The relationship between population density, habitat position and habitat breadth within a neotropical forest bird community

We examined the relationship between local abundance, habitat position and habitat breadth across bird species in a large Atlantic forest reserve in Brazil. This appears to be the first such study for any rainforest taxon. Habitat position for a species was its mean foraging height, along with the mean scores on three principal habitat axes for census stations at which it was recorded. Habitat breadth was the standard deviation of recorded foraging heights and the standard deviations of "positive" station scores on the habitat axes. We also examined differences in habitat position and breadth between endemic and wide-ranging taxa and amongst dietary groups. Amongst 31 species for which density estimation was possible, there were no correlations between local abundance and breadth of habitat use on any of the habitat axes. Breadth of habitat used did not vary with degree of endemism, but herbivores used a greater breadth of habitats on the axis describing canopy closure than did omnivores. Habitat position did not vary with endemic status, but herbivores preferred higher-biomass habitats than faunivores, and higher foraging heights than either faunivores or omnivores. Local abundance was linked weakly to habitat position with commoner species tending to forage in the lower strata of open-canopied areas. The 31 most commonly recorded species tended to occupy "middle-range" habitat positions, while 28 rarer species occupied habitats toward one or other end of the vegetation axes. These results suggest an association between the local abundance of a species and its habitat position, and especially its preference for common or mid-range habitats, rather than with its ability to utilise a wide range of habitats.     

Relationships between vegetation and bird community composition in grasslands of the Serengeti

The Serengeti–Mara ecosystem holds one of the largest natural grasslands of the world, which is well known for its large herds of mammals. However, the bird community structure of these grasslands has hardly ever been studied. For the first time, a large‐scale study on grassland bird communities has been conducted in all typical open grasslands of the Serengeti National Park. We used ten grassland plots representing a gradient of increasing vegetation height and also including shrubs and trees to analyse the influence of vegetation structure on the composition of grassland bird communities. Three communities of breeding birds were identified in relation to (a) short grass, (b) intermediate and long grass and (c) wooded grasslands. The bird communities of intermediate, long and wooded grassland were very similar, because of identical dominant bird species. Our results suggest that breeding birds of East African grasslands exhibit two contrasting habitat relationships: (1) birds that are restricted to short grass, and (2) species that are tolerant to vegetational shifts from intermediate grass via long grass to early stages of woody vegetation. Because the vegetation is often driven beyond this range in managed tropical grasslands through high grazing pressure or through shrub encroachment, we expect that the long‐grass bird communities will not generally resist anthropogenic disturbance.     

Influences of habitat fragmentation by damming on the genetic structure of masu salmon populations in Hokkaido, Japan

Dam construction dramatically influences riverine ecosystems, with habitat fragmentation being one of the most serious impacts. This habitat fragmentation is particularly relevant for anadromous species such as salmonids. We examined the effects of habitat fragmentation on masu salmon (Oncorhynchus masou) populations in Hokkaido, Japan. Specifically, we sampled from 15 locations located above and below a dam region in the Uryu River system, and analyzed the genetic structure of the populations using 10 microsatellite loci. No indication of a significant reduction in genetic diversity, estimated by allelic richness and heterozygosity, was observed within the above-dam region compared to the below-dam region. However, we also found that reducing the number of alleles had occurred within the above-dam region. The analysis of molecular variance and multidimensional scaling analysis indicated significant genetic differentiation between regions and within each region. A significant relationship between genetic and geographic distance was observed in the below-dam region, while no signal of isolation by distance was detected in the above-dam region. This study suggests a possibility of ongoing loss of alleles coinciding with habitat fragmentation caused by anthropogenic environmental changes such as water-level regulation, which negatively impacts genetic structure.     

Relationships between habitat structure and fish communities on coral

The influence of habitat structure on reef-fish communities at Bar Reef Marine Sanctuary, Sri Lanka, was investigated. The relationship between habitat characteristics and the distribution and abundance of 135 species of fishes was examined on two reef types: coral and sandstone reefs. Results suggested that the reef-fish communities were strongly influenced by various aspects of reef structure. However, relationships between habitat variables and fish communities structure, varied between the two reef types. Fish species diversity was correlated with a number of habitat variables on the sandstone reefs, although structural complexity seemed to play the dominant role. There were no correlations between habitat structure and fish diversity on the coral reefs. Total abundance was not related to any one habitat parameter on either reef type. However, abundances of some species, families and trophic groups were correlated with habitat features. These specific correlations were commonly related to food or shelter availability. For example, coral feeders were correlated with live coral cover, and pomacentrid species, which used branching corals for protection, showed a significant relationship with the density of Acropora colonies. This shows that a summary statistic such as total abundance may hide important information. Effects of habitat structure on the distribution patterns of the fish communities was further investigated using multi-dimensional scaling ordination (MDS) and the RELATE-procedure. With the MDS ordinations for both habitat and fish-community composition it was possible to show that the multivariate pattern between the two ecological components was clearly correlated.     

Fish abundance and habitat relationships in forest and grassland streams, northern Hokkaido, Japan

The relationships between habitat variables and population densities of masu salmon (Oncorhynchus masou), rosyface dace (Leuciscus ezoe), Siberian stone loach (Noemacheilus barbatulus) and wrinklehead sculpin (Cottus nozawae) were examined by data collected at 55 reaches in forest and grassland streams in northern Hokkaido, Japan. Regression analysis suggested that salmon and dace densities were affected by water temperature (negative for salmon, positive for dace) and structural habitat factors (woody debris for salmon, pools for dace). Salmon density was higher in forest reaches than in grassland reaches, whereas dace density was higher in grassland reaches, suggesting that the removal of riparian forest had raised water temperature and allowed upstream invasions by dace. In contrast to salmon and dace, neither the density of loach nor sculpin differed between the forest and grassland reaches. For their densities, a negative effect of each on the other was most important, suggesting a strong effect of interspecific competition between loach and sculpin on their distributions. However, regression models also suggested that substrate heterogeneity mediated the outcome of their interspecific competition. On the basis of the results, a scenario is predicted for a fish-assemblage change with a typical land-development process in Hokkaido, and the importance of leaving or restoring riparian buffer for conservation and restoration of stream habitat is emphasized.     

Plant diversity and habitat structure affect tree growth,herbivory and natural enemies in shelterbelts

Shelterbelts have become a refuge and source of food for wildlife because of habitat loss in farmlands. However, effects of shelterbelt attributes such as plant diversity and habitat structure on different trophic levels within shelterbelts are unclear. Effects of shelterbelt woody plant diversity and habitat structure (lower vegetation strata, logs, litter and rocks) were measured on the growth and herbivory of Eucalyptus blakelyi saplings that were caged from birds, caged from birds and arthropods and un-caged. Arthropod diversity of E. blakelyi saplings and shelterbelts was evaluated. Height and stem diameter of saplings in all treatments was positively correlated with plant diversity. Habitat structure was negatively correlated with numbers of leaves on E. blakelyi saplings and positively correlated with herbivory, which was greater in saplings caged from birds. The overall abundance of arthropods inhabiting shelterbelts correlated positively with plant diversity, but negatively with habitat structure. Araneae and Formicidae were the most common taxa on E. blakelyi saplings and were more numerous on saplings caged from birds, suggesting an important role of these vertebrates as predators of shelterbelt arthropods.     

The effects of individual interactions and habitat preferences on spatial structure in a grassland bird community

Spatial structure and the distribution of individuals within a community might be influenced by several factors such as habitat heterogeneity and local interactions among individuals of the same and different species. We investigated the spatial distributions of eight bird species in a grassland community during the breeding season and examined whether the spatial distributions of individuals were influenced by interactions among neighboring individuals or different habitat preferences of different bird species.
In order to identify the effects of the interactions among neighboring individuals and habitat preference, we developed a randomization test in which species identifications were randomly allocated to the observed individual positions within areas with the same vegetation structure. The randomization test indicated that individuals tend to have territories near the territories of individuals of the same species or of a particular species more frequently (or less frequently) than those expected from random distributions of individuals.
Among these associations, only one case was explained by individual interactions, and 19 cases were explained by habitat preference.
The results suggest that both individual interactions and habitat preference affected the spatial distributions of individuals and possibly influence the species compositions and diversity in grassland bird communities.     

Temporal variation in habitat structure and shrubsteppe bird dynamics

Summary We investigate the role of temporal variation in habitat physiognomy in influencing the dynamics of shrubsteppe bird populations and communities. During a 3-y (1977–1979) study of 14 sites in the northern Great Basin of North America, annual precipitation varied substantially, with one of the driest years on record followed by one of the wettest. This resulted in significant physiognomic variation (increasing height and coverage of vegetation, decreasing horizontal patchiness), mediated largely by changes in the annual elements of the flora, particularly forbs and grasses. Shrub species coverage values, on the other hand, demonstrated no statistically detectable year-to-year changes, nor were they correlated with any physiognomic variation. Despite large scale physiognomic changes, no bird species' abundance varied in a statistically significant fashion; neither could variation in bird abundances be correlated with variation in either physiognomy or shrub species coverages.Multivariate analyses revealed essentially the same patterns as the univariate analyses: substantial changes in physiognomy, few changes in shrub species coverages or bird species abundances, and little correlation of temporal variation among the three data sets. Calculation of the Euclidean distances that sites moved in multivariate physiognomic, bird species, or shrub species hyperspaces yields synthetic gradients of annual turnover of sites with respect to those data sets. Sites identified as demonstrating high physiognomic turnover were characterized by high coverage of grass and forbs, while low turnover sites had greater coverage of shrubs and higher shrub species diversity. Relatively high bird turnover sites had greater numbers of Western Meadowlarks and Black-throated Sparrows, while more stable sites had high numbers of Brewer's Sparrows. Physiognomically, high bird turnover sites were grassier and had greater total vegetation coverage, while low bird turnover sites had more bare ground and higher horizontal patchiness. A site's position on the avifauna turnover axis, however, was uncorrelated with its position on the physiognomic turnover axis. Shrub species showed virtually no annual turnover.Reanalysis of a previous Principal Components Analysis (PCA) of these same data sets that was applied without regard to year of sampling revealed that the first physiognomic component (41% of the total physiognomic variability) did in fact have a strong temporal element, and that this element was consistent with the changes in univariate characters noted above. No other physiognomic component could be associated with annual variation, nor could any components of parallel bird abundance or shrub species coverage PCA's.Regional patterns indicate that sites tended to be very consistent from year to year in their relationships to one another as defined by their relative locations in either physiognomic or shrub species hyperspaces, but varied independently of one another with respect to their bird species abundances and composition. Examination of the temporal consistency of site relationships between bird space and vegetation space reveals that bird communities are to a large degree independent of a site's physiognomic position, but instead are strongly associated with its position in shrub species hyperspace.The overall patterns that emerge from these analyses are consistent with the so-called checkerboard effect that results from the apparently random annual redistribution of individual birds, and leads to the conclusion that populations of shrubsteppe birds are not existing at maximum density or carrying capacity. Such observations are consistent with contentions that these populations lack close biological coupling with coexisting species and that interactions among these species (e.g. competition) are likely to play little if any role in the organization of their communities.     

Seasonality,habitat type and locality influenced bird assemblage structure in Nigeria

This is the first report of the avian assemblage in the study area of Dutse, Nigeria. In addition to recording bird species, the effects of season, dominant vegetation structure, locality and anthropogenic activities on bird abundance, species richness and diversity were investigated. Using the point transect method, 264 points on 48 km of transect were used to count birds between 06:30 and 11:00 from August 2015 to February 2016. A total of 122 bird species of 41 families were recorded. Highest bird species richness was recorded in Warwade, highest abundance in Model, and highest diversity in Malamawa. The dry season and woodland habitat showed higher bird species richness, abundance and diversity than the wet season and shrubland habitat. Tree density was more important in increasing bird abundance than shrub density. Small-scale anthropogenic activities and habitat modification, such as farming, grazing, wood removal and human interference did not appear to have impacted the birds; however, loss of high tree-density woodland habitats may pose a major threat to the bird community in Dutse. The presence of birds of concern in the area suggests the need for conservation efforts of avifauna and as well as the forested habitats in Dutse.     

Response of microbial community structure to natural and accelerated hydrarch successions in the boreal wetlands in northern Hokkaido, Japan

We estimated the effect of invading Sasa vegetation and accelerated terrestrialization on the microbial community structure in Sarobetsu-genya wetland (SGW) and Nakanominedaira wetland (NW) (original vegetation, Sphagnum). All examined peat-pore water samples were acidic. Electrical conductivity significantly differed between SGW and NW. Nonmetric multidimensional scaling (NMDS) and analysis of similarity based on denaturing gradient gel electrophoresis (DGGE) band patterns revealed differences in the bacterial community structure between the Sasa and Sphagnum vegetations at a depth of 10 cm in NW. In contrast, the bacterial NMDS profiles at all depths differed between the 2 wetlands rather than between the 2 vegetations. The archaeal community structure significantly differed between the wetlands at depths of 30 and 50 cm. The bacterial diversity index derived from the DGGE profiles significantly differed between the wetlands at all depths. The archaeal diversity index significantly differed between the wetlands at a depth of 50 cm. Sasa invasion affected the microbial community structure in the rhizosphere, up to a depth of 10 cm; this effect differed with the terrestrialization speed. These results suggest that in peat bogs subjected to artificially accelerated terrestrialization, the microbial community changes before the occurrence of the natural hydrarch ecological succession involving ground vegetation.     

Photoprotective responses of an ice algal community in Saroma-Ko Lagoon, Hokkaido, Japan

In polar seas, ice algal communities can acclimate to extremely low light conditions. Reduced acclimation to shade in ice algal communities, as a result of shortened ice seasons at the lower latitude limits of sea ice distribution, has been suggested as advantageous for avoiding strong photoinhibition when cells are released into high light levels at the water’s surface. Thermal dissipation of excess energy by xanthophyll cycle pigments in the de-epoxidated state may occur in ice algal communities released from retreating sea ice. A light exposure experiment was conducted on ice algal communities obtained from sea ice at Saroma-Ko Lagoon in Hokkaido, Japan. Photoprotective responses to direct sunlight were examined through non-photochemical quenching (NPQ) of chlorophyll fluorescence and xanthophyll pigments. De-epoxidation of diadinoxanthin (DD) to diatoxanthin (DT) occurred rapidly, and NPQ showed a dynamic response to high light exposure. The linear relationship between the ratio of DT to chlorophyll a and NPQ followed a steeper slope than previously observed for mesophilic diatoms. The steeper slope could be explained by an apparent increase in DT for the mesophilic diatoms and induction of NPQ in response to low temperatures only in the ice algal communities. Enhanced production of DT in mesophilic diatoms could be the result of de-epoxidation of DD plus de novo synthesis, and the enhancement of NPQ might be caused by low temperature stress in the ice algae. Although the response of NPQ might be related to temperature, NPQ independent of DT synthesis should also be studied.     

Relationships of bird community structure and species distributions to two environmental gradients in the northern boreal forest

Few studies have explicitly examined avian community structure in the North American northern boreal forest Herein we report upon the results of bird surveys in mature stands of boreal forest in the Great Clay Belt Ontario. Canada We related trends in avian community structure and individual bird species abundance to two environmental gradients described in a landbase classification scheme called the Forest Ecosystem Classification a moisture and a nutrient-richness gradient Variation in environmental characteristics is limited in the Ontario Clay Belt and this was reflected in short environmental gradient lengths However major trends in avian community structure were strongly associated with the nutrient-richness gradient axis summarized by this scheme Analyses of avian community composition indicated a continuum from moist coniferous habitats to drier aspen-dominated mixed woodlands with several bird species occurring in varying abundances across the width of both gradients 48 of the 58 species examined showed statistically significant associations with at least one of the two multivariate gradient axes A smaller proportion of short-distance migrant species were associated with these gradients than were species in either the neotropical migrant or resident categories We used a multivariate variable (habitat breadth) to compare degree of habitat specialization across different migratory groups A large proportion of neotropical migrants showed a high degree of habitat specialization m mature Clay Belt forests, and neotropical species with small habitat breadths were more commonly associated with habitats dominated by broad-leaved deciduous tree species than either short-distance or permanent resident species We discuss our findings in relation to the post-glacial history of the Clay Belt region     

Hierarchical genetic structure of native masu salmon populations in Hokkaido,Japan

Identification of the spatial extent of genetic structuring that may be influenced by evolutionary, ecological and historical factors is critical for effective conservation or management strategies. Masu salmon Oncorhynchus masou is commonly distributed in Far East, however, many local populations have been under threats of decline due to habitat destruction, overexploitation, and genetic introgression. To reveal the spatial genetic structure of native masu salmon populations in Hokkaido, masu salmon samples were collected from 16 rivers in which there was no official record of artificial releases of any masu salmon stock and were analyzed using 15 microsatellite loci. A Bayesian assignment test revealed that masu salmon populations were divided into two genetically distinct groups: the northeastern and southwestern groups. For within-group genetic structure, all populations, except for geographically proximate populations, were significantly different from each other. AMOVA revealed that genetic variation at among-group level based on groups identified assignment test was greater than that of groups based on geographic locations. There was no significant IBD for the 16 populations. However, the Mantel test revealed significant IBD for the northeastern group, but did not for the southwestern group. This study suggested that native masu salmon populations in Hokkaido exhibit a hierarchical genetic structure that is largely a result of their precise homing behavior. The results of this study also highlight the importance of defining populations by using genetic data rather than by using predefined populations based on geographic locations for the correct determination of genetic structure.     

城市公园生境类型对鸟类群落的影响

2011年12月—2012年11月,在上海世纪公园和滨江森林公园对鸟类群落和植物群落进行调查,通过对12个植被变量进行主成分分析,将两个公园分为8种不同的生境类型。结果表明:2个公园生境构成存在显著差异,滨江森林公园灌木层植物发达的生境(Habitat with developed shrub layer,S型)以及灌木层和地被层植物都发达的生境(Habitat with developed tree layer and shrub layer,T+S型)数量显著多于世纪公园,世纪公园地被层发达的生境(Habitat with developed ground cover layer,G型)以及乔木层和地被层植物都发达的生境(Habitat with developed tree layer and ground cover layer,T+G型)数量显著多于滨江森林公园。世纪公园不同生境中鸟种数差异显著,而滨江森林公园中差异不显著。2个公园有24种共有鸟种,对共有鸟种生境利用率的配对t检验结果表明,滨江森林公园鸟类生境利用率显著高于世纪公园。对2个公园共有生境类型中鸟种数进行分析,发现滨江森林公园鹟科(Muscicapidae)鸟类种数显著大于世纪公园。根据以上结果,上海城市公园不同生境类型对鸟类群落结构存在显著影响。因此,建议在规划和建设大型城市公园时,应构建植被分层结构复杂的生境,多样化种植各类乔木,林下多样化搭配灌木。在保留供游客休憩草坪区域的同时种植各类草本植物,以此提高鸟类生境利用率,增加城市公园的鸟类多样性。     

Interaction between seed crypsis and habitat structure influence patch choice in a granivorous bird, the chaffinch Fringilla coelebs

Food abundance is an important determinant in habitat and patch selection but food accessibility and detectability is less often considered. Foraging on more cryptic seeds may increase predation risk by increasing the length of head down periods. Habitat structure may interact with this as birds are less able to detect predators with their head lowered in riskier obstructed habitats. We investigated patch choice in chaffinches Fringilla coelebs foraging in obstructed and open habitats and artificially manipulated the search times of seeds by colouring them either yellow or black. One trial consisted of a choice between the conspicuous seed in the open patch, and the cryptic seed in the obstructed patch; in the second trial the treatments were reversed. Individuals were more willing to forage in the obstructed habitat when the yellow seeds were present (43% of pecks made in the obstructed patch) than when the black seeds were present (18% of pecks in the obstructed patch). Differences in search time are likely to explain this result: yellow seeds were located almost twice as fast (1.26±0.60 seconds) as black ones (2.36±0.88 seconds). This experiment shows that individual foraging decisions may be influenced not only by food abundance but by the properties of individual food items (in this case seed crypsis) and the structure of the habitat they are present in.     

Relationships between microbial community structure and hydrochemistry in a landfill leachate-polluted aquifer

Knowledge about the relationship between microbial community structure and hydrogeochemistry (e.g., pollution, redox and degradation processes) in landfill leachate-polluted aquifers is required to develop tools for predicting and monitoring natural attenuation. In this study analyses of pollutant and redox chemistry were conducted in parallel with culture-independent profiling of microbial communities present in a well-defined aquifer (Banisveld, The Netherlands). Degradation of organic contaminants occurred under iron-reducing conditions in the plume of pollution, while upstream of the landfill and above the plume denitrification was the dominant redox process. Beneath the plume iron reduction occurred. Numerical comparison of 16S ribosomal DNA (rDNA)-based denaturing gradient gel electrophoresis (DGGE) profiles of Bacteria and Archaea in 29 groundwater samples revealed a clear difference between the microbial community structures inside and outside the contaminant plume. A similar relationship was not evident in sediment samples. DGGE data were supported by sequencing cloned 16S rDNA. Upstream of the landfill members of the beta subclass of the class Proteobacteria (beta-proteobacteria) dominated. This group was not encountered beneath the landfill, where gram-positive bacteria dominated. Further downstream the contribution of gram-positive bacteria to the clone library decreased, while the contribution of delta-proteobacteria strongly increased and beta-proteobacteria reappeared. The beta-proteobacteria (Acidovorax, Rhodoferax) differed considerably from those found upstream (Gallionella, Azoarcus). Direct comparisons of cloned 16S rDNA with bands in DGGE profiles revealed that the data from each analysis were comparable. A relationship was observed between the dominant redox processes and the bacteria identified. In the iron-reducing plume members of the family Geobacteraceae made a strong contribution to the microbial communities. Because the only known aromatic hydrocarbon-degrading, iron-reducing bacteria are Geobacter spp., their occurrence in landfill leachate-contaminated aquifers deserves more detailed consideration.     

Patterns of bird abundance and habitat use in rice fields of the Kanto Plain, central Japan

Rice fields, the most widespread cropland in Japan, provide important habitat for birds, but few studies have examined bird communities that are influenced by agriculture in rice fields. I studied the seasonal pattern of bird abundance and their habitat preferences in terms of agricultural habitats in the rice fields of the central Kanto Plain, central Japan. In total, 19 waterbird species and 31 landbird species were recorded over the study year. Waterbird occurrence was largely restricted to the cultivation season (i.e. the flooded season, May–August), with maximum abundance in August. Rice fields dried up during winter and supported few waterbirds except for irregular occurrences of little egrets (Egretta garzetta) and common snipes (Gallinago gallinago), which selectively used ditches with shallow water. Landbird abundance increased after the start of cultivation (May) to August, but more birds were attracted to the rice fields in midwinter (around January). For both waterbirds and landbirds, most species preferred levees and fallow grass fields, but avoided fields with rice vegetation. Unplowed fields after harvest were preferred by several species including skylarks (Alauda arvensis), while plowed fields were less attractive to most species. These results suggest the need for advanced agricultural practices to include improvement in habitat quality for birds.