Increased grazing and dominance of an exotic pasture (Bothriochloa pertusa) affects vertebrate fauna species composition, abundance and habitat in savanna woodland

2011 ◽  
Vol 33 (1) ◽  
pp. 49 ◽  
Author(s):  
Alex S. Kutt ◽  
Alaric Fisher
Keyword(s):  
Species Composition ◽  
Bird Species ◽  
Information Criteria ◽  
Tree Cover ◽  
Theoretic Approach ◽  
Pasture Grass ◽  
Bird Abundance ◽  
Vertebrate Fauna ◽  
Species Response ◽  
Information Theoretic Approach

The invasion of exotic pasture species into intact woodlands has the potential to affect native fauna by altering habitat structure and ecosystem function. The spread of these weeds is generally in concert with cattle grazing, so that fauna or habitat change is due to multiple interrelated causes. In this study we investigated whether the spread of the introduced pasture grass Bothriochloa pertusa and replacement of the native bluegrass B. ewartiana in eucalypt woodlands of northern Queensland has had an effect on terrestrial vertebrate fauna. We located 40 sites that sampled a range of native and introduced pastures cover, and investigated the spatial pattern of abundance with canonical analysis of principle coordinates, and correlation of the habitat attributes on the ordination space. We then selected a subset of four habitat attributes (eliminating highly colinear variables) and modelled species response to each using an information-theoretic approach. Thirty-one species (26 birds, one mammal and four reptiles) and two summary variables (bird abundance and richness) had best subset Akaike Information Criteria models with reliable parameters estimates. Seventeen models contained the B. pertusa frequency term and a further 16 had a term relating to upper storey cover (tree cover >10, 5–10 or 3–5 m). Though pasture grass cover, grazing and habitat features were correlated and thus we cannot ascribe B. pertusa as the sole determinant of fauna species change, this study has demonstrated that tropical savanna woodlands with changing Bothriochloa dominance from native to introduced species have different fauna species composition. In particular bird species richness, ground nesting species (e.g. rufous songlark Cincloramphus mathewsi, golden-headed cisticola Cisticola exilis) and terrestrial reptiles (e.g. Carlia munda and Ctenotus taeniolatus) declined. Disturbance-tolerant species such as Australian magpie Cracticus tibicen and yellow-throated miners Manorina flavigula increased in abundance in exotic pasture-dominated sites. As pastoral intensification continues in northern Australian rangelands there is a potential for significant change in the relative abundance and composition of vertebrate fauna and the reduction or loss of some species in the landscape.

Bird communities and vegetation associations across a treeline ecotone in the Mealy Mountains, Labrador, which is an understudied part of the boreal forest

2015 ◽  
Vol 93 (6) ◽  
pp. 477-486 ◽  
Author(s):  
Keith P. Lewis ◽  
Brian M. Starzomski
Keyword(s):  
Species Composition ◽  
Bird Species ◽  
Bird Communities ◽  
Tree Cover ◽  
Strong Impact ◽  
Avian Diversity ◽  
Bird Abundance ◽  
Treeline Ecotone ◽  
Point Counts ◽  
Deciduous Shrub

We examined the factors structuring bird communities across a complex subarctic treeline in the Mealy Mountains, Labrador, Canada. Using point counts of bird abundance in 2007 and 2008, we show that changes in vegetation driven by elevation are strongly correlated with avian community structure in this treeline ecotone system. Overall, avian diversity was higher in the forest compared with other habitat classes (krummholz, deciduous shrub, and alpine). There were strong correlations between avian diversity and vegetation richness, as well as structure, among and within habitat class in 2008. Numerous habitat types (subset of habitat class) were correlated with avian composition, although some species were clearly habitat generalists. Contrary to expectation, avian species composition was associated with physiognomy (vegetation structure) in alpine and deciduous shrub, and with either physiognomy or floristics (vegetation species composition) in krummholz and forest. Given the strong impact of elevation on vegetation and the demonstrated influence on bird communities, we note that for bird species whose near-southernmost populations are found in the Mealy Mountains, climate change is likely to have a strong negative effect if alpine tundra habitat is lost. Furthermore, forest bird species are likely to benefit from the increased tree cover as treeline moves poleward and upward.

scholarly journals Does organic farming benefit farmland birds in winter?

2009 ◽  
Vol 6 (1) ◽  
pp. 82-84 ◽  
Author(s):  
D. E. Chamberlain ◽  
A. Joys ◽  
P. J. Johnson ◽  
L. Norton ◽  
R. E. Feber ◽  
...  
Keyword(s):  
Organic Farming ◽  
Bird Species ◽  
Theoretic Approach ◽  
Farmland Birds ◽  
Organic Farms ◽  
Bird Abundance ◽  
Farm Type ◽  
Habitat Differences ◽  
Synthetic Pesticide ◽  
Information Theoretic Approach

The generally higher biodiversity on organic farms may be influenced by management features such as no synthetic pesticide and fertilizer inputs and/or by differences in uncropped habitat at the site and landscape scale. We analysed bird and habitat data collected on 48 paired organic and conventional farms over two winters to determine the extent to which broad-scale habitat differences between systems could explain overall differences in farmland bird abundance. Density was significantly higher on organic farms for six out of 16 species, and none on conventional. Total abundance of all species combined was higher on organic farms in both years. Analyses using an information-theoretic approach suggested that both habitat extent and farm type were important predictors only for starling and greenfinch. Organic farming as currently practised may not provide significant benefits to those bird species that are limited by winter food resources, in particular, several declining granivores.

Abundance and species composition of amphibians, small mammals, and songbirds in riparian forest buffer strips of varying widths in the boreal mixedwood of Alberta

2002 ◽  
Vol 32 (10) ◽  
pp. 1784-1800 ◽  
Author(s):  
Susan J Hannon ◽  
Cynthia A Paszkowski ◽  
Stan Boutin ◽  
Jordan DeGroot ◽  
S Ellen Macdonald ◽  
...  
Keyword(s):  
Species Composition ◽  
Small Mammals ◽  
Riparian Forest ◽  
Bird Species ◽  
Bird Community ◽  
Forest Harvesting ◽  
Buffer Strips ◽  
Bird Abundance ◽  
Post Harvest ◽  
Managed Landscapes

Forested buffer strips are left along water bodies after forest harvesting to protect water quality and fish stocks, but little is known about their utility as reserves for forest species in managed landscapes. We report on changes in terrestrial vertebrate communities from pre- to post-harvest in experimentally created buffer strips (20, 100, 200, and 800 m wide) in a boreal mixedwood forest in Alberta, Canada. We trapped anuran amphibians and small mammals and spot-mapped bird territories around 12 lakes (4 treatment levels, 3 replicates) before and after harvesting. Changes in small mammal or amphibian abundance were not detected for any treatment relative to controls; however, these species are habitat generalists that used and even bred in clearcuts. Total bird abundance did not change after harvesting, with the exception of crowding in 20-m buffers 1 year post-harvest. Species composition did not change for amphibians and small mammals after harvest, but forest-dependent bird species declined as buffer width narrowed from 200 to 100 m and narrower. We concluded that 20–100 m buffers would not serve as reserves for forest songbirds in managed landscapes, but that 200 m wide strips conserved the pre-harvest passerine bird community, at least up to 3 years post-harvest.

scholarly journals When growth models are not universal: evidence from marine invertebrates

2013 ◽  
Vol 280 (1768) ◽  
pp. 20131546 ◽  
Author(s):  
Andrew G. Hirst ◽  
Jack Forster
Keyword(s):  
Marine Invertebrates ◽  
Growth Models ◽  
Marine Invertebrate ◽  
Exponential Model ◽  
Early Ontogeny ◽  
Information Criteria ◽  
Growth Patterns ◽  
Theoretic Approach ◽  
Important Challenge ◽  
Information Theoretic Approach

The accumulation of body mass, as growth, is fundamental to all organisms. Being able to understand which model(s) best describe this growth trajectory, both empirically and ultimately mechanistically, is an important challenge. A variety of equations have been proposed to describe growth during ontogeny. Recently, the West Brown Enquist (WBE) equation, formulated as part of the metabolic theory of ecology, has been proposed as a universal model of growth. This equation has the advantage of having a biological basis, but its ability to describe invertebrate growth patterns has not been well tested against other, more simple models. In this study, we collected data for 58 species of marine invertebrate from 15 different taxa. The data were fitted to three growth models (power, exponential and WBE), and their abilities were examined using an information theoretic approach. Using Akaike information criteria, we found changes in mass through time to fit an exponential equation form best (in approx. 73% of cases). The WBE model predominantly overestimates body size in early ontogeny and underestimates it in later ontogeny; it was the best fit in approximately 14% of cases. The exponential model described growth well in nine taxa, whereas the WBE described growth well in one of the 15 taxa, the Amphipoda. Although the WBE has the advantage of being developed with an underlying proximate mechanism, it provides a poor fit to the majority of marine invertebrates examined here, including species with determinate and indeterminate growth types. In the original formulation of the WBE model, it was tested almost exclusively against vertebrates, to which it fitted well; the model does not however appear to be universal given its poor ability to describe growth in benthic or pelagic marine invertebrates.

A cross-continental look at the patterns of avian species diversity and composition across an urbanisation gradient

2015 ◽  
Vol 42 (7) ◽  
pp. 554 ◽  
Author(s):  
Barbara Clucas ◽  
John M. Marzluff
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Urban Areas ◽  
Gradient Methods ◽  
Bird Species ◽  
Bird Diversity ◽  
Biological Traits ◽  
Bird Abundance ◽  
Bird Feeders ◽  
Urbanisation Gradient

Context As humans become increasingly urban, the need for conservation of nature in cities increases and requires an understanding of the patterns and processes of urban ecosystems. In particular, because humans are the most dominant species in urban areas, understanding the role humans play in these ecosystems (direct and indirect) will be of primary importance. Aims We examine the diversity and composition of bird species across an urbanisation gradient in two cities (Berlin, Germany, and Seattle, Washington, USA). We determine the degrees of species urban tolerance and examine how certain biological traits of species, namely, diet, whether or not species use bird feeders, nest sites and innovation rate, characterise species urban tolerance. Finally, we determine whether human provisioning (bird feeders and nest boxes) influences what types of species persist across the urbanisation gradient. Methods We surveyed bird abundance and species richness using point counts and surveyed human provisioning by conducting door-to-door interviews of residents across an urbanisation gradient in Berlin and Seattle. Key results We found that patterns of species richness were similar in both cities, but that species composition in Berlin changed less across the urbanisation gradient than it did in Seattle. The majority of birds in Berlin were urban tolerant, whereas in Seattle, they were moderately urban tolerant and intolerant. A cluster analysis revealed that, in general, in Berlin, omnivorous, open-nesting birds that use bird feeders and have relatively high innovation rates tended to be urban tolerant. In Seattle, birds that were mostly omnivorous, nested in open cups, and used bird feeders tended to be moderately urban tolerant and they were influenced by provisioning of food by humans. Conclusion Urbanisation and human interactions with birds can act as ecological filters, favouring certain bird species that can lead to varying species compositions across an urban gradient. These differences in species composition across the gradient may be more noticeable in younger cities than in older cities where the filtering process has been occurring for longer time. Implications By providing a variety of habitats and supplementing natural foods and nesting places, urban planners and residents can help conserve bird diversity in urban areas.

Effects of mechanical strip thinning of aspen on small mammals and breeding birds in northern Minnesota, U.S.A.

1996 ◽  
Vol 26 (7) ◽  
pp. 1284-1294 ◽  
Author(s):  
Donald P. Christian ◽  
Marlys Reuvers-House ◽  
Joann M. Hanowski ◽  
Gerald J. Niemi ◽  
John G. Blake ◽  
...  
Keyword(s):  
Species Composition ◽  
Community Composition ◽  
Small Mammals ◽  
Bird Species ◽  
Breeding Birds ◽  
Deciduous Forests ◽  
Negative Effects ◽  
Long Distance ◽  
Bird Abundance ◽  
Forest Songbirds

Abundance and species composition of small mammals and breeding birds were studied on mechanically strip-thinned aspen stands and comparable reference stands in northern Minnesota. Strip-thinned stands included sapling-sized stands thinned 1 or 2 years before the study and pole-sized stands thinned 7–11 years previously. Fewer individual birds were observed on sapling-sized thinned than reference stands, reflecting primarily decreases in abundances of bird species that select midsuccessional deciduous forests; several of these species are long-distance migrants. Bird abundance and community composition on thinned and reference pole-sized stands were similar, differing most notably in the presence of Canada Warbler (Wilsoniacanadensis (L.)) and Downy Woodpecker (Picoidespubescens (L.)) in thinned but not reference stands. Significantly more individual small mammals were captured on thinned than reference stands, and most other measures of abundance indicated positive numerical responses of small mammals to strip thinning. Mechanical strip thinning of aspen shows promise for enhancing aspen supply by allowing trees to grow more rapidly to harvestable size. Our results suggest that use of this practice has no negative effects on small mammals and relatively short-lived negative effects on forest songbirds at the stand level.

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