Environmentalists in Cumbria say they are fearful of an attack on nesting ospreys from wildlife vandals.
Nesting chicks have survived in Cumbria
The comments, from the Royal Society for the Protection of Birds (RSPB), follows the shooting of an osprey in Lincolnshire.
A pair of nesting birds is using a site at Bassenthwaite in the Lake District for the fourth year running.
On Friday, the Lake District Osprey project announced two eggs had been laid.
A 24-hour guard has now been mounted to protect the Lake District nest from egg thieves and vandals.
An adult osprey was taken into care on Monday night suffering from two wounds, and had major surgery to remove pellets.
The injured bird was discovered in the North Scarle area near Lincoln.
David Hirst, of the RSPB said: "We believe that the main risk to the Lakes ospreys comes from the illegal activities of egg thieves and we already have security in place to try and thwart any attempts to steal the eggs.
"We will be continuing the round-the-clock guard on the nest and the many thousands of enthusiastic and supportive visitors to the two osprey viewpoints also act as vital lookouts for us.
"The Lincolnshire incident is a stark reminder that ospreys can still be the target of wildlife vandals when they are away from the nest fishing.
"The Lake District Osprey Project would want to remind people that ospreys are a specially protected species under UK law and anyone convicted of intentionally killing or injuring an osprey is liable to a fine of up to £5,000 or to imprisonment for a term of up to six months.
"We would encourage anybody who suspects that they have witnessed a crime against wildlife to report it to the police.
Four young birds
"Each police force has a dedicated wildlife liaison officer."
A team of 30 staff and volunteers are now helping to guard the Lake District nest.
The ospreys have been using the Bassenthwaite nest since 2001, which marked a natural recolonisation of England by the birds after an absence of at least 150 years.
They have raised four young since they first nested.
There are public viewpoints near Keswick and live images from a camera overlooking the ospreys' nest can be seen on a screen at he Forestry Commission's Whinlatter Visitor Centre as well as on the internet.