Daphné Durant

Management of agricultural wet grasslands for breeding waders: integrating ecological and livestock system perspectives. A review

Although agriculture is pointed to as being one of the major causes of biodiversity loss, it is now recognised that some farming practices, grazing in particular, represent central issues in the on-running debate on wildlife conservation. This paper analyses the relationship between agricultural pasture management and bird preservation, by focusing on the illustrative case study of breeding waders in wet grasslands. After a brief account of the knowledge on research investigating the effect of grazing management on wader distribution or abundance, we reviewed (i) sward structure (i.e. mean sward height and frequency of tussocks) requirements, and (ii) breeding phenologies of five wader species commonly associated with wet grasslands for nesting in Europe. We found differences between species in these two aspects of their biology. Investigating grassland management thus underlines that the question of the timing of grazing should be considered. Moreover, the fragmented characteristic of agricultural landscapes (i.e. a mosaic of fields) in which waders breed emphasises the spatial nature of this management. We examine three spatial scales (i.e. field, set of adjacent fields, landscape) relevant to bird biology and influenced by agricultural activities. Based on these findings, we analyse which livestock system constraints are essential to take into account in order to minimise conflicts between livestock production and conservation aims in marshes. Finally, we highlight possible directions for future research.

The cost of vigilance for intake rate in the mallard (Anas platyrhynchos): an approach through foraging experiments

Vigilance while foraging incurs costs such as a reduction of the time available for feeding or a reduction in instantaneous intake rate. Vigilance has two major components: scan rate and scan duration. We investigated the cost of these components for the instantaneous intake rate in Mallard. We first modelled the relationship between food availability and instantaneous intake rate (i.e. the functional response), and looked at the relationship between the residuals of this relationship and scan rate and scan duration. Both scan rate and scan duration were negatively correlated with the residuals, but the cost associated with an increase in each component of vigilance differed. The average time spent in vigilance by ducks was 5 sec per minute: 5 scans of 1 sec decreased the maximum instantaneous intake rate by 2.4% whereas one scan of 5 sec decreased the maximum intake rate by 6%. This shows that an increase in the duration of scans has a greater effect than an increase in their frequency and confirms that vigilance not only affects the time spent feeding but also feeding efficiency through instantaneous intake rate. We explored the potential consequences of such costs in the time spent foraging on a daily basis.

Towards biodiversity-based livestock systems: review of evidence and options for improvement

A major challenge for livestock farming systems (LFSs) is to reconcile production with the management of natural resources, especially biodiversity and ecosystem services. Based on a review of research conducted on grassland- and rangeland-based LFSs, this paper addresses this challenge by analysing biodiversity as a product of and a key resource for LFSs. Although most studies reveal antagonisms between biodiversity and production, our findings show that it is possible to move towards synergies. The literature review sheds light on five points: (i) moving beyond an antagonistic view of biodiversity and production by considering biodiversity as a resource requires new criteria for biodiversity categorization from a taxonomic view to a functional one; (ii) functional biodiversity (both domestic and wild) considered as a resource provides beneficial properties (e.g. stability and resilience) to LFSs; (iii) links between production and biodiversity cannot be simply summarized as having a negative impact of production intensity as management practices have various impacts on the different components of biodiversity; (iv) impact assessment studies linking management of LFSs and biodiversity reveal complex multi-level interactions between grassland or rangeland management and biodiversity; (v) a large range of management options are available to move towards biodiversitybased LFSs. We conclude that future research should address the challenge of collective management of wild biodiversity at higher levels of organization (landscapes, territories, etc.) and that such collective management would greatly benefit from the experience of domestic biodiversity.

Farmland birds and arable farming, a meta-analysis

Declines in farmland bird populations have been principally attributed to the intensification of agriculture. In response, agri-environmental schemes and organic farming have been introduced with the aim of making farmland better able to support wildlife populations. These “bird-friendly” agricultural practices include using more diverse crop rotations, stopping the use of pesticides, and creating more heterogeneous landscapes and are expected to create more food resources and nesting habitats for birds. Many studies have been published that evaluate the success or failure of agricultural practices to increase bird abundance. While many studies have found that most organic farming practices are beneficial to birds, other studies have found that some organic farming practices, such as using increased tillage passes, are not beneficial to birds. We conducted a search of the literature and used a meta-analysis approach to analyze the relationship between farming practices and bird populations. We first tested whether organic agriculture is more favorable to farmland birds of Europe and North America compared to conventional agriculture. We used data from 16 experiments and six publications that fulfilled fixed criteria for inclusion in the meta-analysis. We found that organic agriculture had a global positive effect on bird abundance compared to conventional agriculture. However, this effect was significant in only five out of the 16 site-year combinations tested. We also found that the effects varied with the bird species. Ten out of the thirty six species tested show a significant higher abundance value in organic agriculture. When the ratio was significantly different from zero, the abundance was 1.5–18 times higher in organic systems in comparison to conventional systems.

Effect of cattle trampling on ground nesting birds on pastures: an experiment with artificial nests

Abstract 1. In semi-natural grasslands, nest trampling by cattle can have a strong effect on hatching success but the relationship linking cattle density, incubation time and nest survival has for now only been hypothesized. 2. Based on an experiment with artificial nests, the objective of this study was to test the theoretical model generally used to estimate nest survival. In spring 2009, we conducted a one-month experiment on permanent grasslands of the French western marshlands grazed at three different stocking rates (1 LU.ha-1, 2 LU.ha-1 and 4 LU.ha-1). 3. The results confirmed that trampling depended on stocking rates. 4. Trampling had a major effect on nest survival (32-85% of nests destroyed). 5. The theoretical model classically used by managers and modellers proved to be a good approximation of the dynamics of nest trampling. 6. Synthesis and applications: We conclude that nest trampling has a major impact on nest survival in pastures and that the use of such a model could help managers to define acceptable levels of cattle densities.