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Agriculture & woodland

 

Implications of lowland broadleaved woodland management for the conservation of target bird species,

This study investigated management for birds in lowland broadleaved woodlands in Britain. It considered the effect of woodland management interventions, such as silviculture (the growing and cultivation of trees) and control of deer browsing, on vegetation structure. The relationship between vegetation culture and woodlands was then explored.

Six woodland stand structures were created and defined as follows: A – dense low shrub layer, B – dense high shrub layer, C – open understorey, D – open canopy, E – closed canopy, few strata, F – closed canopy, multiple strata.

Most woodlands fell into category E, meaning they have low structural heterogeneity and silvicultural interventions are primarily mid to late rotational thinning leading to reduced stem and understorey density. High deer browsing pressure also reduces understorey density.

The results showed these vegetation structures to be less favourable to the target bird species. This suggests that vegetation structures for birds can be described, and if provided, bird populations enhanced. Woodland managers are encouraged to move type E woodlands towards other types to help meet conservation objectives.

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The SAFFIE (Sustainable Arable Farming for an Improved Environment) Project

The Sustainable Arable Farming For an Improved Environment (SAFFIE) project started in 2002 and experimental work continued until the end of 2006. When the project was conceived, arable farmers needed to optimise inputs and improve efficiency, and the UK was committed to increase biodiversity, especially for farmland birds. The SAFFIE project aimed to reconcile these pressures by developing new crop and margin management techniques for winter cereals and quantifying the associated costs and environmental benefits. The SAFFIE project developed Skylark Plots, confirmed the benefits of adding wildflowers to grass margins, evaluated a range of in crop weed control programmes and tested two margin management techniques (graminicides and scarification) that had potential to create new habitats. The studies quantified: (a) the impact of these techniques on key species of grasses and flowering plants, beetles, bugs, flies, grasshoppers, soil invertebrates, spiders, bees, butterflies and birds; and (b) the costs of the techniques.

 

 

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Agri-environmental measures and the breeding ecology of a declining farmland bird

e sparrow (Passer montanus), and/or the formation of larger breeding colonies. 428 breeding attempts were compared in Wiltshire, England in 2013 and 2014. The results showed that the area of margin AES, an insect-rich habitat, was positively correlated with fledgling success per breeding attempt and per breeding pair. Colony size increased with increasing wild bird seed mix AES area, a winter seed food resource, but this option negatively affected hatching success and the number of fledglings produced per breeding attempt. The observed association between colony size and this habitat was expected given that wild bird seed mixtures provide important seed food resources for granivorous birds during winter. The negative correlation with fledgling success, on the other hand, requires further investigation to determine whether this relationship relates to a lack of invertebrate and seed food during the breeding period. These results highlight the importance of providing a suite of AES habitats that are appropriately located to deliver both overwintering and breeding requirements of target, declining farmland birds.

 

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Using fledged brood counts of hedgerow birds to assess the effect of summer agri-environment scheme options

This study sought to identify a new method of determining indicators to measure the impact of European agri-environment schemes on biodiversity. In the past, trends in the spring adult population size of a target group of farmland birds have been used as indicators. This method can be problematic due to the time lag between deployment of those designed to enhance bird breeding success in summer, and the spring surveys the following year. At the other end of the scale detailed studies of breeding success in farmland birds have practical/cost restraints.

The study assessed the likelihood of encountering fledged broods of hedgerow nesting bird species during transect surveys without finding nests, and then applying a simple mark-recapture analysis technique to provide an index of breeding success for those species. Following spring adult assessments, counts of fledged broods were undertaken four times a week during April, May, June and July, in four 2.5 km hedgerow transects, at four sites in southern England in 2010. Mean daily detection probabilities of fledged broods of 16 common hedgerow birds were calculated from these counts using the software Presence. For 15 out of these 16 species these detection probabilities were sufficiently high for a programme of fledged brood surveys, involving just two or three visits per week from mid-May to mid-July, to provide a useful estimate of breeding success.

The survey technique and associated analyses make certain assumptions when providing estimates of breeding success and these are discussed. Little is known about initial dispersal in passerine fledglings and a study in hedgerows may be useful here. However this pilot study suggests that the method could have application as a relatively easily derived productivity index for hedgerow birds, and hence an additional method available to study the impact of certain AES options on indicator species, or for research studies.

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