricultural areas in western Finland during 1985-2021, which we combined with density indices of their main prey species (voles), spatial data consisting of land cover classification of kestrel territories, and weather data, to study the effects of different environmental drivers on breeding density and success. We found that the density of inhabited nests rose with vole abundance and springtime snow depth, with the overall trend of population growth being stronger in areas with more heterogeneous landscapes. Clutch size was influenced negatively by the age of male parent and landscape heterogeneity, and positively by vole abundance, with rainfall having a negative influence conditional to other variables. Likewise, the number of produced fledglings was affected by male age, but it was additionally positively associated with landscape heterogeneity and its interaction with rainfall, with greater fledgling output in heterogeneous landscapes during high precipitation. The discrepancy between factors predicting large clutches and high numbers of fledglings suggests that while kestrels do not prefer heterogeneous landscapes when prospecting for territories, heterogeneous habitats provide better circumstances for foraging during the nestling period, which ensures nestling survival, particularly during adverse environmental conditions. Therefore, breeding in areas under intense agricultural use is more suboptimal to kestrels than their territory preferences would indicate. As changing climate may reduce prey availability and heighten the probability of weather extremities, agricultural intensification may lead to weaker reproductive success in densely populated farmland habitats.

Distribution, density and trends of the Eurasian eagle owl (Bubo bubo) population breeding in March-Thaya floodplain forests: impact of owlets on sustainability of natural nests

Abstract In this study, we investigated the Eurasian eagle owl (Bubo bubo) breeding in lowland forests in the trans-border area between western Slovakia, eastern Austria, and southern Moravia. The research provides new information on the reuse of nests by eagle owls and presents initial insights into population density and trends of eagle owls in the March-Thaya floodplains. Our 19-year monitoring has shown that the eagle owl has become a widespread breeder over the study area, with an increasing population trend. A total of 151 breeding attempts by eagle owls have been identified, occupying 82 natural nests (originally built by at least nine species of birds) and 12 artificial nests. With an average of 6.2 active nests per 100 km2 and a maximum of 17 active nests found in 2021 (~10.6 pairs per 100 km2), our findings represent one of the highest eagle owl breeding densities found, especially in comparison with core populations nesting in the mountains (the Carpathians, north-eastern Alps and the Bohemian Massif). Regarding the dynamics of nest reuse, our results reveal that only a third of nests used by eagle owls were reused by other raptors or storks (Ciconia sp.). Almost 50% of the natural nests in which eagle owl bred, subsequently disintegrated after the owlets had fledged. Lastly, black stork (Ciconia nigra) nests re-used by eagle owls were twice as likely to have disintegrated after the owlets had fledged than nests built by other bird species. Our results suggest that black stork nests in the March and Thaya floodplain forests are most susceptible to destruction.

Morphological and Molecular Changes during Limb Regeneration of the Exopalaemon carinicauda.

With the increase in breeding density of Exopalaemon carinicauda, appendage breakage may occur, which seriously affects survival and economic benefits. To study the limb regeneration process of E. carinicauda, we induced autotomy of the pereopods. After a period of time, wound swelling disappeared, the pigment gradually accumulated, and a tawny film subsequently formed in the wound. The healing period of the wound occurred 24 h after autotomy, and the blastema formation stage occurred 48 h after autotomy. After 4 days of cutting, the limb buds began to differentiate, grow, and expand rapidly, and this process lasted approximately 15 days. Microscopic observations revealed significant changes in the type and number of associated cells including outer epithelial cells, granulocytes, embryonic cells, columnar epidermal cells, elongated cells, and blastoma cells, during the process from limb fracture to regeneration. A comparative transcriptome analysis identified 1415 genes differentially expressed between the J0h (0 h post autotomy) and J18h (18 h post autotomy), and 3952 and 4366 differentially expressed genes for J0 and J14d (14 days post autotomy) and J18h and J14d, respectively. Some of these genes may be related to muscle growth or molting, as indicated by the presence of troponin C, chitinase, actin, innexin, and cathepsin L. As a functional gene involved in epidermal formation, the mRNA expression level of the innexin inx2 in the pereopod of E. carinicauda changed significantly in the experimental groups (p < 0.05). The results of this study contribute to existing knowledge of regeneration mechanisms in crustaceans.

Breeding birds of high-elevation mixed-conifer forests have declined in national parks of the southwestern U.S. while lower-elevation species have increased, with responses to drought varying by habitat

Abstract Climate change is considered a major driver of recent avian population declines, particularly in the drought-stricken southwestern United States. Predicting how bird populations will respond requires understanding the climatic drivers influencing population density across the region’s diverse habitats. We modelled breeding-season densities of 50 bird species in relation to spring and summer drought and the timing of North American monsoon rainfall over a 12-year period (2007–2018) and across 4 habitats comprising an approximately 1,500 m elevational gradient. We estimated annual breeding-season population density in relation to climate in the previous year by fitting a Bayesian hierarchical N-mixture model to point-count data from each of 6 national parks on the Colorado Plateau. Specifically, we asked whether (1) population trends were stable, increasing, or decreasing in the focal parks; (2) breeding densities were affected by drought or the timing of monsoon rains; and (3) climatic effects differed across habitat types and among species that molt on the breeding grounds, the nonbreeding grounds, or stopover to molt in the monsoon region of northwestern Mexico (molt migrants). Population trends varied with habitat. Species of high-elevation mixed-conifer forest declined over the study period, matching regional Breeding Bird Survey trends, likely in response to climate-related habitat loss and disturbance. By contrast, lower-elevation pinyon-juniper and grassland-shrubland species density generally increased. Effects of drought varied by habitat with elevation: mixed-conifer species responded positively to drought in the previous year, likely due to earlier snowmelt and breeding phenology, whereas pinyon-juniper species were unaffected, and grassland-shrubland species responded negatively, perhaps due to reduced nest survival. Later arrival of monsoon rains, a common prediction of climate models, had a positive effect on grassland bird densities, but a negative effect on molt-migrant densities. Late monsoon rains may result in a phenological mismatch between migration timing and the pulse of resources required to molt.