Long-term species richness-abundance dynamics in relation to species departures and arrivals in wintering urban bird assemblages

Temporal dynamics of local assemblages depend on the species richness and the total abundance of individuals as well as local departure and arrival rates of species. We used urban bird survey data collected from the same 31 study plots and methods during three winters (1991–1992; 1999–2000 and 2009–2010) to analyze the temporal relationship between bird species richness and total number of individuals (abundance). We also evaluated local departures and arrivals of species in each assemblage. In total, 13,812 individuals of 35 species were detected. The temporal variation in bird species richness followed the variation in the total number of individuals. The numbers of local departure and arrival events were similar. Also, the mean number of individuals of the recently arrived species (8.6) was almost the same as the mean number of individuals of the departed species (8.2). Risk of species departure was inversely related to number of individuals. Local species richness increased by one species when the total abundance of individuals increased by around 125 individuals and vice versa. Our results highlight the important role of local population departures and arrivals in determining the local species richness-abundance dynamics in human-dominated landscapes. Local species richness patterns depend on the total number of individuals as well as both the departure-arrival dynamics of individual species as well as the dynamics of all the species together. Our results support the more individuals hypothesis, which suggests that individual-rich assemblages have more species

Landscape properties mediate the homogenization of bird assemblages during climatic extremes

Extreme weather events, such as drought, have marked impacts on biotic communities. In many regions, a predicted increase in occurrence of such events will be imposed on landscapes already heavily modified by human land use. There is an urgency, therefore, to understand the way in which the effects of such events may be exacerbated, or moderated, by different patterns of landscape change. We used empirical data on woodlanddependent birds in southeast Australia, collected during and after a severe drought, to document temporal change in the composition of bird assemblages in 24 landscapes (each 100 km2) representing a gradient in the cover of native wooded vegetation (from 60% to <2%). We examined (a) whether drought caused region-wide homogenization of the composition of landscape bird assemblages, and (b) whether landscape properties influenced the way assemblages changed in response to drought. To quantify change, we used pairwise indices of assemblage dissimilarity, partitioned into components that represented change in the richness of assemblages and change in the identity of constituent species (turnover). There was widespread loss of woodland birds in response to drought, with only partial recovery following drought-breaking rains. Region-wide, the composition of landscape assemblages became more different over time, primarily caused by turnover-related differentiation. The response of bird assemblages to drought varied between landscapes and was strongly associated with landscape properties. The extent of wooded vegetation had the greatest influence on assemblage change: landscapes with more native vegetation had more stable bird assemblages over time. However, for the component processes of richness- and turnoverrelated compositional change, measures of landscape productivity had a stronger effect. For example, landscapes with more riparian vegetation maintained more stable assemblages in terms of richness. These results emphasize the importance of the total extent of native vegetation, both overall cover and that occurring in productive parts of the landscape, for maintaining bird communities whose composition is resistant to severe drought. While extreme climatic events cannot be prevented, their effects can be ameliorated by managing the pattern of native vegetation in anthropogenic landscapes, with associated benefits for maintaining ecological processes and human well-being

Domesticating Mathematics: Taxonomic Diversity in Archaeozoological Assemblages

Understanding taxonomic richness is indispensable in studying the choices made in the exploitation of the local fauna such as those of the broad-spectrum revolution in the Near East. Such investigations, however, sometimes disregard the stochastic nature of human decision-making, while others present complex mathematical models. The basic nature of samples is rarely discussed. The fundamental thesis of our study is that assemblages of different sizes can be compared only exercising extreme caution. When species richness is studied as a function of assemblage size, the remains of birds, large and “micro-” mammals show strongly differing statistics. Diversity increases along with the number of identifiable bones in the case of birds, while the same trend is most protracted in the case of large mammals. This means that taxonomic diversity in animal bone assemblages is a function of not only assemblage size but also of taxonomic composition. The structure of “input” data is thus qualitatively dependent on assemblage size. The underlying factors influencing the archaeological representation of the fauna, including sampling, anatomical and taphonomic traits of the three types of vertebrates are discussed by animal groups. Taxonomically different animal remains should not be included within the same faunal list as their culture historical interpretations (animal keeping, hunting, random natural deposition) also differ. These phenomena must all be considered when a reliable interpretation of animal remains is attempted in various archaeological periods. A régészeti állatcsont-anyagok fajgazdagságának megértése nélkülözhetetlen olyan kérdések kutatásában, mint pl. a közel-keleti őskori közösségek által fogyasztott állatfajok rendszertani spektrumának szélessége, választékának kihasználása. Az ilyen vizsgálatok során sokan figyelmen kívül hagyják az emberi döntések sztochasztikus természetét, míg mások bonyolult matematikai modellekkel igyekeznek leírni azt. A minták alapvető természetére kevesen fordítanak figyelmet. Vizsgálataink alaptétele, hogy a különböző nagyságú minták csak rendkívüli körültekintéssel hasonlíthatók össze. Amikor a meghatározott fajok számát a mintanagyságok függvényében vizsgáljuk, a madarak, a nagytestű emlősállatok és a „mikrofauna” emlős fajai más-más értékeket mutatnak. A fajgazdagság nem lineárisan követi a csontok darabszámának alakulását: ahhoz viszonyítva a madarak esetében növekszik a legintenzívebben, leginkább pedig a nagytestű emlősök csoportjában marad el a mintanagyság gyarapodásától. Eszerint az egyes leletegyüttesek állattani változatossága nemcsak a mintanagyságtól, hanem a taxonómiai összetételtől is függ. Ez azt mutatja, hogy a régészeti értelmezésben már a „bejövő” alapadatok összetétele is minőségileg függ a mintanagyságtól. A tanulmányban körvonalazzuk a háttérben meghúzódó okokat, a három vizsgált gerinces állatcsoport reprezentáltságát meghatározó mintavételi, tafonómiai és anatómiai különbségeket. E maradványok értelmezése nem mosható egybe egyetlen „faunalistában”, hiszen kultúrtörténeti jelentésük (állattartás/vadászat, madarászat és véletlenszerű, természetes lerakódás) is változó. Mindez nem mellőzhető az állatok különböző régészeti korszakokban játszott szerepének hitelességre törekvő értékelésekor

Bird Population Changes Following the Establishment of a Diverse Stand of Woody Plants in a Former Crop Field in North Dakota, 1975– 2015

Changes in the coverage of trees and shrubs on the North Dakota landscape since Euro- American settlement have likely had a pronounced impact on bird species that favor woody vegetation. Long- term data sets on breeding bird populations in wooded habitats in North Dakota or in the Great Plains are scarce. In 1975 a wildlife habitat plot was established in a 10.5 ha cropland field with a long history of small- grain production. Th e objective of this article is to evaluate the successional changes in bird populations as the habitat at this site became more biologically and structurally complex aft er the establishment of a diverse stand of shrubs and trees. Between 1975 and 2015, 103 species or varieties of native and non- native trees, shrubs, or vines were planted in this wildlife habitat plot (hereaft er woodlot); 58.2% of those species were still present in 2016. Th e avian community in the woodlot increased in abundance and diversity as the woody vegetation increased in complexity and maturity, but the changes in abundance varied among ecological bird groups. Grassland bird abundance remained relatively constant but uncommon throughout the four decades aft er woody vegetation was first established. Bird species associated with shrublands and open woodlands and edges responded positively and showed the greatest increases in abundance during the 41- year period. Th e abundance of bird species associated with open areas with scattered trees or shrubs (i.e., savanna habitat) increased during the first half of the study but declined during the second half. Bird species associated with forest habitats were rare throughout the 41- year period, but their abundance increased during the most recent two decades. Results of this study are important for informing decisions about restoration efforts of riparian forests and other native wooded areas in the Great Plains and setting expectations for the time- scale required for the return of assemblages of species of woodland birds

Winter Bird Assemblages in Rural and Urban Environments: A National Survey

Urban development has a marked effect on the ecological and behavioural traits of many living organisms, including birds. In this paper, we analysed differences in the numbers of wintering birds between rural and urban areas in Poland. We also analysed species richness and abundance in relation to longitude, latitude, human population size, and landscape structure. All these parameters were analysed using modern statistical techniques incorporating species detectability. We counted birds in 156 squares (0.25 km2 each) in December 2012 and again in January 2013 in locations in and around 26 urban areas across Poland (in each urban area we surveyed 3 squares and 3 squares in nearby rural areas). The influence of twelve potential environmental variables on species abundance and richness was assessed with Generalized Linear Mixed Models, Principal Components and Detrended Correspondence Analyses. Totals of 72 bird species and 89,710 individual birds were recorded in this study. On average (±SE) 13.3 ± 0.3 species and 288 ± 14 individuals were recorded in each square in each survey. A formal comparison of rural and urban areas revealed that 27 species had a significant preference; 17 to rural areas and 10 to urban areas. Moreover, overall abundance in urban areas was more than double that of rural areas. There was almost a complete separation of rural and urban bird communities. Significantly more birds and more bird species were recorded in January compared to December. We conclude that differences between rural and urban areas in terms of winter conditions and the availability of resources are reflected in different bird communities in the two environments

A new role for pond management in farmland bird conservation

Biodiversity declines in agricultural landscapes represent a major conservation challenge. In the UK, some agricultural landscapes contain high pond densities, but many farmland ponds have become terrestrialised since the 1960s, with input of organic material resulting in a decrease in the size and depth of ponds that eventually transform into wet woodland habitats. Pond management, including removal of overhanging scrub and sediment, has proven highly effective in enhancing freshwater biodiversity. However, the implications of this management for farmland bird assemblages are unknown. Bird surveys were undertaken at recently managed, open, macrophyte-dominated and at highly terrestrialised, macrophyte-free ponds in the intensively cultivated farmland of North Norfolk, UK. The diversity, abundance and composition of bird assemblages visiting these ponds were compared to determine responses to pond management by tree and mud removal. Avian species richness, abundance and bird-visit frequencies were all higher at open farmland ponds. The observed patterns of bird occurrence were best explained by management-induced reductions in tree shading that resulted in aquatic macrophyte-dominance likely associated with high emergent invertebrate prey abundance. Moreover, we predict that open-canopy ponds offer greater habitat heterogeneity than overgrown ponds, allowing diversified bird use. Overgrown, terrestrialised ponds were preferred by some woodland bird species. Gamma diversity across the entire pondscape exceeded all individual pond alpha diversity measures by an order of magnitude, suggesting distinct variation in the bird assemblages visiting farmland ponds during different successional stages. Pond management that generates a mosaic of pond successional stages, including open-canopy, macrophyte-dominated ponds, could help to address the long-term decline of farmland birds. We strongly advocate increased agro-ecological research in this field, combined with greater emphasis on ponds and pond management options in agri-environment schemes

Geographic trends in range sizes explain patterns in bird responses to urbanization in Europe

The probability of occurrence of bird species in towns/cities increases with their range sizes, and Rapoport’s rule states that range sizes increase with latitude. To test the hypothesis that the increasing number of bird species persisting in cities at higher latitudes of Europe is linked to their larger range sizes, we compiled data on bird communities of: a) 41 urban bird atlases; b) 37 city core zones from published sources; c) regions of nine grid cells of the EBCC Atlas of European Breeding Birds around each city. We tested whether the proportion of species from particular regional bird assemblages entering cities (i.e., proportional richness) was related to the geographical  position, mean range size of regional avifaunas, proportion of vegetated areas and city habitat heterogeneity. The mean range sizes of the observed and randomly selected urban avifaunas were contrasted. The proportional richness of urban avifaunas was positively related to the geographic position and mean range size of birds in regional assemblages. The evidence favoured range sizes if considering the European range sizes or latitudinal extents, but was limited for global range sizes. Randomizations tended to show larger range sizes for the real avifaunas than in the randomly selected ones. For urban core zones, the results were less clear-cut with some evidence only in favour of the European range sizes. No role of vegetation or habitat heterogeneity was found. In conclusion, while vegetation availability or heterogeneity did not show any effects, spatial position and range sizes of birds in regional assemblages seemed to influence the proportional richness of cities and their core zones. Factors correlated with spatial position (e.g., climate) might increase the attractivity of particular cities to birds. However, the effects of range sizes indicated that urbanization possibly has more negative impacts on the avifauna in the regions occupied by less widespread species

Reconciling timber extraction with biodiversity conservation in tropical forests using reduced-impact logging

Over 20% of the world's tropical forests have been selectively logged, and large expanses are allocated for future timber extraction. Reduced-impact logging (RIL) is being promoted as best practice forestry that increases sustainability and lowers CO2 emissions from logging, by reducing collateral damage associated with timber extraction. RIL is also expected to minimize the impacts of selective logging on biodiversity, although this is yet to be thoroughly tested. We undertake the most comprehensive study to date to investigate the biodiversity impacts of RIL across multiple taxonomic groups. We quantified birds, bats and large mammal assemblage structures, using a before-after control-impact (BACI) design across 20 sample sites over a 5-year period. Faunal surveys utilized point counts, mist nets and line transects and yielded >250 species. We examined assemblage responses to logging, as well as partitions of feeding guild and strata (understorey vs. canopy), and then tested for relationships with logging intensity to assess the primary determinants of community composition. Community analysis revealed little effect of RIL on overall assemblages, as structure and composition were similar before and after logging, and between logging and control sites. Variation in bird assemblages was explained by natural rates of change over time, and not logging intensity. However, when partitioned by feeding guild and strata, the frugivorous and canopy bird ensembles changed as a result of RIL, although the latter was also associated with change over time. Bats exhibited variable changes post-logging that were not related to logging, whereas large mammals showed no change at all. Indicator species analysis and correlations with logging intensities revealed that some species exhibited idiosyncratic responses to RIL, whilst abundance change of most others was associated with time. Synthesis and applications. Our study demonstrates the relatively benign effect of reduced-impact logging (RIL) on birds, bats and large mammals in a neotropical forest context, and therefore, we propose that forest managers should improve timber extraction techniques more widely. If RIL is extensively adopted, forestry concessions could represent sizeable and important additions to the global conservation estate – over 4 million km2