Habitat Associations Research Articles

Species distribution modeling of northern sea otters (Enhydra lutris kenyoni) in a data-limited ecosystem.

Species distribution models (SDMs) are used to map and predict the geographic distributions of animals based on environmental covariates. Typically, SDMs require high-resolution habitat data and time series information on animal locations. For data-limited regions, defined as having scarce habitat or animal survey data, modeling is more challenging, often failing to incorporate important environmental attributes. For example, for sea otters (Enhydra lutris), a federally protected keystone species with variable population trends across the species' range, predictive modeling of distributions has been successfully conducted in areas with robust sea otter population and habitat data. We used open-access data and employed a presence-only model, maximum entropy (MaxEnt), to investigate subtidal habitat associations (substrate and algal cover, bathymetry, and rugosity) of northern sea otters (E. lutris kenyoni) for a data-limited ecosystem, represented by Kachemak Bay, Alaska. Habitat association results corroborated previous findings regarding the importance of bathymetry and understory kelp as predictors of sea otter presence. Novel associations were detected as filamentous algae and shell litter were positively and negatively associated with northern sea otter presence, respectively, advancing existing knowledge of sea otter benthic habitat associations useful for predicting habitat suitability. This study provides a quantitative framework for conducting species distribution modeling with limited temporal and spatial animal distribution and abundance data. Utilizing drop camera information, our novel approach allowed for a better understanding of habitat requirements for a stable northern sea otter population, including bathymetry, understory kelp, and filamentous algae as positive predictors of sea otter presence in Kachemak Bay, Alaska.

A simulation study comparing common methods for analyzing species–habitat associations of plants

AbstractQuestionSpecies‐specific habitat associations are one of several processes that lead to a clustered spatial pattern of plant populations. This pattern occurs in tropical and temperate forests. To analyze species–habitat associations, four methods are commonly used when determining species–habitat associations from spatial point pattern and environmental raster data. Two of the methods randomize the spatial point pattern of plants, and two randomize the raster data of habitat patches. However, the strengths and weaknesses of the four methods have never been analyzed in detail.MethodsWe conducted a simulation study to analyze the strengths and weaknesses of the four most used methods. The methods are the gamma test, pattern reconstruction, the torus‐translation test and the randomized‐habitats procedure. We simulated neutral landscapes representing habitat patches and point patterns representing fine‐scale plant distributions. We built into our simulations known positive and negative species–habitat associations.ResultsAll four methods were equally good at detecting species–habitat associations. Detected positive associations better than negative ones. Furthermore, correct detections were mostly influenced by the initial spatial distribution of the point patterns, landscape fragmentation and the number of simulated null model randomizations.ConclusionsThe four methods have advantages and disadvantages, and which is the most suitable method largely depends on the characteristics of the available data. However, our simulation study shows that the results are consistent between methods.

Citizen-science data identifies the daily movement patterns and habitat associations of a nocturnal urban-invading bird species (Corvus frugilegus)

Rooks (Corvus frugilegus) are an invasive bird species in South Korea that are deemed harmful due to nocturnal urban invasions and agricultural damage. Employing citizen science data, we document the daily movement patterns and habitat associations of nocturnal urban-invading rooks in Suwon, South Korea. We collected 4,522 geolocated observations from December 2021 to March 2022, categorized by the timings of sunrise and sunset and segmented into 3-h intervals. Using the MaxENT (Maximum Entropy Model) and k-fold cross-validation (k = 10) with a 25% random test sample, we analyzed daily movement patterns and habitat preferences. Our results show that rooks forage in agricultural areas shortly after sunrise and roost in urban environments after sunset. Urban roosts tend to occur in areas near buildings of medium height (6–20 stories) that are illuminated by artificial light and contain utility poles. The variables with the highest percent contribution to rooks’ presence after sunset were buildings of medium height (20.7%), land use type (19.4%), elevation (29%), and utility pole (14.5%). Our findings emphasize the potential of citizen science initiatives to generate insights into the ecology of invasive bird species within large urban environments.

Meta-analysis reveals weak associations between reef fishes and corals.

Habitat associations underpin species ecologies in high-diversity systems. Within tropical, shallow water coral reefs, the relationship between fishes and corals is arguably the most iconic and highly scrutinized. A strong relationship between fishes and reef-building hard corals is often assumed, a belief supported by studies that document the decline of reef fishes following coral loss. However, the extent of this relationship is often unclear, as evidenced by conflicting reports. Here we assess the strength of this ecological association by relying on literature that has surveyed both fishes and corals synchronously. We quantitatively synthesize 723 bivariate correlation coefficients (from 66 papers), published over 38 years, that relate fish metrics (abundance, biomass and species richness) with the percentage of hard coral cover. Remarkably, despite extensive variation, the pattern of association on a global scale reveals a predominantly positive, albeit weak (|r| < 0.4), correlation. Even for commonly hypothesized drivers of fish-coral associations, fish family and trophic group, associations were consistently weak. These findings question our assumptions regarding the strength and ubiquity of fish-coral associations, and caution against assuming a direct and omnipresent relationship between these two iconic animal groups.

Habitat associations of day-flying Lepidoptera and their foodplants within nature reserves in Bedfordshire, UK

Species often associate with specific habitat characteristics, resulting in patchy distributions, whereby they only occupy a proportion of available habitat. Understanding which characteristics species require is a valuable tool for informing conservation management. We investigated the associations of eleven species of day-flying Lepidoptera larvae and their foodplants with habitat characteristics within calcareous grassland reserves in Bedfordshire, UK, across two scales relevant to land managers and target species: the reserve (cardinal aspect, vegetation type) and foodplant patch scale (foodplant height and density). We investigated whether ecological traits (habitat specialism, as defined at a national-scale, and overwintering life stage) influenced the strength of associations. At the reserve scale, we found variation in associations with habitat characteristics across species, with species that overwinter at non-adult life stages having more restricted associations, indicating that they may be more vulnerable to environmental change. Associations were generally stronger with vegetation type than aspect, which can be manipulated more easily by land managers. Seven species had similar associations with habitat characteristics to their foodplants, implying that management to benefit foodplants will also benefit larvae. However, the remaining four species had different associations to their foodplants, and may require alternative management approaches. At the foodplant patch scale, four species were associated with foodplant characteristics, which could be used to inform effective fine-scale management.Implications for insect conservationImplications for insect conservation: Diverse habitat associations imply that topographic and vegetation variation are valuable for supporting diverse assemblages of butterflies and their foodplants.

Modelling complex spatial–temporal drivers of habitat suitability for an imperilled stream fish

Fish populations rely on complex environmental conditions involving physical, chemical, and biological factors. Understanding the factors that control population persistence and productivity is essential for species management. We assessed the distribution and associated habitat features of a species at risk in Canada, Silver Shiner (Notropis photogenis), within Sixteen Mile Creek, a tributary of Lake Ontario. Using random forest models, we quantified a range of ecological factors (n = 25) to estimate habitat associations for sampled populations and life stages (juvenile, adult). A complex set of ecological factors were informative predictors of Silver Shiner distribution, including physical (stream morphology, water velocity, substrate type), and biological (aquatic and riparian vegetation) conditions. Juveniles were less responsive to habitat conditions but exhibited high seasonal variability in occurrence. Adults were most common in stream sections with greater than 0.5 m depth and stream velocity less than 0.6 m/s, and areas without silt substrate. Broadly, the models predicted Silver Shiner distribution with 68–92% accuracy in non-training data. Our findings describe the habitat conditions that Silver Shiner currently occupies in an urban drainage, which may serve as a point of reference for habitat protection and restoration. Further, predictive species distribution models can serve to identify habitat for further monitoring and restoration.

Land use predicts proportion of West Nile virus vector‐competent mosquitoes

AbstractLand use and land cover (LULC) change has been identified as an important driver of emerging mosquito‐borne zoonotic diseases. However, studies are often limited to individual vector species, despite the potential for interspecific variation in vector competency within mosquito assemblages. This variation can affect transmission hazard, particularly in complex multi‐vector disease systems. Here, we used a joint species distribution modeling approach that included mosquito species vector competency for West Nile virus (WNV) as a trait to understand community‐level responses to land cover and predict joint species distributions in Manatee County, Florida. We assembled species presence/absence data across 61 sites and 44 species sampled from 2016 to 2020 and percent land cover within 2500 m of trap locations for five common land cover types. These data were used to investigate patterns in species richness and community‐weighted proportions of WNV‐competent vector species. The results revealed that land cover effects on individual species aligned with known habitat associations: the highest proportions of WNV‐competent species were predicted in less diverse urbanized areas, and species richness increased as urbanized areas decreased. Our findings highlight the value of community‐level analyses to predict joint vector distributions that can inform where greatest transmission hazard may occur. This information can be used by public health agencies, mosquito control, and land managers to plan more effective and optimized prevention and control efforts.

Fewer bowl traps and more hand netting can increase effective number of bee species and reduce excessive captures.

Reports increasingly point to substantial declines in wild bee abundance and diversity, yet there is uncertainty about how best to measure these attributes in wild bee populations. Two commonly used methods are passive trapping with bee bowls or active netting of bees on flowers, but each of these has drawbacks. Comparing the outcomes of the two methods is complicated by their uncomparable units of effort. The abundance distribution of bee species is also typically highly skewed, making it difficult to accurately assess diversity when rarer species are unlikely to be caught. The effective number of species, or Hill numbers, provides a way forward by basing the response metric on the number of equally abundant species. Our goal is to compare the effective number of bee species captured between hand netting and bowl trapping in wheatgrass prairie in South Dakota and tallgrass prairie in Minnesota, USA. Species overlap between the two methods ranged from ~40% to ~60%. Emphasis placed on rare species was important, so that 95% confidence limits overlapped between the two methods for species richness but netting exceeded trapping for Shannon's and Simpson's diversities. Netting always captured more bee species with fewer bee individuals than trapping. In most cases, the number of bees captured in bowl traps indicated substantial over-sampling, with little increase in bee species detected. Correlations between bee and floral abundance, richness, and diversity differed between netted and trapped samples. We conclude that netting and trapping together produce a more complete account of species richness, but shifting sampling emphasis from trapping to netting will result in fewer bees, but more bee species captured. Due to the different relationships between bee and floral diversities that depended on sampling method, it is unwise to compare habitat associations determined by netting with those determined by trapping.

Dynamic, multi-scale analyses indicate site- and landscape-level forest cover drive Yellow-billed and Black-billed Cuckoo interannual turnover.

Studies of habitat use in breeding birds often assume species have relatively stable breeding distributions. Some species, however, display considerable year-to-year variability, complicating efforts to determine suitable or preferred habitats. After returning to their breeding range, Black-billed Cuckoos (Coccyzus erythropthalmus) and Yellow-billed Cuckoos (C. americanus) are thought to range widely before nesting, resulting in high rates of interannual breeding-site turnover, potentially contributing to conflicting habitat associations found in past studies. However, difficulty detecting these rare and declining species could lead to overinflated estimates of interannual turnover. Using broadcast surveys to increase detection probability, we collected detection/non-detection data in 2019 and 2020 at 41 publicly owned sites in Illinois and performed a dynamic, multi-scale occupancy analysis for each species to separate detection probability from potential interannual turnover and determine landscape and small-scale variables driving habitat use and occupancy dynamics. We found strong support for interannual turnover for both species based on poor performance of non-dynamic models and variation in estimated annual occupancy (20% and 21% increase between years for Black-billed and Yellow-billed Cuckoos, respectively). Black-billed Cuckoos persisted at sites with less forest in the surrounding landscape and used areas with denser understory vegetation. Yellow-billed Cuckoos colonized sites with greater canopy cover, avoided developed landscapes, and used areas with a shorter subcanopy layer. The dynamic nature of habitat use in these two cuckoo species suggests the importance of coordinating management and conservation across a broader spatial scale. Managing for larger patches of dense shrubs in less forested landscapes would benefit Black-billed Cuckoos while Yellow-billed cuckoos would benefit from management creating forested areas with open understories in less-developed landscapes.

Using butterfly survey data to model habitat associations in urban developments

Abstract One approach for measuring the potential biodiversity in new urban construction projects is through ecological models that predict how wildlife will respond. For the United Kingdom, such models have only been developed for birds, but to maximise the extent to which models represent overall biodiversity, species from different indicator groups must be considered. Here, we assess this possibility for butterflies by combining citizen science survey data with high‐resolution digital maps. We derive detailed characteristics of urban landscapes around survey sites using previously established methods and quantify their relationship to counts of adults of 18 butterfly species in urban and peri‐urban settings. Higher butterfly counts were found when traversing urban sites with larger areas of semi‐natural grassland, other managed greenspaces and adjacent arable land. Most of the butterfly community were found to have negative relationships with highly built‐up or fragmented landscapes. We found high species‐specificity for different details of urban form, particularly in habitat elements such as gardens, vegetation around railways and grass verges. Policy implications. Improving biodiversity is now part of legislation governing new construction projects from England and Wales. However, predicting quantitative changes from hypothetical land‐use modifications remains challenging. Our models provide the foundation through which butterfly abundance could be integrated into an urban biodiversity assessment tool, providing species‐ and community‐level statistics to non‐specialists from the urban planning and design sector. This would allow them to hone configurations for built surfaces, private gardens, greenspaces and wildlife areas and assess their capacity to provide residents with the intended access to nature.

Habitat and morphological characteristics affect juvenile mortality in five coral reef damselfishes

The abundance and distribution of demersal fishes rely on larvae successfully settling from the pelagic environment to a benthic habitat and their subsequent survival. With high mortality rates during this life stage, settling to a habitat that maximizes survival is critical. However, relationships between settlement choices and subsequent survival are poorly understood and may vary among species with different habitat preferences. To test this, we focused on five congeneric (Pomacentrus) damselfish species that are known to differ in their habitat choices and explored whether habitat associations at settlement influenced survival. Newly settled individuals were tagged and monitored daily for two weeks to estimate natural mortality rates. Morphological attributes of fish and characteristics of settlement habitats, including depth, rugosity, benthic substrata, and local fish assemblages, were used to predict mortality. We found that some species displayed stronger associations with specific benthic substrata at settlement, but contrary to expectations, these selected habitat characteristics were relatively weak predictors of survivorship. Our survival analysis revealed that the best predictors of survivorship were rugosity (P. adelus and P. amboinensis) and two morphological traits, body depth and ocellus size (P. chrysurus and P. adelus). Interestingly, we found that P. moluccensis that settled in areas of high coverage of mounding coral experienced increased mortality. Of the remaining substrata, analysis showed that instead of associating with habitat characteristics enhancing survivorship, individuals tended not to associate with habitats characteristics that increased mortality (e.g., Turbinaria and sand). This study highlights the species-specific drivers of early post-settlement mortality in coral reef fishes.

Abundance of five sympatric stream dwelling mussels varies with physical habitat

Abstract Freshwater mussel species regularly co‐occur in streams forming assemblages, but the extent of shared versus unique instream habitat features that contribute to their distribution and abundance is poorly understood. In Massachusetts, a rare species, Alasmidonta varicosa, is often found with four other species: Alasmidonta undulata, Strophitus undulatus, Margaritifera margaritifera, and Elliptio complanata, yet variation in species composition within assemblages raises questions of potential species‐specific habitat associations. Identifying species‐level habitat information is critical at a spatial scale that malacologists can use to identify translocation or restoration areas. This study investigated whether species abundance varied by mesohabitat type (riffle, run, dam pool, scour pool), instream habitat characteristics, and within‐reach location (centre versus edge). From 2016 to 2019, freshwater mussel surveys were conducted in nine streams across Massachusetts and associated habitat information was collected. Species abundances were similar across mesohabitat types. Elliptio complanata was the exception, whereby higher abundances occurred in runs and dammed pools than in riffles. Unique species relationships with habitat existed for M. margaritifera with macroalgae and emergent vegetation, and A. varicosa with heterogeneous substrate. Flow transitions, such as depositional areas that create heterogeneous substrates, may provide habitats for A. varicosa. Most mussel species were distributed with higher abundance in the river centre than the edge; E. complanata was the only species with a higher abundance at the river edge. Locations with high abundance varied based on unique relationships with pebble heterogeneity (A. varicosa), depth (A. undulata), large wood (A. undulata), and canopy closure (E. complanata). Including physical characteristics in a holistic assessment of habitat that incorporates fish and landscape attributes may further an understanding of river reaches that best support translocated and propagated freshwater mussels.

The influence of landscape composition and configuration on breeding waterfowl pair abundance in Wisconsin

AbstractHabitat loss and fragmentation have negatively impacted breeding birds across the world. Across guilds, grassland‐dependent birds have experienced the largest proportional loss of their breeding population while wetland‐dependent birds have realized overall net gains in part due to focused conservation efforts. However, some species within the wetland‐dependent guild have a strong dependence on non‐wetland land cover types during the annual cycle and therefore may be equally sensitive to reductions in the composition and altered configuration of upland landcover, such as grasslands. We explored the influence of landcover composition and configuration on the number of breeding pairs of a breeding habitat generalist, the mallard (Anas platyrhynchos), and a grassland‐dependent breeding species, the blue‐winged teal (Spatula discors), in agriculturally‐intensive landscapes of Wisconsin, USA. Because of the extensive landscape alteration and habitat fragmentation that has occurred, we expected mallards to have a more utilitarian response to varying landscape composition compared to a grassland nesting obligate like blue‐winged teal. We used helicopter surveys conducted across 8 years (2001–2003, 2006–2009, and 2012) and remotely‐sensed land cover data to investigate the influence of habitat associations on relative abundance of breeding pairs. Model selection indicated that landscape composition models outperformed landscape configuration and null models for both species. Consistent with our predictions, we found that mallard pair counts were positively influenced by a greater number of land cover covariates compared to blue‐winged teal. Both blue‐winged teal and mallard breeding pairs were positively related to increased composition of emergent and scrub‐shrub wetlands as well as upland grassland. Additionally, we found that mallard pairs were positively related to forested, cattail (Typha sp.), and open water wetland types, whereas predicted blue‐winged teal pair abundance was negatively related to forested wetlands and had a nonlinear relationship and declined when surveyed land sections were comprised of more than 30% cattail‐dominated wetlands and 20% open‐water wetlands. Increased quantities of cattail‐dominated and open‐water wetland cover types comparatively provide less habitat for blue‐winged teal and may reflect broader shifts in habitat composition that have likely resulted from agricultural intensification and stabilized hydrology. Conservation activities that preserve existing nesting land cover types or restore hydrologically‐dynamic emergent wetlands in proximity to upland grassland cover could mutually benefit both species.

Species composition, relative abundance, and habitat association of birds in Dodola dry evergreen afro-montane forest and sub-afro-alpine scrubland vegetation, southeast Ethiopia.

Birds' functional groups are useful for maintaining fundamental ecological processes, ecosystem services, and economic benefits. Negative consequences of loss of functional groups are substantial. Birds are usually found at a high trophic level in food webs and are relatively sensitive to environmental change. The first surveillance bird study was carried out southeast of Ethiopia adjacent to Bale Mountain National Park aimed at investigating the composition, relative abundance, and distribution of Aves. Using regular systematic point transact sampling, the density and species composition were analyzed through the mark recapture distance sampling engine assisted by R statistical software. This study recorded a total of seventy-eight bird species over two distinct seasons. Among these, fifteen species were exclusive to Erica habitats, twenty-six were found in natural forest habitats, and three were specific to plantation forest habitats. The study also discovered three endemic species. Based on the 2018 IUCN Red List categories, six of the species are globally threatened, three are near threatened, and the remaining sixty-nine are classified as least concern. The relative abundance of birds did not significantly differ across habitats and seasons, but variations were observed among blocks. Bird density was found to fluctuate across the three habitats and two seasons; however, these habitat differences were not influenced by seasonal changes. The findings of this study reveal that the differences in composition and relative abundance are not merely seasonal changes in the forest and Erica habitats. Instead, these habitats create microclimates that cater to specific bird species. However, this localized endemism also presents challenges. The concentration of endemic species and potential resource constraints could pose a threat to these habitat-specialist birds.

A framework to support the identification of critical habitat for wide-ranging species at risk under climate change

To recover species at risk, it is necessary to identify habitat critical to their recovery. Challenges for species with large ranges (thousands of square kilometres) include delineating management unit boundaries within which habitat use differs from other units, along with assessing any differences among units in amounts of and threats to habitat over time. We developed a reproducible framework to support identification of critical habitat for wide-ranging species at risk. The framework (i) reviews species distribution and life history; (ii) delineates management units across the range; (iii) evaluates and compares current and (iv) potential future habitat and population size and (v) prioritizes areas within management units based on current and future conditions under various scenarios of climate change and land-use. We used Canada Warbler (Cardellina canadensis) and Wood Thrush (Hylocichla mustelina) in Canada as case studies. Using geographically weighted regression models and cluster analysis to measure spatial variation in model coefficients, we found geographic differences in habitat association only for Canada Warbler. Using other models to predict current habitat amount for each species in different management units, then future habitat amount under land use and climate change, we projected that: (1) Canada Warbler populations would decrease in Alberta but increase in Nova Scotia and (2) Wood Thrush populations would increase under most scenarios run in Quebec, New Brunswick and Nova Scotia, but not in Ontario. By comparing results from future scenarios and spatial prioritization exercises, our framework supports identification of critical habitat in ways that incorporate climate and land-use projections.

Population parameters and conservation implications for one of the world's rarest marine fishes, the red handfish (Thymichthys politus).

Population estimates are required for effective conservation of many rare marine species, but can be difficult to obtain. The critically endangered red handfish (Thymichthys politus) is a coastal anglerfish known only from two fragmented populations in southeast Tasmania, Australia. It is at a high risk of extinction due to low numbers, loss of habitat, and the impacts of climate change. To aid conservation efforts, we provide the first empirical population size estimates of red handfish and investigate other important aspects of the species' life history, such as growth, habitat association, and movement. We surveyed both red handfish local populations via underwater visual census on scuba over 3 years and used photographic mark-recapture techniques to estimate biological parameters. In 2020, the local adult population size was estimated to be 94 (95% confidence interval [CI] 40-231) adults at one site, and 7 (95% CI 5-10) at the other site, suggesting an estimated global population of 101 adults. Movement of individuals was extremely limited at 48.5 m (± 77.7 S.D.) per year. We also found evidence of declining fish density, a declining proportion of juveniles, and increasing average fish size during the study. These results provide a serious warning that red handfish are likely sliding toward extinction, and highlight the urgent need to expand efforts for ex situ captive breeding to bolster numbers in the wild and maintain captive insurance populations, and to protect vital habitat to safeguard the species' ongoing survival in the wild.

Using multiplatform LiDAR to identify relationships between vegetation structure and the abundance and diversity of woodland reptiles and amphibians

AbstractRemotely sensed measures of vegetation structure have been shown to explain patterns in the occurrence and diversity of several animal taxa, including birds, mammals, and invertebrates. However, very little research in this area has focused on reptiles and amphibians (herpetofauna). Moreover, most remote sensing studies on animal–habitat associations have relied on airborne or satellite data that provide coverage over relatively large areas but may not have the resolution or viewing angle necessary to measure vegetation features at scales that are meaningful to herpetofauna. Here, we combined terrestrial laser scanning (TLS), unmanned aerial vehicle laser scanning (ULS), and fused (FLS) data to provide the first test of whether vegetation structural attributes can help explain variation in herpetofauna abundance, species richness, and diversity across a woodland landscape. We identified relationships between the abundance and diversity of herpetofauna and several vegetation metrics, including canopy height, skewedness, vertical complexity, volume of vegetation, and coarse woody debris. These relationships varied across species, groups, and sensors. ULS models tended to perform as well or better than TLS or FLS models based on the methods we used in this study. In open woodland landscapes, ULS data may have some benefits over TLS data for modeling relationships between herpetofauna and vegetation structure, which we discuss. However, for some species, only TLS data identified significant predictor variables among the LiDAR‐derived structural metrics. While the overall predictive power of models was relatively low (i.e., at most R2 = 0.32 for ULS overall abundance and R2 = 0.32 for abundance at the individual species level [three‐toed skink (Chalcides striatus)]), the ability to identify relationships between specific LiDAR structural metrics and the abundance and diversity of herpetofauna could be useful for understanding their habitat associations and managing reptile and amphibian populations.

Rangewide occupancy of a flagship species, the Coastal California Gnatcatcher (Polioptila californica californica) in southern California: Habitat associations and recovery from wildfire.

The Coastal California Gnatcatcher (Polioptila californica californica), a federally threatened species, is a flagship species for regional conservation planning in southern California (USA). An inhabitant of coastal sage scrub vegetation, the gnatcatcher has declined in response to habitat loss and fragmentation, exacerbated by catastrophic wildfires. We documented the status of gnatcatchers throughout their California range and examined post-fire recovery of gnatcatchers and their habitat. We used GIS to develop a habitat suitability model for Coastal California Gnatcatchers using climate and topography covariates and selected over 700 sampling points in a spatially balanced manner. Bird and vegetation data were collected at each point between March and May in 2015 and 2016. Presence/absence of gnatcatchers was determined during three visits to points, using area searches within 150 x 150 m plots. We used an occupancy framework to generate Percent Area Occupied (PAO) by gnatcatchers, and analyzed PAO as a function of time since fire. At the regional scale in 2016, 23% of the points surveyed were occupied by gnatcatchers, reflecting the effect of massive wildfires in the last 15 years. Similarly, PAO in the post-fire subset of points was 24%, with the highest occupancy in unburned (last fire <2002) habitat. Positive predictors of occupancy included percent cover of California sagebrush (Artemisia californica), California buckwheat (Eriogonom fasciculatum), and sunflowers (Encelia spp., Bahiopsis laciniata), while negative predictors included laurel sumac (Malosma laurina) and total herbaceous cover; in particular, non-native grasses. Our findings indicate that recovery from wildfire may take decades, and provide information to speed up recovery through habitat restoration.

Habitat association and community classification of woody plants in the 20 ha forest dynamics plot of subtropical semi-humid evergreen broad-leaved forest in the Jizu Mountains, Yunnan

Habitat association and community classification of woody plants in the 20 ha forest dynamics plot of subtropical semi-humid evergreen broad-leaved forest in the Jizu Mountains, Yunnan

Cropland can support high bird diversity in heterogeneous rural tropical landscapes

Summary Land-use change for crop production is one of the key drivers of habitat loss and fragmentation and consequently biodiversity loss and change in tropical regions. This may impact biodiversity-regulated ecosystem services; birds are important to crop health regulating services (e.g. seed dispersal, pest control) and disservices (e.g. seed predation, grain herbivory). However, knowledge is limited on how birds use heterogeneous agricultural landscapes and the consequences for spatial distribution and flow of services and disservices. We studied crop and non-crop–habitat associations of birds in forest–agricultural landscapes of the Kilombero Valley, Tanzania. We focused on dietary preference as a key trait impacting bird responses to land-use change, services, and disservices to crops. We surveyed birds across four main habitat types using repeated point counts, recording a total of 148 species. We found that crop habitats supported higher species richness and larger communities of potentially beneficial species to crop health, whereby 34.5% of invertebrate-feeding species were recorded in cropland. We found that habitat heterogeneity within the landscape supports bird functional diversity and that each habitat type supported unique communities of species. Furthermore, the number of species unique to forest habitats increased with increasing forest canopy closure. Our findings suggest that management strategies for maintaining trees and shrubs, and enhancing tree cover within the crop production landscape, can be effective approaches for maintaining bird diversity and services. However, in-depth studies on trade-offs with disservices need further exploration to mitigate negative impacts of birds on crop yields.