Professor Ian Newton

Bear with me while I explain. One of the main ecological benefits derived from domestic livestock stems from their dung which, when deposited naturally on pasture, can support huge numbers of insects. These insects in turn may serve as food for birds. My aim here is to draw attention to the importance of livestock dung in the lives of birds, and the adverse trends of recent decades which have greatly reduced its value as a source of insects. Generally speaking, large herbivores are not good at digesting their food. Typically, they extract only 10–30% of the nourishment it contains, and shunt out the rest as dung. Many small animals have evolved to take advantage of this. Worldwide, thousands of species of flies and beetles are dung specialists, and many other insects eat it along with other organic matter. Among the specialist beetles, both larvae and adults eat dung, but in many of the flies only the larvae develop on dung while the adults eat different things. Cow dung has been most studied, and each pat can feed hundreds of insects and other organisms (Lawrence 1954; Jones 2017). It is one of the wettest of types, with a moisture content of 73–89%. When it emerges, as a more or less homogeneous stream, it is fresh, fragrant and glistening, but as soon as it hits the ground it starts to dry, and a crust forms over its surface, slowing further moisture loss. Masses of flies and beetles arrive within minutes of its release, and by the second day their numbers are high, up to 200 beetles having been found in a single pat. Predatory insects arrive soon afterwards, feeding on the dung-feeders. During the first 2–3 weeks, eggs continue to hatch within the dung and insect numbers reach an overall peak, declining thereafter. By about the second week, the pat no longer attracts hordes of new visitors, but the developing larvae and maggots feed quietly within. Some adult beetles are still present, but others have moved off to new pats. By about eight weeks, the dung begins to look more fibrous. It has lost its smell and it begins to crumble, in places looking powdery, and attracting some different creatures. Gradually, mainly by the actions of dung beetles, the pat becomes buried underground, where it rots and contributes to further plant growth. Earthworms accumulate below and grass returns to the site. Standard decay times for cowpats in Britain vary from about seven to more than 20 weeks, depending mainly on ambient temperatures (Jones 2017). Different insects feed on dung at different times of year, and in addition more earthworms occur within pats in winter than in summer. In a pioneering study, Lawrence (1954) found that, on average, each cowpat produced about 1,000 developing insects. Each animal deposited 7–10 pats per day, but some were destroyed by trampling or in other ways, so he assumed six suitable pats per day. This was equivalent to 6,000 insects per day, or nearly 2.2 million insects per year (mostly flies) for each beast kept outside year-round (these estimates are not, of course, applicable to dung stored as muck-heaps or slurry). Accepting seasonal and other variations, Lawrence went on to estimate the total annual production of insect biomass from the dung of each cow or bullock kept on pasture. He concluded that ‘a cow leaves in its faeces enough food material in a year to support an insect population, mostly dipterous larvae, equal to at least one-fifth of its own weight.’ Not all insects that used the dung could be included in his calculation, so for this and other reasons, his estimate should be regarded as minimal. It also excludes worms of various kinds, which are also eaten by birds. But as a rough guide, we could say that, in five years, each cow or bullock kept outside on pasture can produce its own weight in dung insects. Many bird species in Britain exploit the insects associated with cow dung, and each pat can provide food over many weeks. Wagtails and others pick flies off the surface; Jackdaws Coloeus monedula and other corvids, Common Starlings Sturnus vulgaris, BB eye In praise of cow dung Northern Lapwings Vanellus vanellus and other waders, Black-headed Gulls Chroicocephalus ridibundus and others dig into dung pats and turn over the pieces to expose the insect larvae and beetles within. Barn Swallows Hirundo rustica and others catch the aerial insects above, as do many species of bats. Oystercatchers Haematopus ostralegus nesting on inland pastures first pick the flies and beetles off the surface of fresh pats; 10–15 days later they start to probe into the pats for beetle larvae; and after two months, when the pat has mostly rotted, they probe in the soil beneath for earthworms (Briggs 1984). During autumn and winter, the majority of cowpats present in the countryside can be pecked open by birds in search of worms and beetles. Eurasian Curlews Numenius arquata probe deeply for the larvae of Dor Beetles Geotrupes stercorarius buried beneath each pat (Potts 2012). Insects from cattle dung can be especially important to Lapwing and other wader chicks. On the Solway, such insects formed more than 80% of the diets of adult and young waders (Rankin 1979). In the Netherlands, some 21%, 30% and 49% of faecal samples from Lapwing chicks contained the remains of dung fly (Scathophaga), dung beetle Aphodius (Scarabaeidae) and soldier fly (Stratio myidae) larvae respectively (Beintema et al. 1991). The equivalent figures for Black-tailed Godwit Limosa limosa were 73%, 18% and 66%; for Ruff Calidris pugnax 33%, 29% and 46%; and for Common Redshank Tringa totanus 17%, 9% and 26%. These and other dung insects were evidently important to growing waders, and often more than one type was found in the same sample. But whereas Lapwing chicks fed on insects from within the dung, godwit chicks picked insects mainly from the surface of the pats and nearby vegetation. The other species exploited both sources more or less equally. However, there is another ‘fly’ in this story. Livestock dung deposited naturally on pasture now produces much less bird food than in the past. Not only have cattle almost disappeared from parts of the country in recent decades, but many are now kept inside buildings or yards, in winter only or year-round. In the 1950s, almost all farms in Britain kept cattle, but now the estimated figure is less than 40%. But another important development, from around 1980, was the introduction of anthelmintic drugs given to livestock to destroy gut parasites. These drugs are administered in various ways, but for weeks after dosing, they are excreted in the dung, where they last for a further several weeks, killing many of the creatures that could otherwise live in it, as well as others in the soil below, including earthworms (McCracken 1989, 1993; Madsen et al. 1990; McCracken & Foster 1994; Edwards 2004).

Dung flies and dung beetles are major casualties. The most widely used compounds for this purpose are the avermectins, particularly ‘ivermectin’ introduced in 1981. At the concentrations normally found in dung, adult beetles are seldom killed, but their egg-laying may be reduced, and larval development is slowed or prevented (Strong 1993; O’Hea et al. 2010). Fly larvae are more often killed outright, especially those of Cyclorrhapha, which is one of the most sensitive genera, showing a range of responses from death of larvae to developmental abnormalities in adults (McCracken & Foster 1993). Other British Birds 111 • November 2018 • 636 – 638 637 BB eye 413. A fresh cowpat with Yellow Dung Flies Scathophaga stercoraria, Dumfries & Galloway, 2015. Richard & Barbara Mearns chemicals are also administered to cattle to destroy other parasites. The net effects are that the numbers of insects emerging from cowpats of treated animals are much reduced compared with those from untreated ones and that, over time, dung-feeding insects have gradually declined. So much so, that a special group was recently set up to assess the current status of dung beetles and foster their conservation (the Dung Beetle UK Mapping Project, or DUMP). Little is known of the impact of this food loss on birds. However, Red-billed Choughs Pyrrhocorax pyrrhocorax depend heavily on dung-based invertebrates, and a halving of their numbers on Islay between 1988 and 2013 was associated with a large reduction of dung insects in the diet (MacGillivray et al. 2018). In fact, most of the bird species that feed on dung-feeding insects have declined markedly in recent decades, raising the question of how much their individual declines could also be linked with this massive reduction in food supplies provided by dung. Interestingly, organic farms now hold significantly greater numbers and variety of dung beetles than conventional farms (Hutton & Giller 2003; Geiger et al. 2010). The important message, however, is that dung insects – so important to many birds in the past – represent a sizeable component of insect loss over recent decades which has so far been largely ignored in assessments of the factors involved in farmland bird declines.

References Beintema, A. J., Thissen, J. B.,Tensen, D., & Visser, G. H. 1991. Feeding ecology of Charadriiform chicks in agricultural grassland. Ardea 79: 31–43. Briggs, K. B. 1984. The breeding ecology of coastal and inland Oystercatchers in north Lancashire. Bird Study 31: 141–147. Edwards, C. A. 2004. Earthworm Ecology. 2nd edn. CRC Press, London. Geiger, F., van der Lubbe, C. T. M., Brunsting, A. M. H., & de Snoo, G. R. 2010. Insect abundance in cow pats in different farming systems. Entomologische Berichten 70: 106–110. Hutton, S. A., & Giller, P. S. 2003. The effects of the intensification of agriculture on northern temperate dung beetle communities. J. Appl. Ecol. 40: 994–1007. Jones, R. 2017. Call of Nature: the secret life of dung. Pelagic Publishing, Exeter. Lawrence, B. R. 1954. The larval inhabitants of cowpats. J. Anim. Ecol. 23: 234–260. MacGillivray, F. S., Gilbert, G., & McKay, C. R. 2018. The diet of a declining Red-billed Chough Pyrrhocorax pyrrhocorax population on Islay. Bird Study doi.org/10.1080/00063657.2018.1505826 Madsen, M., et al. 1990. Treating cattle with ivermectin: effects on the fauna and decomposition of dung pats. J. Appl. Ecol. 27: 1–15. McCracken, D. I. 1989. Ivermectin in cow dung: possible adverse effects on the Chough? In: Choughs and Land-use in Europe. Proceedings of an international workshop on the conservation of the Chough Pyrrhocorax pyrrhocorax in the EC. The Scottish Chough Study Group. — 1993. The potential for avermectins to affect wildlife. Veterinary Parasitology 48: 273–280. — & Foster, G. N. 1993. The effect of ivermectin on the invertebrate fauna associated with cow dung. Environ. Toxicol. & Chem. 12: 73–84. — & — 1994. Invertebrates, cow-dung and the availability of potential food for the Chough (Pyrrhocorax pyrrhocorax L.) on pastures in Northwest Islay. Environ. Conserv. 21: 262–266. O’Hea, N. M., Kirwan, L., Giller, P. S., & Finn, J. A. 2010. Lethal and sub-lethal effects of ivermectin on north temperate dung beetles, Aphodius ater and Aphodius rufipes (Coleoptera: Scarabaeidae). Insect Conserv. & Diversity 3: 24–33. Potts, G. R. 2012. Partridges. Collins, London. Rankin. 1979. Breeding waders on Rockcliffe Marsh. Wader Study Group Bull. 26: 25. Strong, L. 1993. Overview: the impact of avermectins on pastureland ecology. Veterinary Parasitology 48: 3–17. Ian Newton 638 British Birds 111 • November 2018 • 636 – 638

The View from the Hill

Not really what you need when towing a 10 ton load of seed through town, right outside the Hall and Woodhouse brewery in fact, during a short break in the weather, sufficient to sow around 60ha of our 220ha spring sowing programme.  Pat from Blandford Tyres was on the scene very quickly and we managed to get the tyre blown up, the trailer unhitched and the tractor into the brewery car park for a proper repair to be made. (An old factory repair on the previously tubeless tyre had given out, so Pat had to put in a £150 tube.) Brendan came to the rescue with another tractor and took the seed trailer on to the drill, and we got the barley sown by the skin of our teeth before it rained again, but the soil was too wet to roll, like every other field this spring, and half the autumn sown crops too. 

Before I wallow too indulgently in self-pity I’d better put in a word for the farmers who farm land a good deal wetter than ours.  Our chalk based soils drain quite quickly compared to the heavier clays on which much of the country depends for its food.  Countless thousands of hectares of winter crops have been under water for many months in some parts of the country, and of course the crops will have been destroyed with precious little chance of the soil drying out in time to sow a viable crop this spring as the rain has continued almost without relief until mid April.  A great many of those fields will need more than a year to recover their productivity, one option would be to plant a summer fallow of mixed flowering species, and hope for an opportunity to sow a crop in the autumn, otherwise leave well alone until spring next year, but who knows how much it will rain next winter? The financial consequences of all this are eye-watering.

A week in Herefordshire recently showed how bad things can look, every river brim full or overflowing, and so many fields under water or with water sitting on top of the soil.  This particular erosion was on the River Lugg, not far from the infamous spot where a farmer with a digger was jailed for causing damage to the river bank. There were also many sheep with young lambs looking utterly miserable with little to eat.  I really don’t understand why so many farmers persist in lambing their sheep so early, when there is little grass and miserable weather most years. The sight below should be a huge embarrassment to the farmer responsible.

For the nerds, our 7 month winter rainfall (Sept-March) exceeded the amount that normally falls in a whole year. (1090mm v 1040mm).  Our soils are still very moist, and as the crops emerge, which we managed to finish sowing on Saturday 13^th April, several weeks later than the optimum, we are trying to get them rolled, to push stones in and reduce slug grazing.

Moving on from the horror and stress of the weather and trying to get crops sown, our cows have been pumping calves out steadily for the last few weeks, all of our 60 cows have now calved, and as of just last week are enjoying fresh grass outside.  We couldn’t risk them going out earlier and turning fields to mud before enough grass has grown to sustain them.  The tiny flock of ewes are not due to lamb, until mid May, just in time to entertain a number of school visits booked for this term.

Several Durweston Primary classes visited the farm last term, and it’s great to see them feature in the school newsletter, the lad hugging the sheep is a classic pic, the ewes were so fluffy, their wool is so clean after all the rain, and luckily on this occasion they were lovely and dry. The school logo already has a significant agricultural influence…….

Our mid Stour Valley Cluster group has met several times over the winter, in January we enjoyed a technical session with soil specialist from Devon, Andrew Sincock.  He talked muck, soil, cover crops and compost, and then we trudged out into a damp field to look at grazed cover crop and then some very cold and wet looking compost windrows.  Andrew had shown us a curious graph which is supposed to tell us all we need to know in order to get compost right.  If you can understand this you are cleverer than me.

Our own composting efforts had worked well earlier last year, we made and spread all the muck-based batches successfully before sowing this winter’s cover crops, but the compost rows that were only built in the autumn, using straw, horse manure, and material cut from our flower margins, didn’t contain enough nitrogen to get the composting process going before winter.  We are about to liven up the windrows with fresh muck from the cow shed, then get the turner going to start it up again.  We need it to reach 70 degrees temperature, to kill weed seeds and to encourage the right kind of organisms in the compost.

A couple of weeks ago Claire our cluster group leader organised a bat walk, led by Jim Mulholland of the Vincent Wildlife Trust.  He gave us a fascinating talk with slides to begin with, focussing on the Greater Horseshoe bat which has a colony containing around 500 bats very local to the farm.  We learnt many years ago that our land was highly likely to be providing foraging habitat for this endangered species, and we, as well as neighbouring farms, were encouraged by the Vincent Trust to manage our hedges to benefit the bats, and to refrain from using Ivermectin wormers on our cattle, this family of medicines kill the flies and beetles that feed on and live in cowpats, and which at the same time provide an essential food source for bats and many other species.  From a low of just 2,200 individuals 30 years ago, the greater horseshoe bat UK population is now said to number around 10,000, thanks not least to the Vincent Trust, which has spent huge amounts of money purchasing buildings used as roosts, and then adapting them to suit bat requirements as closely as possible. 

Jim took us to the roost, gave us bat detectors and encouraged us to stand quietly, watching the sky and listening for the GH bat’s unmistakeable sonar-like noise.  Normally undetectable by the human ear, through the detectors they sound a bit like the Clangers, with a rising pitch phrase of 5 or 6 blips.  The sound of approaching bats on the detectors made us look upwards to be treated to swoops of individuals leaving or returning to the roost, with the bats silhouetted against the dusky sky the combination of sound and vision was captivating. This link takes you to a leaflet about the GH bat, with some great pictures.

https://www.vwt.org.uk/wp-content/uploads/2015/04/horseshoe-bat-leaflet.pdf

Interesting fact of the week; apparently the weight of all the creatures generated from the manure produced by a cow in a year is equivalent to 20% of the weight of the animal.

And a second one for good measure; the mites carried by dung beetles hop on and off the beetles as they travel from cowpat to cowpat, they spend much of their time consuming the fly eggs they find in the dung, therefore a good healthy cow pat which does not contain the residue of the most powerful wormers, can itself reduce the number of flies that it might well otherwise have produced.            https://www.dungbeetlesforfarmers.co.uk/what-is-in-dung

For those keen to explore this subject further, here is an article (from which much of the last paragraph was borrowed),  by Prof Ian Newton, who is described by my naturalist farmer friend Martin as our greatest ever ornithologist.

In praise of cow dung

And finally for this episode, a developing situation is causing concern in various quarters in the county. Nutrient Neutrality is one feature of the Environment Act of 2021, the basic principles of which are enshrined in the act’s Environmental Principles Policy Statement.  The five environmental principles set out in the act are:

1. the integration principle (that environmental protection be integrated into the making of policies);
2. the prevention principle;
3. the precautionary principle;
4. the rectification of environmental damage at source principle; and
5. the polluter pays principle

All of which make plenty of sense.  But start digging deeper and it gets complicated.

The nutrient neutrality bit is where developers of new housing or commercial property on green field sites, have to lodge large sums of money with the local authority, or Natural England, which allegedly enables them to offset the likely future pollution produced from those new sites, and thus be awarded planning permission for the development.  The six million dollar question is what happens to that money ?  Well in two cases here in Dorset, the Dorset Wildlife Trust appears to have got its hands on some of it, and has used it to buy two farms, in order to rewild them.  Now whatever you may think of rewilding, and I would need to write another 2000 words to do it justice here, my question is does the spending of let’s say £12 million for the two farms (total approx. 1000 acres) represent good value for public money ?  The Trust will rewild 1000 acres (400 hectares) , which frankly will make little difference to the overall environmental condition of the Poole Harbour catchment (80,000ha) in which both farms sit, and where the Environment Agency (EA) has for the last five years been trying to persuade farmers to rein back on their nitrogen usage and manure production, in order to significantly reduce the amount of nitrogen reaching Poole harbour.  The harbour is a globally important area for wildlife, and excessive nitrogen causes algal blooms which can starve the water of oxygen, and consequently seriously harm water dwelling species.  So far the EA has worked with a large number of farmers in the catchment, and they have formed the Poole Harbour Nutrient Management Scheme, however it has become mired in difficulty due to the EA’s inability to devise an effective computer model that farmers can use to calculate their N leaching risk. (The now infamous nitrate leaching tool). The EA claims to be strapped for cash, and hence does not have the resources to invest in a programme sophisticated enough to provide the information required.  It strikes me that this is exactly the kind of thing that the Nutrient neutrality money should be spent on, it could have a hugely beneficial effect through persuading farmers to reduce their riskier activities, over a very wide area, not just the 400ha that DWT are trumpeting as a huge environmental gain.  Cynics might say vanity project.

£12 million could go a very long way in persuading farmers over a very wide area to farm in a more environmentally friendly way. In a nutshell, it’s land sparing versus land sharing, and I know which I favour.

If anyone can shed further light on what happens to NN money in different areas of the country, please feel free to illuminate those like me who find it all a bit mysterious right now,  in the comment box below

From DWT’s website:

“We are delighted to be partnering with Dorset Wildlife Trust and others in this significant project which has the potential to substantially boost nature’s recovery in this part of Dorset. This is a great example of thinking creatively and bringing partners and different types of funding together. A large proportion of the funding is from Natural England’s nutrient mitigation scheme, meaning this work will offset the nutrient impact of much needed housing elsewhere in the Poole harbour catchment. While crucially playing its part in creating a beautiful landscape for people to come and enjoy for many years to come.”

Rachel Williams, Deputy Director  – Natural England

We have done a bit more hedge coppicing this winter, admittedly it looks pretty drastic, but by the time we have filled in the gaps, and the stumps have sprouted new growth, we will end up with a much healthier hedge, with a thick bottom and lots of growth which can provide shelter for nests and fledglings. We hired a man and machine for the day to chip up all the brush wood, the chipper is huge and can munch it up faster than the operator can feed it with his long armed grab. We will use the wood chip in the cow shed next winter, to give the straw bedding a good base, and to mulch new hedge and trees around the farm. Fencing it in is now high on the list of ongoing work, to prevent deer and our livestock eating the new growth. Gary has been down there this week getting posts knocked in with Brendan, and will get the wire up in no time with our fencing machine and electric staple gun, (see last issue).

It’s time to get the wool off the ewes, a couple of weeks before they lamb. Newly learnt lessons with a Kiwi shearing gang have meant the shearing can be done in house once again.

Turnip seed coming along nicely for next winter’s cover crops, along with phacelia, clover, linseed and radish, with a few more about to be sown, such as buckwheat, vetch and camelina.

Mr Red enjoying the company of 11 heifers, replacements for the herd for next year, and the cowslips.

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