By Claire Marshall
BBC environment correspondent
Two of the rarest birds of prey in England, which had been satellite tagged, have vanished in unexplained circumstances, conservationists say.
The young female hen harriers had left their nest sites in Lancashire only a few weeks ago.
Last year, no chicks were born after the only two nesting pairs failed to breed.
As part of an ongoing conservation project, Sky and Hope had been fitted with lightweight solar-powered tags.
Scientists examining the satellite data became worried when their tags stopped transmitting. Sky's signal stopped suddenly on 10 September and Hope's signal died three days later.
Searches of the area have failed to find any trace of them.
The tracking devices are designed to operate for at least three years. The scientists say it's "improbable" that this is due to technical failure. The more likely cause is that the birds were killed by other animal predators, or humans.