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Birds of Indian Subcontinent

Changes in breeding wader assemblages, vegetation and land use within machair environments over three decades

Publication Type:Journal Article
Year of Publication:2014
Authors:Calladine, J, Pakeman, RJ, Humphreys, E, Huband, S, Fuller, RJ
Journal:Bird Study
Volume:61
Issue:3
Date Published:2014
ISBN Number:0006-3657
Keywords:Calidris, Calidris alpina, Charadriidae, Charadrius, Charadrius hiaticula, Gallinago, Gallinago gallinago, Haematopodidae, Haematopus, Haematopus ostralegus, Scolopacidae, Tringa, Tringa totanus, Vanellus, Vanellus vanellus
Abstract:Capsule Changing agricultural activity and soil chemistry appear to be associated with some changes in breeding wader assemblages on the machair of the Outer Hebrides, Scotland, between the 1980s and 2000s.Aims To identify potential factors in addition to nest predation by Hedgehogs that could have driven changes in machair breeding wader assemblage of the Western Isles.Methods Surveys of breeding waders in the 1980s, 1990s and 2000s and of vegetation in 1976 and 2009 were carried out on machair habitats on the west coast of Uist (four study sites). Generalized linear mixed models were used to identify associations between: (1) breeding wader densities in 2007?2010 and vegetation metrics (Ellenberg indicator values, axes determined by detrended correspondence analyses and structural measures) derived from the 2009 vegetation survey and (2) changes in breeding wader densities between 1983?1987 and 2007?2010 and changes in vegetation metrics derived from surveys in 1976 and 2009. Reported changes in agricultural use were assessed from interviews with local land managers to assess the likely influence of land-use changes on vegetation and breeding waders.Results Changes in population densities of breeding waders differed between species and sites over the three decades. Overall, Eurasian Oystercatcher and Common Redshank increased. Common Ringed Plover, Dunlin and possibly Common Snipe decreased and there were no significant changes for Northern Lapwing. Changes in vegetation indicated relatively small decreases in soil fertility of machair grassland cultivation, increased soil salinity and a decrease in overall vegetation cover. Higher breeding wader densities were associated with higher values of soil moisture, pH, fertility, salinity, vegetation height, vegetation density and extent of cultivation with inter-specific differences mostly associated with vegetation structure. Where soil fertility declined, Ringed Plover and Dunlin tended to decline while Oystercatcher increased. Temporal changes in Lapwing density were positively associated with changes in soil moisture. Ringed Plover density changes were positively associated with indicators of vegetation shade intolerance, soil acidity, soil fertility and reduced soil salinity. Changes of Redshank were positively associated with vegetation height. Reported changes in land use included a reduction in the number of people practising cultivation, though not necessarily in the area cultivated, reductions in numbers of grazing cattle and increases in numbers of sheep, a switch from using seaweed and farmyard manure to using compound fertilizers and deeper ploughing.Conclusions Although pointing to some interesting changes in machair systems associated with soil fertility, moisture and salinity that may have affected breeding waders, possibly acting through alterations to food supplies, further understanding of how waders use the mosaic of habitats is required to understand potential mechanisms. The importance of vegetation changes relative to, and interacting with, predation deserves further attention.Capsule Changing agricultural activity and soil chemistry appear to be associated with some changes in breeding wader assemblages on the machair of the Outer Hebrides, Scotland, between the 1980s and 2000s.Aims To identify potential factors in addition to nest predation by Hedgehogs that could have driven changes in machair breeding wader assemblage of the Western Isles.Methods Surveys of breeding waders in the 1980s, 1990s and 2000s and of vegetation in 1976 and 2009 were carried out on machair habitats on the west coast of Uist (four study sites). Generalized linear mixed models were used to identify associations between: (1) breeding wader densities in 2007?2010 and vegetation metrics (Ellenberg indicator values, axes determined by detrended correspondence analyses and structural measures) derived from the 2009 vegetation survey and (2) changes in breeding wader densities between 1983?1987 and 2007?2010 and changes in vegetation metrics derived from surveys in 1976 and 2009. Reported changes in agricultural use were assessed from interviews with local land managers to assess the likely influence of land-use changes on vegetation and breeding waders.Results Changes in population densities of breeding waders differed between species and sites over the three decades. Overall, Eurasian Oystercatcher and Common Redshank increased. Common Ringed Plover, Dunlin and possibly Common Snipe decreased and there were no significant changes for Northern Lapwing. Changes in vegetation indicated relatively small decreases in soil fertility of machair grassland cultivation, increased soil salinity and a decrease in overall vegetation cover. Higher breeding wader densities were associated with higher values of soil moisture, pH, fertility, salinity, vegetation height, vegetation density and extent of cultivation with inter-specific differences mostly associated with vegetation structure. Where soil fertility declined, Ringed Plover and Dunlin tended to decline while Oystercatcher increased. Temporal changes in Lapwing density were positively associated with changes in soil moisture. Ringed Plover density changes were positively associated with indicators of vegetation shade intolerance, soil acidity, soil fertility and reduced soil salinity. Changes of Redshank were positively associated with vegetation height. Reported changes in land use included a reduction in the number of people practising cultivation, though not necessarily in the area cultivated, reductions in numbers of grazing cattle and increases in numbers of sheep, a switch from using seaweed and farmyard manure to using compound fertilizers and deeper ploughing.Conclusions Although pointing to some interesting changes in machair systems associated with soil fertility, moisture and salinity that may have affected breeding waders, possibly acting through alterations to food supplies, further understanding of how waders use the mosaic of habitats is required to understand potential mechanisms. The importance of vegetation changes relative to, and interacting with, predation deserves further attention.
URL:http://dx.doi.org/10.1080/00063657.2014.917604
Short Title:Bird Study
Scratchpads developed and conceived by (alphabetical): Ed Baker, Katherine Bouton Alice Heaton Dimitris Koureas, Laurence Livermore, Dave Roberts, Simon Rycroft, Ben Scott, Vince Smith