An investigation by Science for Sustainable Agriculture (SSA) into a recent Government report charting further declines in farmland bird numbers has raised serious questions about the scientific basis on which these statistics are collected and interpreted. Based on a highly selective (and unchanged) list of 19 ‘farmland birds’ used to determine changes in populations over the past 50+ years, the Defra report suggests that numbers are still in rapid decline and have declined by a further 9% over the past 5 years. Although no supporting evidence is provided, farming practice is cited as the main reason for the continuing declines. However, an alternative, much more comprehensive inventory of 64 British ‘songbirds’, which includes many species commonly found on farmland but not included on the Defra list, indicates that while there are fluctuations between species, the total number of birds in the UK has remained remarkably stable over the past 27 years, in fact numbers have increased slightly by 1.5%. The total bird ‘biomass’ has also remained unchanged over that period. This serious discrepancy calls into question the scientific basis on which Defra is reporting the status of farmland birds in Britain. It also raises concerns about the Government’s reliance on analysis and presentation of bird population data by campaigning NGOs whose existence depends on pessimistic forecasts of bird numbers, and on criticising ‘modern intensive farming practices’, argue SSA members Peter Button, Daniel Pearsall and Matt Ridley.  

 

When the latest official report from Defra charting continued declines in farmland bird populations was published, one graph in particular caught our eye. Here it is: 

 

 

 

 

 

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Whether deliberately or inadvertently intended to mislead, the left-hand graphic showing what has been happening to farmland bird numbers over the long-term lifted the lid on a potential Pandora’s Box of revelations. 

 

By visually cutting off population changes at 100%, the graph as presented conceals the true extent of population growth in a number of key species – including some birds which could also be having a detrimental impact on a number of the species in decline. 

 

Rather crudely drawn, this is what the long-term graph should have looked like:

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We also wondered why population increases of well over 100% were described as ‘weak increases’, while much lower corresponding reductions in the populations of other species were classed as ‘strong declines.’

 

And with some bird populations doing so well on Britain’s farms, this prompted us to question the selection of bird species on the indicator list, and to wonder why these had been chosen.

 

There are 19 species in total, comprising 12 ‘specialists’ and seven ‘generalists’. But when the list excludes a number of very common and important species on British farmland, such as the carrion crow and chaffinch, as well as increasingly prominent species such as the herring and lesser black-backed gulls, and burgeoning birds of prey such as the buzzard and red kite, we wondered how relevant it was as an up-to-date indicator of bird life in today’s farmed environment.        

 

According to the Defra indicator list, farmland bird populations have experienced a long-term decline of 61% from 1970 to 2022. It is truly shocking to consider that more than three-fifths of birds have disappeared from the British countryside in a little over 50 years.

 

The Defra report acknowledges that the most severe population declines occurred between the mid-1970s and the early 1990s, largely due to rapid changes in farmland management – primarily a switch from spring to autumn cropping. But it also suggests that “populations have continued to decline at a fast rate, declining by 9% in the 5 years since 2018.”

 

Again, this is a worrying figure, but at the same time, it doesn’t feel quite right. It doesn’t chime with our own experiences, as bird enthusiasts in regular contact with farmland, of the current state of biodiversity on Britain’s farms. 

 

Since around 70% of the UK land area is farmed, Defra might equally have referred to the conservation status of 64 songbirds on the Songbird Survival list monitored by the British Trust for Ornithology (BTO) as a guide to what is happening to bird life in the British countryside.

 

This much more comprehensive list includes a number of species also typically found on farmland but not included on the Defra indicator list, and covers additional predatory species such as the magpie, hooded crow and carrion crow.   

 

The BTO songbird list compares population changes over the past 25+ years since 1997, a period over which the Defra report says farmland bird populations continued to decline at a fast rate.

 

It classifies species as either red, amber or green according to their conservation status. Some 20 species are classified by the BTO as ‘red’, indicating that their populations have declined by more than 50% over the past 25+ years. Another 15 species are classified as ‘amber’, having declined by 25-50%, leaving 29 species as ‘green’, and not considered to be of conservation concern.

 

What these lists do not emphasise, however, is that across all 64 species monitored, the total number of birds has remained largely unchanged. In fact, the total UK songbird population has grown marginally since 1997 from 70,339,741 to 71,347,200 today, an increase of just under 1.5%. This is because, per species, the increases in abundance are often larger than the declines.   

 

And what about the physical amount of bird life? Bird ‘biomass’ could provide a useful indicator of the food sources available to sustain our wild bird populations.     

 

Again, with reference to the BTO data categorising different species according to their average adult weight, we found that the physical amount of bird life being sustained in the British countryside has remained remarkably stable in recent decades, declining only marginally by 0.4% since 1997. 

 

The Defra report was compiled with the help of BTO, the Royal Society for the Protection of Birds (RSPB) and the Joint Nature Conservancy Committee (JNCC). The discrepancies between our findings and the Defra report must raise questions about the evidence base Ministers are relying on for conservation advice when other, more comprehensive data sources paint such a different picture.

 

And surely this must be good news for bird lovers? The total number of birds in Britain does not appear to have declined at all in almost three decades.

 

Of course, the species profile has evolved over time, and this may explain the distorted trend signalled by the highly selective indicator species used in the farmland bird list.   

 

The reality is that this is the natural ecosystem, and the biodiversity which inhabits it, at work. Climate change is another factor which does not seem to have been accounted for in comparing the make-up of today’s farmland bird populations with 1970. The distribution of species is not set in stone, nor preserved in aspic at some nostalgic point in time 50 years ago, however much some people might wish it to be.

 

Over time, the increased success of some species can obviously have detrimental effects on other populations, for example by stealing their eggs, killing their young, or usurping their nests.

 

Other species are simply adapting to different habitats. Starling populations were impacted when they were forced out of city-centre roosting sites to protect buildings, only to recover in new reed bed habitats. And herring and lesser black-backed gulls are increasingly breeding on town roofs inland while finding rich pickings - on farmland!

 

These inter-species variations each have their own story to tell.

 

There is also an impact from garden bird feeders. The remarkable rise of the goldfinch may have had an impact on other finches such as redpolls and linnets, which don’t use bird tables as much. It is certainly established now that garden bird feeders have boosted blue tit numbers at the expense of willow tits (though neither are primarily farmland birds). Greater spotted woodpeckers, boosted by bird tables, have also taken to boring into nest boxes and taking tit chicks, a habit that may be new. The Defra figures also include greenfinch, a bird that rarely uses farmland, whose numbers have declined mainly due to a disease caught at bird tables, not because of any changes in farming.

 

Migratory species are generally faring worse than those that overwinter here, so – ironically – the best strategy may be to stay at home in Britain and eat human-provided food from bird tables and gardens instead of risking travel to often degraded habitats in the Mediterranean and Africa.

 

So, the robin strategy works better than the redstart strategy, the stonechat is doing better than the whinchat, the grey wagtail than the yellow, the collared dove than the turtle, the blackbird than the ring ouzel.

 

Predation is also a key factor. Research by the Game & Wildlife Conservation Trust at Loddington has shown that controlling magpie, jackdaw and carrion crow numbers can have a very beneficial effect on songbird numbers.

 

These anecdotal examples all have one thing in common. The likely factors impacting changes in populations within and between species today do not appear to be driven by changes in farming practice.

 

Attacks on ‘modern intensive farming practices’ as the main reason for declining bird life populations are now well past their sell-by date.

 

This is why it was so disturbing to read in the Defra report that “some farming practices continue to have negative impacts on bird populations […]. Changes in numbers experienced by some species may, to a lesser extent, be driven by other pressures”.

 

This sweeping statement is made without referencing or providing any evidence of farming practice as the cause of declines in some species. One concession to non-farming causes is the single example that “there is evidence of an adverse impact from disease for some species, most notably greenfinch”.            

 

Headlining bad news and keeping good news to the small print may be expected in some circles, but not in what should be an objective, scientific study that will guide government policy.

 

There is no perfect blueprint for biodiversity. It is constantly evolving. But while some species are faring better than others, there is good evidence to indicate that individual bird numbers and the physical ‘biomass’ of bird life in the farmed countryside have remained broadly stable for the past three decades.

 

That’s good news.

 

And that’s why we would urge Government to review the quality of its evidence base for measuring biodiversity status, and to seriously question whether the indicator list used to assess the health of bird life on Britain’s farms is relevant and fit-for-purpose.

 

But above all, we would encourage Defra Ministers to question the Government’s reliance on data and analysis from environmental NGOs actively campaigning against modern farming practices, and whose very existence depends on pessimistic assessments of the status of bird populations on Britain’s farms.

 

Peter Button is the former Vice Secretary-General at the International Union for the Protection of New Varieties of Plants (UPOV), based in Geneva, an intergovernmental organisation whose mission is to provide and promote an effective system of plant variety protection, with the aim of encouraging the development of new varieties of plants for the benefit of society. Originally from a UK commercial plant breeding background, Peter previously served in technical advisory roles in the UK with the British Society of Plant Breeders (BSPB) and the Ministry of Agriculture, Fisheries & Food (MAFF). He is a member of the Science for Sustainable Agriculture advisory board.   

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Daniel Pearsall is an independent consultant specialising in communication and policy development in the farming, food chain and agri-science sectors. He runs a small livestock farm in Scotland. He co-ordinates the Science for Sustainable Agriculture initiative. 

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Matt Ridley is the author of numerous books on science. He has been a journalist and a businessman and served for nine years in the House of Lords. He lives on a farm in Northumberland.