Cirl bunting recovery: What next?

The English cirl bunting recovery programme has so far been a huge success. Sterling efforts by the RSPB and farmers in the south-west have seen the residual cirl population in the South Hams increase very dramatically, and the re-establishment, through translocation, of a population down in Cornwall appears to have gone to plan.

Here, I ask if it’s about time we moved to the next phase – a further translocation much further east, somewhere close to the English south coast. This has long been an objective of the UK Species Action Plan for the cirl bunting, and the RSPB has demonstrated that translocation of cirl buntings can work.

To recap, the UK cirl population was once very widespread across the south of the country. In the UK, cirl buntings are very much a farmland bird: it’s probable that their population expanded with the expansion of low-intensity mixed farming.

As agricultural technologies developed, farming systems began to specialise, with arable concentrating in the east, and pastoralism in the west. Cirl buntings love – well, in the UK they required – mixed farming. The loss of spring-sown cereals and over-winter stubbles, rich in seeding broadleaved weeds, denied cirl buntings access to seed-rich habitats critical to over-winter survival. A dramatic decline in the abundance of grasshoppers across farmed landscapes was one consequence of the application of chemical fertilisers to agricultural grasslands. Cirl buntings love to feed grasshoppers to their broods, particularly in late summer.

These key factors driving the collapse of the cirl bunting population were revealed by intensive research conducted primarily by Dr Andy Evans at the RSPB. Having worked out the causes, the RSPB worked with Natural England (or was it the NCC?!) and the Countryside Commission (CoCo) to build cirl-bunting-friendly options into the pilot Countryside Stewardship Scheme then being tested in the South Hams. A particular problem at the time was the conversion of small coastal arable fields, upon which the surviving cirl bunting population depended for winter seed, to grassland. Local RSPB staff – particularly Leigh Lock and Cath Jeffs – worked with CoCo and local land owners to ensure that valuable spring-tilled arable was retained and weedy stubbles left over winter, and that grasshopper-rich pasture was managed sensitively to provide and maintain tussocky grassland foraging habitat over summer. Tussocky grass margins were established around arable fields too, enabling grasshopper populations to build up along the bases of thick hedgerows in which cirl buntings like to nest.

Having demonstrated that an agri-environment scheme can be used to provide all that cirl buntings need, Leigh, Cath and their local RSPB advisory team then worked to expand advice to farmers across the remaining range of cirl buntings in south Devon. Thanks to their heroic advisory efforts, and sustained funding from NCC…English Nature...Natural England and the RSPB, the cirl bunting population was stabilised, and their numbers proceeded to increase.

The trouble was that, although the numbers of cirl buntings increased, their range didn’t – in fact, in some places they continued to decline. A key objective of the UK Biodiversity Action Plan for cirl buntings was to increase their range, and establish populations elsewhere in southern England, away from south Devon. One reason for this was that a population of birds confined to a very small part of the country – like south Devon – could be vulnerable to a chance event, such as a very cold and prolonged winter. If you have a second population some distance away, chances are one or other will not be affected by the same event.

Given that the cirl bunting population in Devon was (and still is) showing very little evidence of expanding out of its South Hams stronghold, plans were devised to translocate some birds in an attempt to establish a second population. Cornwall – an area reasonably close to the existing population and with increasingly suitable habitat (because Stewardship agreements were maturing) – was chosen as an area in which to test translocation techniques.

The Cornwall translocation – Phase 2 of the recovery project, if you like – appears to have been a great success too. A breeding population has been established and this appears to be increasing of its own accord, without the need to supplement the population with further translocations.

Now, having proven the concept of translocation, is it time to move to the next phase – to establish a population away from the south west, somewhere in southern or south-east England?

I’d argue Yes, absolutely. The south-west populations remain vulnerable; there remains very little sign that the South Devon population is expanding east of the Exe estuary, into east Devon, from which it would then continue east into Dorset. Maybe we’ll arrive at a point where the density of pairs in some parts of south Devon is so high that range expansion suddenly takes off, but that could be decades away, and the northern portion of the Devon population (around Dawlish, Exminster and Exeter) remains at a pretty low density and is increasingly threatened by built development, so it seems unlikely that this will provide a source at the leading edge of an expanding range. And presumably appreciable range expansion of what’s proving to be a very sedentary species would take tens of decades – will they ever reach Dorset?! Basically, new cirl bunting pairs appear to establish territories as close as possible to where they were raised – a few tens or hundreds of metres away. Range expansion could therefore be a very, very slow process indeed.

Where, then, might we attempt the next translocation? Somewhere right on the coast would seem sensible, because the cirl bunting population held on along the coast of the South Hams, so the mild coastal strip may be the best area to create a new source population. Mixed farming – arable and grassland on the same holdings – is essential. And, I’d suggest, a reasonable long history of high quality agri-environment schemes in place: features like grassy margins take time to mature, to build up good grasshopper populations, and benign arable flora populations take time to build up in arable rotations.

How about The Fleet hinterland in west Dorset, Purbeck, or the Isle of Wight? The Isle of Wight certainly retains some promising habitat, but it’s an island, and it would take some determination on the part of non-dispersive cirl buntings to cross the Solent from the Isle of Wight. Those that make it across will be confronted by the New Forest and the sprawl of Southampton and Portsmouth – neither of which appear to provide particularly attractive habitat for an expanding cirl bunting population. The Fleet? I’m not sure to be honest, but it looks pretty good to me.

Personally, I’d settle on Purbeck, an area that has a history of farmland bird focused land management advice, which retains ample nesting and summer foraging habitat, and where I assume we might readily expand suitable over-winter stubble and other seed-rich habitats.

There is another possibility, if we’re prepared to look further inland: Salisbury Plain. Salisbury Plain Training Area and Porton Down cover about 40,000ha, of which about 28,000 ha is grasshopper-rich calcareous grassland, all in public ownership. Fringing the chalk grassland core is public-owned arable, where there is great potential to work with tenant farmers to establish weed-rich stubble and patches of wild bird seed crops. Crossing the plain and extending beyond it are chalk river valleys, the steep margins of which support some cracking chalk grassland and scrubby slopes – further potential nesting habitat. So maybe a bunting rear-and-release facility could be established somewhere within the training area.

So, is it time to move to a new phase in the cirl bunting recovery project – a translocation to central southern England?

 

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