A recently published review studied evidence on the best ways to provide habitat for birds in arable field margins.
In general, grass-only margins provide limited food resources for birds, and are greatly improved by adding perennial flowering plants to the mixtures. As no margin type provides reliable food sources year-round, it is better to have a different margin types around the farm. The value of margins can vary with location, soil type, age, nature of adjacent field boundary and management of the adjacent crop. Perennial grass and flower-rich margins provide a source of colonising insects to ameliorate the effects of insecticide applications in the adjacent crop.
Grass-only margins have low plant and structural diversity. They benefit invertebrates which overwinter in tussocky grassland and those that benefit from lack of soil disturbance. Although they can provide grass seed and insect food for birds, the density of the sward often prevents access for effective foraging. The high densities of small mammals make them ideal for hunting barn owls and kestrels.
Flower-rich margins have a higher plant and structural diversity, and offer more pollen and nectar sources, with the result that they hold a greater range of plant-feeding and pollinating insects. Seed and insect food, and accessibility for birds are all dependent on the variability and plant composition of the sward. In general, they provide the greatest abundance and diversity of invertebrate food.
Margins established by natural regeneration are variable, but tend to provide good habitats for plants, invertebrates and birds where soil fertility is low and there is a rich seed bank. Initially dominated by annual weeds, these margins gradually become colonised by perennial plants. Birds benefit from the high seed value of the margins in the establishment phase. The invertebrate food benefits depend on the variability and plant composition of the mature sward.
Conservation headlands generally create a sparser, weedier crop, beneficial for arable plants and their associated insect fauna (e.g. sawflies, bugs and pollinators). Invertebrate diversity is lower than in the uncropped margin types above. They are particularly beneficial for gamebirds, but benefits for other farmland birds are unclear.
Seed crops (e.g. wild bird seed mixtures) have a lower invertebrate abundance than uncropped margin types, but offer the highest abundance of seed food, and their open structure allows easy access for foraging birds.
Cultivated margins benefit annual arable plants and associated insects. The abundance and diversity of these groups may be greater in cultivated uncropped margins than in conservation headlands, due to the lack of crop competition, but overall insect abundance and diversity is still lower than uncultivated margin types. For birds, these provide an abundant and accessible source of seeds and insects, but are only generally applied to areas with light soils.
Cutting of uncropped margins: cutting may help maintain plant species richness, especially if fertility levels can be reduced by cutting anf removing the vegetation in the autumn. It temporarily reduces the structural diversity and removes nectar sources, which can have negative impacts on invertebrates, but may be beneficial in the longer-term if it helps maintain plant diversity. Ground-feeding birds can benefit from opening up the sward, but spring/summer cutting is clearly a risk to ground-nesting birds.
Reference: Vickery JA, Feber RE and Fuller RJ (2009) Arable field margins of rbiodiversity conservation: a review of food resource provision for farmland birds. Agriculture, Ecosystems and Environment 133: 1-13.
Wild flower margins provide the greatest benefit for wildlife, says latest report.
Flower-rich field margins are a greater boost to wildlife than grass-only margins, according to a new report.
The paper published in the latest edition of the scientific journal Agriculture, Ecosystems and Environment highlights the significant benefits for biodiversity of creating flower-rich margins around arable fields.
The RSPB is urging farmers to consider incorporating flowering plants such as knapweed, scabious, yarrow and bird’s-foot trefoil to any grass mixtures in margins that they will be sowing this coming autumn.
Richard Winspear, the RSPB’s Senior Agricultural Adviser, said: “Flower-rich margins hold the greatest variety and abundance of insects of any margin type. Such margins alongside watercourses could be a simple way for farmers to benefit both wildlife and water quality.
“Grass margins are amongst the most popular options taken up by farmers through agri-environment schemes. They do have wildlife benefits, such as boosting predatory insects and small mammals, and providing hunting areas for barn owls and kestrels. However, if farmers are planting further margins this autumn then there are significant further benefits to adding flowers to the mixtures.
“As with all wildlife management, increasing the diversity of habitats you create increases the range of wildlife that will benefit.”
The Campaign for the Farmed Environment – which the RSPB has signed up to – encourages farmers to put measures in place to benefit biodiversity, farmland birds and natural resources such as watercourses. The report – entitled Arable Field Margins Managed for Biodiversity Conservation – shows that creating a diversity of wildflowers in field margins can help farmers achieve all three of these aims.
Within the industry there is currently a move towards establishing six metre margins to protect watercourses. In the Entry Level Stewardship scheme, a mixture that includes at least four species of flowering plants can be managed under the Nectar Flower Mixture option, worth 450 points per hectare.
Hi Sue
Thanks for your comments and we would very much appreciate your input into developing an option that might be taken up by a high proportion of arable farmers (ie as low-maintenance as we can get away with). The reason why we are keen to find a solution for easy establishment of flower-rich margins is that arable farmers in England are being encouraged to manage their land to benefit farmland biodiversity, farmland birds and resource protection through the Campaign for the Farmed Environment. As this largely depends on management within the 30 points per hectare threshold of Entry Level Stewardship, we are looking for multi-functional options maximise the benefits within the scheme.Flower-rich margins managed under the 'nectar flower mixture' option could potentially tick all three boxes by boosting floristic and invertebrate diversity, providing insect food for chicks and buffering watercourses (hence the focus on margins rather than blocks). If a wild flower / grass mix was used under this option, then half would be cut in June/July and the whole in September/October. Farmers are encouraged to remove cuttings where possible and graze in the autumn, but many do not have the kit or livestock to do this.
Admittedly, the margin management as costed by Smiths Gore would at best only retain flowers in the half cut annually. The other half would become grass-only. Some farmers have retained flower-rich margins by cutting. Some species do better than others in this regard, and it would be good to learn from everyones experiences of which species fare best in different soils and situations.
I visited Nicholas Watts yesterday to look at his flower-rich margins (which looked fantastic and were humming with insect life). He has good margins that are 15 years old. He only cuts area once per year, but also uses Fusilade (grass herbicide) to suppress coarse grasses, which may not be acceptable next to watercourses if we want to develop this multi-functional approach.
Regards
Richard
Agree with what Sue says, but raises a few points:
· Current payment rates (at least in ELS) certainly would not cover extra costs of seed and management involved.
· Even if payment rates were higher, many farmers may deem cutting and baling the margins too onerous.
Nicholas Watts will be contributing case studies on his wild flower margins and cultivated margins to this website shortly. We are certainly looking at cultivated margins as the preferred insect-rich habitat on arable fields, but looking for alternatives on (e.g.) heavy soils where cultivated margins would impose too great a noxious weed problem.
In answer to your question of who 'we' are: NE, RSPB, GWCT, FWAG and the Wildlife Farming Company have been discussing the best ways that farmers can help the environment through the Campaign for the Farmed Environment: the NFU and CLA-led industry campaign to replace the wildlife and resource protection benefits of set-aside. This is constrained by the fact that most of it has to be delivered by Entry Level Stewardship (ELS), which is limited to a requirement of 30 points per hectare. Whilst we could have grass margins abutting all watercourses, this would use up a lot of the ELS points, so if we could create these 6m margins using something that is more beneficial for wildlife then it would be a bonus.
We may have more questions for you on what might work on different soil types, and which species might be more tolerant of low-maintenance in the near future. Whilst I realise that cutting and removing will give the best results, we are unlikely to be able to encourage farmers to buy new kit to do their Stewardship agreements, so we would like to be armed with suggestions for farmers in every scenario.
Thanks
Wildflowers margins and fields should be managed as such if soil type and conditions (as well as the ability and keenness of the farmer) are suitable, this would normally be funded under HLS.
Floristically enhanced margins (HLS), nectar flower mixtures (ELS) are to be used in a variety of situations to give a sustained provision of nectar for insects and in turn provide insect food for birds. Increasing the array of arable flora can be delivered through a variety of means whether that is through cultivated margins or plots for arable flora, low input or reduced herbicide cereal crop management or conservation headland management (amongst others)
It’s a process of selecting the right options to deliver the achievable benefits in certain situations, for instance trying to manage cultivated margins on heavy land in Lincs can cause problems with regards to non-target weed infestation, whist on light land in the Brecks this would be an option to target.
I've seen a lot of pollen and nectar mixes that have needed resowing in their 10-year lifetime (established under CSS), but this has generally been largely due to the previous mixes that included a significant grass element in them. Under the prescription farmers worked to, this often lead to the grasses out-competing the flowering (usually legume) elements, and hence the need to re-establish. By contrast, I've seen more flowering-plant only mixes being created under EF4 that are a lot more long-lived and should certainly last at least the 5 years of the ELS agreement.
Of course these are a bit of a sticking-plaster option. They're not going to last over the long-term, and they're almost certainly using agriculturally improved cultivars of legumes. However, they're better than nothing, and I think the payment rate and placement in ELS as opposed to HLS is a good reflection of this. For a long-term habitat of native provenance, native wildflowers, you look to HLS and the additional financial and advisory support that goes with it.
Interesting comment on the long-term drainage issue though. Would you like to start a separate thread to it and name areas? There's bound to be several folk all with an eye to the same locations.