Die Entwicklung der Brutvogelbest?nde am Bodensee: Vergleich halbquantitativer Rasterkartierungen 1980/81 und 1990/91

Zusammenfassung Die halb-quantitative Rasterkartierung Bodensee wurde 1990/91 auf 88.3 % der zehn Jahre zuvor kartierten Fläche wiederholt. Nur 25 % der Rasterfelder wurden von denselben Beobachtern kartiert wie vor zehn Jahren. Daher wurden Veränderungen nur dann als gesichert betrachtet, wenn sie mindestens auf dem 2 %-Niveau signifikant waren. Dies war bei 62 Arten der Fall, wovon 29 Arten zu- und 33 abnahmen. 145 Vogelarten wurden registriert (vorher 143), die Artenzahl pro Rasterfläche ist jedoch ebenso rückläufig wie der Gesamtbestand aller Vogelarten. Neben Zunahmen bei einigen Vogelarten der menschlichen Siedlungsflächen und des Waldes ragen solche von Feuchtgebiets- und Wasservögeln hervor, die am Bodensee effizient geschützt sind. Bemerkenswert sind der erhebliche Bestandsrückgang beim Haussperling und die insgesamt stark negative Entwicklung bei den Langstreckenziehern, unter denen keine Singvogelart mehr eine gesicherte Zunahme verzeichnen konnte. Drastische Bestandseinbrüche fast aller Bodenbrüter des offenen Kulturlandes wurden festgestellt.

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The development in the breeding birds of Lake Constance: comparison of grid mapping in 1980/81 and 1990/91

Summary The distribution and number of breeding birds at Lake Constance was mapped on 278 grids of 4 km² in 1990/91, covering 88.3 % of the area of 1980/81. As only 25 % of the grids were censused by the same observers as in 1980/81, changes were only considered real if significant on the 2 % level at least. This was the case in 62 species, 29 of which were increasing, 33 decreasing. A total of 145 breeding species was found (143 before), however, the number of species per grid and the total number of territories registered were lower than ten years ago. Apart from increases of species of urban settlements (e.g. Feral Pigeon, Collared dove, Black Redstart, Serin) and forests (e.g. Sparrowhawk, Goshawk, Great Spotted Woodpecker, Mistle thrush), the favourable development in species living in reedbeds and in waterbirds was notable. The latter is due to effective conservation measures at Lake Constance. Remarkable was the considerable loss in breeding numbers of the House Sparrow and the generally negative development of long-distance migrants, especially passerine species. A drastic population decline was found for almost the complete guild of ground-nesting birds in open habitats.

     

Modeling Spatial Trends in Estimated Species Richness using Breeding Bird Survey Data: A Valuable Tool in Biodiversity Assessment

We used data from the French breeding bird survey to estimate local bird species richness within sampled sites, using capture–recapture models. We investigated the possible effects of habitat structure and composition (landscape fragmentation, habitat cover and diversity) on estimated species richness at a local scale, and used the identified trends to help with modeling species richness at a large spatial scale. We performed geostatistical analyses based on spatial autocorrelation – cokriging models – to interpolate estimated species richness over the entire country, providing an opportunity to predict species-rich areas. We further compared species richness obtained with this method to species and rarity richness obtained using a national atlas of breeding birds. Estimated species richness was higher in species richness hotspots identified by the atlas. Combining informations on rare species from Atlas and species richness estimates from sound sampling based schemes should help with identifying species-rich areas for various taxa and locating biodiversity hotspots to be protected as high conservation value areas, especially in temperate zones where diversity hotspots are likely to match centers of high species richness because of very few centers of true endemicity.     

Seasonal Abundance and Species Richness of Birds in Common Reed Habitats in Lake Erie

Abstract: Common reed (Phragmites australis) forms dense stands with deep layers of residual organic matter that negatively affects plant diversity and possibly habitat use by wetland birds. We sought to determine whether seasonal relative abundance and species richness of birds varied among 3 habitat types in Great Lakes coastal wetland complexes recently invaded by common reed. We used fixed-distance point counts to determine species relative abundances and species richness in edge and interior locales within common reed, cattail (Typha spp.), and meadow marsh habitats of various sizes during 2 summers (2001 and 2002) and 1 autumn (2001) at Long Point, Lake Erie, Ontario, Canada. We found that total relative abundance and species richness of birds were greater in common reed habitat compared to cattail or meadow marsh habitats. However, we also found that relative abundance of marsh-nesting birds was greater in meadow marsh habitat than in cattail and common reed during summer. Lastly, we found that, irrespective of habitat type, habitat edges had higher total relative abundance and species richness of birds than did habitat interiors. Our results show that common reed provides suitable habitat for a diversity of landbirds during summer and autumn but only limited habitat for many marsh-nesting birds during summer. Based on these results, we recommend restoration of meadow marsh habitat through reduction of common reed in Great Lakes wetlands where providing habitat for breeding marsh-nesting birds is an objective. Managers also might consider reducing the size of nonnative common reed stands to increase edge effect and use by birds, possibly including wetland birds.     

Changes in the trophic interactions and the community structure of Lake Taihu (China) ecosystem from the 1960s to 1990s

As the third largest freshwater lake in China, Lake Taihu has suffered from overfishing, eutrophication, and physical disturbance over the last several decades. Evaluating and quantifying changes in the ecosystem can help us better understand and develop hypotheses to explain the dynamics of the ecosystem. In this study, trophic interactions and community structure of commercial fisheries species of Lake Taihu ecosystem were analyzed and compared for three time periods (1961–1965, 1981–1987, and 1991–1995) using the Ecopath with Ecosim model with the aim of evaluating the changes in the population dynamics and ecosystem development mechanism spanning the period from the 1960s to 1990s. The results show that the biomass of large predators decreased over the three decades, while the biomass of small species increased. Increases in the P/B ratios and fishing mortality levels observed for species groups reveal rapidly intensifying fishery stress over the three decades. The fisheries operated at the highest trophic level during the 1980s, and there are some indications of “fishing down the food web” in this ecosystem between the 1980s and the 1990s. Drawing upon Odum’s theory of ecosystem maturity, the structured, web-like ecosystem of the 1960s developed into a highly mature system during the 1980s; yet, in the 1990s, this structure became less complex and the system’s maturity fell to its lowest observed level. During this period, the successional development of the system occurred in reverse.     

Biodiversity and fish farming intensification in French fishpond systems

Fishponds are artificial ecosystems in which biodiversity may be strongly affected by fish farming management. We studied biodiversity variation along a gradient of fish farming intensification within a 180-pond sample of a French region to establish whether biodiversity primarily depended on extensive management with the alternative hypothesis that some habitat characteristics could compensate for the effect of intensification. We compared the relationships of three biodiversity indicators (breeding birds, protected plants, macrophytes) to an index of intensification and to habitat characteristics likely to influence each indicator. In all selected indicators, species richness did not vary according to the composite intensification gradient. Protected plant richness was best explained by periodic drainage, which could thus benefit biodiversity in intensified fishponds provided that shallow littoral areas are still present. Bird richness was linked to macrophyte cover and probably to reed bed areas. Macrophyte richness and coverage were negatively influenced by low water transparency and high fish biomass which seemed likely to affect bird habitat above 350–400 kg/ha. Aquatic vegetation, which may reflect interactive effects of environmental factors and fish farming management, may then contribute to assessment of the ecological status of fishponds under the E.U. Water Framework Directive.     

Revealing Beta-Diversity Patterns of Breeding Bird and Lizard Communities on Inundated Land-Bridge Islands by Separating the Turnover and Nestedness Components

Beta diversity describes changes in species composition among sites in a region and has particular relevance for explaining ecological patterns in fragmented habitats. However, it is difficult to reveal the mechanisms if broad sense beta-diversity indices (i.e. yielding identical values under nestedness and species replacement) are used. Partitioning beta diversity into turnover (caused by species replacement from site to site) and nestedness-resultant components (caused by nested species losses) could provide a unique way to understand the variation of species composition in fragmented habitats. Here, we collected occupancy data of breeding birds and lizards on land-bridge islands in an inundated lake in eastern China. We decomposed beta diversity of breeding bird and lizard communities into spatial turnover and nestedness-resultant components to assess their relative contributions and respective relationships to differences in island area, isolation, and habitat richness. Our results showed that spatial turnover contributed more to beta diversity than the nestedness-resultant component. The degree of isolation had no significant effect on overall beta diversity or its components, neither for breeding birds nor for lizards. In turn, in both groups the nestedness-resultant component increased with larger differences in island area and habitat richness, respectively, while turnover component decreased with them. The major difference among birds and lizards was a higher relevance of nestedness-resultant dissimilarity in lizards, suggesting that they are more prone to local extinctions derived from habitat fragmentation. The dominance of the spatial turnover component of beta diversity suggests that all islands have potential conservation value for breeding bird and lizard communities.     

Estimating the Spatial and Temporal Distribution of Species Richness within Sequoia and Kings Canyon National Parks

Evidence for significant losses of species richness or biodiversity, even within protected natural areas, is mounting. Managers are increasingly being asked to monitor biodiversity, yet estimating biodiversity is often prohibitively expensive. As a cost-effective option, we estimated the spatial and temporal distribution of species richness for four taxonomic groups (birds, mammals, herpetofauna (reptiles and amphibians), and plants) within Sequoia and Kings Canyon National Parks using only existing biological studies undertaken within the Parks and the Parks'' long-term wildlife observation database. We used a rarefaction approach to model species richness for the four taxonomic groups and analyzed those groups by habitat type, elevation zone, and time period. We then mapped the spatial distributions of species richness values for the four taxonomic groups, as well as total species richness, for the Parks. We also estimated changes in species richness for birds, mammals, and herpetofauna since 1980. The modeled patterns of species richness either peaked at mid elevations (mammals, plants, and total species richness) or declined consistently with increasing elevation (herpetofauna and birds). Plants reached maximum species richness values at much higher elevations than did vertebrate taxa, and non-flying mammals reached maximum species richness values at higher elevations than did birds. Alpine plant communities, including sagebrush, had higher species richness values than did subalpine plant communities located below them in elevation. These results are supported by other papers published in the scientific literature. Perhaps reflecting climate change: birds and herpetofauna displayed declines in species richness since 1980 at low and middle elevations and mammals displayed declines in species richness since 1980 at all elevations.     

Bird Communities and Biomass Yields in Potential Bioenergy Grasslands

Demand for bioenergy is increasing, but the ecological consequences of bioenergy crop production on working lands remain unresolved. Corn is currently a dominant bioenergy crop, but perennial grasslands could produce renewable bioenergy resources and enhance biodiversity. Grassland bird populations have declined in recent decades and may particularly benefit from perennial grasslands grown for bioenergy. We asked how breeding bird community assemblages, vegetation characteristics, and biomass yields varied among three types of potential bioenergy grassland fields (grass monocultures, grass-dominated fields, and forb-dominated fields), and assessed tradeoffs between grassland biomass production and bird habitat. We also compared the bird communities in grassland fields to nearby cornfields. Cornfields had few birds compared to perennial grassland fields. Ten bird Species of Greatest Conservation Need (SGCN) were observed in perennial grassland fields. Bird species richness and total bird density increased with forb cover and were greater in forb-dominated fields than grass monocultures. SGCN density declined with increasing vertical vegetation density, indicating that tall, dense grassland fields managed for maximum biomass yield would be of lesser value to imperiled grassland bird species. The proportion of grassland habitat within 1 km of study sites was positively associated with bird species richness and the density of total birds and SGCNs, suggesting that grassland bioenergy fields may be more beneficial for grassland birds if they are established near other grassland parcels. Predicted total bird density peaked below maximum biomass yields and predicted SGCN density was negatively related to biomass yields. Our results indicate that perennial grassland fields could produce bioenergy feedstocks while providing bird habitat. Bioenergy grasslands promote agricultural multifunctionality and conservation of biodiversity in working landscapes.     

Changes in bird distribution in a Central European country between 1985–1989 and 2001–2003

European birds have been significantly affected by dramatic environmental changes during the last decades. The effects of these changes on species richness and distribution in particular countries are still poorly understood because of a lack of high-quality, large-scale data standardized over time. This is especially true in Central and Eastern Europe. On a model group of birds in the Czech Republic (countrywide atlas mapping data), we examined whether long-term changes of species richness and distribution between 1985–1989 and 2001–2003 differed among groups of species defined by their habitat requirements, type of distribution in Europe, migratory strategy and the degree of national legal protection. Further, we investigated the effects of colonizers and local extinctions on these changes. Whereas the number of species in the whole country remained the same in both periods (208 species), species composition had changed. Increasing occupancy (i.e., number of occupied mapping squares) was observed in species of forest and wetland habitats, in short-distance migrants and in non-protected species. Southern species also positively changed their occupancy, but this pattern disappeared after the inclusion of six species dependent on extensively cultivated farmland that went extinct between mappings. The overall occupancy of all species together showed positive changes after excluding colonizers and extinct species. We suggest that the improvement of environmental conditions after 1990 caused the stability of or increased the distribution of common birds in the Czech Republic, and it was the disappearance of specific farmland practices that might have caused the loss of several species.     

Factors affecting otter (<Emphasis Type="Italic">Lutra lutra</Emphasis>) abundance and breeding success in freshwater habitats of the northeastern Iberian Peninsula

Otters are elusive semi-aquatic mammals, occurring in low densities and difficult to count. A study was conducted in 15 stretches (10–12 km) of four tributaries of the Ebro River, with the aims to understand spatial and temporal changes in otter abundance and breeding success and the causes of such variations. Between 1990 and 2009, both otter parameters were assessed by means of visual spring–early summer censuses, carried out by sets of observers located every 500 m. A total of 134 censuses were carried out, involving 4,540 twilight watches (7,896.5 h) and 520 otter sightings were recorded. Also, 39 different habitat characteristics (including prey species) were established for each stretch. Otter abundance was assessed by means of three indexes related to the census effort and the length and surface units (in terms of otter habitat). Excluding the upper stretches, we found on average 0.07–0.26 adult and subadults per kilometre (1.45–6.26/km²). Important interannual fluctuations in otter abundance and breeding success were found in some Pyrenean stretches located downstream of a large reservoir. This was linked to the effect of autumn floods (in part due to the opening of dams) on the fish stocks (mainly Barbels). Similar habitat conditions resulted in similar abundances between stretches, and different habitat conditions generated different abundances in adjacent stretches of the same river. No significant differences were found for litter size between small cubs (1.60 ± 0.70 cubs per litter) and large cubs (1.39 ± 0.50) as a whole, but differences between stretches were found. On average we found between 0.009 and 0.130 large cubs per year per kilometre. Otters bred more successfully in stretches with higher otter densities. Otter abundance and breeding success correlated negatively with altitude as a consequence of the interaction of several habitat characteristics with altitude. The stepwise linear regression linked the number of adult otters per kilometre with the ecosystem production (chlorophyll a concentration), while the number of large cubs per kilometre per year was linked with the food (fish + crayfish) abundance. The findings bring about a consistent and congruent scenario of otter abundance and breeding success explained by the different steps along the food chain.     

Quantitative Brutvogelbestandsaufnahmen im Bodenseegebiet 1980 und 1985

Zusammenfassung Im Bodenseegebiet wurden 1980/81 alle Brutvogelreviere kartiert. 1985 fand mit derselben Methode eine Zwischenzählung auf 15% der Fläche statt (Abb. 1). Auf 31 Probeflächen nahm die Zahl der Brutvogelarten ab, auf 9 Flächen nahm sie zu und auf 6 Flächen blieb sie gleich (Abb. 2). 39 Brutvogelarten zeigten deutliche Abnahmen, 11 Arten deutliche Zunahmen (Tab. 2). Zunahmen bei Waldvögeln hängen vielleicht mit dem Waldsterben zusammen. Vor allem Zugvögel sind vom Rückgang betroffen. Bei den Feldvögeln und den Heckenbrütern nehmen jedoch Standvögel genauso im Bestand ab wie Zugvögel. 6 der 8 häufigsten Arten nahmen weiter zu — das wird als ökologisches Alarmsignal gewertet. In zahlreichen Einzelfällen lassen sich Rückgänge durch Veränderungen der Landschaft belegen.

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Breeding bird counts round Lake Constance in 1980 and 1985

Summary In 1980/81 a complete mapping census of all territory-holding birds round Lake Constance was carried out. In 1985 there was an intermediate census covering 15 percent of the original area using the same method (Fig. 1). The number of birds decreased in 31 study plots, increased in 9 and was constant in 6 (Fig. 2). There was a significant decrease in 39 and a significant increase in 11 species (Table 1). An increase in woodland species was possibly due to dying forests. Mainly migratory birds were affected. In birds holding territories on fields and in shrubs, however, nonmigratory as well as a migratory species, decreased. 6 of the 8 most common species were still increasing, being considered as an ecological alarm signal. In numerous cases a decrease can be proved by structural changes of habitat.

     

Species richness and abundance of forest birds in relation to radiation at Chernobyl

The effects of low-level radiation on the abundance of animals are poorly known, as are the effects on ecosystems and their functioning. Recent conclusions from the UN Chernobyl forum and reports in the popular media concerning the effects of radiation from Chernobyl on animals have left the impression that the Chernobyl exclusion zone is a thriving ecosystem, filled with an increasing number of rare species. Surprisingly, there are no standardized censuses of common animals in relation to radiation, leaving the question about the ecological effects of radiation unresolved. We conducted standardized point counts of breeding birds at forest sites around Chernobyl differing in level of background radiation by over three orders of magnitude. Species richness, abundance and population density of breeding birds decreased with increasing level of radiation, even after controlling statistically for the effects of potentially confounding factors such as soil type, habitat and height of the vegetation. This effect was differential for birds eating soil invertebrates living in the most contaminated top soil layer. These results imply that the ecological effects of Chernobyl on animals are considerably greater than previously assumed.     

Bird assemblages in fragmented agricultural landscapes: the role of small brigalow remnants and adjoining land uses

Agricultural intensification typically leads to changes in bird diversity and community composition, with fewer species and foraging guilds present in more intensively managed parts of the landscape. In this study, we compare bird communities in small (2–32 ha) brigalow (Acacia harpophylla) remnants with those in adjacent uncultivated grassland, previously cultivated grassland and current cropland, to determine the contribution of different land uses to bird diversity in the agricultural landscape. Twenty remnant brigalow patches and adjacent agricultural (‘matrix’) areas in southern inland Queensland, Australia were sampled for bird composition and habitat characteristics. The richness, abundance and diversity of birds were all significantly higher in brigalow remnants than in the adjacent matrix of cropping and grassland. Within the matrix, species richness and diversity were higher in uncultivated grasslands than in current cultivation or previously cultivated grasslands. Forty-four percent of bird species were recorded only in brigalow remnants and 78% of species were recorded in brigalow and at least one other land management category. Despite high levels of landscape fragmentation and modification, small patches of remnant brigalow vegetation provide important habitat for a unique and diverse assemblage of native birds. The less intensively managed components of the agricultural matrix also support diverse bird assemblages and thus, may be important for local and regional biodiversity conservation.     

水位变动影响下三峡库区汉丰湖鸟类群落及多样性

受三峡水库夏落冬涨的水位调控方式影响,位于三峡库区腹心的重庆开州区汉丰湖形成22.5m水位落差。为了解汉丰湖鸟类群落结构与动态水位变化之间的响应关系,2015年3月—2016年2月对汉丰湖鸟类群落结构及多样性进行了调查。共记录鸟类97种,隶属12目32科,其中湿地鸟类49种,主要包括雁鸭类(18种)、鸻鹬类(13种)、鹭类(7种)及秧鸡类(5种)。研究表明:受水位变化影响,鸟类群落结构及其多样性变化显著。夏季(8月)低水位期(水位高程152.50m),鸟种数最高,为34种,Shannon-Wiener指数最高;肉食性鸟与食虫鸟是主要取食功能群;与夏季低水位期生境类型多样、消落带植物正处于生长旺盛期、食物资源丰富有关,是雀形目鸟类、鹭类、秧鸡类等适宜的栖息地。冬季(12月)高水位期(水位高程174.50m),鸟种数为30种,Shannon-Wiener指数、均匀度指数均最低,植食性鸟类是主要的取食功能群,鸟类数量最高;与冬季高水位期水面开阔、生境类型单一有关,高水位期的大水面有利于鸭类集群越冬。冬季在退水期(水位高程170.01m),水位下降导致汉丰湖生境结构变化,越冬鸟类数量和物种丰度降低,空间分布格局也随之变化。鸟类是三峡水库生物多样性的重要组成部分,为保护和提升三峡水库生物多样性,恢复和营造鸟类栖息地,应针对繁殖鸟和越冬水鸟的功能需求进行生态设计。     

千岛湖陆桥岛屿鸟类集团对栖息地片段化的敏感性及其季节变化

为探究千岛湖陆桥岛屿不同鸟类集团对栖息地片段化敏感性的差异和季节变化,于2009年4月—2012年1月鸟类繁殖季(4、5、6月)和冬季(11、12、1月)对千岛湖41个陆桥岛屿鸟类集团进行了研究。结果表明,冬季杂食鸟对片段化敏感性高于食虫鸟,繁殖季时二者无显著差异,繁殖季和冬季时下层鸟对片段化敏感性均高于林冠鸟,冬季留鸟对片段化敏感性高于候鸟,繁殖季则无显著差异。杂食鸟和留鸟对片段化敏感性存在季节差异,而食虫鸟、林冠鸟、下层鸟和候鸟对片段化敏感性均无季节差异。不同鸟类集团对栖息地片段化敏感性的差异和季节变化规律,有助于人们在栖息地管理和保护区设计时采取更有针对性的鸟类保护措施。     

Birds as marine–terrestrial linkages in sub-polar archipelagic systems: avian community composition, function and seasonal dynamics in the Cape Horn Biosphere Reserve (54–55°S), Chile

Marine environments are known to affect adjacent terrestrial biotic communities. In South America’s sub-Antarctic archipelago, birds are the most abundant and diverse terrestrial vertebrate assemblage. We hypothesized that birds would reflect a marine influence that would gradually decrease inland, expecting to find greater species richness, abundance, and biomass near the sea with decreases toward the island interior. We seasonally compared these parameters, with identified indicator species and assessed functional groups at 0, 150, and 300 m from the coast. Unexpectedly, we found a marked marine (0) and terrestrial (150–300) patterns for avian assemblages, rather than a gradient. In addition, seasonal patterns were warm (spring–summer) and cold (autumn–winter). The only parameter that displayed a true gradient was avian biomass in spring. During the cold season, higher values were observed in all variables for coastal assemblages, compared to inland sites. In the warm season, abundance and richness of coastal and terrestrial assemblages were similar, owing to migratory species. Milvago chimango was the only species abundant and frequent in both terrestrial and coastal systems, thereby indicating potential as a marine–terrestrial vector. Functionally, coastal assemblages were conformed of herbivores, carnivores, and scavengers, while terrestrial communities were made up of omnivores and insectivores. We conclude that the sea coast is a unique habitat in this archipelago, providing refuge for both marine and terrestrial sub-Antarctic birdlife particularly in the cold season. The relevance of the land/sea ecotone is poorly known, but important is given to high demand for the installation of salmon aquaculture facilities along the southern Chilean coastline.     

Interspecific interactions and co-existence in dabbling ducks: observations and an experiment

We studied the possible role of resource limitation and interspecific competition in assemblages of dabbling ducks on breeding lakes in Finland and Sweden with observational and experimental data. After initial vegetation mapping and yearly censuses of ducks in 1985–1990, we collected observational data in 1991–1994 from 28 lakes with natural populations of mallard Anas platyrhynchos and teal A. crecca. Mallard and teal co-occur over vast areas in the Holarctic and they are the only breeding dabbling ducks on many oligotrophic lakes. Both species are migratory in our study regions, teal arriving later in spring than mallards. Log-linear model analysis of observational presence/absence data revealed a positive, not a negative, association between the species. This association was independent of habitat diversity as well as of lake size. Mallard-teal interaction was also studied in a cross-over introduction experiment in 32 other lakes in two years. Wing-clipped mallards were introduced to breeding lakes before the arrival of teal to induce resource limitation and interspecific competition, hypothesized to reduce lake use by teal. The density of mallard pairs on experimental lakes was 2.9–8.0 times higher than on controls, but there was no negative response by teal to the treatment. This is the first combined observational-experimental demonstration of lack of interspecific competition in waterfowl. Our results indicate that heterospecific attraction may affect species co-existence in dabbling ducks. Received: 28 October 1996 / Accepted: 13 January 1997     

Avian use of perennial biomass feedstocks as post-breeding and migratory stopover habitat

Increased production of biomass crops in North America will require new agricultural land, intensify the cultivation of land already under production and introduce new types of biomass crops. Assessing the potential biodiversity impacts of novel agricultural systems is fundamental to the maintenance of biodiversity in agricultural landscapes, yet the consequences of expanded biomass production remain unclear. We evaluate the ability of two candidate second generation biomass feedstocks (switchgrass, Panicum virgatum, and mixed-grass prairie) not currently managed as crops to act as post-breeding and fall migratory stopover habitat for birds. In total, we detected 41 bird species, including grassland specialists and species of state and national conservation concern (e.g. Henslow's Sparrow, Ammodramus henslowii). Avian species richness was generally comparable in switchgrass and prairie and increased with patch size in both patch types. Grassland specialists were less abundant and less likely to occur in patches within highly forested landscapes and were more common and likely to occur in larger patches, indicating that this group is also area-sensitive outside of the breeding season. Variation in the biomass and richness of arthropod food within patches was generally unrelated to richness and abundance metrics. Total bird abundance and that of grassland specialists was higher in patches with greater vegetation structural heterogeneity. Collectively, we find that perennial biomass feedstocks have potential to provide post-breeding and migratory stopover habitat for birds, but that the placement and management of crops will be critical factors in determining their suitability for species of conservation concern. Industrialization of cellulosic bioenergy production that results in reduced crop structural heterogeneity is likely to dramatically reduce the suitability of perennial biomass crops for birds.     

Landscape composition and habitat area affects butterfly species richness in semi-natural grasslands

During the last 50 years, the distribution and abundance of many European butterfly species associated with semi-natural grasslands have declined. This may be the result of deteriorating habitat quality, but habitat loss, resulting in decreasing area and increasing isolation of remaining habitat, is also predicted to result in reduced species richness. To investigate the effects of habitat loss on species richness, we surveyed butterflies in semi-natural grasslands of similar quality and structure, but situated in landscapes of different habitat composition. Using spatially explicit habitat data, we selected one large (6–10 ha) and one small (0.5–2 ha) grassland site (pasture) in each of 24 non-overlapping 28.2 km² landscapes belonging to three categories differing in the proportion of the area that consisted of semi-natural grasslands. After controlling for local habitat quality, species richness was higher in grassland sites situated in landscapes consisting of a high proportion of grasslands. Species richness was also higher in larger grassland sites, and this effect was more pronounced for sedentary than for mobile species. However, the number of species for a given area did not differ between large and small grasslands. There was also a significant relationship between butterfly species richness and habitat quality in the form of vegetation height and abundance of flowers. In contrast, butterfly density was not related to landscape composition or grassland size. When species respond differently to habitat area or landscape composition this leads to effects on community structure, and nestedness analysis showed that depauperate communities were subsets of richer ones. Both grassland area and landscape composition may have contributed to this pattern, implying that small habitat fragments and landscapes with low proportions of habitat are both likely to mainly contain common generalist species. Based on these results, conservation efforts should aim at preserving landscapes with high proportions of the focal habitat.