Avian Habitat Research Articles

Mapping Avian Habitat Suitability Using Linear and Non-Linear Techniques in the Case of Wetland Landscapes

Habitat quality is crucial for wildlife management that impacts the conservation of sensitive landscapes such as wetlands. With advancements in GIS, habitat modelling now effectively predicts species occurrences and habitat suitability. This study aims to model and map habitat suitability for case bird species of Kentish plover in Tuzla Lagoon using multiple techniques. Kentish plover nesting data were collected from 293 nests, and reproductive success measures such as lay date, egg volume, and nest fate were analysed. Spatial habitat modelling techniques, including regression, co-kriging, artificial neural networks, and decision trees, were used with IKONOS imagery and ground data. The overall prediction accuracies were poor for lay date across all techniques, with the decision tree being the most accurate, while egg volume was best predicted by co-kriging, egg success by linear regression, and nest fate by both binomial logistic regression and ANN with 75% accuracy.

Conservation of paramo birds in Ecuador in the face of climate change: on the need for a detailed classification of high-altitude habitats

When we think of "the paramo" most of us would think of waves of grass moving in the wind. However, our concept of paramo is limited by the lack of prehistoric data on what this ecosystem would have been like in the absence of human activity. Throughout the Holocene, humans have been part of the Andean landscape, shaping it through fire and by hunting important herbivores, such as deer and cottontails. Pollen records are scant due to glaciers having scraped high Andean lakes and peatlands off the landscape. What we find today at high altitudes is not "one paramo" but "several types of paramo" that are likely the result of various intensities of human activity. The different vegetation forms we see today are habitats for various birds within the ecosystem. The classification of vegetation for the Ecuadorian Andes by Sierra 1 recognizes several high Andean plant assemblages, yet these do not accurately describe the diversity of plant communities vis-à-vis avian habitats.

Conservation of paramo birds in Ecuador in the face of climate change: on the need for a detailed classification of high-altitude habitats

When we think of "the paramo," most of us think of waves of grass moving in the wind. However, our concept of paramo is limited by the lack of prehistoric data on what this ecosystem would have been like without human activity. Throughout the Holocene, humans have been part of the Andean landscape, shaping it through fire and by hunting important herbivores, such as deer and cottontails. Pollen records are scant due to glaciers having scraped high Andean lakes and peatlands off the landscape. What we find today at high altitudes is not "one paramo" but "several types of paramo" that are likely the result of various intensities of human activity. The different vegetation forms we see today are habitats for various birds within the ecosystem. The classification of vegetation for the Ecuadorian Andes by Sierra 1 recognizes several high Andean plant assemblages, yet these do not accurately describe the diversity of plant communities vis-à-vis avian habitats. For instance, the Antisana paramo is composed of a mixture of plant formations not recognized in previous classifications 2 that birds depend on for at least one life stage.

Threshold of anthropogenic sound levels within protected landscapes in Kerala, India, for avian habitat quality and conservation.

Anthrophony is an important determinant of habitat quality in the Anthropocene. Acoustic adaptation of birds at lower levels of anthrophony is known. However, threshold anthrophony, beyond which biophony starts decreasing, is less explored. Here, we present empirical results of the relationship between anthrophony and biophony in four terrestrial soundscapes. The constancy of the predicted threshold vector normalised anthropogenic power spectral density (~ 0.40 Watts/Hz) at all the study sites is intriguing. We propose the threshold value of anthropogenic power spectral density as an indicator of the avian acoustic tolerance level in the study sites. The findings pave the way to determine permissible sound levels within protected landscapes and directly contribute to conservation planning.

Snowmobile noise alters bird vocalization patterns during winter and pre‐breeding season

Abstract Noise pollution poses a significant threat to ecosystems worldwide, disrupting animal communication and causing cascading effects on biodiversity. In this study, we focus on the impact of snowmobile noise on avian vocalizations during the non‐breeding winter season, a less‐studied area in soundscape ecology. We developed a pipeline relying on deep learning methods to detect snowmobile noise and applied it to a large acoustic monitoring dataset collected in Yellowstone National Park. Our results demonstrate the effectiveness of the snowmobile detection model in identifying snowmobile noise and reveal an association between snowmobile passage and changes in avian vocalization patterns. Snowmobile noise led to a decrease in the frequency of bird vocalizations during mornings and evenings, potentially affecting winter and pre‐breeding behaviours such as foraging, predator avoidance and successfully finding a mate. However, we observed a recovery in avian vocalizations after detection of snowmobiles during mornings and afternoons, indicating some resilience to sporadic noise events. Synthesis and applications: Our findings emphasize the need to consider noise impacts in the non‐breeding season and provide valuable insights for natural resource managers to minimize disturbance and protect critical avian habitats. The deep learning approach presented in this study offers an efficient and accurate means of analysing large‐scale acoustic monitoring data and contributes to a comprehensive understanding of the cumulative impacts of multiple stressors on avian communities.

Avian Taxonomic and Functional Diversity in Contrasting Habitats: A Comparative Study of Urban and Remote Forests in Arusha, Tanzania

Urbanisation globally transforms landscapes, impacting biodiversity significantly. In Arusha, Tanzania, rapid urban expansion accentuates the interplay between urbanisation and avian biodiversity. This study investigates urbanisation's influence on avian communities in two contrasting forested habitats: the urban "Themi River Forest" and the remote "Lake Duluti Forest." We explore taxonomic and functional avian diversity, elucidating underlying mechanisms. Taxonomic diversity analysis reveals "Lake Duluti Forest" with slightly higher species richness and "Themi River Forest" with a more even species distribution, reflecting urbanisation's influence. This aligns with global trends indicating reduced urban species richness due to habitat fragmentation. The urban forest, however, demonstrates avian adaptability to urbanised landscapes. Functional diversity analysis uncovers "Lake Duluti Forest" with greater functional richness, indicating a wider array of ecological roles. In contrast, "Themi River Forest" maintains comparable functional evenness, suggesting ecological balance despite urbanisation. Both forests exhibit distinct ecological niches, highlighting avian community flexibility. These findings hold significance for avian conservation and urban planning in Arusha and similar urbanising regions. Higher taxonomic diversity in remote forests underscores conservation importance. The urban forest showcases avian adaptability, emphasising green spaces in urban planning. Long-term conservation should protect both urban and remote forests, integrating strategies for avian habitat preservation and connectivity. This study advances understanding of urbanisation, forest type, and avian biodiversity's intricate relationship, offering insights for effective conservation in evolving urban landscapes

Passive monitoring of avian habitat on working lands.

Intensive agricultural landscapes are a challenge for wildlife managers, policy makers, and landowners hoping to increase the diversity of desired wildlife species, such as grassland birds, which require urgent conservation action. In intensive agricultural landscapes, like those of the midwestern USA, most land area is privately owned and operated and managed primarily for production. Conducting ecological research in intensive agricultural landscapes thus requires collaborative approaches aimed at farm owners and operators. Recent advances in acoustic data collection and high-resolution habitat mapping, including low-cost acoustic recorders and satellite remote sensing, may be well positioned to address this challenge by enabling expanded assessments and monitoring of wildlife populations and habitats across regions. This study examined fine grain habitat characteristics and their relationship with avian biodiversity in intensive agricultural landscapes at 44 agricultural sites across Iowa, USA. Passive acoustic monitoring and manual identification of bird species allowed for measurement of vocalizing bird richness. High resolution mapping of noncrop vegetation provided detailed information on small noncrop vegetation habitat complexes within row-crop agriculture. Measures of image texture provided characterizations of compositional heterogeneity within noncrop vegetation. General linear Poisson modeling demonstrated robust associations between noncrop vegetation and vocalizing bird richness, yet variation in grassland bird richness was not well predicted by noncrop vegetation. Noncrop vegetation texture demonstrated potential as a predictor of vocalizing bird richness, though not better than or when combined with noncrop vegetated area, indicating it may not be an independent measure of habitat quality. Passive acoustic monitoring resulted in useful data at 44 out of 60 originally selected sites, with some lost to failed recorders and/or collaboration issues. Challenges remain in detecting habitat characteristics that promote grassland birds in row crop landscapes. Working toward probabilistic research design across privately owned working landscapes and incorporating more detailed management practice information would improve the transferability of this approach to farmland management and policy.

Management of U.S. Agricultural Lands Differentially Affects Avian Habitat Connectivity

Despite frequently being implicated in species declines, agricultural lands may nonetheless play an important role in connecting wildlife populations by serving as movement corridors or stopover sites between areas of high-quality habitat. For many North American bird species, agricultural intensification over the past half century has substantially impacted populations, yet recent studies have noted the potential for supporting avian biodiversity on agricultural lands through the promotion of functional connectivity. To support avian conservation efforts on agricultural lands across the United States, we used publicly available data from eBird to quantify and map the effects of agriculture on habitat suitability (using random forest models) and functional connectivity (via circuit theory) for three focal species that have experienced agriculture-linked declines or range contractions in recent decades: Greater Sage-grouse (Centrocercus urophasianus), American Black Duck (Anas rubripes), and Bobolink (Dolichonyx oryzivorus). Our analysis drew on novel, remotely sensed estimates of agricultural management intensity to quantify the effects of management practices on avian habitat and movement, revealing complex, species-specific relationships between agriculture and habitat value for the three focal species. Rangelands and croplands exhibited relatively high connectivity values for Greater Sage-grouse and Bobolink, respectively, mirroring these species’ strong habitat preferences for open sagebrush and cultivated grasslands. By contrast, American Black Duck migratory connectivity was low on all agricultural cover types. Mapping our model results across each species’ geographic range in the U.S. revealed key areas for agricultural management action to preserve high-quality habitat and connectivity, and we link these spatial recommendations to government incentive programs that can be used to increase wildlife-friendly management on U.S. agricultural lands.

Influence of habitat heterogeneity on avian diversity in the Rajparian Wildlife Sanctuary, Kashmir Himalaya

BackgroundThe value of local and regional landscapes for avian conservation requires a thorough understanding of the diversity and structure of bird communities. Avifauna serves as an important biological indicator in monitoring the health of an ecosystem or environment. The present study was conducted to examine the relationship between avian diversity, richness, composition and habitat characteristics at the Rajparian Wildlife Sanctuary.ResultsUsing geographic information systems and remote sensing techniques, we analyzed habitat heterogeneity based on land use and land cover classification. For sampling birds, extensive surveys were conducted in different land-use types from 2019 to 2021, following the line transect method. During the study period, 102 bird species were recorded from the five studied vegetation types of the study area, including one near threatened (Bearded Vulture) and one vulnerable (Kashmir Flycatcher) bird species. The highest numbers of avian species were recorded from the forest (71 species) (42.61 ± 16; mean ± SD) and the lowest from the rocky land-use type (12 species) (7.83 ± 1.95). The individual rarefaction and extrapolation curves showed higher species richness for forest and the lowest for rocky habitats. Numerous pairwise comparisons revealed significant differences in species richness among studied habitat types, except for riverine vs. grassland, scrub vs. grassland and rocky vs. riverine land uses. The partitioning of the spatio-temporal β-diversity patterns revealed a relatively large contribution of the turnover component to the observed overall dissimilarity compared to the nestedness component.ConclusionsIt can be concluded that avian communities in the Rajparian Wildlife Sanctuary are influenced by habitat heterogeneity, topography, and the availability of water. The results of the present study indicate that the Rajparian Wildlife Sanctuary provides an important habitat for the conservation of birds, as it harbors a rich avian diversity. The study is the first scientific survey of the avian habitat associations in the protected area and will serve as a baseline for future avian research, as well as for management implications in the region.

Meta-analysis of avian behavioural responses to aircraft noise

Natural environments are now seriously affected by human-made noise, creating complex acoustic circumstances that are unheard of in most locations. Expansion of aero industry and increase in air traffic whether civilian or military is accompanied by large scale noise pollution and habitat disturbances. The present communication is based on meta-analysis of 47 research papers highlighting impact of aircraft noise on avian behavior and communication related to both routine and breeding activities. Aircraft acoustics have been reported to modify behavior of 22 species of birds by changing their specific song structure, communication, population abundance, territorial defence behavior, modifications to reproductive success, impaired vocalization and predator-prey interactions. Recent studies have also uncovered additional negative effects of aeroplane noise on avian behavioral responses by modifying their stress reactions, foraging activity, flight or flushing reactions and avoidance of noisy environments. The ability of bird species to counteract the masking effect of noise through changes in vocal amplitude, song and call frequency, song component redundancy, as well as temporal shifts to avoid noise have been revealed by comparative avian studies conducted in noise free environment. There seems to be a big lacuna in our understanding of influence of aircraft noise on avian community structure, intra/inter species relationships and their prey populations having possibilities of destabilizing effect on intertwined food webs. Detailed studies are required on aircraft noise versus avian population interactions so as to come up with interventions to mitigate their impacts on avian habitats, breeding potential and population abundance; in addition to reduction in noise levels in aviation, maneuvers to reduce noise during landings and take-offs, and to safeguard wildlife in airport influenced areas.

Bird community structure is driven by urbanization level, blue-green infrastructure configuration and precision farming in Taizhou, China

Land use/land cover (LULC) changes and high urbanization rates are the main drivers of avian habitat loss in developing countries. However, few studies have examined the effects of urbanization intensity on avian diversity distribution and its importance in guiding eco-friendly urban planning. We surveyed bird distribution (n = 67 species) in different seasons using local ecological knowledge (LEK) and transect line methods in Jiangyan District from July 2018 to May 2019. One-way analysis of variance (ANOVA) was used to assess the effects of urbanization levels on birds relative density and richness during spring-summer (breeding season) and autumn-winter seasons (non-breeding season). Generalized linear models (GLM) were identified for the landscape composition and configuration that drive relative density and richness in native bird communities. Using redundancy analysis (RDA), we identified the landscape composition and configuration factors affecting bird foraging and roosting at urbanization levels. The results showed high dependency of waders and granivores on paddy fields and dry arable land respectively during the breeding season. During non-breeding season, wetland abundance, land cover, connectivity and total area of BGI were important habitat factors in attracting birds. Moreover, the landscape composition and configuration factors of BGI: wetlands as well as farmland habitats, are the main environmental cues that influence bird foraging. Therefore, to increase habitat suitability over landscape matrix, we propose creation of multiple waterbodies and green corridors of variable types and sizes on natural patches to improve the connectivity of ecological network. We also recommend land management interventions in farmland ecosystems, which could contribute to natural habitat restoration and improve bird biodiversity in urban areas.

Effect of enviromental factors at multiple landscape scales on bird community in riparian ecosystem at Mun-Chi River confluence, Thailand

Abstract. Chaleekarn W, Duengkae P, Pongcharoen C, Sutummawong N, Nakmuenwai P, Siripin S, Chirachitmichi C, Kummoo W, Paansri P, Suksavate W. 2022. Effect of environmental factors at multiple landscape scales on bird community in riparian ecosystem at Mun-Chi River confluence, Thailand. Biodiversitas 23: 5194-5204. Wetland and riparian ecosystem is an important migratory stopover for land and water birds in the East Asian - Australasian Flyway. Understanding relationship patterns between bird communities and environmental factors at multi-spatial scales within a landscape context could contribute to the conservation and management of bird biodiversity in wetland ecosystems. The landscape metrics index is critical in revealing the relationship between the composition of bird communities and habitats at both local and landscape scales. This study aims to determine the effect of the environmental factors at different designated spatial scales on the composition of local bird communities in terms of species and feeding guilds. Our study conducted a bird survey using 227-point transects along 40 tracks across different land cover types surrounding the Mun-Chi River confluence. Canonical correspondence analysis (CCA) was used to quantify the association between bird communities, represented by species and feeding guilds, and environmental factors with the integration of multilevel habitat metrics. From the results, the CCA showed patterns of the community-environmental association at multiple scales of patch, class, and landscape characteristics with the proportional explanation of 54% and 61.82% for the composition of species and feeding guilds, respectively. The results indicated the premise that the majority of bird species respond to the habitat at the local scale. Large forest patches can maintain migratory and resident bird species. Moreover, most avian groups were arranged primarily in a large forest core area, forest area, and Shrubland PA. The results confirmed existing information on feeding guilds. The prediction map of the principal component of avian species composition was created from the association with the drivers of land use, including crops, perennial farmland, and water body on the edge of forests. Therefore, wetland management must be done at both local and landscape scales to preserve suitable avian habitats.

Urban forest fragments vs residential neighborhoods: Urban habitat preference of migratory birds

Both residential areas and urban forest fragments can provide stopover habitat for migrating birds. However, it is not clear which migrant species use urban forest fragments versus residential areas. Objectives for this study were to determine: (1) which species primarily use urban forest fragments versus adjacent residential areas during migration; (2) whether birds in different vertical strata guilds (canopy and under canopy) are associated with urban forest fragments versus residential areas, and which vegetation characteristics are important for certain species that preferentially utilize one habitat over the other. Conducted in Gainesville, Florida, 39 random point counts were situated in urban forest fragments, adjacent residential areas, and forest-residential edges during spring and fall migration. We recorded 44 migrant species across all point counts. Ten (38%) under-canopy birds significantly preferred urban forest fragments compared to residential neighborhoods. Canopy birds typically used forest fragments and residential areas more equally, with only one species showing significant preference for the residential habitat. Residential neighborhoods that retain vertical vegetation structure were more likely to have more species of birds. These results show the importance of conserving and restoring certain vegetative characteristics in urban ecosystems: preserving large trees in residential neighborhoods, retaining small forest remnant patches throughout the urban matrix, and increasing vertical vegetation structure in yards. These practices will help provide avian habitat during migration, increasing avian diversity in urban areas.

Assessing the effects of Close-to-Nature Forestry on forest birds in the eastern United States: A case study and way forward

Over the last half-century, North American forest birds have experienced staggering declines, while at the same time, many metrics indicate that North American forest health has improved. While the United States has been recognised for global leadership in innovation and research in forestry, the negative impacts of high-severity harvesting methods and forest fragmentation are sometimes overlooked, and a dearth of research studies exist that assess the impacts of lower-severity forestry practices on birds. Globally, some regions are pursuing markedly different forestry practices, and one example is Europe’s Close-To-Nature Forestry (CTNF) that protects forest canopies. Historically, CTNF methods have not been promoted to help avian abundance or diversity; however, forest bird populations in Europe have increased 7% over the last two decades, and we posit whether similar forest management approaches in the eastern USA could benefit North American birds. Therefore, we sought to 1) assess the effects of forest structural characteristics on avian species richness in a CTNF-managed forest in the eastern USA; 2) compare our results to county-level eBird data to identify the challenges of assessing the impacts of forestry practices on birds at landscape scales; 3) highlight the ambiguities in current forest management guidelines for improving avian habitats in the USA and 4) suggest long-term direction for evaluating the impacts of alternative forest management practices on birds. Our case study provides preliminary evidence that CTNF-managed forests may support diverse birds of high conservation value that are normally drawn to different forest management extremes. We also provide recommendations for utilising eBird data to assess alternative forest management strategies at landscape scales and a synthesised look at the forest management guidelines provided by many of the major players in American ornithology. While there may be multiple reasons for forest bird declines noted in the past 50 years in North America, long-standing forest management practices and policies should not be overlooked.

Hemi‐marsh concept prevails? Kaminski and Prince (1981) revisited

AbstractThe hemi‐marsh concept has prevailed in avian habitat selection and wetland ecology and management since the 1970s. Hemi‐marsh is a stage of wetland succession when approximately equal proportions of emergent vegetation and open water occur. In 1981, researchers reported on a field experiment in Delta Marsh, Manitoba, Canada, where they artificially created interspersion levels of emergent vegetation and open water (30%:70%, 50:50 [hemi‐marsh], and 70:30) by mowing or rototilling to test for hypothesized differences in indicated breeding pair indices (IBPs/ha; pairs + lone males) of dabbling ducks and species diversity among treatment combinations. Greatest dabbler densities and species diversity were in 50:50 hemi‐marsh plots. This research has been widely cited; however, the experiment was pseudo‐replicated because of non‐independence of IBP counts within and among weeks and years of surveys. We reanalyzed data from the study to support or refute original results. More robust and generalized analyses revealed vegetation:water interspersion characteristics influenced IBP densities of blue‐winged teal (Spatula discors), mallard (Anas platyrhynchos), gadwall (Mareca strepera), northern shoveler (S. clypeata), and species diversity. We estimated greatest IBP densities and species diversity in 50:50 hemi‐marsh plots, agreeing with the previous study. Including nested random effects to account for temporal pseudo‐replication improved model fits by 2–30%. Despite accounting for temporal variation in dabbler density and species diversity, 61–93% of variation remained unexplained, indicating unresolved complexities of breeding dabbler habitat use. Nonetheless, our reanalysis generalized and strengthened the original finding that dabbling duck densities and species diversity were greatest in hemi‐marsh plots. Managers may strive to reproduce hemi‐marsh conditions for dabbling ducks and evaluate other waterbird responses. Our reanalysis also emphasized the need for researchers to account for or prevent temporal and spatial pseudo‐replication, examine model fit, and provide reproducible documentation of data and code, especially now that analytical tools and databases are freely available.

Drivers of avian habitat use and detection of backyard birds in the Pacific Northwest during COVID-19 pandemic lockdowns

Birds living in developed areas contend with numerous stressors, including human disturbance and light, noise, and air pollution. COVID-19 pandemic lockdowns presented a unique opportunity to disentangle these effects during a period of reduced human activity. We launched a community science project in spring 2020 to explore drivers of site use by and detection of common birds in cities under lockdown in the U.S. Pacific Northwest. Our goals were twofold: (1) consider how intensity of urbanization, canopy cover, and availability of bird feeders and bird baths influenced avian habitat use; and (2) quantify how daily changes in weather, air pollution, and human mobility influenced detection of birds. We analyzed 6,640 surveys from 367 volunteers at 429 monitoring sites using occupancy models for 46 study species. Neither land cover nor canopy cover influenced site use by 50% of study species, suggesting that backyard birds may have used a wider range of habitats during lockdowns. Human mobility affected detection of 76% of study species, suggesting that birds exhibited species-specific behavioral responses to day-to-day changes in human activity beginning shortly after initial lockdown restrictions were implemented. Our study also showcases how existing community science platforms can be leveraged to support local monitoring efforts.

Forest degradation drives widespread avian habitat and population declines.

In many regions of the world, forest management has reduced old forest and simplified forest structure and composition. We hypothesized that such forest degradation has resulted in long-term habitat loss for forest-associated bird species of eastern Canada (130,017 km2) which, in turn, has caused bird-population declines. Despite little change in overall forest cover, we found substantial reductions in old forest as a result of frequent clear-cutting and a broad-scale transformation to intensified forestry. Back-cast species distribution models revealed that breeding habitat loss occurred for 66% of the 54 most common species from 1985 to 2020 and was strongly associated with reduction in old age classes. Using a long-term, independent dataset, we found that habitat amount predicted population size for 94% of species, and habitat loss was associated with population declines for old-forest species. Forest degradation may therefore be a primary cause of biodiversity decline in managed forest landscapes.

Avian Communities of Alatish National Park, Ethiopia

Alatish National Park, which is located in the Amhara National Regional State at the border with the Republic of Sudan, is rich in its avian resources. To study the park’s avian communities, the study area was classified based on its vegetation structures into riverine woodland, wooded grassland, woodland, and bamboo woodland. Data were collected from July 2017 to April 2018 using line transect and point count methods. As a result, 132 species of birds belonging to 18 orders and 55 families were identified. The highest species diversities during the wet (H’ = 3.53) and dry (H’ = 3.55) seasons were recorded in the riverine woodland habitat. Species evenness was also the highest during the wet (E = 0.79) and dry (E = 0.77) seasons in the riverine woodland habitat. The bamboo woodland habitat harboured the lowest species diversity during the wet (H’ = 2.81) and dry (H’ = 2.45) seasons. More species similarity (SI = 0.90) was recorded between wooded grassland and bamboo woodland habitats during the dry season. Relative abundance of birds among the different species showed significant differences (F131, 1452 = 2.94,P<0.05), and most birds in the area were identified as uncommon species. Forest fire, logging, and overgrazing by cattle have significantly contributed to habitat destruction in the park which might act as the cause for reduction in avian diversity. Therefore, appropriate conservation strategies should be designed and implemented to minimize avian habitat destruction due to various anthropogenic activities within the park.

Resource allocation effects on the timing of reproduction in an avian habitat specialist

AbstractVariation in nutrient allocation can influence the timing of breeding and ultimately reproductive output. Time and space constraints might exist, however, if fewer food resources are available to meet the costs of reproduction early during the reproductive season. Here, for the first time, we test whether nutrient‐allocation strategies for reproduction in a shrub‐dependent avian species differ with timing of breeding in different ecoregions: a high‐elevation landscape, containing spatially complex vegetation (Rocky Mountains) vs. a low‐elevation, more homogenous landscape (Great Plains). We analyzed data collected from radio‐telemetry and stable isotopes to assess the degree to which endogenous (body) reserves are used for reproduction and whether variation in allocation strategies was associated with time of year, ecoregion, habitat quality (including sagebrush type and plant greenness), or maternal characteristics. Using a Bayesian statistical framework, we found that females relied on a similar amount of endogenous reserves for reproduction in first nesting and renesting attempts. Additionally, endogenous contributions declined more rapidly throughout the nesting season in the Rocky Mountains than in the Great Plains. Individuals in high‐ and intermediate‐elevation sagebrush types in the Rocky Mountains used similar amounts of endogenous reserves, whereas females nesting in low‐elevation sagebrush used less. Females nesting at intermediate elevations, which experience the greatest flush of new green vegetation during the nesting season, switched their reliance from endogenous‐to‐exogenous sources for reproduction as green vegetation became available during spring. Our study highlights adaptations of a nutrient‐allocation strategy across areas with varying levels of resources in time and space in a habitat specialist bird. Nutrient allocation by individuals residing in high‐elevation areas favors a strategy that mainly uses nutrients gained from wintering habitats, whereas individuals residing in low‐elevation areas mainly use exogenous sources for reproduction.

Diet-induced microbiome shifts of sympatric overwintering birds.

Gut microbiota have a significant impact on host physiology and health, and host genetics and diet are considered as two important factors, but it is difficult to discriminate the influence of each single factor (host or diet) on gut microbiota under natural conditions. Moreover, current studies of avian microbiota mainly focus on domestic or captive birds, and it is still uncertain how host and diet take part in changing avian gut microbiota composition, diversity, and function in the wild. Here, high-throughput sequencing of 16S rRNA was used to identify the gut microbiota communities for sympatric wintering Great Bustards and Common Cranes at different diets. The results showed that 8.87% operational taxonomic units (OTUs) were shared among all sampling birds; in contrast, 39.43% of Kyoto Encyclopedia of Genes and Genomes (KEGG) functional pathways were common among all individuals, indicating the existence of gut microbiota conservatism both in microbiota structure and function. Microbiota abundance and diversity differed between Great Bustards and Common Cranes in a specific wintering site, and microbiota variation was detected for the same host species under two different sites, suggesting that the change of gut microbiota was induced by both host and diet. Furthermore, we found that changes of both microbial communities and functional pathways were larger between hosts than those between diets, which revealed that host might be the dominant factor determining microbiota characteristics and function, while diet further drove the divergence of gut microbiota. Gut microbiota functions appeared to be more conserved than bacterial community structure, indicating that different bacteria may function in a similar way, while microbiota OTU diversity might not be necessarily associated with functional diversity. With diet shifting, gut microbiota changed both in terms of microbial communities and functional pathways for the sympatric birds, which implies that avian habitats and their physiological microbiota would be influenced by different farmland management regimes. KEY POINTS: • Gut microbiota can be shaped by both diets and hosts in sympatric species. • Host was the dominant factor shaping the gut microbiota communities and functional pathways. • Gut microbiota were conservative both in structure and in function, but more conservative in function.