They follow the release last week of the latest Defra figures – which show that farmland bird populations fell by 5% last year – their lowest levels in 40 years.
The statistics measured the populations of 19 bird species between 2008 and 2009. RSPB scientists believe the one-year decline could in part be due to a cold winter and the loss of set-aside in the countryside.
Some of the largest declines were seen in lapwings – a 12% decline, corn bunting – a 7% and grey partridge – a 23% decline.
RSPB director of conservation Dr Mark Avery said: "It’s difficult to draw any hard and fast conclusions from a short one-year time span, but this certainly makes for some depressing reading."
"The winter before last was a moderately cold one which could have impacted on birds’ ability to find food. We may also be seeing the knock on effect of set-aside being abolished in 2007, removing valuable foraging and nesting habitats for wild birds in the farmed countryside."
"Lapwings – known to some as the ‘farmer’s friend’ - are particularly vulnerable and their populations have been steadily falling for more than 30 years, so a decline of 12% in one year across England is really bad news."
Higher Level Stewardship (HLS) – the advanced environmental subsidy package for farmers – was designed to boost individual threatened farmland bird species like these.
Where HLS has been deployed, farmers and growers have achieved successes for wildlife - but it currently covers just 1% of farmland.
The RSPB fears that the scheme is now under threat from the coalition Government’s proposed budget cuts.
"Those farmers who are helping to save this beautiful, threatened bird through the Higher Level Stewardship are achieving some great results. So to cut this important environmental scheme now could be disastrous."
The figures also show a new long term five-year decline of 10%. Farmland bird researchers say this long term decline shows that the Entry Level Stewardship (ELS) scheme – the basic environmental subsidy package - is not working as well as it should be.
While the High Level Stewardship scheme is designed to save threatened species, ELS is designed to reverse the overall decline in farmland birds – with 56 per cent of farmland in England in ELS.
"The five year decline of 10% is a real cause for concern. It indicates that ELS is not working as intended," said Avery.
"On the RSPB’s own farm in Cambridgeshire we have seen bird numbers almost triple thanks to ELS, so we know it can be done. There are many different options in the ELS scheme but unfortunately we are not seeing the right options used in the right ways.
"Farmland birds need farmers. The NFU and CLA-led Campaign for the Farmed Environment aims to boost wildlife-friendly activities on farms. These results show how crucial this effort is. The Campaign has the RSPB's full support, and we applaud those farmers who are adapting their farms to care for wildlife as well as producing high-quality food. We just need more people to join in."