Do field margins enrich the diet of the Eurasian Skylark Alauda arvensis on intensive farmland?
Ottens, H.J. ; Kuiper, M.W. ; Flinks, H. ; Ruijven, J. van; Siepel, H. ; Koks, B.J. ; Berendse, F. ; Snoo, G.R. de - \ 2014
Ardea 102 (2014)2. - ISSN 0373-2266 - p. 161 - 174.
false discovery rate - sown weed strips - food resources - nestling diet - agricultural intensification - bird populations - breeding-season - adjacent fields - perdix-perdix - prey quality
To help restore food availability for birds, arable field margins (extensively managed strips of land sown with grasses and forbs) have been established on European farmland. In this study we describe the effect of field margins on the diet of Eurasian Skylark nestlings and adults living on intensively managed Dutch farmland. We tested the hypotheses that field margins offer a higher diversity of invertebrate prey than intensively managed crops, and that the diet of nestlings receiving food from field margins will therefore be more diverse than that of other nestlings. Field margins had a greater variety of invertebrate prey groups to offer than the intensively managed crops. Coleoptera were the most frequently and most abundantly eaten prey group by both adults and nestlings. Together, Coleoptera, Diptera, Lepidoptera, Hymenoptera and Araneae accounted for 91% of the nestling diet. Nestlings ate larger prey items and a larger proportion of larvae than adults. Almost 75% of both adults and nestlings consumed plant material, perhaps indicating a scarcity of invertebrate resources. When provided with food from field margins, the mean number of invertebrate orders in the nestling diet increased significantly from 4.7 to 5.5 and the number of families from 4.2 to 5.8 per sample. Thus, birds that used field margins for foraging could indeed provide their young with more invertebrate prey groups than birds only foraging in crops and grassland.
Field margins as foraging habitat for skylarks (Alauda arvensis) in the breeding season
Kuiper, M.W. ; Ottens, H.J. ; Cenin, L. ; Schaffers, A.P. ; Ruijven, J. van; Koks, B.J. ; Berendse, F. ; Snoo, G.R. de - \ 2013
Agriculture, Ecosystems and Environment 170 (2013). - ISSN 0167-8809 - p. 10 - 15.
agri-environment schemes - farmland birds - agricultural intensification - food resources - ecological effectiveness - population trends - landscape context - biodiversity - management - invertebrates
Agri-environment schemes have been established in many European countries to counteract the ongoing decline of farmland birds. In this study, the selection of foraging habitat by breeding skylarks was examined in relation to agri-environmental management on Dutch farmland. Field margin use was quantified and, based on the observed flight distances, the appropriateness of the current spatial arrangement of field margins in the study landscape was evaluated. Skylarks preferred field margins for foraging over all other habitat types relative to their surface area within the territories. The visiting rate of field margins decreased with increasing distance to the nest, and especially dropped markedly when the distance between the nest and a field margin exceeded 100 m. Analysis of the current spatial arrangement of field margins in the landscape suggested that the area of skylark breeding habitat within 100 m of a field margin could be increased by 46%. This was due to the placement of field margins alongside unsuitable breeding habitat and to the positioning of field margins at short distances from each other. The efficiency of agri-environmental management for skylarks can likely be improved by a more careful spatial arrangement of field margins in the landscape.
Multicriteria performance and sustainability in livestock farming systems: Functional diversity matters
Tichit, M. ; Puillet, L. ; Sabatier, R. ; Teillard, F. - \ 2011
Livestock Science 139 (2011)1-2. - ISSN 1871-1413 - p. 161 - 171.
agricultural intensification - floristic diversity - breeding waders - viability model - food resources - trade-offs - management - biodiversity - grassland - birds
Agricultural intensification drastically reduces diversity at different scales of livestock farming systems (LFS). This homogenization process leads to environmental degradation and ignores the fact that multiple performance criterions often come in conflict. Taking advantage of diversity at different scales of LFS is a new challenge to improve sustainability. The diversity is considered here on a functional viewpoint, i.e. a variety of functions played by individual production entities involved in overall performance. The objective of this study was to examine how the diversity of individual production entities shapes the relationship between different performance criterions at the upper scale. We used two types of dynamic models representing contrasting LFS: extensive grassland suckling farms and intensive dairy herds. Both models include a certain level of functional diversity with production entities corresponding to different types of management practices (grassland farm model) or different types of females (herd model). With the grassland farm model, we studied how the biodiversity/production relationship was influenced by the functional diversity of management practices. With the herd model, we explored how production/efficiency relationship was influenced by the functional diversity of females. At the farm scale, we showed that interactions between the diverse management practices shaped the relationship between ecological and productive performance from a convex to a concave trade-off. Complementary effects resulting from the diversity of management practices thus improved the trade-off. Trade-off shape also depended on the level of farm intensity and it was less costly for the extensive farms to achieve viable levels of ecological performance. Increasing the complementary effect through increased diversity in management practices is likely to improve the conciliation between productive and ecological performance. At the herd scale, we observed a win–win situation between production and efficiency. However, at the highest levels of production, there was a production/efficiency trade-off; increases in either production or efficiency corresponded to distinct functional groups of females. Managing the functional groups of females with targeted practices is likely to improve the production/efficiency trade-off. We concluded from both case studies that functional diversity plays a key role in the relationship between multiple performance criterions. The next steps on the research agenda include exploring new spatial and temporal scales and accounting for environmental variability. A better understanding of the role of functional diversity can benefit from multi-criterions and multi-scale modelling approaches.
Seasonal distribution of meadow birds in relation to in-field heterogeneity and management
Verhulst, J. ; Kleijn, D. ; Loonen, W. ; Berendse, F. ; Smit, C. - \ 2011
Agriculture, Ecosystems and Environment 142 (2011)3-4. - ISSN 0167-8809 - p. 161 - 166.
agri-environment schemes - lapwings vanellus-vanellus - godwit limosa-limosa - agricultural intensification - farmland birds - food resources - habitat - grasslands - success - england
Effectiveness of European initiatives to restore populations of meadow breeding waders is heavily debated. We studied field preference of meadow birds throughout the breeding season in four areas of over 100 ha each and related observed patterns of individual birds to in-field heterogeneity, sward height and management. Over the four areas, most waders were observed in the more heterogeneous fields at both the period of nest site selection and incubation. Additionally, fields grazed at relatively low-intensity for longer consecutive periods (on average 6 cows/ha for 30 d instead of 20 cows/ha for 2 d) were hosting high densities of lapwings but also black-tailed godwits. Our results suggest that in-field heterogeneity may be important for meadow breeding waders at the nest site selection and incubation stages. Conservation initiatives aimed at meadow breeding waders might improve their effectiveness when they increase the heterogeneity of fields. Grazing for longer consecutive periods at relatively low stocking rates might be a way to achieve this, if carried out at stocking rates low enough to allow waders to reproduce successfully.
The effect of 'mosaic management' on the demography of black-tailed godwit Limosa limosa on farmland
Schekkerman, H. ; Teunissen, W. ; Oosterveld, E. - \ 2008
Journal of Applied Ecology 45 (2008)4. - ISSN 0021-8901 - p. 1067 - 1075.
agri-environment schemes - bird populations - agricultural intensification - food resources - success - chicks - biodiversity - netherlands - grasslands - survival
1. Like many farmland birds, the largest European population of the black-tailed godwit Limosa limosa, in The Netherlands, has been declining for decades despite conservation measures including agri-environment schemes (AES). In a new experimental AES aiming to reverse this decline, collectives of farmers implemented spatially coordinated site-level habitat management ('mosaic management') including delayed and staggered mowing of fields, refuge strips and active nest protection. 2. We evaluated the effectiveness of mosaic management by measuring godwit breeding success in six experimental sites and paired controls. Productivity was higher in mosaics than in controls due to fewer agricultural nest losses. Chick fledging success was poor in both treatments. Productivity compensated for adult mortality in only one AES site. 3. Although creating chick habitat was a major management goal, the availability of tall grass during the fledging period did not differ between treatments, mainly because rainfall delayed mowing in all sites and study years. However, chick survival increased with the availability of tall grass among sites. Higher chick survival will thus enhance the positive effect of mosaic management in drier years, but sensitivity to weather represents a weakness of the AES design. 4. Available estimates of productivity in Dutch godwits suggest a strong reduction over the past 20 years and implicate chick survival as the main driver of their decline. Earlier mowing of grassland is the main causal mechanism, but changes in vegetation structure and composition, and increased predation may also have contributed. 5. Synthesis and applications. Demographic rates like breeding success are useful parameters for evaluating effects of management. Mosaic management increases the productivity of black-tailed godwits, but does not ensure long-term population viability for this flagship species of wet grassland bird communities. More stringent management prescriptions need to improve both the area and the quality (vegetation structure) of grassland mown late. Management efforts should be concentrated in areas with favourable pre-conditions in order to improve overall effectiveness.
Direct and indirect effects of the most widely implemented Dutch agri-environment schemes on breeding waders
Verhulst, J. ; Kleijn, D. ; Berendse, F. - \ 2007
Journal of Applied Ecology 44 (2007)1. - ISSN 0021-8901 - p. 70 - 80.
lapwings vanellus-vanellus - site-fidelity - agricultural intensification - natal philopatry - food resources - birds - management - habitat - farmland - biodiversity
1. In the Netherlands, agri-environment schemes are an important tool for halting the ongoing decline of meadow birds and, in particular, waders breeding on wet meadows. The effectiveness of the main scheme, postponed mowing, is heavily debated because it does not result in higher breeding densities. Recently, agri-environmental collectives have become involved in the co-ordination of scheme applications and additional measures have been introduced. One of them is per-clutch payment: farmers are paid per wader clutch without being restricted in their farming practices. 2. We evaluated the effectiveness of the combination of the two measures, postponed mowing and per-clutch payment, by determining the number of birds and territories on 12.5-ha plots where both measures (on average 1.6 ha postponed mowing and 10.9 ha per-clutch payment) were being implemented. Conventionally managed grasslands served as controls. Additionally, on a field with postponed mowing and a paired control field, we measured a number of environmental factors that might influence wader distribution. 3. On plots operating a combination of postponed mowing and per-clutch payment, more territories of all bird species were found and more redshanks Tringa totanus were observed. The same pattern occurred on fields with per-clutch payment alone. On fields with postponed mowing alone, we found more territories of the most abundant wader species but on conventional fields we observed more lapwings Vanellus vanellus. 4. The positive effects of postponed mowing on wader territories were probably caused by small differences in soil moisture and groundwater level between the two field types, as inclusion of these factors in a general linear model rendered all scheme effects insignificant. 5. Postponed mowing affected the form and amount of fertilizer applied to the fields as well as available nitrogen, but none of the other environmental factors that were measured. Additional analyses identified groundwater depth, penetration resistance and prey density (earthworms, Lumbricidae, and leatherjackets, Tipulidae larvae) as the main factors determining wader density. 6. Synthesis and applications. Our results show that conservation measures consisting of postponed mowing and per-clutch payment implemented by agri-environment collectives do not support a higher abundance of waders but do support marginally higher breeding densities of waders compared to conventional farms. These results are probably due to differences in soil moisture and groundwater depth. The effectiveness of agri-environment schemes directed towards conservation of waders might be enhanced by including raised groundwater levels into scheme prescriptions.
Population dynamics and spawning of the flatfish Solea bleekeri and Pseudorhombus arsius in the intertidal area of Inhaca Island, Mocambique
Boer, W.F. de; Schie, A.M.P. van - \ 2003
African Journal of Marine Science 25 (2003). - ISSN 1814-2338 - p. 49 - 60.
lake st-lucia - south-african estuaries - juvenile flatfish - ecological observations - southeastern coast - food resources - surf zone - fish - mozambique - teleostei
The population dynamics of flatfish Solea bleekeri and Pseudorhombus arsius within the intertidal area of Inhaca Island, Moçambique, was investigated using bottom trawl data collected during summer (December 1996 – March 1997) and winter (June 1997 – August 1997). The endemic S. bleekeri is a small, relatively slowgrowing species with low rates of natural mortality. Densities of juveniles were significantly greater in winter (24.7 fish 1 000 m-2) than in summer (10.8 fish 1 000 m-2), probably because of intensive spawning during summer. Greater catches of S. bleekeri were taken by night than by day. Densities of P. arsius did not differ significantly between day and night or among seasons. Mean density of P. arsius was 53 fish 1 000 m-2 for the survey. Both species preferred the same substrata, significantly greater densities being found on the mudflats and in the tidal channels. Both seem to complete two life cycles within a year.