Britain's birds are busy building nests as the breeding season gets under way. But they are not the only ones making preparations. A hard core of thieves - many from the North - plan to steal the eggs for illegal collections which can put the existence of these rare creatures at risk.
An osprey glides through the air above a North lake in search of food. It spots what it's looking for a fish near the surface.
A tilt of its wings and down it plunges, catching the fish in steely talons and lifting it into the air with ease. But it won't be eating the fish itself.
The food is for its mate, sitting on a nest not far away, incubating the precious clutch of eggs which will become the next generation.
But the osprey is not the only hunter in the vicinity. Hidden in nearby bushes sits a man with binoculars. He is not after food . . . he wants the osprey's eggs to add to his collection and he is willing to risk his life and limbs to possess them.
Taking one last glance back towards the nest, he walks away. He will return in the hours of darkness when the hillwalkers and birdwatchers have gone home and the ospreys are at their most vulnerable.
Fiction? Yes, but sadly this kind of scenario is played out for real in the habitats of Britain's rarest birds every season.
A hard core of about 300 individuals - many from the North - are already planning such raids with potentially devastating results. That is why, for example, there is such tight security around the Bassenthwaite ospreys in the Lake District, which have recently laid two eggs.
Graham Elliott, head of investigations for the Royal Society for the Protection of Birds, said: "Birds such as the osprey and white-tailed eagle suffer significantly if nests are raided.
"They have such small populations that raids on nests can cause severe damage to their numbers. But the egg collectors don't care about that. All they are interested in is adding to their collections."
The good news is that the law is fighting back. The Countryside and Rights of Way Act 2000 now allows courts to jail egg collectors for up to six months and impose fines of up to #5000 per egg.
Prior to that the "eggers", as they are known, could only be fined and have their collections confiscated.
Most of them saw this as an occupational hazard and quickly went back to egg-thieving.
Unemployed Barry Sheavills of Blyth, Northumberland, became the first person in Britain to be jailed for egg stealing when he received a four-month sentence in 2001.
Mr Elliott said: "In the last few seasons there's been a significant decrease in the number of nest robberies since the introduction of prison sentences.
"Since the new law came into force seven egg collectors, including two from the North East, have received custodial sentences. This is having a deterrent effect."
According to the RSPB there are about 300 persistent offenders who have stolen tens of thousands of eggs over the years, including many from Britain's rarest birds.
They plan and record their raids with military precision and catalogue their collections. Although there is great rivalry between them, they will also join forces to go on difficult hunts.
But they can't show the world their collections. Instead, they hide them away to enjoy in solitude or in clandestine meetings with other eggers.
Usually their collections are held in the homes of relatives or at lock-up garages.
Mr Elliott said: "They are compelled to get more and more eggs of increasingly rare species. They're also driven by the danger aspect of what they do.
"They will make dangerous descents down sheer rock faces and swim hazardous rivers and lakes just to get eggs. Some have fallen to their deaths or drowned.
"They risk life and limb just to possess any empty egg shell that has no financial value because there is no real market for them."
Page 2: How stealing became a passion
How stealing became a passion
A reformed egger, who did not want to be identified, said: "It's not just about possessing the eggs - although that's definitely a major part of it - it's about the hunting and gathering.
"It's the thrill of locating a nest of a rare bird and getting around any defences that have been put in place to protect it. It's like a big adventure, doing something wrong and taking the chance of getting caught.
"Then there's the danger and challenge of climbing large trees and rock faces to get at the eggs. You know you could fall and die but that just adds to the excitement. It's an adrenaline rush.
"You have to be willing to spend long hours in all kinds of weather and harsh environments just to get what you want. I've seen myself walking with my former mate for 20-odd miles in pouring rain just to get into position for a raid without being detected.
"I have swum lakes in the middle of the night to get to birds nesting in little islands, and climbed cliffs with ropes to get at nests of sea birds.
"The harder it is to get at the nests the bigger the challenge and the greater the thrill when you succeed.
"Once you've got the eggs you've got to get out of the area without being detected. If you are caught with them in your possession the game's up.
"The challenge is to get something that no one else has got . . . so the rarer the bird the better the egg."