By Victoria Gill
Science and nature reporter, BBC News
A wild, endangered goose chase
They are colourful and rather charismatic geese, which chatter and squeak rather than honk.
Huge flocks of them pepper a bleak, wintry scene with flashes of orange.
But the beautiful views here on the Black Sea coast in northern Bulgaria, where thousands of red-breasted geese gather, mask the fact that the birds are in trouble.
The population of these geese has declined by 50% in the last decade. At the last count, scientists estimate that there were just 40,000 of the birds left in the wild.
That makes them the world's most endangered goose.
Colourful character: Red-breasted geese are under threat
Most of those 40,000 birds spend the winter close to the Black Sea coast, where the wheat fields make ideal feeding grounds.
But the landscape here is changing in a way that could be damaging the geese. Many of the formerly lush, green winter wheat fields are being used for more profitable crops. They are often ploughed in the winter so that vegetables or sunflowers can be sown.
"Particularly since Bulgaria joined the EU, farmers are switching to these 'cash crops'," says Peter Cranswick from the UK-based Wildfowl and Wetlands Trust (WWT).
Mr Cranswick is leading a research and rescue project in Bulgaria. The aim is to catch and attach tags to about 30 of the geese and to shed light on what is driving their decline.
"We know some of the threats that the birds face," he says.
"For example, we know that hunting is a problem. It's not that the hunters are killing a significant number of the birds, but the shots disturb the whole flock."
The wheat fields in Bulgaria make ideal winter feeding grounds for the birds
If the birds are scared away by gunfire while they are feeding, they spend enough time building up their food reserves for the long migration north, back to Russia, where they breed.
In a chilly early morning visit to a protected area around Durankulak Lake, we see hundreds of the geese flying from their roosts on the sea to the wheat fields.
Hunting is banned immediately around the lake, but in the small area we explore, there are about a dozen spent shotgun cartridges. We even find one dead red-breasted goose lying in the grass.
A dawn start affords a stunning view of the sky over Durankulak Lake
Local hunters are allowed to shoot the more common white-fronted geese, but they occasionally hit the endangered red-breasts by mistake.
This is hard to avoid, as the two species flock together. And it is even more difficult for the local authorities to police any illegal hunting of the endangered red-breasts on these open landscapes.
The WWT team is working on the tagging project with the Bulgarian Society for the Protection of Birds (BSPB).
They set out from their base in the seaside village of Tuylenovo on a dark January night - while the geese are roosting on the sea - to set a cannon-net in a nearby field.
The net, fired from a cannon, allows the scientists to retrieve the geese
"We have to disguise the net and then wait, and hope, that the geese come close enough to it," says Mr Cranswick.
The following morning, the team is expecting a long wait in a cold, damp field for the geese to wander into the catching area.
But, just two hours after their dawn stake-out begins, the geese amble into just the right spot and the researchers make the snap decision to hit the trigger.
The nets also capture the more common white-fronted geese
With a boom and a cloud of white smoke, a large net is fired over the flock, capturing about 25 birds, including six red-breasted geese.
The birds struggle a little bit at first, but eventually settle and seem to sit patiently (if somewhat confused by their inability to move) waiting for the scientists to retrieve them.
After an exhausting run of about half a mile (0.8km) across a field of the most glutinous mud I have ever negotiated, the team carefully peel back the net and remove the geese.
"We weigh and measure the birds and then the biggest male geese get the tags," Mr Cranswick explains.
It's a painstaking process to tag the birds - carefully strapping on these miniature backpacks of lightweight technology with soft, teflon straps that disappear under the feathers.
The researchers transport the geese in sacks to keep them calm
"You have to be careful to put the straps in the right place," says Mr Cranswick.
"Just like if you were wearing a backpack, if the straps were rubbing on a bony area, it would be uncomfortable."
In this catch, three of the birds are large enough (and male enough) to be tagged.
With their trackers securely in place, the birds have a rather comic little aerial protruding from their backs.
These satellite transmitters will give the scientists precise co-ordinates of the birds' whereabouts.
The team will follow the geese as they move around the wintering ground and, eventually, as they migrate north.
This should reveal which areas are important stop-off points for them and when - and hopefully why - they may be veering off course or being disturbed.
"We will get very precise information about where they are," says Mr Cranswick.
"That'll be very useful, for example, to assess the impact of hunting. If we follow individual birds, we will see if they're forced to move around more when there is hunting [activity]."
"It's very important that we try to do what we can to stem this decline as quickly as possible," says Debbie Pain, head of conservation at the WWT.
A big part of that, she explains, is working with local communities, and especially with farmers, to make the case for these charismatic birds.
"The geese do feed on the winter wheat, so the farmers may think they're damaging their crops," she explains.
The birds roost on the sea to protect themselves from predators. On their Arctic breeding grounds, they often nest close to large birds of prey
The geese have a distinctive "squeaking" call
The red-breast is the only goose listed as endangered by the International Union for the Conservation of Nature
"But, because they have such sharp bills, they tend not to pull the wheat up but to cut the top off. That can cause the wheat to branch and give you a nice, strong crop."
The BSPB and WWT are combining their efforts and expertise to make the case for the red-breasted goose to farmers and policy-makers in Bulgaria.
The researchers are even hoping to inspire the next generation of local conservationists.
Brian Morrell, , learning manager from the WWT's Caerlaverock Wetland Centre in Scotland has helped organise an exchange between children at Caerlaverock primary school and a local school in Shabla, close to Durankulak.
The children exchange letters, drawings and paintings of their local wildlife. At Shabla school, an entire hallway is given over to a colourful art project dedicated to the red-breasted goose.
The biggest breakthrough here though is the tagging success.
"The project is very exciting as well as important," says Dr Pain.
"This is the first time the birds have ever been caught on the wintering grounds and the first time they've been tagged.
"The information we'll get from [the tags] will tell us what the birds are doing and where they're going throughout the year - on their long migration to the breeding ground as well as here.
"That information will be invaluable in helping us to conserve this vulnerable species."