Patrick E. Osborne

Responses of birds of different biogeographic origins and habitat requirements to agricultural land abandonment in northern Spain

Abstract Agricultural land-use changes in Europe have taken two opposing directions: towards agricultural intensification or land abandonment. While in the Mediterranean region land abandonment is a main cause of avian diversity decline, in northern Europe species diversity often increases with successional age. We examined the hypothesis that the biogeographic origin of the avifauna determines whether abandonment brings conservation benefits or detriment by studying the bird community of agricultural land in northern Spain, at the boundary of the Mediterranean and Eurosiberian regions. Using a successional gradient, we examined landscape-scale effects of agricultural abandonment on birds during the breeding and non-breeding seasons. The trend in avian diversity with successional stage differed little between Mediterranean and Eurosiberian species in winter. In the spring, however, there was an increase in diversity with stage in abandonment for Eurosiberian birds but not for Mediterranean species. Analysis of individual species showed a preference among Eurosiberian birds for more wooded habitats whereas Mediterranean birds preferred open areas and shrubland. The introduction of agricultural policies to geo-political units that do not coincide with eco-regions cannot be assumed to bring uniform conservation benefits. In the Mediterranean region, agricultural mosaics of low intensity cultivation maintain the highest diversity of priority bird species. Agricultural land abandonment should not be assumed to benefit conservation.

The distribution of Passerine birds in hedgerows during the breeding season in relation to characteristics of the hedgerow and adjacent farmland

1. Passerine birds were surveyed during the breeding season in hedgerows on 46 farms in lowland England. The incidence of each species was recorded in 50-m lengths of hedgerow and various attributes of these hedgerow sections were also recorded. 2. Logistic regression models were fitted to the data to describe the effects on the incidence of 18 bird species of the number of trees, hedge height and width, dominant plant species in the woody hedge, under the hedge and adjacent to the hedge in the uncultivated strip, the number of woody species in a standard length and other hedgerow characteristics. The effects of adjacent land use and cropping, reduced use of pesticides on cereal field edges and the geographical location of the study farms were also included in the models. 3. Most bird species preferred tall hedges with many trees, but there were some (dunnock, willow warbler and lesser whitethroat) which preferred tall hedges with few trees and others (whitethroat, linnet, yellowhammer) which preferred short hedges with few trees. 4. The differences among bird species in response to a sevenfold reduction in the height of hedges estimated from the models showed good agreement with the variation among species in the effects of severe hedge cutting on bird populations at one farm observed in an independent study. 5. The incidence of six bird species was positively influenced by the number of woody species in a standard length of hedgerow. 6. The incidence of two bird species was significantly affected by the identity of the dominant woody plant species in the hedge and one species by the identity of the dominant plant species at the base of the hedge. 7. Land use adjacent to the hedgerow, categorized as grass, tillage and roadside, had a significant influence on the incidence of five species. However, there was no evidence of consistency among species in the direction of effects. 8. The crops grown on tilled land adjacent to the hedgerow had a significant influence on the incidence of the blackbird. There was a significant degree of consistency among bird species in the ranking of crops, with oil-seed rape the most preferred and spring-sown cereal the least preferred. 9. The incidence of greenfinch, robin and song thrush was significantly lower in hedgerows adjacent to autumn-sown cereals which had received reduced levels of spraying of pesticides than in those adjacent to autumn-sown cereals which were fully sprayed. Most of the other species showed non-significant differences in the same direction. Most of the species studied also showed a non-significant tendency towards higher incidence in hedgerows adjacent to spring-sown cereals with reduced spraying than in those adjacent to fully sprayed spring-sown cereals.

Interpreting bird atlas data using logistic models: an example from Lesotho, Southern Africa

1. Presence-absence maps of the occurrence of species may be difficult to interpret because of uneven coverage in field surveys. 2. Using data collected in the mountain Kingdom of Lesotho, southern Africa, where even coverage was virtually impossible to achieve, a method is presented to improve bird atlas maps by plotting predicted probabilities of occurrence calculated from logistic models. 3. A set of habitat variables derived from maps was reduced to principal components and then used in logistic models to predict the occurrence of bird species across the country. The models generate a probability of occurrence for all survey squares irrespective of coverage. Maps for the Cape vulture Gyps coprotheres (Forster), ground woodpecker Geocolaptes olivaceus (Gmelin) and pied crow Corvus albus Muller are presented as examples. 4. The models were assessed by jack-knife analysis and correctly predicted presence and absence in the field data. 5. Relationships between the predicted probabilities, recording frequency (reporting rate) and density are discussed.

Should data be partitioned spatially before building large-scale distribution models?

There is growing interest in building predictive models of species distributions over large geographic areas. As larger areas are modelled, however, it is highly likely that heterogeneity in the predictors variable increases and that areas are included where animals respond to habitats in different ways, for example, due to social status. These effects (spatial non-stationary) may weaken model performance. This paper explores whether data partitioning prior to analysis can improve the tit of models and provide ecological insight into distribution patterns. Data on three bird species were modelled for the whole of Spain at 1 km(2) resolution using logistic regression analysis. Data were partitioned into geographic quarters, concentric rings around the centroid of the distribution, and into random samples for comparison. In all cases, data partitioning produced better models as assessed by Receiver Operating Characteristic curve (AUC) statistics than analysis of the global data set. Inclusion of latitude and longitude improved the global models only when added as smoothed splines but produced different probabilities to the partitioned data. Geographic partitioning is a very crude local modelling approach and we suggest that some form of geographically-weighted regression could offer the best solution to large-scale modelling but is computationally intensive on Geographical Information Systems (GIs) data. It is concluded that simple partitioning by geographic quarters may detect spatial non-stationary and alert the modeller to possible problems; that partitioning into more novel arrangements may be used to test ecological hypotheses; and that data should not be partitioned spatially to build and test models if non-stationary is suspected.

Bird numbers and habitat characteristics in farmland hedgerows

A statistical analysis is presented of the relationship between bird numbers and the charecteristics of forty-two hedges on a Dorset farm. Multiple regression, principal components analysis and regression of actors, and canonical correlation analysis were used and compared.

GIS and remote sensing applications in biogeography and ecology

Co-Editors: Abbreviated Profiles. Acknowledgements: List of Reviewers. 1. Introduction - Thinking Spatially A.C. Millington, et al. 2. A Spectral Unmixing Approach to Leaf Area Index (LAI) Estimation at the Alpine Treeline Ecotone D.G. Brown. 3. The Utilization of Airborne Digital Multispectral Image Dynamics and Kinematic Global Positioning Systems for Assessing and Monitoring Salt Marsh Habitats in Southern California D. Stow, et al. 4. Spatial Variability in Satellite-Derived Seasonal Vegetation Dynamics S.D. Jones, et al. 5. Documenting Land-Cover History of a Humid Tropical Environment in Northeastern Costa Rica Using Time-Series Remotely Sensed Data J.M. Read, et al. 6. Patterns of Change in Land-Use and Land-Cover and Plant Biomass: Separating Intra- and Inter-Annual Signals in Monsoon-Driven Northeast Thailand S.J. Walsh, et al. 7. Barriers and Species Persistence in a Simulated Grassland D.M. Cairns. 8. Feedback and Pattern in Computer Simulations of the Alpine Treeline Ecotone M.F. Bekker, et al. 9. Spatial Pattern and Dynamics of an Annual Woodland Herb L. Bastin, C.D. Thomas. 10. Spatial Analysis of Micro-Environmental Change and Forest Composition in Belize P.A. Furley, et al. 11. The Radiate Capitulum Morph of Senecio Vulgaris L. within Sussex: the Use of GIS in Establishing Origins S. Waite, N. Burnside. 12. A Geographical Information Science (GISci) Approach to Exploring Variation in the Bush Cricket Ephippiger Ephippiger D.M. Kidd, M.G. Ritchie. 13. The GIS Representation of Wildlife Movements: A Framework L. Bian. 14.Stratified Sampling for Field Survey of Environmental Gradients in the Mojave Desert Ecoregion J. Franklin, et al. 15. Development of Vegetation Pattern in Primary Successions on Glacier Forelands in Southern Norway G.A. Grimm. 16. Multi-Scale Analysis of Land-Cover Composition and Landscape Management of Public and Private Lands in Indiana T.P. Evans, et al. 17. Shifting Cultivation Without Deforestation: A Case Study in the Mountains of Northwestern Vietnam J. Fox, et al. 18. Linking Biogeography and Environmental Management in the Wetland Landscape of Coastal North Carolina, The difference between nationwide and individual wetland permits N.M. Kelly. Index.

Identifying the global potential for baobab tree cultivation using ecological niche modelling

The benefits provided by underutilised fruit tree species such as baobab (Adansonia digitata L.) in combating increasing malnutrition and poverty become more apparent as awareness grows regarding concerns of climate change and food security. Due to its multiple uses, its high nutritional and medicinal value, drought tolerance and relatively easy cultivation, baobab has been identified as one of the most important edible forest trees to be conserved, domesticated and valued in Africa. In order to contribute towards the cultivation of the species, suitability of sites in Africa and worldwide was evaluated for potential cultivation using species’ locality data and spatial environmental data in MAXENT modelling framework. A total of 450 geo-referenced records of the baobab tree were assembled from herbarium records, commercial firm’s databases and fieldwork for modelling site suitability for global cultivation of the baobab tree. Climatic and topographic data were acquired from the Worldclim data while soil data was obtained from the Harmonized World Soil Database. MAXENT was found to be a successful modelling method for studying cultivation potential. The main variables that contributed towards predicting baobab’s global cultivation potential were annual precipitation and temperature seasonality. Results suggest that baobab tree could be widely cultivated in most countries in southern Africa and in the Sudano-Sahelian zone of West Africa from Senegal to Sudan. Angola and Somalia were found to be highly suitable for cultivating baobab in Africa. Model suggests, India, where the baobab tree already exists and is used, to be the most suitable country for baobab cultivation outside Africa. North-west Australia, Madagascar, north-east Brazil and Mexico resulted to be other suitable places for cultivating the tree species. Although it is recommended model results be validated with in situ seedling experiments, there seems to be a great potential for the cultivation of this species globally.

Effects of geographical data sampling bias on habitat models of species distributions: a case study with steppe birds in southern Portugal

Habitat models of species distributions provide useful information about species and biodiversity spatial patterns, which form the basis of many ecological applications and management decisions such as the definition of conservation priorities and reserve selection. These models, however, are frequently based on existing datasets which have been collected in an unbalanced (biased) manner. In this study we investigated the effects of data sampling bias on model performance, interpretation and particularly spatial predictions. We collected a large steppe bird dataset in southern Portugal, following a carefully designed sampling scheme and then sub-sampled this dataset, roughly discarding between 80% and 90% of the observations, with varying degrees of geographical bias and random sampling. We characterised the data subsets in terms of data reduction and environmental bias. Multivariate adaptive regression splines (MARS) models were run on all datasets, and all the subset models compared with the baseline to assess the effect of the respective biases. We found that environmental bias in the datasets was very influential on the predicted spatial patterns of species occurrences. It is therefore important that special attention is paid to the quality of existing datasets used in habitat modelling, as well as the sampling design for collection of new data. Also, when modelling with biased datasets, the ecological interpretation of such models should be made with caution and explicit awareness of the existing bias.

Wintering habitat use by houbara bustards Chlamydotis undulata in Abu Dhabi and implications for management

Abstract Houbara bustards Chlamydotis undulata are uncommon winter visitors to Abu Dhabi. People attempting to increase numbers are considering establishing reserves and restoring habitats but they are hampered by poor knowledge of the birds requirements. We studied winter habitat use by recording the locations of three satellite-tagged houbara, verified by the presence of tracks, and detailed habitat assessments at the landscape scale. Our initial results show that houbara used habitat in patches averaging about 40 km2 and spaced 14–34 km apart. Patches were used for up to three weeks before the birds moved on. Habitats were characterised by flat or gently undulating terrain, and a higher than average incidence of vegetation. These results indicate a conflict between rural development and houbara, both of which favour flat, vegetated plains over sand dunes. We suggest that Managed Resource Protected Areas should be established for the houbara and that relatively small changes to forestry practice could provide the birds with suitable wintering habitat within developed areas.

Insect pests associated with rural maize stores in Mexico with particular reference to Prostephanus truncatus (Coleoptera: bostrichidae)

Abstract A survey was carried out into the occurrence of insect pests infesting rural stores in five regions of Mexico. Stores were sampled using pheromone-baited crevice traps, bait-bags and maize samples every 28 d for an entire storage season. Maize and store temperatures, and grain moisture content were measured. The most numerous primary pests were Sitophilus zeamais Motsch., Sitotroga cerealella (Olivier) and Prostephanus truncatus (Horn). P. truncatus was more abundant in stores in the drier, temperature regions of Guanajuato, La Laguna and Jalisco than in the more tropical regions, Veracruz or Chiapas. In La Laguna (and to some extent in Jalisco), many more P. truncatus were detected in the store using the crevice trap than were counted in the maize samples, perhaps because crevice traps may attract beetles from outside the store. La Laguna and Chiapas had significantly fewer larvae of P. truncatus in the samples than other regions, probably a result of the lower grain moisture content. Grain damage levels were very low in La Laguna and they occurred later in Guanajuato than elsewhere. The three pest species causing most damage were S. zeamais, S. cerealella and P. truncatus . It is suggested that P. truncatus was important in causing damage primarily in Guanajuato, whereas S. zeamais and S. cerealella caused more damage elsewhere, particularly in more humid areas.