Influence of Landscape Scale on Farmland Birds Breeding in Semi‐Natural Pastures

: Little attention has been paid to fragmentation effects on organisms living in open habitats in which species may have high mobility and generalized habitat use. We investigated landscape effects on 23 farmland bird species breeding in 72 semi-natural dry pastures distributed equally among three landscape types (agricultural-dominated, mosaic, and forest-dominated) in southcentral Sweden. There were generally higher local abundances of farmland birds in pastures located in agricultural-dominated and mosaic landscapes than in forest-dominated landscapes. Species feeding on a mixed diet as well as resident species and temperate migrants were most numerous in pastures located in agricultural-dominated landscapes and least numerous in forest-dominated landscapes. While controlling for the effects of local pasture area and vegetation structure, we found that the local abundance of 18 ( 78%) farmland bird species was significantly associated with the composition and structure of the surrounding landscape. The landscape distance that explained the largest part of local variation in abundance varied among species according to the size of their breeding territories or foraging home ranges. Our results suggest that habitat use of farmland birds breeding in pastures is affected both by suitable foraging habitats in the surrounding landscape and by nest sites within local pastures. Despite the generally higher abundances of farmland birds in pastures located in agricultural-dominated landscapes, most species of European and Swedish conservation concern had higher abundance in pastures located in more forested landscapes. Thus, the rapid loss of semi-natural dry pastures in forest-dominated landscapes is a serious threat to the future of these species in Sweden. Resumen: Se ha prestado poca atencion a los efectos de la fragmentacion sobre organismos que viven en habitats abiertos, en los que las especies tienen alta movilidad y uso generalizado del habitat. Investigamos el efecto del paisaje sobre 23 especies de aves que anidan en 73 pastizales secos semi-naturales distribuidos en tres tipos de paisaje (agricola, mosaico y bosque) en el sur de Suecia central. Generalmente hubo mayores abundancias locales de aves en pastizales localizados en paisajes agricolas y mosaico que en los bosques. Las especies de dieta mixta, asi como especies residentes y migratorias, fueron mas numerosas en pastizales localizados en paisaje agricola y menos numerosas en el bosque. Al controlar los efectos del area del pastizal local y la estructura de la vegetacion, encontramos que la abundancia local de 18 ( 78 %) de las especies de aves estaba asociada significativamente con la composicion y estructura del paisaje circundante. La distancia que explico la mayor parte de la variacion local de la abundancia vario entre especies en funcion del tamano de sus territorios reproductivos o de los rangos de hogar para forrajeo. Nuestros resultados sugieren que el uso de habitat por aves que anidan en pastizales es afectado tanto por los habitats de forrajeo adecuados en el paisaje circundante como por sitios para anidar dentro de los pastizales locales. A pesar de la generalmente mayor abundancia de aves en pastizales localizados en paisajes agricolas, la mayoria de las especies europeas y suecas de valor en conservacion fueron mas abundantes en pastizales ubicados en paisajes mas boscosos. Asi, la rapida perdida de pastizales secos, semi-naturales en paisajes boscosos es una seria amenaza para la ocurrencia de esas especies en Suecia en el futuro.

[1]  Byron K. Williams,et al.  Some Observations of the Use of Discriminant Analysis in Ecology , 1983 .

[2]  R. Levins.  Some Demographic and Genetic Consequences of Environmental Heterogeneity for Biological Control , 1969 .

[3]  T. E. Martin,et al.  On the advantage of being different: Nest predation and the coexistence of bird species. , 1988, Proceedings of the National Academy of Sciences of the United States of America.

[4]  R. R. Hocking.  The analysis and selection of variables in linear regression , 1976 .

[5]  R. Hobbs,et al.  Biological Consequences of Ecosystem Fragmentation: A Review , 1991 .

[6]  J. Wiens.  Spatial Scaling in Ecology , 1989 .

[7]  J. Stamps.  Conspecific Attraction and Aggregation in Territorial Species , 1988, The American Naturalist.

[8]  B. Söderström,et al.  Different nest predator faunas and nest predation risk on ground and shrub nests at forest ecotones: an experiment and a review , 1998, Oecologia.

[9]  S. A. Temple,et al.  Area-Dependent Changes in the Bird Communities and Vegetation of Southern Wisconsin Forests , 1983 .

[10]  Benjamin B. Steele,et al.  Habitat selection by breeding Black-throated Blue Warblers at two spatial scales , 1992 .

[11]  Deborah J. Pain,et al.  Farming and birds in Europe: the common agricultural policy and its implications for bird conservation , 1997 .

[12]  B. Söderström,et al.  Conservation Value of Semi‐Natural Pastures in Sweden: Contrasting Botanical and Avian Measures , 1999 .

[13]  H. Pulliam,et al.  Ecological Processes That Affect Populations in Complex Landscapes , 1992 .

[14]  M. Soulé,et al.  The effects of habitat fragmentation on chaparral plants and vertebrates , 1992 .

[15]  S. Levin.  The problem of pattern and scale in ecology , 1992 .

[16]  John A. Wiens,et al.  Habitat occupancy patterns of North American shrubsteppe birds: the effects of spatial scale , 1987 .

[17]  Steven T Knick,et al.  Landscape Characteristics of Fragmented Shrubsteppe Habitats and Breeding Passerine Birds. , 1995, Conservation biology : the journal of the Society for Conservation Biology.

[18]  Therese M. Donovan,et al.  Regional Forest Fragmentation and the Nesting Success of Migratory Birds , 1995, Science.

[19]  T. Pärt,et al.  Abundance of breeding farmland birds on arable and set‐aside fields at forest edges , 1994 .

[20]  Sue McIntyre,et al.  Habitat Variegation, An Alternative to Fragmentation , 1992 .

[21]  Henrik Andrén,et al.  Corvid Density and Nest Predation in Relation to Forest Fragmentation: A Landscape Perspective , 1992 .

[22]  L. Fahrig,et al.  Conservation of fragmented populations , 1994 .

[23]  R. Ricklefs.  Nest predation and the species diversity of birds. , 1989, Trends in ecology & evolution.

[24]  Stephen R. Baillie,et al.  Population declines and range contractions among lowland farmland birds in Britain , 1995 .

[25]  H. Andrén,et al.  Effects of habitat fragmentation on birds and mammals in landscapes with different proportions of suitable habitat: a review , 1994 .

[26]  B. Söderström,et al.  The effects of management regimes and location in landscape on the conservation of farmland birds breeding in semi-natural pastures , 1999 .

[27]  M. Marini.  Predation-mediated bird nest diversity: an experimental test , 1997 .

[28]  P. Ehrlich,et al.  BIRD ASSEMBLAGES IN PATCHY WOODLANDS: MODELING THE EFFECTS OF EDGE AND MATRIX HABITATS , 1997 .

[29]  R. Fuller,et al.  Landscape composition models for breeding bird populations in lowland English farmland over a 20 year period , 1997 .

[30]  J. Rotenberry,et al.  Breeding Bird Abundance in an Urbanizing Landscape in Coastal Southern California , 1997 .

[31]  Peter W. C. Paton,et al.  The Effect of Edge on Avian Nest Success: How Strong Is the Evidence? , 1994 .

[32]  Shelley A. Hinsley,et al.  Habitat and landscape factors influencing the presence of individual breeding bird species in woodland fragments , 1995 .

[33]  Stephen T. Buckland,et al.  Trends in the abundance of farmland birds: a quantitative comparison of smoothed Common Birds Census indices , 1998 .

[34]  I. Hanski.  A Practical Model of Metapopulation Dynamics , 1994 .