Mean Species Richness Of Birds Research Articles

Acoustic indices estimate breeding bird species richness with daily and seasonally variable effectiveness in lowland temperate Białowieża forest

Acoustic indices have been proposed as rapid and easy to apply tool for biodiversity estimation of vocalising animals without the need for individual species identification. However, inconclusive, or even opposite dependencies between acoustic indices and animal biodiversity found in various studies suggest that their effectiveness is environmentally variable.Here we examined how three acoustic indices: Bioacoustic Index (BI), Acoustic Complexity Index (ACI) and Acoustic Diversity Index (ADI) predict bird species richness in a species-rich, lowland temperate forest in Europe – the Białowieża Forest. We recorded soundscape in early and late spring at 84 recording points. We analysed 72 1-min sound samples collected per recording point to evaluate how well acoustic indices predict bird species richness from the perspective of a single sound sample, survey and recording point and how they follow the daily pattern of singing activity.When we compared the values of acoustic indices with the number of bird species detected manually in 1-min sound samples, we found BI to best predict the bird species richness, independently of time in the season but variably across the day, while ACI and ADI showed weaker dependency, variable both seasonally and daily. The correlation between each index and number of bird species was stronger in the early part of the season. Averaged by survey or recording point, the acoustic indices correlated more strongly with the mean compared to the total bird species richness, and provided better estimation of bird biodiversity in the early than the late survey. At the level of the recording point, BI correlated most strongly with mean bird species richness (rho = 0.584), while ADI correlated most strongly with total bird species richness (rho = -0.347). Acoustic indices followed daily bird activity pattern, yet they provided greater values before the peak of the species richness estimated by manual spectrogram scanning and listening to recordings.In this study acoustic indices correlated moderately to strongly with the bird species richness, providing a useful tool for rapid estimation of bird biodiversity in temperate forests. However, daily and seasonal variation in effectiveness of acoustic indices should be taken into account in the analysis. Using the mean instead of the total number of bird species in comparisons improved the effectiveness of indices but measured different aspects of biodiversity.

The response of plants, carabid beetles and birds to 30 years of native reforestation in the Scottish Highlands

Abstract Globally, there is increasing interest in tree planting, leading to many country‐level commitments to reforestation. In the UK, current commitments would achieve 17% forest cover by 2050, with the highest rates of forest expansion expected in Scotland. Forest expansion with native trees is expected to increase biodiversity, particularly woodland specialist species, and associated ecosystem services. Despite this, data on biodiversity changes over the early stages of reforestation are sparse, particularly for upland areas in Scotland where opportunities for forest expansion are greatest. We collected data on the response of plants, carabid beetles and birds to native reforestation and grazing exclusion, using sites reforested over the last 30 years in the Scottish Highlands. Biodiversity in ungrazed, reforested sites was compared to unforested controls and mature native forest, both grazed and ungrazed. Mean bird species richness in reforested plots (4.4 [95% CI: 3.2, 5.9]) was higher than in unforested plots (0.8 [0.5, 1.3]), but lower than in mature forest plots (7.0 [5.4, 8.3]). In contrast, there was no systematic difference in plant or carabid beetle species richness in reforested, unforested or mature forest plots, or between grazed and ungrazed plots for the species richness of any groups. Woodland specialist bird and plant species were found in the reforested plots, and richness of woodland specialist bird species was predicted to reach levels in mature forest c. 36 years after reforestation. Species assemblages differed across habitat categories. For birds and plants, species assemblages in reforested sites were intermediate to unforested and mature sites. For carabid beetles, the assemblages in mature and reforested sites were comparable and differed from unforested sites. Grazing did not strongly influence species assemblages. Policy implications. We show that woodland specialists colonise reforested sites and species assemblages transition towards those found in the target habitat within the first 30 years of reforestation with native species. Native forest should be prioritised in Scotland's future forest expansion targets, given that mature native forest is scarce and fragmented in the Scottish Highlands and that the ultimate gain from native forest expansion may accrue over long time‐scales.

The species and functional diversity of birds in almond orchards, apple orchards, vineyards and eucalypt woodlots

Agriculture is the predominant land use in Australia. Yet, there is limited knowledge of which bird species use particular agricultural crops and the implications this has for crop damage or the provision of ecosystem services. We measured species and functional diversity of bird communities in almond and apple orchards, vineyards and eucalypt woodlots. Mean bird species richness was highest in almond orchards and eucalypt woodlots and lowest in vineyards. Species diversity was highest in almond orchards, but similar among the other land uses. Bird community composition clearly differed among land uses, indicating the need to treat particular crop types as different ‘habitats’. The functional diversity of bird communities differed across land uses dependent on the functional traits and metric used to calculate diversity. Eucalypt woodlots had the highest functional richness of bird reproductive traits, whereas the highest richness of bird foraging traits was recorded in almond orchards. Importantly, increasing land-use intensification did not reduce functional diversity in a consistent way. Bird species that may damage crops or help control crop pests were common across land uses. Moreover, we recorded large numbers of the threatened eastern subspecies of the Regent Parrot (Polytelis anthopeplus monarchoides) in almond orchards. Future management of Australian agro-ecosystems should find an appropriate balance between bird conservation, limiting costs from bird damage, and promoting the provision of ecosystem services by birds.

Breeding Bird Response to Field Border Presence and Width

Avian communities can benefit from reconstructed herbaceous, strip habitats among agriculture; however, any benefits may be limited by width-dependent factors such as edge effects. We used 2 years of strip-transect surveys to evaluate avian density, richness, and conservation value between non-, narrow (mean width = 8.2 m), and wide (mean width = 40.7 m) field borders on intensive row-cropped field margins in the agriculture-dominated Mississippi Alluvial Valley. Wide field borders supported two times more birds (7.0 birds/0.2 ha) than narrow borders (3.6 birds/0.2 ha), which supported six times more birds than no border (0.6 birds/0.2 ha). Mean bird species richness was over five times greater in bordered (0.80–1.10 species/0.2 ha) than non-bordered margins (0.14 species/0.2 ha), but was largely uninfluenced by border width. We documented more bird use of agricultural fields and wooded fencerows adjacent to bordered than non-bordered margins. Red-winged Blackbirds (Agelaius phoeniceus) and Dickcissels (Spiza americana) had the strongest positive response to field border presence and width. Wide borders attracted high densities (2.0 birds/0.2 ha) of Dickcissels, an edge-sensitive species, suggesting the conservation potential of herbaceous vegetation patches <50 m of wooded edges for grassland birds. Extensive implementation of field borders, particularly of enhanced width, may contribute substantially to grassland bird conservation strategies in intensive, agricultural landscapes, although confirmation of these benefits requires additional demographic information.

Rapid assessment indicator of wetland integrity as an unintended predictor of avian diversity

Rapid assessment of aquatic ecosystems has been widely implemented, sometimes without thorough evaluation of the robustness of rapid assessment metrics as indicators of ecological integrity. Here, we evaluate whether the Ohio Rapid Assessment Method (ORAM) for Wetlands Version 5.0 is a useful indicator of ecological integrity beyond its intended purpose. ORAM was developed to categorize natural wetlands for regulatory purposes and to contribute to the development of indicators of biotic integrity. It was never intended for use as an index of the quality of habitat for wetland birds. Nonetheless, it is conceivable that ORAM scores could serve as adequate predictors of avian diversity. We evaluated whether avian species richness in wetlands could be reliably predicted from each of the following variables: (1) total ORAM score, (2) total score minus the score for one metric that did not apply to all wetlands, and (3) sum of scores for the four ORAM components (of 16 scored) with the highest potential point total. These four components corresponded to aquatic vegetation communities, microtopography, modifications to natural hydrologic regime, and sources of water. All three variables were significant predictors of both total species richness and mean species richness of birds of conservation concern. Variable (3) was a significant predictor of mean species richness of wetland-dependent birds. Variable (2) was a weak predictor of both total and mean species richness of all birds combined. These results extend the robustness of ORAM as an indicator of the ecological integrity of wetlands.

Black-tailed prairie dogs and the structure of avian communities on the shortgrass plains.

We tested the hypothesis that black-tailed prairie dogs (Cynomys ludovicianus) influence avian community structure on the shortgrass prairie. We surveyed 36 prairie dog towns and 36 paired sites without prairie dogs during summer and fall of 1997, 1998, and 1999 in the Oklahoma Panhandle. Our surveys totaled 9,040 individual observations for 73 avian species. Significantly distinct avian communities were present on prairie dog towns when compared to sites within four different macrohabitats of the surrounding landscape: open rangeland, scrub/sandsage (Artemisia filifolia) habitats, Conservation Reserve Program (CRP) plots, and fallow crop fields. Relative densities of all bird species combined was higher on prairie dog towns versus paired sites in summer and fall. Mean species richness of birds was significantly higher on prairie dog towns than paired sites during summer, but there were no significant differences in fall. Open rangeland had the highest mean species richness in fall. Assemblages of avian communities differed significantly between prairie dog towns and the four macrohabitat types during summer. Burrowing owls (Athene cunicularia), killdeer (Charadrius vociferous), horned larks (Eremophila alpestris), and meadowlarks (Sturnella spp.) were positively and significantly associated with prairie dog towns during summer, while horned larks and ferruginous hawks (Buteo regalis) were significantly associated with prairie dog towns during fall. Even in their current remnant state, black-tailed prairie dogs continue to play a significant role in the assembly of ecological communities across the Great Plains. Conservation of prairie dogs goes well beyond a single species, and is an important strategy for the preservation of the prairie ecosystem as a whole.

AN EVALUATION OF CANADA'S PERMANENT COVER PROGRAM: HABITAT FOR GRASSLAND BIRDS?

In the early 1990s Agriculture Canada's Permanent Cover Program (PCP) converted over 445,000 ha of cropland to perennial vegetative cover. The wildlife benefits of the PCP have not been the subject of previous research. We conducted grassland bird surveys on 629 PCP sites and 564 cropland sites across Alberta, Saskatchewan, and Manitoba between 25 May and 3 July 1998. PCP sites showed higher avian species richness than cropland, and nine of 10 commonly detected grassland bird species occurred at higher frequencies in PCP than cropland. PCP sites were characterized by taller, denser vegetation and less bare ground than cropland sites. Hayed and grazed PCP sites differed significantly in their vegetative structure and avian community composition, but did not differ in species richness or evenness. Mean bird species richness at both cropland and PCP sites was significantly lower in the aspen parkland ecoregion than in the mixed and moist-mixed grassland ecoregions. Logistic regression identified 18 geographic and vegetative variables that significantly influenced the occurrence of individual species, but models for only two species predicted both presence and absence with greater than 50% accuracy. Avian productivity on PCP lands must be determined to appraise definitively the quality of this habitat for grassland birds.