For the first time since the 1960s, hen harriers have failed to nest successfully in England.
Just two pairs attempted to nest this year in England, but both failed.
The RSPB had been working with one landowner to ensure that the nest at that site was protected but the eggs then did not hatch.
"The hen harrier is one of our most charismatic birds of prey enjoyed by many visitors to the uplands. However, managers on some intensively managed shooting estates have been attempting to remove this bird since it re-colonised.
"The latest news is a huge set-back and only a victory for those who want to see this bird of prey disappear from England's skies, but we will continue to fight to ensure that this bird has a future in some of our most iconic landscapes."
– Martin Harper
The Government's wildlife advisors say that the population has been forced into this position by illegal killing.
The RSPB is now working with stakeholders as part of a Defra group to produce an emergency recovery plan for the hen harrier in England.
"We are only a few days away from 'the Glorious 12th' - the traditional August start of the grouse shooting season.
"My challenge to those who run grouse moors is simple: respect the law and allow hen harriers and other birds of prey to flourish again."