What future do Scotland's white-tailed eagles face?
Britain's biggest bird of prey was nearly knocked out of our skies for good almost a century ago.
The sight of the white-tailed eagle's impressive two-metre wingspan in our skies was eventually saved by a reintroduction scheme in Scotland.
But, even as its recovery is being hailed as a conservation success, the mighty bird may be under threat once again.
The population remains small, vulnerable and limited to just one area of the country. Will the eagles ever spread their giant wings beyond Scotland?
Island pride
Widespread throughout Great Britain and Ireland since the Dark Ages, it is estimated that up to 90% of the birds were lost by the time of the Industrial Revolution.
Destruction of habitat and human persecution drove the species to extinction in the early part of the 20th Century, when the last pair nested on Skye.
The bird's reintroduction to Scotland, which began almost half a century ago with an attempt to put the species back on Fair Isle has, on the face of it, been a huge success.
A recent report by the RSPB, 'Wildlife at Work', estimated that 'eagle tourism' contributes up to £5 million to the economy of the island of Mull each year.
It also brings less tangible, but equally important, benefits.
These include a sense of collective success for the island's people, a pride in seeing the eagles not just in real life but on TV programmes such as Springwatch and, most importantly perhaps, the ecological benefits such a flagship species brings to the rest of the island's wildlife.
Nor is this success confined to Mull. Skye also welcomes a steady influx of visitors wanting to see the eagles and other iconic west of Scotland species such as golden eagle, hen harrier and otter.
While the Fair Isle birds eventually dispersed without forming a sustainable population, that first release taught the teams valuable lessons.
Sea eagles can live 20-25 years in the wild
From the mid-1970s, white-tailed eagles bred from Norwegian stock were released into more suitable habitat. Sites included the uninhabited Isle of Rum in the Inner Hebrides, and in Wester Ross on the Scottish mainland.
Later, in the early 21st century, the scheme was extended to the east coast of Scotland, in Fife.
White-tailed eagles, like all large, long-lived birds of prey, breed slowly, and numbers took time to grow, during which time the project had to withstand some criticism.
Some local communities did not want the birds there at all. Conservationists persuaded islanders to give the eagles a chance and to accept that, in some cases, the potential harm the birds might cause was overstated.
There were objections from other conservationists however, who thought reintroduction schemes were somehow "not natural", or considered this particular scheme to be proceeding too slowly.
In the face of their critics, the birds not only survived, but gradually grew in numbers until they started to spread around the Western Isles.
Where next?
But all this effort may be at risk of failing: the white-tailed eagle could still disappear from our skies.
One reason is the relatively low numbers. Despite the project's undoubted success, the UK population of white-tailed eagles is still only about 60 pairs, almost 40 years after the Rum reintroduction began.
Although the birds are not subject to the same pressures as they were in the past, such as shooting and egg-collecting, there are still many other threats facing them.
Last month, wildfires swept the Highlandsthreatening nesting habitats of both the golden and white-tailed eagle.
Young, inexperienced eagles face all sorts of hazards from collision with power lines and vehicles to the continued use of poisoned bait by some land managers on the mainland which although illegal, is still widespread.
But perhaps the biggest threat to the continued survival and prosperity of white-tailed eagles in Britain is inaction.
In 2007, Natural England and the RSPB proposed a plan to release the eagles into East Anglia but resistance from local communities meant the plan did not go ahead.
Roy Dennis was warden of Fair Isle Bird Observatory when the very first birds were released and he told the BBC that an opportunity had been missed in Suffolk:
"The disappointing thing was that I think many people thought that as soon as we had twenty pairs of eagles breeding in the Hebrides the job was done. Whereas others of us felt the job is not done until we have them breeding back all the way from the Channel coast to Shetland," he said.
Could white-tailed eagles be put back into other great British wetlands? The question provokes a plethora of different reactions from those living on and managing the land.
Personally, I think my own home patch of the Somerset Levels, the site of the biggest wetland rewilding project currently underway in the UK, seems an ideal place to start.
I for one look forward to seeing this majestic bird soaring not just over the Isle of Mull, but also across Glastonbury Tor, within my lifetime.
The eagles can be seen in Hebrides: Islands on the Edge which continues of BBC One (Scotland), Monday 13 May at 2100 BST and is available on iPlayer.
Why hedgehogs are not welcome in the Hebrides
The hedgehog is arguably one of Britain's favourite mammals and possibly our most threatened.
Since the 1940s hedgehog numbers have dropped from an estimated 30 million to fewer than one million and conservationists warn they could even be extinct in Britain by 2025.
But during the past decade hundreds of hedgehogs have been deliberately killed by official government bodies, at eye-watering costs to the taxpayer.
In the Western Isles of Scotland, the non-native hogs have a bad reputation. But are they really to blame for a decline in wading birds?
Machair nightmare
The story begins almost 40 years ago, in 1974, when some hedgehogs were released into a garden on the Hebridean island of South Uist, in order to help control slugs and snails.
Here, the hedgehogs faced few of the hazards that have so reduced numbers of their mainland cousins, such as heavy traffic on trunk roads and city streets, pesticides in gardens, or predation by badgers.
No wonder they soon multiplied and spread, and within a couple of decades had a population estimated at about 5,000 individuals.
By then they had also spread to the neighbouring islands of Benbecula and North Uist, which are connected to South Uist by causeways along which the hedgehogs were able to travel.
Every spring, the sandy soils along the western side of these islands are covered with a carpet of grasses wild flowers, known as 'machair'.
Machair is home to some of the densest breeding populations of wading birds anywhere in the world; with dunlin, ringed plover, oystercatcher and redshank filling the air with their calls throughout the spring and summer months. The numbers of these birds are so high that the islands are an internationally important site for them.
When the wader population on the islands began to drop rapidly, the invading hedgehogs were soon implicated in the decline: the wader nests provided easy pickings in the form of tasty eggs.
Machair develops in wet and windy conditions
Almost 30 years after the hedgehogs were first introduced to the islands, an organisation called the Uist Wader Project was formed to launch a cull of the hedgehogs, in order to prevent the nesting waders being wiped out.
The project - a coalition between Scottish Natural Heritage, RSPB Scotland and the Scottish Government - did manage to cull about 700 hedgehogs, but this soon attracted criticism: partly because there were still so many hedgehogs remaining at large, and partly because this had reportedly cost more than £800 per hedgehog in taxpayers' money.
The biggest barrier to the continuation of the cull however was not financial, but emotional. Many people - both on the islands and elsewhere - were angry that the hedgehog, an otherwise harmless mammal, was being targeted and killed at the same time as it was disappearing from much of mainland Britain.
So in the same year as the cull began, a coalition of animal welfare organisations and charities formed Uist Hedgehog Rescue (UHR).
Tender trapping
UHR agreed that hedgehogs were causing problems to wading birds on the islands, but offered an radical alternative solution: instead of killing the animals, why not trap them and relocate them to the mainland, to help boost declining populations there?
During the next three years they relocated more than 700 hedgehogs, and once they had shown that relocation was both feasible and effective - and most importantly did not cause any problems such as the spread of disease back to the mainland population - then in February 2007 the cull was halted.
Hedgehogs thrive where traffic is absent
Instead of killing the animals, Scottish Natural Heritage began to fund the translocation project run by UHR instead. So far about 1600 hedgehogs have been safely removed from the islands and relocated elsewhere.
But what might appear to be a triumph of common sense over a knee-jerk reaction against 'illegal immigrants' may be more complicated than it looks.
In February 2010, hedgehog expert Hugh Warwick, questioned the validity of the original hypothesis. Although no one would deny that hedgehogs do take the eggs of ground-nesting birds, does that necessarily mean that the rapid decline in breeding waders has been caused by the arrival of the hedgehogs?
He suggested that other factors - including changes in farming methods and climate change - might be equally, if not more, to blame than the hedgehogs. Might the hedgehogs even have become convenient scapegoats?
Earlier this year Scottish Natural Heritage announced that it was increasing funding into research on the decline of waders on the Uists.
According to the organisation, this is specifically because there are "still a number of unanswered questions about the full extent of predation on Uist waders, and the degree to which hedgehogs are responsible."
The British Trust for Ornithology in Scotland is also involved in trying to find the root cause of the waders' decline.
With many hedgehogs still at large on the islands, and a fear that the animals are becoming more firmly established on North Uist, this investigation could not be timelier.
Meanwhile trapping of hedgehogs continues, and those captured are still being relocated to the mainland rather than killed.
Whether the hedgehogs are fully, or only partly, to blame for the decrease in the numbers of waders on the Hebrides, one thing is certain: the results of releasing an animal into a new environment can have massive consequences not only for our delicate ecosystems and their wildlife, but also for conservationists, scientists and taxpayers.
Almost forty years on, we still do not know the full implications of that first innocent, but ultimately misguided release.
Hebrides: Islands on the Edge begins on BBC One, Monday 6 May at 2100 BST for viewers in Scotland and is available on iPlayer.
Stink bugs: the scientific battle against an insect invasion
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Millions of stink bugs are emerging from their hibernation, a sign of spring that strikes fear into the hearts of farmers across the US. Could a tiny wasp be the ultimate weapon in the battle against the foreign bug invasion?
Anybody who has dealt with an infestation of stink bugs knows what a nuisance these armoured insects can be. They cluster in the thousands and release a foul odour when squashed or threatened.
And for farmers, they can be devastating.
Unlike many insects that feed on a small group or even a single plant, the brown marmorated stink bugs, which originated in Asia, eat pretty much anything. More than a hundred different crops have been recorded in their diet so far.
The devastating effect of the bugs' appetite became apparent to farmers in 2010 when swarms destroyed fruit crops across several states in the mid-Atlantic region. The attacks cost the apple industry alone an estimated $37m (£24m).
Hunt for a killer
Matt Buffington, a research entomologist at the US Department of Agriculture (USDA), says the stink bugs arrived in the US sometime between the late 1990s and 2003 to find an "enemy-free space".
"That means it can expand its population infinitely because there is nothing keeping it in check," he says.
"Birds haven't learned to eat it - possibly because it tastes gross - and native insect predators that would normally eat something like a stink bug don't recognise it."
The stink bug killer? A parasitoid wasp - in close-up (inset) - attacks stink bug eggs and may be the best hope for ending the bug's crop destruction
In Asia, brown marmorated stink bugs are naturally controlled by parasitoid wasps. This genus of wasp, called Trissolcus, contains around 70 different species, many of which have yet to be properly described.
These wasps could prove to be the bulwark against the invasion - but identifying the most effective type to take on the Asian stink bug in the US could take years.
That is why Dr Buffington is working at the Smithsonian's National Museum of Natural History in Washington DC, home to the National Insect Collection and its 36 million specimens. The collection offers his best chance of finding the right wasp.
"We consider it a national treasure - there's nothing like it in the world," says Dr Buffington. "It's the single reference centre for US agriculture."
There are wasps native to the US that prey on indigenous stink bugs but are ineffective against the Asian variety.
In China and other Asian countries, stink bugs and wasps have evolved together over millions of years. Importing a Trissolcus species from Asia may be the solution.
But researchers have to be sure the same wasp will not attack other insects, such as native stink bugs that are not a threat to agriculture.
"Otherwise we could be investing millions of taxpayers' dollars in a biological control programme that is either going to be ineffective or potentially disastrous for North American agriculture," says Dr Buffington, "because we might release the wrong wasp."
Stink bugs lay batches of 25-30 eggs at a time. Female parasitoid wasps then attack the bugs' eggs by laying one of their own inside each stink bug egg. The developing wasp completely devours the embryonic stink bug before hatching.
Stink bugs are stored on sticks in the lab
To have any effect, tens of thousands of wasps would need to be released into carefully selected areas to enable them to establish numbers large enough to control stink bugs. And any release would have to be sanctioned by the USDA.
But wasps are not the only possible answer. At the USDA's Appalachian Fruit Research Station in West Virginia, researchers are learning about the stink bugs themselves in the hope of developing other natural controls.
"There isn't a single solution," says Tracy Leskey, head of the stink bug task force, an alliance of government agencies and university scientists.
"First we have to understand the basic behaviour of the stink bug, its biology and ecology. We need to know what plants it feeds on and how far it can move."
Know your enemy
To measure the insects' flight range, stink bugs are tethered to miniature windmills that revolve as they fly. By counting the laps, Dr Leskey's team have discovered that most cover a distance of one to two miles - but that some can travel more than 20.
"We call them super-fliers," she says.
A scientist uses radar to track stink bugs' flight across an orchard
Stink bugs are also monitored by radar using miniscule radio transmitters that are glued onto their backs. That data will help scientists track the food they eat.
Experts say pesticides are not a sustainable solution because the problem is so widespread. In the last decade or so, brown marmorated stinkbugs have established themselves on the east and west coasts of the country. And although they do not harm people, they can be a nuisance - hundreds of thousands can congregate in warm houses to hibernate through the winter.
"We're still trying to work out why they do that, what attracts them," says Dr Leskey.
Insects recognise each other using chemical markers and it is possible that areas laced with pheromones may keep stink bugs away from crops. Other options might include tempting them away with other tasty plants.
Whatever the solution, researchers know they have to act fast. The 2010 stink bug invasion was the worst on record. But stink bugs have already been found earlier than usual in Maryland - and 2013 could be another bad year for farmers.
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