Guest blog by Dr John Mallord, Senior Conservation Scientist, RSPB Centre for Conservation Science
Titan our 2014-16 satellite tagged Turtle dove was a superstar; the first UK-breeding turtle dove that was followed on its entire migratory journey from his breeding grounds in Suffolk to Mali and back again – and back to Mali a second time. Nevertheless, he was just one bird, and to get a broader picture of turtle dove migration, we needed to track more birds.
Tagging Turtle doves in the UK earlier this year
Fortunately, the success of Titan helped us get permission to tag more birds in East Anglia in the summer of 2016, and we caught birds at four sites, including our reserve at RSPB Frampton, and three farms in Norfolk, Suffolk and Essex. Sadly, the season didn’t get off to the most promising of starts, as we lost some birds before they had even set off from the UK. You can find out more about what happened to each bird that we tagged on our website.
Challenges on migration from UK to Africa
Of course, once the birds leave the UK on their epic 5000 km southward journey, they are then faced with a whole host of other challenges. This includes the largest natural barrier, the Sahara. Yet, it’s amazing how many birds don’t even make it this far. This year, we lost two birds during this phase of autumn migration, including one on the edge of the desert in Morocco.
Usually when we stop receiving satellite transmissions from birds, we conclude that the birds have died, but we have no way of knowing what the cause of death was. However, one of our satellite tagged Turtle doves was legally shot in Spain and was handed in to the authorities in mid-September near Córdoba in the region of Andalusia in southern Spain. Although a sad end for this particular individual, at least we were able to determine the cause of death.
3 x satellite tagged birds in their African wintering grounds
The three remaining satellite tagged Turtle doves are still going strong, and we continue to pick up daily transmissions from them as they spend the winter in Mali.
Photo caption: Satellite tagged Turtle doves. (Left to right) Bird 160997, Bird 161005 and Angela (Bird 161002).
Interestingly, all three birds are within 250km of each other along the Niger River and its tributaries, and only 70km from where Titan spent winter 2014/15.
In fact, the whole of their southward journeys show great similarities, and highlight important places along the route, such as the tributaries and floodplain of the Senegal River in southern Mauretania, where all tracked birds, from the UK and France, have lingered after crossing the Sahara in autumn.
In a previous blog I spoke of an area in Mali, near the town of Kayes, that Titan returned to in two successive winters; well, this area has proved popular with quite a few birds, including one of this year’s birds and a number of birds tagged in France. This is important information; although the political situation in Mali may prevent us from travelling to these areas, knowing the location of key places can help us understand the particular threats facing turtle doves while they are on the wintering grounds.
Figure legend: the routes taken by the birds tagged in 2016, along with Titan’s two southward migrations (in yellow and pink) for comparison. [Click on the image to enlarge].
Understanding the requirements of Turtle doves in Africa
As mentioned in previous blogs , we have a team of researchers out in the field in Senegal, learning first-hand what is important to turtle doves in Africa.
They are based at a roost site that holds tens of thousands of turtle doves and other species. However, one piece of information we do not know is where these birds originate from, which breeding populations they are from.
We know that many will be from the North African race; in fact, we had a report of a bird ringed by the team in February 2016 being shot by a hunter in Morocco the following July. However, there are likely to be thousands of birds from Europe.
Satellite tagging Turtle doves in Senegal this winter
We have retrieved three of the satellite tags from birds that died this year, and now we have been given permission to fit these satellite tags to 3 x birds in Senegal, so soon we will get a better idea of... where these birds come from.
Find out more
To follow our satellite tagged Turtle doves visit www.rspb.org.uk/turtledovetracking or follow @RSPBScience on twitter
Find out more about our work on turtles doves through Operation Turtle Dove.
Guest blog by Rosemary Setchfield, Conservation Scientist, RSPB Centre for Conservation Science
RSPB research has shown that areas near field edges with extra crop seed frequently attract corn buntings to nest. However a nest near the edge of a field is more at risk from predation and is less likely to produce fledged chicks. Through adding more seed in the middle of the field, corn buntings could be encouraged to nest away from field edges allowing more nests to fledge chicks. This is at little extra cost and effort for the farmer and the measure is now recommended in the Countryside Stewardship scheme as a Threatened Species Advisory Measure.
“Farmer’s bird” disappears
Corn buntings were the quintessential ‘farmer’s bird’ in former decades. The endearing song of the male rattled around cereal crops all summer and busy flocks visited grain stores during winter. But today, farmers barely know this bird. Along with many other farmland birds, it has disappeared from most farms during the last four decades.
Click here to play this audio clip
Listen to the wonderful jangly song of corn buntings (and skylarks). This sound has been disappearing from our fields for the last forty years (Xeno Canto)
Eastern England is still a stronghold of corn buntings in Britain. They typically breed in cereal fields where crop plants, including wheat, barley and oats, have stiff stems and abundant leaves for protecting and concealing nests on the ground. Intensive cultivation and years of herbicide use has removed most weeds from the crops, so females rely heavily on the cover of crop plants alone to protect their nest.
Photo of corn bunting male singing in a wheat crop (RSPB images).
Joint funding from Natural England has enabled us to investigate exactly what limits the number of corn bunting chicks produced from nests in autumn-sown cereal crops. This is what we have found:
Thick areas within crops are selected for building nests
Our data shows that females prefer to lay their clutches in parts of fields where the crop grows thicker than elsewhere. These areas probably help conceal females from predators when they are sitting on eggs or chicks.
Photo of corn bunting nest in winter wheat crop with five chicks (Rosemary Setchfield).
Thick crops near crop edges attract nest predators
Farmers often sow more crop seed near field edges, known as ‘seed overlaps’ or ‘double drilling’, which is due to the technological constraints of farming machinery. Female corn buntings are attracted to these areas for building nests because thicker crop develops, and this thickness is hard to find elsewhere in fields. We found that nests close to crop edges are more frequently targeted by predators than nests in field centres, particularly in the later summer months. This is when females produce second (or even third) clutches, so many of these nests produce no chicks.
Thick crops encourage more second clutches
Corn buntings, like many other ground nesting birds such as the skylark, should normally produce more than one clutch each summer. This ensures that enough chicks survive to breed in the following year. Along with our previous research in Cornwall, we found that crops that were thicker overall or had dense weed growth, allowed more females to produce second clutches. This is probably because thicker vegetation can better conceal females and nests from predators late in the summer, at a time when crop leaves are withering.
Designing an effective solution for corn buntings
These findings suggested a cheap and easy farmer-friendly solution to boost numbers of corn buntings fledging the nest. If extra seed produces thicker crop and attracts females to nest, then farmers could intentionally sow more seed in areas away from dangerous crop edges. If females then select these areas for nesting, many more chicks could be produced each summer because these nests would be less vulnerable to predators and females might be encouraged to produce more second clutches. An experiment has already shown that this is possible, and we are currently running final trials to confirm the full benefits.
Aerial photo of a strip sown with extra seed by a farmer for corn buntings (Andrew Asque). Taken in autumn, humans have difficultly seeing these areas in the summer.
Predicting recovery with a solution
An important part of our work was to build a model for predicting corn bunting population increase using this new solution, made possible because we understand both why females choose to nest close to crop edges, and how nest survival changes in time and space. Our model allows us to calculate how many chicks each female could produce each summer on average when extra seed is sown at increasing distance from crop edges. From this, we expect populations to rise if extra seed is sown about 100m from crop edges, as long as females happily nest at this distance. This is what we are currently testing.
A brighter future for corn buntings?
Although final trials are still underway, this solution has already been adopted in the new Countryside Stewardship scheme as a Threatened Species Advisory Measure. Farmers are happy to sow extra seed in their fields as it is cheap, easy, and does not affect their yield or the tidiness of their crop. We have also shown that extra seed can reduce the growth of blackgrass, which is enemy number one for most farmers. So, with creative advocacy, there may even be scope for farmers to provide this management voluntarily. This offers new hope that landscapes once occupied by this enigmatic farmer’s bird can again, one day, be restored to full song for future generations to enjoy.
Please read the paper: ‘The influence of crop tiller density on the breeding performance of a cereal-nesting specialist’ published in the Journal of Applied Ecology to find out more about the research project.
Find out more about our work to test farming solutions to reverse corn bunting population decline in England here.
This work is funded by the Action for Birds in England partnership between RSPB and Natural England.