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Intensive forest management has caused a decline in the numbers of birds specialized on old growth. Understanding how forest stand attributes influence the distribution of these specialists has hence become a prerequisite for sustainable forest management. In this study, we evaluated the conservation value of managed forests for old-growth forest specialists using the poorly studied Semi-collared Flycatcher as an example. We applied a boosted generalized additive model to identify forest characteristics that determine the occurrence of the bird in Bulgaria. We found that on a national scale, forest stand age and percent cover of broad-leaved forests best explain the breeding distribution of the flycatcher. Although, forest stands became suitable habitat at an age of around 70 years for this species, stands in the interior forest featuring trees older than 160 years and composed of more than 80% broad-leaved trees were preferred by the species. At a local scale, the amount of dead wood positively influenced nest site choice of the flycatcher. In total, 22.3% of all studied broad-leaved forests in Bulgaria showed a predicted habitat suitability higher than 50%. High-stem forests that are old enough to develop old-growth characteristics had the highest potential to serve as habitat for the Semi-collared Flycatcher in Bulgaria. Therefore, we conclude that a decrease in logging of forests stands older than 160 years decreases the risk of decline of the Semi-collared Flycatcher.

Understanding the rules of habitat selection and the individual behavioural routines in the home-range is crucial for developing evidence-based conservation action. We investigated habitat selection and range use of adult little owls Athene noctua in relation to landscape configuration, habitat structure and resource distribution. We determined the preference of habitat structures by VHF-telemetry. Large- and fine-scale distribution patterns of voles – the main prey during the breeding season – were assessed by transect counts of signs of vole presence. An experiment using artificial perches was carried out to determine the fine-scale adjustment of the owls' range use in relation to prey abundance and vegetation height. Habitat selection and resource exploitation by little owls were structured at all spatial levels: (1) at the landscape scale, orchards were highly preferred over other areas. This accords with the patchy large-scale occurrence of voles, which were absent in cropland, but abundant in orchards and grassland; (2) within home-ranges, the spatial distribution of voles was highly inhomogeneous and structures with high prey abundance were used over-proportionally; (3) at the scale of foraging sites, little owls preferred patches with low vegetation over those with high prey abundance, establishing that prey availability is the crux. The results suggest that all levels of habitat selection and range use were related to farming practices and affected by current cultivation. Conservation measures should focus on the conservation and restoration of orchards on the landscape level and habitat management measures should focus on grasslands – the main food providers – by creating a mosaic of patches with short grass and tall grass. Together with other habitat structures providing food resources such as field edges, wildflower areas and structures facilitating access to prey, the quality of habitat patches in terms of food availability may be highly improved.

Within the European Union, national approaches of a ‘High Nature Value (HNV) farmland’ indicator have been developed to inform about the potential of agricultural landscapes to maintain biodiversity. We assessed how bird species abundance, richness and community composition, particularly of specialist species, were associated with the German HNV farmland indicator as an area-based aggregate and with its particular components which were semi-natural landscape elements and agricultural patches with characteristic plant species mapped in representative sample plots. The aggregated HNV indicator score showed a weak but positive relationship with generalist bird species only, while specialist species were associated with individual HNV farmland features characterizing wet grasslands and open farmland. Bird community analysis revealed three groups of HNV farmland features representative of particular landscape types: (1) complex landscapes with vertical woody structures such as hedgerows or small woodlands, (2) wet grasslands and (3) open agricultural land of low land-use intensity. Large portions of unexplained variance, however, indicated that the small-scaled HNV farmland features recorded without considering the landscape context may not have fully captured all important drivers of bird diversity in agricultural landscapes. To achieve a better representation of habitat requirements particularly of specialist bird species we propose surveying HNV farmland in a landscape context and calculating landscape-specific scores for highly structured, wetland-dominated and open landscapes of low land-use intensity. As compared to the aggregated indicator, the small-scale HNV farmland survey data would more efficiently enfold its potential for tailoring conservation schemes specifically to a given landscape type and its associated bird species.

Central Europe has the responsibility to protect the Red Kite Milvus milvus as it holds the majority (>50 % of all breeding pairs) of the global population. This entails the need for comprehensive knowledge of the birds’ ecology and distribution. Currently, only little is known about the factors limiting both the global occurrence of the Red Kite and its distribution on regional scales. In this study we analysed the effect of land use on the breeding distribution of Red Kites throughout Germany, the species’ core distribution area, using a distribution model. For the first time, an extensive data set was used for modelling comprising a sample size of 2,625 Red Kite breeding sites, high-resolution land-use data (10 m × 10 m) and climatic as well as topographic variables. The model revealed a strong relationship between land-use patterns and the Red Kite’s distribution. Furthermore, a comparison of the predicted habitat suitability map with the actual distribution of Red Kites showed that not all suitable habitats were occupied by the species and thus, the species’ distribution seems not to be in equilibrium with its environment. The differences between actual and predicted distribution may stem from present or former high mortality rates which are not compensated for by current reproduction rates. Additionally, low juvenile dispersal of Red Kites reduces recolonisation of unoccupied patches.

The use of artificial nest boxes to bolster populations of endangered cavity-nesting birds has increased significantly, but spatial variation of nest-box occupancy rates and breeding success within a nest-box population has been little studied. In a case study with 798 Little Owl (Athene noctua) nest boxes established in central Germany, we analyzed the dependence of occupancy rate and breeding success on the characteristics of the surrounding habitat. The analysis focused on two aspects of general concern for nest-box management: (1) whether nest boxes were occupied for breeding or were left unoccupied, and (2) whether Little Owls had different reproductive rates, depending on the location of nest boxes. A high resolution (1 × 1 m) land-use map was used to analyze species-habitat relationships, and Generalized Linear Mixed Models were used to predict suitable nest-box locations. During the period from 2004 to 2006, 544 (68%) of the nest boxes were never occupied, 144 (18%) housed birds with low ...

Distance sampling (DS) and territory mapping (TM) are globally applied bird survey techniques. However, specifically designed studies comparing results of both methods in different habitats in the framework of a scientific experiment have rarely been conducted. To provide a more generalized guidance for the field surveyor, here we evaluated estimates of bird abundances and number of bird species in four different habitats (broad-leaved forest, coniferous forest, open woodland and farmland) in central Germany. Abundances were estimated in parallel by TM and DS in 2006 and 2008, following standard protocols. Detection probability differed significantly among habitats and species. Density estimates by DS were in total 24% lower than those estimated by standardized TM. While the number of bird species detected with both methods was approximately the same, the estimated abundances of 15 bird species showed significant differences. Increasing the number from two to four and five registrations to count a territory by using TM decreased the density on average about 28 and 42%, respectively. Using standardized TM resulted in an overestimation of abundances of species showing a high detection probability. In contrast, DS estimated very high densities for species that had a very low detection probability. In fact, a highly negative correlation was found between the density estimated by DS and the detection probability. Using standardized TM and setting a fixed number of registrations before a location qualifies for a bird territory cannot compensate for the large differences in species detectability. Instead, the number of registrations required to count a territory should be adjusted to differences in detection probabilities and seasonal activity. From our results we can recommend a mean of four registrations if eight visits were conducted to count a territory. However, the lack of any statistically-based quality assessment reduces the serious usability of TM for estimating densities for science-based management application, whereas, the clear advantage of DS is that it provides error estimates and considers differences in species detectability.

For a large number of threatened bird species, no information on habitat requirements or population estimates are available. We show for one of the least-studied African birds, the Oberlander's Ground-Thrush Zoothera oberlaenderi, how a first assessment of its habitat preferences and population size can be done if a short-term census is combined with a GIS-based species–habitat analysis. Between 9 February and 14 March 2008, we made intensive field surveys, using point counts and mist-netting in Semliki and Bwindi Impenetrable National Parks (BINP), two forests in Uganda from which there are previous records. While the species was not recorded in Semliki, eight were heard singing in BINP. We made the first analysis of this species’ habitat preferences by analysing all records of the species with variables extracted from GIS layers for the BINP. It preferred dense forest types, close to rivers and at elevations of 1 500–1 935 m. Using detailed habitat information we calculated 30 km2 of suitable habitat (o...

The Caucasian black grouse (CBG) is classified as “data deficient” by the IUCN. Lack of information to guide conservation measures is mainly due to the bird’s elusive behaviour for much of the year and to its remote distribution at higher altitudes of the Caucasus Mountains. In order to fill some of the knowledge gaps, we mapped potential suitable habitat across the Turkish part of the Lesser Caucasus using a spatial regression model, and estimated the total CBG population from alternative assumptions on population density and habitat separation. The CBG model was derived from 167 CBG records obtained during a survey in representative areas of the Turkish Caucasus, in conjunction with a supervised habitat classification of satellite images and with topographic parameters calculated from a digital elevation model. In total, approx. 5,000 km2 of suitable habitat were predicted to exist within the borders of Turkey, including areas where the CBG has not previously been searched for. Under conservative assumptions, this area can carry more than 4,800 individuals, which is higher than previously estimated. The predicted distribution map can be used to select priority areas for conservation and to specify additional survey locations of the species in areas, which so far have been less well sampled.

The Serengeti–Mara ecosystem holds one of the largest natural grasslands of the world, which is well known for its large herds of mammals. However, the bird community structure of these grasslands has hardly ever been studied. For the first time, a large-scale study on grassland bird communities has been conducted in all typical open grasslands of the Serengeti National Park. We used ten grassland plots representing a gradient of increasing vegetation height and also including shrubs and trees to analyse the influence of vegetation structure on the composition of grassland bird communities. Three communities of breeding birds were identified in relation to (a) short grass, (b) intermediate and long grass and (c) wooded grasslands. The bird communities of intermediate, long and wooded grassland were very similar, because of identical dominant bird species. Our results suggest that breeding birds of East African grasslands exhibit two contrasting habitat relationships: (1) birds that are restricted to short grass, and (2) species that are tolerant to vegetational shifts from intermediate grass via long grass to early stages of woody vegetation. Because the vegetation is often driven beyond this range in managed tropical grasslands through high grazing pressure or through shrub encroachment, we expect that the long-grass bird communities will not generally resist anthropogenic disturbance. Resume L’ecosysteme Mara-Serengeti contient une des plus vastes prairies naturelles du monde, bien connue pour ses importantes populations de mammiferes. Cependant, la structure de la communaute aviaire a a peine eteetudiee. Pour la premiere fois, une etude a grande echelle a ete realisee sur les communautes d'oiseaux des savanes herbeuses dans toutes les prairies ouvertes typiques du Parc National de Serengeti. Nous avons delimite 10 plots de prairies representant un gradient de hauteur de vegetation croissant et comprenant aussi des arbustes et des arbres, afin d'analyser l'influence de la structure de la vegetation sur la composition des communautes aviaires en savane herbeuse. On a identifie trois communautes d'oiseaux reproducteurs liees (a) a l'herbe rase, (b) a l'herbe intermediaire ou haute et (c) a la savane arboree. Les communautes d'oiseaux des herbes intermediaires, hautes et arborees etaient tres semblables en raison de l'espece d'oiseau dominante identique dans les deux milieux. Nos resultats laissent penser que les oiseaux reproducteurs des prairies est-africaines presentent deux types contrastes de relation avec leur habitat: (1) les oiseaux qui se limitent aux herbes courtes et (2) les especes qui tolerent des changements de vegetation entre herbes intermediaires et hautes et les stades precoces de vegetation ligneuse. Comme la vegetation evolue souvent au-dela de cet etat dans les prairies tropicales gerees qui connaissent un pâturage intense ou l'envahissement des buissons, nous nous attendons a ce que les communautes qui vivent dans les hautes herbes ne resistent generalement pas aux perturbations d'origine humaine.

In this study we assess possible benefits of using satellite sensor data in large-scale landscape ecology. The study was conducted on the Serengeti Plains, Tanzania, combining (1) records from a bird survey, (2) local measurements of vegetation structure and precipitation, and (3) a habitat map derived from a Landsat satellite image classification. The question of whether ground-based or satellite data explained more of the species-environment relationships was explored by means of multivariate regression. On average across all 62 bird species recorded, the combination of satellite-based and groundbased data improved explained variance (R 2 = 0.26), as compared to satellite sensor data, or ground-based data alone (R 2 = 0.18 and 0.21, respectively). In spite of this low level of explained variance in the regressions, a classification of bird species according to utilised parameter space yielded reasonable results. Satellite image data seem to be suited to this kind of investigation. Ostrich 2007, 78(2): 259–263

High resolution remote sensing data facilitate the use of small-scale habitat features such as trees or hedges in the analysis of species–habitat relationships. Such data potentially enable more accurate species–habitat mapping than lower resolution data. Here, for the first time, we systematically investigated this hypothesis by altering the spatial resolution from 1 m up to 1000 m grain size in species–habitat models of 13 bird species. The study area covered the Nidda river catchment in central Germany, a large heterogeneous landscape of 1620 km 2 . A high resolution habitat map of the area was converted to coarser spatial and thematic resolutions in seven steps. We investigated how model performance responded to grain size, and we compared the differential effects of spatial resolution and thematic resolution on model performance. Explained deviance ( D 2 ) of the bird models generally decreased with coarser spatial resolution of the data, although it did not decrease monotonically in all species. On average across all species, model D 2 decreased from 41.5 at 1 m grain size to 15.9 at 1000 m grain size. Ten species were best modelled at 1 m, two species at 3 m and one species at 32 m grain size. Model performance degraded continuously with increasing grain size, both in habitat generalist and habitat specialist bird species, and was systematically lower in habitat generalists. The higher model performance observed at finer grain sizes was most likely caused by the combination of three factors: (1) high spatial accuracy of bird records and (2) a more precise location and delineation of habitat features and, (3) to a lesser degree, by more habitat types differentiated in maps of finer resolution. We conclude that higher spatial and thematic resolution data can be essential for deriving accurate predictions on bird distribution patterns from species–habitat models. Especially for bird species that are sensitive to specific land-use types or to small-scaled habitat features, a grain size of 1–3 m seems most promising.