Paul Cabrisy, research intern at RSPB Hope Farm, tells us about the outcome of our butterfly and bumblebee surveys throughout the monitoring seasons this year.
The butterfly monitoring.
Summer 2019 has been a relatively hot and wet season, but just like last year our butterflies have increased in numbers at Hope Farm. Moreover, we have recorded over 6200 individuals of 24 species. The butterfly index for this year stands at 5.09, a 409% increase since 2001 (fig. 1), thanks to the improved habitats provided on farm since it was bought in 2000.
Figure 1: Hope Farm Farmland Butterfly Index showing the fluctuations in populations since 2001.
In the early season sunshine, species such as Orange-tip, Brimstone were found in record numbers. Later, the Gatekeeper, Meadow Brown and Small Heath also hit new highs. Seventy-nine Small Heath butterflies were recorded this year where we had only recorded 50 individuals in the last 18 years. Over 1300 meadow brown butterflies were also recorded on the farm survey transects this year.
The bumblebee survey.
Credit: Buff-Tailed Bumblebee on white flower, photo by Paul Cabrisy.
With national declines in bumblebees over the last century*, we attach importance of monitoring our bumblebee population at Hope Farm that can be attributed to changes in farm management. We record bumblebees on the farm with three monthly surveys through mid-summer, using the same methodology as the Bumblebee Conservation Trust BeeWalk and contributing to their national monitoring scheme for the sixth year.
This year, bumblebees at hope farm were 19 times more abundant than on a nearby control farm without a Countryside Stewardship Scheme nor a similar abundance wildlife habitat. We have found 6.3 bumblebees recorded for every 100 meters of transect at the farm, which is equivalent to seeing 1 bumblebee every 16 meters, compared to 1 bumblebee every 313 meters on the control farm (fig. 2).
Figure 2: Comparison of bumblebee number per 100m of transect on peak season survey (end June-mid July) between Hope Farm and Control farm since 2013.
Habitat management at Hope Farm.
These records of butterflies and bumblebees show again the difference changes to farmland habitat can make for wildlife. Here are a few ways that we make sure these resources are available on the farm, that in turn help us to grow profitable crops.
At hope farm we entered the Countryside Stewardship Scheme in 2007, funding the establishment of both perennial wildflowers and short-term nectar flowering margins now growing on more than 4% of the farmed area. Not only are these habitats paid for through CSS, but they also pay by providing resources for pollinators that help our crops to grow, and for natural enemies to our insect pests that we want to control on farm. These habitat margins have helped us support species like hoverflies that both pollinate as adults and feed on pest aphids in their larvae stage.
In addition to planted flowering plants for the spring and summer, some pollinator resources can be found in the wild bird seed mixes in the early autumn. In the late season, plants like Phacelia, Mustard and Buckwheat all help the last of the queen bumblebees and late season butterflies to find food.
Hedgerows are also important with plants like Blackthorn and Hawthorn that produce pollen in the early season. Brambles and ivy are fantastic for late season pollen too.
To maximise the value of field boundaries at the farm, we reduce the cutting regime of our hedges to a 3-year rotation, again funded through CSS. By doing so, we have more flowers, fruits and varied shelter habitat for farmland wildlife. As a bonus, we make around £250/year by entering 11km of our 13km of hedgerows into the stewardship scheme.
How other farms can contribute to wildlife.
Pollinators are of major importance to our arable systems with 84 % of the 264 crops cultivated in Europe depend on pollinators*2. Whilst invertebrate pollinators have declined so rapidly in the last century*3, there are a few relatively easy and hugely rewarding ways that farmers can help these species to recover on a landscape scale.
Farmers can make a real difference for wildlife by providing pollinator habitats in margins, plots, field corners and hedgerows. To help pollinators to thrive on farmland the main action plan is to look after existing field boundaries on the farm, and to plant at least 2% of the farmed area as with nectar resources. It is essential to provide flower rich habitats throughout the season that insects are active from March to September.
Well managed margins and hedges on the farm can really help contribute towards crop protection and pollination too.
Other than providing the habitat around the crops, farmers can also reduce the amount of insecticide used and be careful about timings of chemical use. At hope farm we have restricted insecticides use for a few years, to outside spring and summer, and for the first time our harvest this year has been totally insecticide free. By doing so, this will not only help beneficial insects to thrive but will also provide more abundant invertebrate food for chicks to survive.
Other good news on Hope farm monitoring.
As we monitor some of the later breeding birds at Hope Farm, an additional Barn Owl nest has fledged a brood of 4 chicks over the last month. In addition, two Collared Dove chicks were found in one of our barn owl nests and we are hopeful that these have now successfully fledged.
* Kells, A. and Goulson, D. (2003). Preferred nesting sites of bumblebee queens (Hymenoptera: Apidae) in agroecosystems in the UK. Biological Conservation, 109(2), pp.165-174.
*2 Williams, I.H. (1994). The dependence of crop production within the European Union on pollination by honeybees. Agricultural Zoology Reviews, vol. 6, pp.229-257.
*3 Senapathi, D., Carvalheiro, L., Biesmeijer, J., Dodson, C., Evans, R., McKerchar, M., Morton, R., Moss, E., Roberts, S., Kunin, W. and Potts, S. (2015). The impact of over 80 years of land cover changes on bee and wasp pollinator communities in England. Proceedings of the Royal Society B: Biological Sciences, 282(1806).
What happened re. butterflies in 2012? Why just as bad as other farms, was it just the weather?
2012 was a really wet summer so not good for butterflies or many other invertebrates. The national index also has a slight dip in that year. Thanks for the questions!
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