Connecting seas: western Palaearctic continental flyway for water birds in the perspective of changing land use and climate

The western Palaearctic continental flyway that connects the tundra and taiga belts of Russia with north-west Europe is the major migratory avenue for an estimated 9.3 million herbivorous water birds ( swans, geese and ducks). Agricultural practices together with protection measures subsidize the carrying capacity of winter habitats of the birds. Densities of these birds are highest in the Netherlands, where nitrogen (N) inputs to farmland have increased during the last 70 years and became the highest in Europe (> 250 kg manure and fertilizer ha(-1) yr(-1)). A comparison of population trends of 13 species of avian herbivores reveals generally expanding populations in the past 50 years, with the greatest increases from 1970 to 1990. Populations of the smallest avian herbivores, such as ducks, are either stable or have peaked and are now in decline, whereas numbers of larger herbivores ( geese and swans) continue to increase and barnacle and greylag geese now breed in the Netherlands, in addition to northern sites. During the northerly spring migration, stop- over sites, mostly in the agricultural regions of eastern Europe and Scandinavia, lie between the 3 and 6 degrees C mean daily temperature isotherms in April, temperatures at which grasses start to grow, where flooding of riparian wetlands frequently occurs and fertilizers are applied to farmland. However, the restructuring of agricultural practices in an enlarged EU is likely to affect water bird populations and their migration routes. The reduced use of N in the Netherlands is predicted to constrain population growth, especially of the smallest avian herbivores with their high basal metabolic rates, because of the declining food quality of grass leaves. The introduction of large-scale farming of oilseed rape, winter cereals, sugar beet and potatoes at the expense of grassland also will adversely affect these birds, whereas larger species are likely to continue exploiting these crops.

[1]  Daan Bos,et al.  Foraging along a salinity gradient - The effect of tidal inundation on site choice by Dark-Bellied Brent Geese Branta bernicla and Barnacle Geese B-leucopsis , 2002 .

[2]  D. Parrott,et al.  Mute swan grazing on winter crops: Evaluation of three grazing deterrents on oilseed rape , 2002 .

[3]  R. Wal,et al.  Mosses mediate grazer impacts on grass abundance in arctic ecosystems , 2004 .

[4]  Robyn K. Whipp.  Food Webs at the Landscape Level , 2005 .

[5]  J. M. Black,et al.  Food intake, body reserves and reproductive success of barnacle geese Branta leucopsis staging in different habitats , 1998 .

[6]  M. V. Eerden,et al.  Patchwork: Patch use, habitat exploitation and carrying capacityfor water birds in Dutch freshwater wetlands , 1998 .

[7]  H. Southern,et al.  Handbook of the Birds of Europe, the Middle East and North Africa; the Birds of the Western Palearctic , 1978 .

[8]  J. Bakker,et al.  Restoration of salt marshes in the Netherlands , 2002, Hydrobiologia.

[9]  J. Prop.  Food finding: On the trail to successful reproduction in migratory geese , 2004 .

[10]  Thomas Alerstam,et al.  Dark-bellied Brent Geese Branta bernicla bernicla, as recorded by satellite telemetry, do not minimize flight distance during spring migration , 2002 .

[11]  A. Skidmore,et al.  Predicting in situ pasture quality in the Kruger National Park, South Africa, using continuum-removed absorption features , 2004 .

[12]  Jan P. Bakker,et al.  Utilisation of Wadden Sea salt marshes by geese in relation to livestock grazing , 2005 .

[13]  Daan Bos,et al.  Are spring staging brent geese evicted by vegetation succession , 2000 .

[14]  R. Rockwell,et al.  The embarrassment of riches: agricultural food subsidies, high goose numbers, and loss of Arctic wetlands a continuing saga , 2004 .

[15]  M. H. Olson,et al.  The Role of Migratory Waterfowl as Nutrient Vectors in a Managed Wetland , 1998 .

[16]  M. V. Eerden.  Pechora Delta: structure and dynamics of the Pechora Delta ecosystems (1995-1999) , 2000 .

[17]  J. Prop,et al.  Spring staging in Brent Geese Branta bernicla: feeding constraints and the impact of diet on the accumulation of body reserves , 1991, Oecologia.

[18]  J. Heesterbeek,et al.  Density dependent population limitation in dark-bellied brent geese Branta b. bernicla , 2001 .

[19]  D. Scott,et al.  Atlas of Anatidae Populations in Africa and Western Eurasia , 1996 .

[20]  R. Drent,et al.  Short-term and long-term facilitation of goose grazing by livestock in the Dutch Wadden Sea area , 2002 .

[21]  G. Cracknell,et al.  Goose populations of the western palearctic : a review of status and distribution , 1999 .

[22]  D. J. de Jong,et al.  Restoration of salt marshes in the Netherlands , 2002 .

[23]  L. Gustafsson,et al.  From the High Arctic to the Baltic : The successful establishment of a Barnacle Goose Branta leucopsis population on Gotland, Sweden , 1988 .

[24]  R. Bardgett,et al.  Vertebrate herbivores and ecosystem control: cascading effects of faeces on tundra ecosystems , 2004 .

[25]  S. Cramp.  Ostrich to ducks , 1977 .

[26]  W. D. van Marken Lichtenbelt,et al.  Using food quality and retention time to predict digestion efficiency in geese , 2005 .

[27]  J. Vickery.  Goose Populations of the Western Palearctic. A Review of Status and Distribution , 1999 .

[28]  J. Houghton,et al.  Climate change 2001 : the scientific basis , 2001 .

[29]  W. Hagemeijer,et al.  Numbers and distribution of wintering waterbirds in the Western Palearctic and Southwest Asia in 1997, 1998 and 1999; results from the international waterbird census , 2002 .

[30]  H. Hochbaum,et al.  Travels and Traditions of Waterfowl , 1967 .

[31]  D. Stanners,et al.  Europe's environment : the Dobrís assessment , 1995 .

[32]  J. Bakker,et al.  TO GRAZE OR NOT TO GRAZE: THAT IS THE QUESTION , 2003 .

[33]  H. Jeugd,et al.  Breeding barnacle geese in Kolokolkova Bay, Russia: number of breeding pairs, reproductive success and morphology , 2003, Polar Biology.

[34]  J. Bakker,et al.  Long‐term vegetation changes in experimentally grazed and ungrazed back‐barrier marshes in the Wadden Sea , 2002 .

[35]  K. Klasing.  Comparative Avian Nutrition , 1998 .

[36]  M. Müller,et al.  Handbuch ausgewählter Klimastationen der Erde , 1987 .

[37]  A. V. Filchagov,et al.  Breeding range expansion of Barnacle and Brent Geese in the Russian European North , 1992 .

[38]  M. Evans,et al.  Important bird areas in Europe : priority sites for conservation , 2000 .

[39]  H. Boyd,et al.  Wildfowl of the British isles , 1957 .

[40]  J. M. Black,et al.  The spring range of barnacle geese Branta leucopsis in relation to changes in land management and climate , 1998 .

[41]  L. Berg,et al.  Numbers and distribution of wild geese in the Netherlands, 1984-89, with special reference to weather conditions , 1986 .

[42]  R. Rockwell,et al.  The detection of vegetational change by multitemporal analysis of LANDSAT data: the effects of goose foraging , 1998 .

[43]  W. Lichtenbelt,et al.  Food digestion by geese predicted from the quality of the food and retention time , 2005 .

[44]  Daan Bos,et al.  Creating new foraging opportunities for dark-bellied brent Branta bernicla and barnacle geese Branta leucopsis in spring insights from a large-scale experiment , 2003 .

[45]  M. Zijlstra,et al.  The Oostvaardersplassen as a key moulting site for Greylag Geese Anser anser in western Europe , 1991 .

[46]  M. Zijlstra,et al.  The response of Anatidae to changes in agricultural practice : Long-term shifts in the carrying capacity of wintering waterfowl , 1996 .

[47]  J. Madsen,et al.  Trends in annual and seasonal survival of Pink‐footed Geese Anser brachyrhynchus , 2002 .

[48]  Viesturs Melecis,et al.  Long-Term Ecological Research in Latvia , 2005 .

[49]  Theunis Piersma,et al.  Pay-offs and penalties of competing migratory schedules , 2003 .