By Stuart Croft: Cirl Bunting Reintroduction Project Officer, RSPB

The programme to increase numbers of cirl buntings in the south-west of England and especially the translocation of chicks from Devon to Cornwall was a major inspiration in the establishment of Birds On The Edge. Not so long ago cirl bunting was an easy bird to find in Jersey and with so few in England we were regularly asked to show tourists our (then) big four – cirl bunting, serin, short-toed treecreeper and Dartford warbler. The disappearance of our serins and cirls coincided it seemed with dramatic changes in the fortunes of the cirl bunting in England. We then needed to speak to the English for tips on recovering the bunting population. The cirl bunting, meanwhile reappeared and, despite its tenuous foothold back in Jersey, is once again on the Island. Stuart and the RSPB kindly allowed Birds On The Edge to repost this piece previously published on the RSPB Community blog site

The Cirl Bunting Reintroduction Project – a partnership project between the RSPB, Natural England (NE), the National Trust and Paignton Zoo, with assistance from the Zoological Society of London – began in 2006. The aim of the project is to re-establish a self-sustaining population of cirl buntings on the Roseland Peninsula in south Cornwall, by taking chicks (under license from NE) from nests in healthy populations in south Devon, and translocating them to the site in south Cornwall. Here they have been hand-reared by aviculturalists from Paignton Zoo, and released into an area of suitable farmland habitat. Though reintroductions of other bird species, as well as other forms of wildlife, have been successfully undertaken in the UK and further afield, the reintroduction of a small, song bird like the cirl bunting had not been attempted before in Europe.

The first batch of young birds was released in 2006, and releases continued for a total of six years, until 2011. Throughout the project all the birds have been monitored by the field team – a process aided by the fact that all the hand-reared birds have been fitted with a unique combination of coloured leg-rings. This has allowed a great deal of information to be acquired relating to many aspects of the birds’ life histories, e.g. their seasonal movements, habitat selection, breeding ecology and longevity.

We have learnt that, just like in Devon, the Cornish birds do not wander far, choosing to settle in an area that, crucially, contains all their year-round requirements i.e. weedy stubbles to forage for seeds in the winter, thick hedgerows where nests can be located away from disturbance and extensive grasslands rich in variety and abundance of insects to feed chicks in the summer. Thanks to the willingness of the local farming community to adopt Environmental Stewardship, in the form of Higher Level Stewardship (HLS), more of this preferred habitat mosaic exists on the peninsula than it did just a few years ago.

During the breeding season pairs are usually faithful, though we have recorded several instances of polygyny – one male breeding with two (even three!) females simultaneously – whilst ‘divorce’ – with partners from a pair splitting and re-pairing with different partners – is novel behaviour that has been recorded. Though cirl buntings are relatively short-lived, with 2-3 years being typical, the oldest known colour-ringed bird so far, died just one month short of his fifth birthday. We are hopeful that there are still a few remaining ringed individuals that stand a chance of exceeding that lifespan.

Following the first recorded breeding of the reintroduced birds in 2007, the population has been steadily increasing, both as a result of further releases, and due to productivity in the breeding population. Despite some poor summers, which have limited breeding success, the population exceeded its target level of 30 pairs in 2012, with 44 pairs recorded. However, the exceptionally wet summer of that year resulted in very low productivity, resulting in a decline in the population the following year. Fortunately, the following two summers have been a vast improvement and the population has responded well. Last year 39 pairs raised well over 100 fledged young – the highest number in any year by far – and we are optimistic that 50 breeding pairs is a realistic possibility this year – a great milestone to reach in the tenth year of the project and one step further forward in establishing this bird back in the Cornish landscape.

The success so far shown from this project is a great example of team work – where various different individuals and organisations have worked collaboratively. We would like to thank all those who have supported the project over the years, in particular the farmers who have given us access to their land, which has enabled us to monitor the expanding population – without their support this project would not have worked.

For more information on the Cirl Bunting Re-introduction Project see the Project’s pages online

Recently we saw how our partial migrant birds are changing their habits and no longer migrating down to the Mediterranean (here). Now, research by the BTO using detailed distribution maps of 122 species of bird further measures the ways that climate change could be affecting our local bird populations. Species distribution was found to be changing, but the range shifts detected could not be explained by any single climatic factor, indicating that the distribution changes for British birds are complex, multi-directional and species specific.

The BTO drew from breeding bird atlases developed two decades apart. Atlas data are collected in a standardised manner by thousands of volunteer bird surveyors, providing a unique barometer of the impacts of environmental change on this one component of British biodiversity.

From the early 1980s to the early 2000s, temperatures in spring and summer increased, which should have pushed some bird species to the northwest if this aspect of climate is key to their success, whilst higher temperatures in winter should have pushed them to the north and northeast. In contrast, if spring rainfall is critical to species, they should have been pushed to the west. Analyses looking at how bird distributions had actually changed over this period found that birds had indeed shifted to the north, on average by 13.5 km, which continued a trend seen in previous decades. However, more than a quarter of the species had also extended their ranges to the northwest and northeast, while almost half had retreated from southerly directions. The ranges of a few species such as greylag goose and great tit had extended in all directions while others like lesser spotted woodpecker and corn bunting had retreated from all directions. Overall the range shifts could not be explained by any single climatic factor, indicating that the distribution changes for British birds are complex, multi-directional and species specific.

Another report published this month from Sweden shows that short distance migrants to this country had advanced their arrival to southern Sweden more over time than long-distance migrants. However, no such difference between long- and short-distance migrants could be seen in central Sweden suggesting that short distance migrants were either arriving in the south much earlier or even spending the winter there before moving further north. In long-distance migrants, the difference in first arrival between the historical and present-day dataset did not differ between southern and central Sweden. These results further establish that many short-distance migrants are becoming resident further north or shortening their migratory route, possibly due to climate change enabling more northerly wintering areas.According to annual first observation used in this study, this seems to be especially true for chaffinch, whooper swan, starling, and woodcock.

It is clear from this research that many of our birds are undergoing big changes in their patterns of migration and selection of wintering areas. A further change, the impact that the number of arriving species, like the egrets, new to particular areas will have on existing biodiversity is, however, not yet clear. As some of our bird species are not shifting their ranges as fast as others, or aren’t moving in the same direction, our bird communities of the future could be very different from those we know today. There is still much to learn if we are to manage the impacts of anthropogenic climate change on our wildlife, and studies such as these will help policymakers to adopt conservation and land management strategies that effectively assist species survival.

You can see the reports here:

Directionality of recent bird distribution shifts and climate change in Great Britain. Read abstract here

Change in spring arrival of migratory birds under an era of climate change, Swedish data from the last 140 years. Download paper here

Two technical reports just published confirm what local birdwatchers have long known: some of our migratory birds are staying much closer to home in winter these days.

Climate warming and other environmental changes seem to be causing a shift in the wintering grounds of European birds northwards. This was tested in two studies, one looking at numbers of some common northern-European songbirds including robins, chaffinches and wagtails that winter in Spain and one looking more specifically at robins. These birds are partial migrants, species where parts of the overall population are migratory while others remain in place, not like swallows or redstarts whose whole population migrates south. The studies looked at annual numbers reaching Spain using data from recoveries of ringed birds.

Results showed that the numbers of the study species from outside of Spain reaching there in winter has decreased since the 1980s and probably well before. This tendency had to be checked against the species’ overall population numbers in northern Europe to make sure the birds weren’t just getting rarer anyway, and, as they weren’t, this confirmed that these birds are moving less. An understanding of the species’ preferred diet did show some likely patterns since frugivorous (fruit-eating) birds, a group well adapted to tracking changes in food availability, showed sharper reductions in numbers reaching Spain in winter than the more insectivorous species. In addition, larger birds, such as thrushes, less affected by problems of winter temperatures, reduced their migratory movements to the south more than small birds. The results suggest a long-term rearrangement of migratory movements of European birds in which the Mediterranean basin is losing its traditional role as primary wintering ground for many of our birds.

The reduction in numbers of wintering migrant birds in Spain appears to have been taking place since at least the 1970s. However, this reduction may have been in progress earlier, since several partially migratory songbirds began to winter in northern Europe in the mid-twentieth century and earlier. The ability of wintering blackcaps, thrushes and, to a lesser extent, robins to move according to fruit resources is most often observed in their wintering grounds, where their abundances are regulated by the annual availability of fruits. The reported changes in the migratory behaviour of the blackcap, one frugivorous species for which foreign recoveries in Spain has declined despite the sharp increase in the European population, support this interpretation. This change of migratory schedules in blackcaps has been related to this species’ ability to adapt its migratory journeys to increasing food availability offered by urban areas in central Europe and warmer coastal areas like the Channel Islands. Why fly all the way to Spain if you can stay at home or move to someone’s garden?

Partial migratory birds possess the genetic variation required to change from partially migratory to resident in just a few generations, suggesting that, according to current predictions of global warming, such trends will continue to increase the number of sedentary populations in Europe and to reduce the number of overwintering birds in the Mediterranean. In the Channel Islands we have seen big changes in our wintering birds over the last 25 or so years. Fieldfares hardly bother to come here now unless the weather turns really cold whereas the UK is full of them. In their place (but not necessarily in the same habitat) we see lots of chiffchaffs and blackcaps. Interestingly, as reported elsewhere in Europe, our wintering blackcaps are very much a bird of the garden where they hog the feeders rather than out in the wider countryside where they’ll later breed.

What of the true migrants? Well, although this winter we have had several swallows and a wheatear sticking around, these species are unlikely to change their habits very soon.

Read the paper abstracts:

Are European birds leaving traditional wintering grounds in the Mediterranean?

Has the Number of European Robins Erithacus rubecula Wintering in Spain Decreased?