Latitudinal-Zonal and Altitude-Belt Aspects of Ecological Differentiation of Bird Communities in Central Siberia

Population density, species richness, and total biomass of birds in Central Siberia increase toward the south. The greatest values are noted in terrestrial natural landscapes: for the total abundance of birds, they are in the southern forest type of communities; for species richness, they are in the meadow–field type; and for total biomass, they are in the subarctic plain–tundra type. In industrial–technogenic and southern residential types, the density and biomass of bird communities increase and the species richness decreases in comparison with natural ornithocomplexes. In aquatic habitats, the total abundance of birds and their species richness decrease and biomass increases when compared with terrestrial ones. The representation of types of fauna in bird communities (by number of individuals) is determined by the zones of their landscape preference, which have ecological similarity with the areas of their formation. Since birds actively choose tiers with the most favorable thermal, trophic, and protective conditions, their vertical biotopic distribution to some extent does not correspond to the tier structure of their habitats.

Based on extensive information on the numbers and distribution of birds obtained during route surveys over the past 60 years, a classification of the bird communities of Central Siberia is considered at the level of its types. The specificity of this classification is determined by the predominance of latitudinal-zonal types over non-zonal ones. The main directions of territorial changes in the bird communities are determined by afforestation and watering, combined with latitudinal zonation. Less significant differences in ornithocomplexes are associated with the altitudinal zone and built-up area concerned. The main natural and anthropogenic factors and the hierarchy of their importance for the spatial differentiation of the bird populations have been established. The regional specificity of the spatial organization of the bird communities in Central Siberia in comparison with the Eastern European and West Siberian plains is reduced to the manifestation of high-altitude zonation due to differences in mountain-tundra ornithocomplexes, a greater differentiation of forest ornithocomplexes and less represented non-zonal population types.

The basic tendencies of territorial changes in bird communities of the middle taiga on the Central Siberian Plateau are interrelated with the differences in forestation, productivity, swampiness, bushiness, watering, and buildup of habitats and are on the whole similar to those on the West Siberian and Central Yakutsk plains, although there are also some differences. Thus, the community types of upland swamps and low-inundated meadows in combination with lowland swamps are characteristic only of West Siberia. In Central Siberia, forest ornithocomplexes are the most diverse, which is largely due to the presence of communities of woodlands and glades at different stages of overgrowing. The ecotone type of ornithocomplexes was distinguished only for Central Yakutia. In the North Urals, the formation of ornithocomplexes is significantly influenced by forestation and tree species composition but starts to be noticeably affected by altitudinal zonality as well as productivity of biocenoses and development of shrubs in habitats interrelated with this factor.

We compared foraging behavior of foliage-gleaning birds of the boreal forest of two Palaearctic (central Siberia and European Russia) and two Nearctic (Mackenzie and Ontario, Canada) sites. Using discriminant function analysis on paired sites we were able to distinguish foliage-gleaning species from the Nearctic and Palaearctic with few misclassifications. The two variables that most consistently distinguished species of the two avifaunas were the percentage use of conifer foliage and the percentage use of all foliage. Nearctic foliage-gleaner assemblages had more species that foraged predominantly from coniferous foliage and displayed a greater tendency to forage from foliage, both coniferous and broad-leafed, rather than twigs, branches, or other substrates. The greater specialization on foliage and, in particular, conifer foliage by New World canopy foliage insectivores is consistent with previously proposed hypotheses regarding the role of Pleistocene vegetation history on ecological generalization of Eurasian species. Boreal forest, composed primarily of spruce and pine, was widespread in eastern North America, whereas pockets of forest were scattered in Eurasia (mostly the mountains of southern Europe and Asia). This may have affected the populations of birds directly or indirectly through reduction in the diversity and abundance of defoliating outbreak insects. Loss of habitat and resources may have selected against ecological specialization on these habitats and resources.

Bird Fauna and Community of Northern Taiga in Central Siberia

Bird communities of coniferous forests attain their largest species numbers in central Siberia; these numbers are gradually declining towards the periphery of the boreal zone. A secondary maximum of species numbers is found in the Alps. Boreal belts of southern (Mediterranean) mountains are impoverished in numbers of species, although “xenoecious” species inhabit coniferous forests. The uneven geographical dispersion of species is caused by isolation and migration paths during Pleistocene changes of vegetation belts. Considering the subspecies level, Siberian elements reach the Alps and the Rhodope Mountains, Palaearctic elements even extend to the Canaries. Mountain regions along the Mediterranean sea are characterised by many endemic subspecies. Boreal ecosystems include the most specialised species. Similarity of bird fauna assemblages is highest between boreal regions and lowest in Mediterranean areas. Biodiversity diminishes in the boreal forests from central Siberia onwards, in southern extrazonal regions from the Alps to periphery regions. Small isolated populations on southern mountain tops are most endangered.

Spatial Organization of Bird Communities in Central Siberia

Anthropogenic‐driven species extinctions are radically changing the biosphere. Biological communities may become increasingly similar to or dissimilar from one another via the processes of biotic homogenisation or heterogenisation. A key question is how the conversion of native forests to agriculture may influence these processes by driving changes in the occurrence patterns of restricted‐range endemic species versus wide‐ranging generalists. We examined biotic homogenisation and heterogenisation in bird communities on the Southeast Asian islands of Borneo, Sulawesi, Seram, Buru, Talaud and Sangihe. Each island is characterised by high levels of avian endemism and unique spatial configuration of forest conversion to agriculture. Forest conversion to agriculture influenced the patterns of biotic homogenisation on five islands. Bird communities became increasingly dissimilar to forest reference communities relative to localised patterns of deforestation. Turnover led to species with larger global range‐sizes dominating communities at the expense of island endemics and ecological specialists. Within islands, forest conversion did not result in clear changes to β‐diversity, whereas between‐island communities became increasingly similar with greater deforestation, implying that patterns of forest conversion profoundly affect biotic homogenisation. Our findings elucidate how continued conversion of forests is causing the replacement of endemic species by a small cohort of shared ubiquitous species with potentially strong negative consequences for ecosystem functioning and resilience. Halting reorganisation of the biosphere via the loss of range‐restricted species and spread of wide‐ranged generalists will require improved efforts to reduce the impacts of deforestation, particularly in regions with high endemism.

Современная классификация населения птиц Средней Сибири

Landscape-ecological trends of spatial changes in the bird communities of Central Siberia

We studied ecological and evolutionary aspects of habitat choice in a group of closely related bird species to gain insight into factors influencing bird community structure. Seven species of Phylloscopus warblers breed sympatrically in the middle taiga subzone of Central Siberia. We examine how the distribution of species among habitats is related to morphology, phylogeny and competition, and we compare our results with an earlier study on the ecomorphology of Phylloscopus warblers in Kashmir. We found that in Siberia, large warbler species prefer productive habitats with mostly deciduous vegetation, whereas small species occupy poor coniferous forests. Possible explanations for this finding remain to be tested in the future. Moreover, we found a tendency for species with large feet, small bills and short wings to occupy habitats with an abundance of bush thickets near the ground. In the Kashmir study, competition was considered a major factor in structuring the Phylloscopus community, and patterns of habitat choice were not influenced by phylogenetic relationships. In strong contrast, we found that in the Siberian community, closely related species occupy similar habitats. We discuss whether this conservative evolution of habitat preferences in Siberia may be due to low intensity of interspecific competition or to other ecological factors.

Response of avian communities to edges of tropical montane forests: Implications for the future of endemic habitat specialists

Habitat loss often reduces the number of species as well as functional diversity. Dramatic effects to species composition have also been shown, but changes to functional composition have so far been poorly documented, partly owing to a lack of appropriate indices. We here develop three new community indices (i.e. functional integrity, community integrity of ecological groups and community specialization) to investigate how habitat loss affects the diversity and composition of functional traits and species. We used data from more than 5000 individuals of 137 bird species captured in 57 sites in the Brazilian Atlantic Forest, a highly endangered biodiversity hotspot.Results indicate that habitat loss leads to a decrease in functional integrity while measures of functional diversity remain unchanged or are even positively affected. Changes to functional integrity were caused by (i) a decrease in the provisioning of some functions, and an increase in others; (ii) strong within-guild species turnover; and (iii) a replacement of specialists by generalists. Hence, communities from more deforested sites seem to provide different but not fewer functions. We show the importance of investigating changes to both diversity and composition of functional traits and species, as the effects of habitat loss on ecosystem functioning may be more complex than previously thought. Crucially, when only functional diversity is assessed, important changes to ecological functions may remain undetected and negative effects of habitat loss underestimated, thereby imperiling the application of effective conservation actions.

With the rapid process of urbanization at a global scale, university campuses have been viewed as important urban green spaces for biodiversity conservation. However, little is known about the role of university campuses in protecting ecological specialists, the species usually vulnerable to anthropogenic disturbance. We assessed the associations between several ecological variates and ecological specialization of bird communities across 198 Chinese university campuses. A total of 398 bird species were recorded, including 109 diet specialist species and 104 foraging stratum specialist species. We found that the elevation of campuses was positively related to diet specialist species richness, and the campus area was positively related to foraging stratum specialist species richness. NDVI was positively associated with the community-wide foraging stratum specialization index, but negatively associated with the community-wide diet specialization index. Our results suggest that campuses with larger areas or located at high elevations play an important role in maintaining ecological specialization of bird communities.

Newly created oceanic islands slowly accumulate species. In contrast, habitat islands created by rising water level or by human reduction of the area of a habitat (for example, by deforestation) support a full complement of local species at their formation. With time these islands lose species, a phenomenon called relaxation (Diamond 1972, Wilcox 1980). Several explanations may account for relaxation in island relicts. (1) As island size decreases, diversity of habitats present decreases. Species dependent entirely or in part on lost habitats disappear (habitat diversity Able and Connor 1979, Wilcox 1980). (2) Islands passively intercept dispersers in proportion to their area. As island size declines, recolonization probabilities decline. Thus, species lost from a small land bridge island are less likely to recolonize (disperser intercept Able and Connor 1979, Martin 1980, Wilcox 1980). (3) Smaller islands have more species with low sizes, a condition which predisposes such species for extinction from random causes (rarity hypothesis; Willis 1974, Terborgh and Winter 1980). Corollaries of the relate bird size and ecological specialization to extinction probability (Willis 1974). (4) On theoretical grounds, species unable to maintain stable populations in the face of environmental vagaries (species with high population variability) may be prone to local extinction (Leigh 1975, 1981). Terborgh and Winter (1980) suggested from qualitative considerations that species dependent on resources likely to be variable and/or patchy in their distribution (especially frugivores and nectarivores) are prone to extinction. Tracking of those resources in space results in locally variable sizes for such species. To my knowledge, no quantitative field data are available to test the population variability hypothesis. To what extent do these hypotheses account for loss of species on Barro Colorado Island (BCI), Panama, a 14.8-km2 land bridge island formed when the Panama Canal was created by damming the Chagras River early in the 20th century? I have used two approaches to explore that question. First, I have examined in detail the avifauna of BCI and its presumed source fauna in the adjacent mainland forest of the Pipeline Road region of Parque Nacional Soberania. Soberania is a 22 000-ha tract of lowland forest on the mainland adjacent to BCI. At its nearest point, BCI is ;200 m from a peninsular extension of that forest, although less-disturbed forest is not so close. As many as 5060 species of forest birds are missing from BCI (Karr 1982), well above earlier conclusions that 15-18 forest species are extinct on BCI (Terborgh 1974, Willis 1974, Wilson and Willis 1975, Willis and Eisenmann 1979). The approach used in earlier estimates of avian extinctions on BCI led to underestimation of extinction rates. Further, the high extinction rate seems to be due to the restricted habitat mosaic of BCI relative to that found on a similar-sized mainland area. Undergrowth and ground species and species associated with foothill forest are especially prone to extinction (Karr 1982). Second, I have conducted a long-term study of undergrowth species in mainland forest near BCI, with the objective of identifying attributes of species prone to extinction. I report those findings here. Birds of forest undergrowth have been sampled periodically since 1968 with mist nets in an area of 2 km2 along the Pipeline Road (centered at Limbo Hunt Club [LHC]) and 9 km east of BCI. A total of 4722 captures of 114 species of birds is available in samples collected from August 1968 through March 1982. The methodology for this study was operation of 12-14 mist nets in the undergrowth of forest for periods of 3-6 d (see Karr [1979, 1981] for details of methodology). All data were collected by me except for 10 monthly samples (826 captures) from 1977 to 1978 collected by Schemske and Brokaw (1981). Net shyness sometimes occurs in areas that are regularly sampled with mist nets. However, sampling in recent years has been limited to two 3-6 d periods each year, and.there is no sign of net shyness with this low sampling frequency. Indeed, 5070W of captures are of birds banded during earlier sampling periods. In this paper I concentrate on two of the four hypotheses described above: rarity and variability. I do not consider the disperser intercept hypothesis since it is incompatible with the empirical observation that the undergrowth forest birds discussed in detail here are very reluctant to cross water gaps. The habitat diversity hypothesis will be discussed only briefly here as it relates to variability since it is the primary focus of another paper (Karr 1982). I assume that the relative abundances of species today in the vicinity of Limbo Hunt Club are similar to those of the bird community of BCI at the time BCI became an island.