Habitat Associations Of Birds Research Articles

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.

Species composition and habitat associations of birds around Jhilmila Lake at Western Chure Landscape, Nepal

Abstract Wetlands support around 27% of birds in Nepal, however, there is a paucity of information about bird diversity and the wetland habitat of Western Chure Landscape Nepal. The “point count” method along transects was carried out to evaluate the species composition and habitat associations of birds. A total of 2,532 individuals representing 152 species (winter: N = 140 and summer: N = 91) from 19 orders and 51 families were reported from Jhilmila Lake and its surrounding area. The number of birds was reported to be significantly higher during winter than in the summer season. The species diversity was also higher in winter (Shannon’s index (H) = 4.38, Fisher’s alpha = 30.67) than in summer (H = 4.21, Fisher’s alpha = 34.69) as this area is surrounded by old-growth forest that provides available habitats for forest, grassland- and wetland-dwelling birds. This lake is an example of a wetland present in the Chure area that plays an important role in the conservation of biodiversity along with birds. Hence, we recommend its detailed study in terms of biodiversity and water quality.

Using aerial LiDAR to assess regional availability of potential habitat for a conservation dependent forest bird

Remotely-sensed data can inform conservation efforts that target forest wildlife, however, few spatial data products are able to quantify fine-scale aspects of structural variation within forests. Increased availability of Light Detection and Ranging (LiDAR) datasets that cover broad spatial extents and ownership types (e.g., entire states) provide useful information regarding canopy and understory structure within forested landscapes. The fusion of LiDAR data with field-based species surveys can advance our understanding of species-habitat relationships and improve the effectiveness of conservation programs to recover habitat-limited species. The Golden-winged Warbler (Vermivora chrysoptera) is a forest-dependent songbird that nests in structurally-complex young forest across eastern North America. As with many early-successional obligates, this species has been declining for decades due, in part, to the steady loss of young forest/shrubland nesting habitat. Although conservation programs have begun restoring Golden-winged Warbler habitat, these efforts are currently limited by the inability to identify existing habitat across large spatial extents and diverse ownership patterns. Recent availability of state-wide LiDAR data for Pennsylvania provides an opportunity to overcome this limitation. From 2019 to 20, we surveyed for Golden-winged Warblers and structural vegetation at 837 sites across six forest blocks in eastern Pennsylvania. We combined these data with LiDAR derived forest structural metrics to develop statistical models to predict patterns of occupancy. Golden-winged Warbler occupancy probability was explained by models containing several LiDAR-derived structural metrics (e.g., percentage of first returns between 1 and 5 m in height, structural complexity, etc.). Moreover, models fit with LiDAR-derived covariates predicted occupancy much better than those using only field-measured vegetation covariates (ΔAICc = 53.27). Mapped predictions of Golden-winged Warbler occupancy revealed potential habitat (especially regenerating timber harvests) on both private and public lands. These results demonstrate the efficacy of LiDAR for modeling forest bird habitat associations, and how such data sources can provide a valuable tool for conservation planning.

Estimating direct and indirect effects of habitat structure on nesting field sparrows (Spizella pusilla) using structural equation models

Due to consistent population declines across the continent, grassland birds have become a guild of high conservation and management interest. Despite a large number of studies investigating grassland bird habitat associations, we know relatively little about the mechanisms through which habitat characteristics may impact grassland birds, as these mechanisms are often assumed rather than directly tested. For this study, we estimated whether the effects of habitat structure on breeding Field Sparrows are mediated through changes in predator (snake and raccoon) abundance, alternative prey availability, or arthropod biomass using structural equation models. We found no evidence of nest survival or nest density of Field Sparrows being directly influenced by nest predator abundance, alternative prey, or arthropod biomass, although habitat characteristics associated with increased nest survival were also associated with greater arthropod biomass and reduced predator abundance. We suggest that habitat structure in our study area primarily impacts breeding Field Sparrows through direct means, such as influencing nest concealment or foraging efficiency. Our results also suggest that nest success and nest density are decoupled in our study area, so Field Sparrows may be preferentially selecting nest sites with structural characteristics that do not increase nest survival. Ultimately, our findings from this study indicate that while predator avoidance and food provisioning likely play an important role in determining nest survival for grassland birds, predator abundance and arthropod biomass may not necessarily predict predation risk and foraging efficiency to the extent that is often assumed.

Bird community structure and habitat association in Owabi Wildlife Sanctuary, Ashanti Region (Ghana)

Context Globally, an estimated 1.3% of the bird species have gone extinct over the past millennia, largely owing to habitat loss. Aims This study investigated bird–habitat associations and assemblages in the Owabi Ramsar wetland. Methods The study was conducted over 5 months (May–September 2019) in four habitat types (agricultural land, built-up, forest reserve, and open-water area). Data were collected in 84 plots across four habitats (i.e. built-up area = 25, forest reserve = 25, agricultural land = 25 and open-water area = 9 plots), using a point-count technique. The Gambin model, non-metric multidimensional scaling, Chao-1, and Hill numbers models were used to evaluate differences in bird diversity and composition among the habitat types. Key results In all, 1260 individual birds, belonging to 81 species, were encountered. Many of the species occurred in the forest habitat (n = 46, 56.8%. Species from the agricultural land (n = 37) and built-up (n = 30) were mainly habitat generalists that used these two habitats as their shared feeding station. Bird–habitat specialisation grouping equally showed the forest specialists to be the highest (n = 23, 38.4%), whereas the open water had the least number of habitat specialisation associations (e.g. white-faced whistling duck, n = 20, 24.7%). Five species were widely distributed in all four habitats (e.g. bronze-mannikins and white-throated bee-eaters), indicating their broad habitat preferences and ability to adapt to varied conditions. The forest reserve tended to be the most diverse, which was likely mediated by factors such as nesting microhabitats, varied food availability, and human-led activities. Conclusions This study highlighted bird dietary structure and associated habitat type and bird-habitat specialisation in four different land-use types at Owabi Ramsar wetland. Implications Given the increasing level of disturbance, there is the likelihood that the population of forest-dependent and open water-dependent birds will be lost or will have to change or modify their behaviour to be similar to that of open-tolerant or open-country birds if managers of the Owabi Wildlife Sanctuary fail to implement the recommended management interventions highlighted.

Habitat associations and conservation opportunities for priority birds on small, diversified farms in the northeastern USA

Abstract Although the impacts of intensive agriculture on biodiversity and strategies for mitigating these effects have been widely described, small-scale, diversified farms and the opportunities they present for bird conservation have been less thoroughly examined. This omission is potentially significant, because this form of agriculture represents a growing sector of the industry in the populous northeastern USA, and the diverse habitats on these farms contrast with larger, structurally homogeneous intensive agriculture. To evaluate bird-habitat associations and conservation opportunities for supporting species of conservation concern on these small, diversified farms, we conducted avian point count and vegetation surveys across 23 farms in western Massachusetts during the summers of 2017 and 2018. We used Poisson-binomial mixture models and canonical correspondence analysis to assess the effects of a suite of microhabitat-, field- and landscape-scale (1 km buffer around the field) variables on the abundance of bird species. Our results confirmed that shrubland birds, a group of species of elevated conservation concern, accounted for 52% of the total observations, including song sparrow (Melospiza melodia), gray catbird (Dumatella carolinensis), common yellowthroat (Geothlypis trichas) and American goldfinch (Spinus tristis). Species–habitat relationships were diverse; however, smaller field sizes, and increased cover of tall, dense, woody or non-productive vegetation types were associated with higher abundance of shrubland species as well as lower abundance of crop pests such as European starling (Sturnus vulgaris) and house sparrow (Passer domesticus). These findings support the hypothesis that small, diversified farms are supporting birds of high conservation concern, and we provide species-specific guidelines for farmers interested in conserving birds on their land.

In the bleak mid-winter: The value of brownfield sites for birds during the winter

Brownfield sites (e.g., wastelands, disused industrial grounds and power stations) are valuable refuges for urban birds during the breeding season. This owes to the presence of vegetation in different stages of succession, which provide a high diversity of food and breeding resources. However, insufficient research has explored their winter value, when temperatures are lower and food is scarcer. Accordingly, 342 bird and habitat surveys were conducted in brownfield sites, and other land-uses, across Greater Manchester. Bird density estimates were then calculated using Distance software and bird-habitat associations were analysed using Canonical Correspondence Analysis (CCA). Moreover, the impact of brownfield site development on winter bird density from 2000 to 2009 in Greater Manchester was explored using the bird density estimates, and historical image function in Google Earth. In brownfield sites, Pica pica had the highest density estimate (142 per km2), although four species had estimated densities > 100 per km2 (Turdus merula; Cyanistes caeruleus; Passer domesticus; Aegithalos caudatus). The CCA indicated that Aegithalos caudatus, Cyanistes caeruleus, Parus major, Prunella modularis were associated with Fagus sylvatica, Betula pendula, and Buddleja davidii on brownfield sites, which during the winter 1) produce seeds 2) support overwintering insects, providing a valuable food source. Nevertheless, across land-uses, most species favoured green space and pre-2000 housing. Brownfield sites were most replaced between 2000 and 2009, with 17.8 km2, 14.9 km2, and 12 km2 replaced by commercial, industrial, and post-2000 housing respectively. This is likely to have had a negative impact on the winter density of most bird species, owing to 1) the removal of brownfield site vegetation 2) increases in impervious land cover. Future declines in winter bird abundance could be mitigated by retaining brownfield site vegetation and setting aside brownfield sites in close proximity to green space and pre-2000 housing.

Habitat associations of landbirds in southern Texas during migration

It is estimated that about 80% of North American avian migrants travel along the southern coast of Texas. Quality of stopover habitat for landbirds in southern Texas is a concern, however, due to agricultural and wind energy development and increasing urbanization. Since little regional research has been conducted on stopover habitat use, we investigated habitat associations of migratory birds to identify important factors driving density along the southern Texas coast. We did this using data from landbird surveys, which took place during spring and autumn migrations from 1991 to 1993 and 2006 to 2008, within 6 land-cover types common in southern Texas. We found that oak motte had the highest density among most bird guilds. A total of 125 species of birds were detected over the course of our study and species richness was highest in oak motte and lowest in grassland. In general, land-cover types with more woody vegetation cover tended to have higher species richness and diversity than those with minimal to no woody vegetation. Although grassland ranked lowest in other metrics of bird use, it ranked highest in habitat conservation value, which accounts for species of concern. At the time of this study, Golden-winged Warbler (Vermivora chrysoptera) was the only species on Partners in Flight's Red Watch List (highly vulnerable and in need of special attention) that we observed, with recorded observations occurring in oak motte and woodland exclusively. Oak mottes are likely a prime location for species to land after flying over the Gulf of Mexico during their journey north to their breeding grounds, thus land managers that wish to provide high-quality stopover sites for migratory landbirds should preserve them.

Secretive marsh bird habitat associations in the Mississippi Flyway: a meta-analysis

Secretive marsh bird habitat associations in the Mississippi Flyway: a meta-analysis

Distance truncation via sound level for bioacoustic surveys in patchy habitat

ABSTRACT Bioacoustic recordings are often used to conduct auditory surveys, in which human listeners identify vocalising animals on recordings. In these surveys, animals are typically counted regardless of their distance from the survey point. When these surveys are carried out in patchy habitat or near edges, detected individuals may frequently occur in a different land-cover type than the survey point itself, which introduces uncertainty regarding species-habitat associations. We propose a method to restrict detections from single microphones to within a pre-specified survey radius. The method uses logistic regression to select a sound level threshold corresponding to the desired distance threshold. We applied this method to acoustic data from the centre of 21 1-ha oil wellsites in northern Alberta. To compare our approach with the results from auditory surveys from the same locations, we used sound localisation to locate birds detected via both methods. Just 22.4% of birds detected on auditory surveys fell within the desired survey area. Using our distance-truncation method, 96% of detections were within the desired survey area. We propose that distance truncation via sound level will be useful for surveys of patchily distributed habitat, or when greater certainty about bird locations or habitat associations is desired.

Phenology, variation in habitat use, and daily activity patterns of Eleonora’s falcon overwintering in Madagascar

The vast majority of the global population of Eleonora’s falcon overwinters in Madagascar, where the natural environment is threatened by human-induced habitat changes, particularly intensive forest degradation. We described Eleonora’s falcon phenology and habitat use based on fine-scale telemetry data and field surveys, and investigated which environmental parameters shape the observed patterns, to obtain a better insight into the species’ ecological requirements during the wintering season. We used high resolution GPS telemetry and remotely sensed data to establish bird–habitat associations and investigate spatiotemporal activity. We also verified habitat composition through ground surveys. Eleonora’s falcon exploits a variety of habitats, exhibiting a distinct phenological pattern in their use. The species exhibits high site fidelity, moving progressively from more open areas towards landscapes with denser tree cover, possibly as a response to spatiotemporal patterns in food abundance. Time budget analysis revealed that Eleonora’s falcon dedicates just about 15% of its daily activity to foraging, which is performed almost exclusively during daylight hours, with a greater tendency to forage at higher elevations with denser tree cover. On-site assessment of habitat composition revealed that existing habitat maps overlook small fragments of habitat and land use. However, the species’ overall preference for humid forest suggests ongoing deforestation would adversely affect the availability of preferred habitat. Our findings suggest that GPS logger technology, when combined with ground surveys, can enhance our understanding of long-distance migratory bird species’ ecology at finer and more ecologically relevant scales.

Bird Communities of Two Forest Types in Chitwan Valley, Nepal

Maintaining biological diversity is an important objective at Chitwan National Park (CNP), the most visited national park in Nepal. Given human uses and manipulations of forests both in and around CNP, developing forest management guidelines that can both support human use of trees and sustain the biological diversity of the forests is a high priority. In February 2009 we measured bird communities with point counts, woodpecker abundance with playback, and collected vegetation data in Sal Shorea robusta and riverine forests in CHP and a nearby community forest to provide basic data on bird-habitat associations with an emphasis on woodpeckers. Riverine forest had over twice the density of trees per ha (many small trees), higher tree species richness, and greater basal area than Sal forest. Sal forest had more large trees than riverine forest. We detected 71 bird species during the point counts in the study forests, 18 more during playback sessions, and an additional 12 species that were more associated with adjacent habitats (e.g., wetlands or flying overhead) for a total of 101 species. Among resident species, 31% were primary or secondary tree-cavity nesters. On average for point counts, we detected 29.5 bird species (2.2 woodpeckers) on transects located in riverine forest and 23.3 bird species (1.8 woodpeckers) in Sal forests, but the difference was not statistically significant. While riverine forest had several commonly occurring species not detected in Sal forest, the opposite was not the case. The regression of woodpecker species richness against large tree density in both Sal and riverine forests was positive, but not statistically significant. As a method of sampling woodpeckers, playback resulted in approximately twice the number of individuals and species compared to detection from point counts.

Secretive Marsh Bird Densities and Habitat Associations in the Prairie Pothole Region

After centuries of wetland modification, wetland-dependent wildlife are of high conservation concern. Particularly important are secretive marsh birds, a cryptic and understudied guild of wetland-dependent birds, many of which have experienced population declines concurrent with anthropogenic modification of wetlands. We used point-based sampling to investigate densities and habitat associations of secretive marsh birds at multiple spatial scales in the Prairie Pothole Region of North Dakota. We focused on five species for modeling. The most abundant species was Virginia Rail (Rallus limicola; 0.20 individual-ha SE = 0.04), followed by Sora (Porzana carolina; 0.13 individual-ha SE = 0.02), American Coot (Fulica americana; 0.08 individual-ha SE = 0.02), American Bittern (Botaurus lentiginosis; 0.07 individual-ha SE = 0.03), and Pied-billed Grebe (Podilymbus podiceps; 0.06 individual-ha SE = 0.01). Densities of all species were best explained by multi-scale models. Despite a few commonalities, secretive marsh birds have diverse habitat requirements and models suggest species-specific wetland complex management will likely be most effective. This information provides a baseline for species with previously unknown densities and informs conservation actions and policy for secretive marsh birds in the northern Great Plains.

Birds Wintering in Heterogeneous Farmland of Poland: Weather-Dependent Temporal Changes in Abundance and Habitat Associations

Bird communities wintering in the mosaic-like farming landscapes of SW Poland were studied to assess drivers of intra-seasonal changes in numbers and habitat associations of birds. During two severe winters (November–March) the complete area search method was applied to count birds and link their occurrence with weather and habitat in six plots (320 ha in total). A modelling approach was used to test birds' responses to environmental factors at community and species levels. These farmlands were inhabited by diverse and dense populations of wintering birds, including a significant proportion of species of conservation concern. Bird numbers revealed decreasing trends, with winter- and species-specific fluctuations, affected in particular by snow cover. The lowest population indices were recorded in mid-winter (February) and remained low until mid-March. Field margins (6.6% of the total area) supported 35.6% of individuals and 55.0% of flocks. The preference for field margins over other farmland habitats was particularly prominent during severe weather conditions. Our results suggest that during severe winters, complex farmlands are important areas for birds, enhancing their known importance to breeding birds. Intense snowfall in mid-winter rather than temperature drops lead to immediate population declines, aggravating the effects of natural food depletion. Adverse weather keeps populations at low levels until mid-March, despite the influx of spring migrants. Behavioural adjustments to winter conditions elicit the characteristic habitat distribution of birds, exposing the crucial importance of non-cropped landscape elements. In particular, the variety of field margins significantly contributes to the persistence of internationally important populations of farmland birds in Poland.

Effects of development of wind energy and associated changes in land use on bird densities in upland areas.

Wind energy development is the most recent of many pressures on upland bird communities and their habitats. Studies of birds in relation to wind energy development have focused on effects of direct mortality, but the importance of indirect effects (e.g., displacement, habitat loss) on avian community diversity and stability is increasingly being recognized. We used a control-impact study in combination with a gradient design to assess the effects of wind farms on upland bird densities and on bird species grouped by habitat association (forest and open-habitat species). We conducted 506 point count surveys at 12 wind-farm and 12 control sites in Ireland during 2 breeding seasons (2012 and 2013). Total bird densities were lower at wind farms than at control sites, and the greatest differences occurred close to turbines. Densities of forest species were significantly lower within 100 m of turbines than at greater distances, and this difference was mediated by habitat modifications associated with wind-farm development. In particular, reductions in forest cover adjacent to turbines was linked to the observed decrease in densities of forest species. Open-habitat species' densities were lower at wind farms but were not related to distance from turbines and were negatively related to size of the wind farm. This suggests that, for these species, wind-farm effects may occur at a landscape scale. Our findings indicate that the scale and intensity of the displacement effects of wind farms on upland birds depends on bird species' habitat associations and that the observed effects are mediated by changes in land use associated with wind-farm construction. This highlights the importance of construction effects and siting of turbines, tracks, and other infrastructure in understanding the impacts of wind farms on biodiversity.

Influences of spatial variation in vegetation on avian richness and abundance vary by season in the Chihuahuan Desert

Changes in the structure, composition, and distribution of desert vegetation have resulted in altered desert bird communities. One of the most well-known influences on bird diversity and abundance in these ecosystems is the degree of woody shrub dominance. While the influence of vegetation structure and composition gradients on Chihuahuan Desert bird communities of North America has received valuable attention, seasonal variation in these influences is poorly understood. Our goal was to understand how vegetation gradients across space influence bird communities over four seasonal periods. We employed three years of avian survey data and static, spatial vegetation data in generalized linear mixed-effects models, identifying effects of (1) shrub cover in predicting shrubland bird species richness and abundance, (2) grass cover in predicting grassland bird abundance, and (3) grass height in predicting grassland and shrubland species richness and abundance. Effect sizes varied by season, with grass heights exhibiting (1) greatest positive effects on grassland species in the breeding season and (2) greatest negative effects on shrubland species in the winter. In targeting management for birds of the Chihuahuan Desert and other arid regions, managers should consider both bird-habitat associations and the variation in these relationships between seasons.

Temporal and Spatial Scales Matter: Circannual Habitat Selection by Bird Communities in Vineyards.

Vineyards are likely to be regionally important for wildlife, but we lack biodiversity studies in this agroecosystem which is undergoing a rapid management revolution. As vine cultivation is restricted to arid and warm climatic regions, biodiversity-friendly management would promote species typical of southern biomes. Vineyards are often intensively cultivated, mostly surrounded by few natural features and offering a fairly mineral appearance with little ground vegetation cover. Ground vegetation cover and composition may further strongly vary with respect to season, influencing patterns of habitat selection by ecological communities. We investigated season-specific bird-habitat associations to highlight the importance of semi-natural habitat features and vineyard ground vegetation cover throughout the year. Given that avian habitat selection varies according to taxa, guilds and spatial scale, we modelled bird-habitat associations in all months at two spatial scales using mixed effects regression models. At the landscape scale, birds were recorded along 10 1-km long transects in Southwestern Switzerland (February 2014 –January 2015). At the field scale, we compared the characteristics of visited and unvisited vineyard fields (hereafter called parcels). Bird abundance in vineyards tripled in winter compared to summer. Vineyards surrounded by a greater amount of hedges and small woods harboured higher bird abundance, species richness and diversity, especially during the winter season. Regarding ground vegetation, birds showed a season-specific habitat selection pattern, notably a marked preference for ground-vegetated parcels in winter and for intermediate vegetation cover in spring and summer. These season-specific preferences might be related to species-specific life histories: more insectivorous, ground-foraging species occur during the breeding season whereas granivores predominate in winter. These results highlight the importance of investigating habitat selection at different spatial scales and all along the annual cycle in order to draw practical, season-specific management recommendations for promoting avian biodiversity in farmland.

The importance of various stages of succession in preservation of biodiversity among riparian birds in northern Iran.

Every stage of succession may provide certain species with habitat requirements which are impossible in other stages of succession. This study attempts to evaluate the different stages of succession in terms of composition and structure of bird populations in Hyrcanian forests. Bird-habitat relationships were investigated by comparing vegetation characteristics in three successional stages including late, initial stage, and urban areas. Bird richness, diversity, and abundance were measured within a 25-m radius of each of the 120 sampling points in various stages of succession and urban areas from May to April (2014) in the Ziarat catchment. This study indicated that every stage of succession may support certain species. Based on bird-habitat associations along the various stages of succession, two groups were distinguished. Conventional comparative analysis separated two groups of understory birds: interior specialists and edge specialists. The interior-specialist group was positively correlated with the number of dead trees, tall trees with high values of dbh and height and canopy cover. In contrast, edge specialists groups mainly included terrestrial insectivores and were positively correlated with open area and shrub cover, and percentage of shrub cover between 1 and 2m in height. In summary, bird communities in Hyrcanian forests are highly dynamic in different vegetation covers suggesting that it is critical to increase diverse and abundant bird populations by conserving forests composed of mosaics of differently disturbed stands and mature forest patches.

Time trumps habitat in the dynamics of an avian community

AbstractPredictions of change in avian biodiversity often fail to account for the natural dynamism of species assemblages. Information from historical datasets can be useful indicators of how avian communities may change in the future. However, simple comparisons of diversity and abundances over time may overlook additional changes in bird–habitat associations. In 2013, we revisited sites from a unique, highly detailed avian survey from the Willamette Valley, Oregon, conducted in 1952. Our objectives were to quantify and describe the extent of avian community change; relate observed species assemblages to changes in vegetation type and land‐use class; and identify species with specific associations to either survey era. Using nonparametric ordination, we assessed whether the distribution of the avian community within the environmental space varied temporally. We used blocked indicator species analysis to identify species with specific association to historical or modern survey eras. Nonparametric permutation procedures identified both plot, each representing a different major habitat type, and year as significant factors defining communities. Year was more strongly related to the second ordination axis than the other environmental variables examined. Ordination of survey sites in species space confirmed modern avian communities were significantly different from their historical counterparts. Bird species richness increased and community composition changed by at least 50% despite the physiognomic characteristics of each plot's habitat and the surrounding landscape remaining comparatively stable. Because of this, we conclude time trumped, or was more strongly associated with community change, than alterations in physiognomic habitat. These results suggest avian communities are naturally dynamic even in areas with relatively stable habitat conditions. Predictions that only address changes in climate, land use, or vegetation cover type may fail to predict changes in avian community composition. Historical datasets are a valuable means of understanding real‐world changes in avian communities. We suggest additional factors, such as vegetation structure and microhabitat, may predict fine‐scale shifts in avian species assemblages. Nevertheless, major changes in community composition occurred with apparently minor shifts in physiognomic habitat characteristics in our study area.

Habitat associations of birds at Mara Naboisho Conservancy, Kenya

Habitat associations of birds were quantified through fixed-radius timed bird counts at Mara Naboisho Conservancy within the Greater Mara Region, Kenya. We conducted 73 timed counts in four distinct habitats (riparian, woodland, rocky outcrop and plains) in both dry and wet seasons. During this survey, we observed 188 species of birds of which 140 were recorded during the timed counts. The riparian zone had the highest species richness, more than three times that of the plains. The woodlands and rocky outcrops had similar species richness. The mean number of species seen per count was higher in the riparian zone compared with the other three habitats. Bird species composition in the riparian zone and the plains were distinct from each other and from the woodlands and rocky outcrops, although they overlapped significantly in the last two mentioned habitats. The possible conservation implication of an increasing and/or immigrant elephant population and its likely effect on the vegetation is discussed in relation to bird community composition.