Bird Density Research Articles

Should topographic metrics be considered when predicting species density of birds on a large geographical scale? A case of Random Forest approach

Species Distribution Modelling (SDM) is a group of statistical tools that describe species distribution in environmental gradients in order to create their predictive distribution. However, due to the complexity of factors that influence the occurrence or density of species these methods’ effectiveness is still debatable. That is why we decided to explore how topographic metrics, such as altitude, slope, roughness and aspect, would affect the density of farmland (Icterine warbler) and forest (Eurasian golden oriole) bird species. We generated two sets of SDMs for each of the two bird species: One set of models contained topographic metrics as a predictor variable, and the other did not. Out-of-back procedures in the Random Forest approach and evaluation models based on independent dataset scores showed that omitting topographic metrics as predictors resulted in a substantial reduction of model performance for both lowland and upland bird species. Further analysis of predictive maps revealed that neglecting topographic metrics resulted in large over-predictions of species’ densities in regions where these species were rare. Importantly, our results also support the notion that detailed topographic metrics can be considered as a surrogate for elusive climatic factors and the habitat’s condition. Hence, the study emphasises that the process of selecting predictor variables, especially topographic metrics, is one of key elements in developing Species Distribution Models for birds, even for those species which are not directly dependant on the topographic metrics.

Effect of forest composition on bird species abundance in tropical dry deciduous forest: A case of Bhimbandh Wildlife Sanctuary, India

Abstract. Khan MS. 2017. Effect of forest composition on bird species abundance in tropical dry deciduous forest: A case of Bhimbandh Wildlife Sanctuary, India. Biodiversitas 18: 78-85. The tropical dry deciduous forest (TDDF) with 38.2% of total forest cover in India forms the largest forest type of India. TDDF have been managed for centuries in the Indian subcontinent. However, so far it is not clear how different forest compositions and structures influence the abundance and the distribution patterns of faunal species vice versa. To provide further insights in this respect, we analysed how different habitat variables influence the abundance and diversity of forest birds. The difference in relative species abundances and habitat separation between forest specialist and generalist birds was also investigated. Different classes of bird density were discriminated with habitat variables. In general, it was found that higher bird densities were concentrated in the lower tree and shrub densities and diversities, however, high grass density and diversity with low tree density and diversity favoured the overall high bird density. Results further indicate the positive association of relative density of specialist bird species with the high grass density and diversity and low tree density and diversity. Specialists occurred in the lower relative densities (0.75±0.68) than that of generalists (0.86±0.69) and were found restricted to dense, pristine woody forest patches with high tree diversity.
 Keywords: Bhimbandh Wildlife Sanctuary, birds, Forest Composition, India, Tropical Dry Deciduous Forest

Sound attenuation in forest and roadside environments: Implications for avian point-count surveys

ABSTRACT Point counts are one of the most common ways of collecting data to determine the relative abundance of birds. Many studies and monitoring programs, including the North American Breeding Bird Survey, use relative differences in counts of birds to assess changes in abundance over time and space. Many factors influence whether relative differences in counts of birds between various environmental conditions are reflective of actual differences in bird density. A major assumption of relative abundance is that birds with different song frequencies and amplitudes are heard at the same distances in different environmental conditions. We compared sound transmission in forest habitats and along low-use forestry roads, and calculated detection radius for different species to test the assumption that differences in bird counts between forest interior and roadside locations reflect actual differences in bird abundance. A playback–recording experiment was used to broadcast sounds through forest interior, along...

Month-to-Month Variations in Densities and Dominance of Birds Breeding in an Extensive Pine Forest

Abstract Month-to-month changes in avian assembages are considerable in forest habitats. In this study such changes were studied by means of the line transect method (eight transect with total length of 77.7 km) in lowland coniferous forest in SW Poland (dominant forest type in Central European Plain), in three consecutive spring months: April, May and June. Shannon’s diversity index varied between 1.31 and 2.25 in particular month, while Simpson’s diversity index and Pielou’s evenness index were almost identical everywhere: H′ = 0.92-0.93 and J′ = 0.74-0.78, respectively. In overall, the differences in mean densities of breeding species between three months on all transects pooled were not statistically significant, as were also not statistically significant such differences on particular transects. Month-to-month variations in densities in all transects pooled were statistically significant in the case of 26 out of 54 species (48.1 %). Month-to-month changes in population densities recorded on transects, only partly conform to the arrival patterns. Two counts, instead of three, would sufficed for precise estimation of bird population densities in Central European lowland pine forests: one count should be conducted in April, to register mainly resident species, and the second one in May to count mainly the migrant species.

A phylogenetic comparative analysis reveals correlations between body feather structure and habitat

SummaryBody feathers ensure both waterproofing and insulation in waterbirds, but how natural variation in the morphological properties of these appendages relates to environmental constraints remains largely unexplored. Here, we test how habitat and thermal condition affect the morphology of body feathers, using a phylogenetic comparative analysis of five structural traits [i.e., total feather length, the lengths of the pennaceous (distal) and plumulaceous (proximal) sections, barb density, and pennaceous barbule density] from a sample of 194 European bird species.Body feather total length is shorter in aquatic than in terrestrial birds, and this difference between groups is due to the shorter plumulaceous feather section in aquatic birds. Indeed, a reduced plumulaceous section in feather length probably reflects the need to limit air trapped in the plumage to adjust the buoyancy of aquatic birds. In contrast, the high pennaceous barbule density of aquatic birds compared to their terrestrial counterparts reflects water resistance of the plumage in contact with water.Our results show that birds living in environments with low ambient temperature have long plumulaceous feather lengths, low barb density, and low pennaceous barbule density. Data also suggest that plumage probably has limited function in reducing the heat absorption of species living in hot environments.Our results have broad implications for understanding the suite of selection pressures driving the evolution of body feather functional morphology. It remains to be tested, however, how other feather traits, such as the density of plumage (feathers per unit area) and the relative number of different feather types, for example downy feathers, are distributed amongst birds with different water resistance and thermoinsulative needs.Alay summaryis available for this article.

Impact on Base Population Density and Hunter Performance of Stocking with Pen-Raised Bobwhite

In 1962, the Kansas Fish and Game Commission initiated an investigation to determine the effect of semiannual releases of pen-raised bobwhite quail (Colinus virginianus) on population densities of native wild quail populations, on availability of birds to hunters, and on hunter success.Stocking during spring resulted in 7% fewer birds in the fall population on the stocked area than on the control area. Stocking during fall resulted in 14% more birds, at the time hunting season began, on the stocked area than on the control area. Neither of these differences were statistically significant, and it is concluded that there was no significant difference attributable to stocking between population densities of stocked and control areas. On the stocked area, however, there was a significant net increase of 25% in population density between the fall census period and the preseason census period. It is concluded that the density-depressing influence of spring stocking combined with the density-elevating influence of fall stocking, on the stocked area, produced a significant increase, attributable to stocking, between the population density preceding fall release and the population density preceding the hunting season. It is further concluded that in the comparison of preseason population densities for the treatment and control areas, the depressing effect of spring stocking and the elevating effect of fall stocking resulted in a treatment-area population that was significantly larger than that found on the unstacked control area.Some pen-raised birds established themselves as a part of the population on the stocked area, but there was not a proportional increase in population density. There were fewer native quail on the area when treated with semiannual stocking than when under control condition. The difference in density of native birds between stocked and control areas was not statistically significant. Stocking significantly increased hunter success by 30% and 35% on areas in Cherokee and Linn Counties, respectively, but the number of coveys flushed per hour was not significantly increased by stocking pen-raised quail.

Matrix type affects movement behavior of a Neotropical understory forest bird

Fragmentation alters landscape structure and its relationship with organisms, where movement is one of the most affected processes. Movement choices are influenced by a cost and benefit evaluation, associated particularly to risks of predation and access to new resources. We analyzed the effect of matrix type on matrix-transfer success of a bird, Pyriglena leucoptera. We used a translocation-monitoring approach and evaluated time and trajectories used to reach an adjacent forest patch when released inside the matrix. The risk of predation was estimated by quantifying the density of birds of prey in three matrices (pastures, cornfields, and Eucalyptus) with different degrees of exposure given by differences in their vegetation structure. This variation was perceived by individuals, as evidenced by changes in their movement patterns and differences in their matrix-transfer success. The Eucalyptus, a low-risk matrix with the lowest density of predators and with more resources and shelters, resulted in tortuous movements by translocated birds. The pasture, an intermediate-risk with a wide visual field, resulted in straight and fast movements. The cornfields, a high-risk matrix with the highest density of predators and an increased obstruction of the visual field (when compared with pastures), resulted in more tortuous movements and longer exposure to risk, and thus in lower successful arrivals to forest patches. Our results highlight the importance of quantifying the effects of matrix type on movement behavior and on the persistence of species in fragmented landscapes. The proper management of matrices appears as a cost-effective option for improving connectivity in modified landscapes.

Avian Assemblages at Paya Indah Natural Wetland Reserve, Malaysia

Estimating accurate avian assemblages such as density and diversity are key factors for the conservation and management of birds and their habitats. Avian assemblages based on status in five habitats at Paya Indah Natural Wetland Reserve were determined using the distance sampling, point count method, at 121 count stations. A total of 100 bird species (64 resident, 18 migratory, 16 resident-migratory and 2 vagrant bird species) were detected from November 2012 to January 2014. The highest bird density was recorded for resident birds (72.2 ± 3.8 bird’s ha-1) and the lowest for vagrant birds (0.1 ± 0.1 birds ha-1). In which Resident birds have significantly higher density, species diversity, richness and evenness compared to resident-migrant and migratory birds.

Diversity and Abundance of Avian Species of Owena Multipurpose Dam, Ondo State, Southwest, Nigeria

The use of wetlands and their resources is widespread among many diverse bird taxa of the world. The diversity and abundance of avian species in Owena Multipurpose dam was assessed out between January and June, 2016 to provide baseline information of the birds in this area. The line transects method with lengths ranging from 350 m-1000 m was adopted for the survey. Birds recorded were categorized into order, family, species, migratory status and feeding guild. Relative abundance of bird species and diversity indices were determined. Significance in mean bird density in the two seasons was determined using T-test while One-Way ANOVA was used to test for significance in bird diversity indices. A total of 35 bird species belonging to 20 families and 10 orders were recorded in the study area. The common species includes Ardea alba, Vanellus spinosus, Ardea cinerea, Phalacrocorax carbo, Milvus migrans, Ardeola ralloides, Actophilornis africanus, Microcarbo africanus, and Bubulcus ibis. All the bird species recorded were in the Least Concern (LC) category. The bird species were categorized into seven feeding guilds. The granivores, insectivores and canivores were more in abundance than the nectarivores and frugivores. The order Passeriformes had the highest families (9) and species (17), followed by Pelecaniformes and Charadriiformes with 2 families each, 4 and 2 species respectively while others had one family each. The total mean number of bird was 428 ± 5.75/ observation. Lagonosticta sanguinodorsalis had the highest mean number (156.4/ observation) and relative abundance of 36.54% while Ardae cinerea and Phalacrocorax carbo had the lowest mean number (0.2/ observation) and relative abundance of 0.05% each. Transect 1 had the highest Shannon diversity index (Hl=1.664), while transect 3 had the least (1.168). All the transects had similar species evenness index except for transect 4. The findings can be attributed to the heterogeneity of the habitat resulting from alteration of the ecosystem through the construction of the dam. In conclusion, the Owena dam construction has both negative and positive impacts on avian species composition and abundance. The management programme of the Owena dam should incorporate avian conservation in the area.

Eco-biology and conservation of potential insectivorous birds in the arable biomes of central Punjab

The present study was conducted to investigate the eco-biology of insect predator avian species and the effects of environmental factors on the eco-biology and bird populations in Punjab, Pakistan. Data on ecology and other aspects of bank myna was collected from three districts of Central Punjab including Faisalabad (an industrial area with large effects of heavy metals by usage of sewage water of industries in irrigation & pesticides), Sargodha (with medium level of industries & pesticides use) and Mandi Bahauddin (no industry and low use of pesticide). Specimens were collected to observe gut contents. Gut contents were analyzed to account for the prey and feeding niche. Major insect pests of crops were identified and listed from gut contents. Relative population density of useful birds was assessed and continuously monitored for population trends around the year. Breeding ecology of both predacious birds was studied to evaluate breeding success, mortality rate and to weigh up the effects of pesticides used and pollution. Breeding ecology, population dynamics and gut contents analysis were significantly (P ≤ 0.001; R2 ≥ 0.75) influenced by the use of pesticides. It was concluded that use of pesticides without studying their toxic effects is detrimental to these predacious birds. Blind sprays should be prohibited and alternatives should be adopted to conserve the predacious birds in order to achieve effective biological control. Keywords: Predacious birds; Eco-biology; Population dynamics http://dx.doi.org/10.19045/bspab.2016.50150

Small territory sizes and high densities of insectivorous birds in an Atlantic Forest secondary fragment, Brazil

Demographic parameters of birds are essential to understand their ecology and delineate conservation and management plans. This becomes especially important in highly altered biomes such as the Brazilian Atlantic Forest, since the few remaining fragments bear mostly secondary forests where demographic parameters might differ from old-growth forests. Few studies about territory sizes and density have been conducted for entire bird communities or groups of species in the Neotropical region, with a bias towards Central America and the Amazon. In this work we determined territories of Atlantic Forest birds in order to assess their size and density. We conducted spot-mapping in a rectangular 40-ha plot within a 384-ha of secondary semideciduous forest fragment in Vicosa region, state of Minas Gerais, Brazil. We identified 260 territories of 30 species of insectivorous birds. Mean territory size of all species was 2.4 ha, ranging from 0.5 to 7.5 ha. The mean density for all species was 21.7 pairs/100 ha, ranging from 2.5 to 72.5 pairs. The sizes of the territories of many Atlantic Forest birds were by far smaller, and the density higher, than those of conspecific or congeneric species from Amazonian or Central American forests. These geographical differences in territory size and density can be explained by at least two non-exclusive hypotheses: 1) higher primary and secondary productivity in advanced successional secondary forest fragments and; 2) density compensation, given the loss of other competitor species.

Habitat type, food resources, noise and light pollution explain the species composition, abundance and stability of a winter bird assemblage in an urban environment

At present, urban areas cover almost 3% of the Earth’s terrestrial area, and this proportion is constantly increasing. Although urbanization leads to a decline in biodiversity, at the same time it creates extensive habitats that are exploited by an assemblage of organisms, including birds. The species composition and density of birds nesting in towns and cities are determined by the types of buildings, the structure and maturity of urban greenery, and habitat diversity. In contrast, the habitat traits shaping the community of birds wintering in urban areas are not known. The aim of this work was to assess the influence of habitat structure, food resources and the urban effects (pollution, noise, artificial light) on an assemblage of birds overwintering in an urban area. It was carried out in 2014 and 2015 in the city of Kraków (southern Poland), on 56 randomly chosen sample plots, in which the composition, density and interseasonal similarity of bird assemblage were assessed with line transect method. A total of 64 bird species (mean = 17.7 ± 4.9 SD species/plot) was recorded. The mean density was 89.6 ind./km ±63.3 SD. The most numerous species were Great Tit Parus major, Magpie Pica pica, Blackbird Turdus merula, Blue Tit Cyanistes caeruleus, Rook Corvus frugilegus, Fieldfare Turdus pilaris and House Sparrow Passer domesticus. Noise adversely affected species numbers and density, but artificial light acted positively on the density of birds and their interseasonal stability. The species richness and density of birds were also determined by the number of food sources available (e.g. bird-feeders). In addition, the greater the proportion of open areas, the fewer species were recorded. In contrast, the more urban greenery there was, the greater the density of the entire bird assemblage. Urban infrastructure (buildings, roads, refuse tips) had a positive effect on the interseasonal stabilization of the species composition of wintering birds. The results of this work indicate that the urban effect, i.e. noise and light pollution, apart from purely habitat factors, provide a good explanation for the species richness, density and stability of bird assemblage wintering in urban areas.

How well do bird atlas reporting rates reflect bird densities? Correlates of detection from the Fynbos biome, South Africa, with applications for population estimation

Relationships between true population densities and reporting indices from atlas data are important for the calculation of population sizes, though these relationships are remarkably little-known and likely confounded by issues of detection. We examine issues of detection for a single-observer point-count survey across the Fynbos biome in South Africa. We created an index of relative abundance comparable to atlas reporting rate and calculated detection coefficients for each species. We explore various models that explain relative abundance as a function of detection covariates, e.g. mass, colour, group size, vocal behaviour and density. Density was consistently included across models and the best predictor when used alone in a validation exercise. We then calculated mean reporting rates for the citizen science South African Bird Atlas Project2 (SABAP2). A model of species’ reporting rates as determined by density for this set of birds suggested the correlation between atlas reporting rates and density estimates was weak, with species capable of using modified habitats exhibiting higher reporting rates than expected from the density estimates. There was a positive correlation between bird density and reporting rates corrected for by species mass. We used this relationship to calculate densities for the Fynbos bird species and compare results to published data.

Woodland reduction and long‐term change in breeding bird communities

ABSTRACTForested ecosystems in the western United States have been the focus of tree reduction efforts for decades, with the intent of improving forage for livestock and wildlife. Yet, the long‐term consequences of tree removal for biodiversity are virtually unknown. We conducted bird and vegetation surveys in northwestern Colorado where trees were mechanically removed over 40 years ago. We evaluated differences in avian species richness and community composition, and used a Bayesian hierarchical approach to determine if tree removal had long‐term effects on bird density. We found that tree reduction initiates a long‐term change from dense pinyon (Pinus edulis)‐juniper (Juniperus osteosperma) woodlands to sagebrush scrub, fundamentally altering bird community composition. Disturbed sites were used by fewer species and largely dominated by shrubland‐obligate birds. Further, bird densities were markedly different between historically disturbed sites and reference sites. Densities of many species were correlated with specific vegetative characteristics (e.g., mean tree diameter) that could be factored into management decisions to better sustain diverse natural communities. © 2016 The Wildlife Society.

Concentrating or scattering management in agricultural landscapes: Examining the effectiveness and efficiency of conservation measures

A key issue in conservation is where and how much management should be implemented to obtain optimal biodiversity benefits. Cost-effective conservation requires knowledge on whether biodiversity benefits are higher when management is concentrated in a few core areas or scattered across the landscape, and how these effects vary between species. To address these questions, we examined species-specific behavioural responses of over-wintering farmland birds to enhanced seed availability. In a two-year experiment we first examined the relationship between landscape-scale seed availability and farmland bird density. Then we investigated the relative resource delivery (difference in bird densities between landscapes with and without additional management) and the efficiency (number of individuals supported per unit management) of conservation actions, both at the landscape-scale (ca 100ha) and at the scale of the conservation measures (3.6ha). The conservation actions were targeted towards ten seed-eating farmland bird species, but we also considered the responses of seven non-targeted and more generalist seed-eating species, seven species that are less dependent on seeds and three species of birds of prey. We found a positive relationship between bird density and landscape-scale seed availability for eleven species and, for four of these species, the slope of this relationship changed before and after a threshold seed density. For two seed-eating specialists, the number of individuals using conservation patches declined with landscape-scale seed availability. In addition, we found that the relative resource delivery declined with landscape scale seed availability for three seed-eating specialists and was independent of landscape-scale seed availability in four other species. Our results suggest that farmland specialists may benefit most from winter food additions if conservation actions result in high landscape-scale seed availability. This may be achieved by concentrating conservation measures or by establishing measures in areas with high baseline seed availability. By contrast, species that can utilize a wider range of habitats and resources may benefit more from scattering measures across larger areas. Therefore, optimal management for the full range of farmland birds in wintertime may require a combination of core areas with concentrated management and more widely distributed smaller patches of conservation measures.

On-farm starling populations and other environmental and management factors associated with the presence of cefotaxime and ciprofloxacin resistant E. coli among dairy cattle in Ohio

Wild birds that forage around livestock facilities have been implicated as vectors of antimicrobial resistant organisms. Although antimicrobial resistant bacteria have been isolated from European starlings (Sturnus vulgaris), their role in the dissemination of antimicrobial resistant elements in livestock facilities needs further investigation. To determine whether on-farm starling density and other factors were associated with the presence of cefotaxime and ciprofloxacin resistant E. coli among dairy cows in Ohio, bovine fecal pats from 150 farms were tested for the presence of cefotaxime and ciprofloxacin resistant E. coli. Each farm was visited twice (during the summer and fall of 2007–2009). Multi-level logistic regression models with a random intercept to account for fecal pats collected within a specific visit to a farm were used to assess the associations. The percentage of samples with cefotaxime and ciprofloxacin resistant E. coli was 13.4% and 13.6%, respectively. The percentage of farms having at least one sample testing positive for cefotaxime and ciprofloxacin resistant E. coli was 56.7% and 48.7%, respectively. The odds of detecting cefotaxime and ciprofloxacin resistant E. coli in the samples was significantly higher in 2007 compared to 2008 and 2009, in fall compared to summer, and from farms closer than 60km to starling night roost sites compared to the farms further than 60km. The presence of starlings during the day had a negative association with the likelihood of detecting cefotaxime resistant E. coli. Presence of calves also had a negative association with the likelihood of detecting both cefotaxime and ciprofloxacin resistant E. coli. European starlings might play a role in the dissemination of antimicrobial resistant agents in livestock facilities related to their daily population movements rather than the specific density of birds on farm during the day.

Biodiversity and food web indicators of community recovery in intertidal shellfish reefs

In conservation strategies of marine ecosystems, priority is given to habitat-structuring foundation species (e.g. seagrasses, mangroves and reef-building corals, shellfish) with the implicit goal to protect or restore associated communities and their interactions. However, the number and accuracy of community level metrics to measure the success of these strategies are limited. Using intertidal shellfish reefs as a model, we tested to what extent foundation species alter community and food web structure, and explored whether basic metrics of food web structure are useful indicators of ecosystem complexity compared to other often-used indices. We found that shellfish reefs strongly modified community and food web structure by modifying habitat conditions (e.g. hydrodynamics, sediment grain size). Stable isotope-based food web reconstruction captured important differences between communities from bare mudflat and shellfish reefs that did not emerge from classic abundance or diversity measures. On shellfish reefs, link density and the number of top predators were consistently higher, while both connectance and the richness of intermediate species was lower. Species richness (+42%), species density (+79%) and total biomass of benthos, fish and birds (+41%) was also higher on shellfish reefs, but this did not affect the Shannon diversity or Evenness. Hence, our results showed that basic food web metrics such as link density and number of top consumers and intermediate species combined with traditional measures of species richness can provide a robust tool to measure conservation and restoration success. We therefore suggest that these metrics are included as Essential Biodiversity Variables (EBV), and implemented as ecosystem health indicators in legislative frameworks such as the Marine Strategy Framework Directive (MSFD).

Multi-scale responses of breeding birds to experimental forest management in Indiana, USA

Forest managers frequently must balance timber production and wildlife conservation goals when choosing management approaches. We studied the response of the breeding bird community to silvicultural treatments at multiple spatial scales over a 10-year period in 60–90year old oak-hickory forests of Indiana, USA. We conducted point count surveys in a 3603-ha study area both before (n=3years) and after (n=6years) application of silvicultural treatments. Bird responses were analyzed at two spatial scales: management units and individual harvests. At the multi-stand management unit scale, treatments were even-aged management, uneven-aged management, and a no-harvest control. We also analyzed the responses of birds at the spatial scale of individual timber harvests (clearcuts, patch cuts, shelterwood harvests, and single-tree selection). Multi-species N-mixture models were used to estimate bird species density and richness at both spatial scales. At the management unit scale, 4 species increased in density following even-aged management (relative to the control), while 1 species (Red-eyed Vireo [Vireo olivaceus]) declined. A larger number of species responded both positively (n=9) and negatively (n=3) to uneven-aged management. Overall richness was significantly greater in the even- and uneven-aged treatments than in the control. At the harvest scale, only the clearcuts and patch cuts resulted in changes in the density of any species, but a larger number of species were impacted and effect sizes were generally larger in these harvests than at the management unit scale. In the clearcuts, 13 species increased in density relative to the no-harvest control, while 5 species declined. A larger number of species were impacted by patch cut harvests (18 species increasing and 6 decreasing). Overall richness was greatest in the clearcut harvests. At both scales, species that increased were generally those associated with early successional habitat, including the Eastern Towhee (Pipilo erythrophthalmus) and Indigo Bunting (Passerina cyanea), while species that declined were typically associated with mature forest habitat (e.g., Red-eyed Vireo [Vireo olivaceus] and Ovenbird [Seiurus aurocapilla]). Harvesting appeared to benefit several species of conservation concern in Indiana, including the Cerulean Warbler (Setophaga cerulea) and Black-and-white Warbler (Mniotilta varia). Both management treatments appear to be good options for simultaneously conserving bird species diversity (particularly of early-successional specialist species) while meeting other forest management goals. However, the impact of the next phases of the shelterwood harvests remains to be evaluated.

Prevalence of coccidiosis in chickens at three poultry farms at Minna, Niger State, Nigeria

Coccidiosis is an intestinal disease of birds caused by a microscopic protozoan which lives and multiplies in the intestinal tract and causes damage to tissues, and eventually death. This study was carried out in three poultry farms in Minna, Niger State and among birds of ages 2 to 4 weeks and 6 weeks and above. Faecal samples were examined using the sedimentation technique. Out of 200 samples analyzed, 56 (28%) were positive for Eimeria species infection. In farm A, out of the 67 samples analyzed, 20 (29.85%) were infected. While an infection rate of 18 (27.30%) out of 65 and 18 (26.90%) out of 68 samples were infected for Farm B and C respectively. Based on age differences, Eimeria species were detected in 35 (34.65%) out of 101 young birds and 21 (21.21%) for adult birds out of the 99 samples analyzed. In Farm A 10 (30.30%) out of 33 samples were detected in young birds and 10 (29.41%) out of 34 samples in adult birds. In Farms B and C, 12 (36.36%) out of 33 and 6 (18.75%) out of 32; 13 (37.14%) out of 35 and 5 (15.15%) out of 33 samples were detected for Eimeria species for young and old birds respectively. There was a slightly higher prevalence rate among the farms and the various ages of the birds which was not significantly different at (p>0.05). The result of this study showed that the prevalence of infection was low in the 3 farms examined, and increased among the younger birds within the ages of 2 to 4 weeks old. The prescence of Eimeria species in farms could cause great economic losses in birds production. Therefore, farmers are encouraged to ensure adequate bio-security by avoiding wet litter which could encourage oocyst sporulation, and reduce the stocking density of birds. Keywords: coccidiosis, microscopic protozoan, Minna, eimeria , oocyst sporulation

Importance of regional variation in conservation planning: a rangewide example of the Greater Sage‐Grouse

AbstractWe developed rangewide population and habitat models for Greater Sage‐Grouse (Centrocercus urophasianus) that account for regional variation in habitat selection and relative densities of birds for use in conservation planning and risk assessments. We developed a probabilistic model of occupied breeding habitat by statistically linking habitat characteristics within 4 miles of an occupied lek using a nonlinear machine learning technique (Random Forests). Habitat characteristics used were quantified in GIS and represent standard abiotic and biotic variables related to sage‐grouse biology. Statistical model fit was high (mean correctly classified = 82.0%, range = 75.4–88.0%) as were cross‐validation statistics (mean = 80.9%, range = 75.1–85.8%). We also developed a spatially explicit model to quantify the relative density of breeding birds across each Greater Sage‐Grouse management zone. The models demonstrate distinct clustering of relative abundance of sage‐grouse populations across all management zones. On average, approximately half of the breeding population is predicted to be within 10% of the occupied range. We also found that 80% of sage‐grouse populations were contained in 25–34% of the occupied range within each management zone. Our rangewide population and habitat models account for regional variation in habitat selection and the relative densities of birds, and thus, they can serve as a consistent and common currency to assess how sage‐grouse habitat and populations overlap with conservation actions or threats over the entire sage‐grouse range. We also quantified differences in functional habitat responses and disturbance thresholds across the Western Association of Fish and Wildlife Agencies (WAFWA) management zones using statistical relationships identified during habitat modeling. Even for a species as specialized as Greater Sage‐Grouse, our results show that ecological context matters in both the strength of habitat selection (i.e., functional response curves) and response to disturbance.