The wildlife charity the RSPB says it has been "overrun" by reports of birds of prey being illegally killed since the lockdown started six weeks ago.
Species of raptors (birds of prey) that had been targeted include hen harriers, peregrine falcons, red kites, goshawks, buzzards and a barn owl.
The wildlife charity described the crimes as "orchestrated".
It said the "vast majority" had connections with shooting estates, or land managed for shooting.
Some raptors are known to feed on pheasant and grouse chicks.
The head of the RSPB's investigations unit, Mark Thomas, told the BBC it was like "the Wild West" out in the countryside. He said people who wanted to kill birds of prey had been "emboldened" by the absence of walkers and hikers.
He said the surge correlated exactly with the date the lockdown was imposed.
At this time of year he said that the RSPB would normally be getting three or four reports of the killing of protected bird species each week. They now have three or four reports of a killing each day, and they are coming from across the country.
The wildlife charity alleges that the incidents are overwhelmingly connected with land managed for sport shoots. Raptors prey on bird species that have been specifically reared for be killed for sport, like grouse or pheasant.
Mr Thomas said, "I am genuinely disturbed. in more than 20 years of investigating, I've never seen anything like it. We are having to put ongoing investigations on hold in order to triage all these reports... This isn't youngsters with air rifles but orchestrated wildlife crime."
According to the RSPB, on 29 March a buzzard was found shot at Shipton, near York. Its wing was fractured in two places and an X-ray revealed several pieces of shot within the bird's body. The buzzard recovered and was released.
Over the Easter Weekend, a red kite was found shot dead near Leeds. It had 12 shotgun pellets lodged in its body.
The following weekend, a dead red kite was found in Powys, which had been shot.
There were also reports of another two shot red kites in the region. In another case, in South West England, ten buzzards were found, all thought to have been poisoned.
The Investigation Unit suspects that the true number of incidents could be much higher, as there are fewer people out in the countryside who might report cases, with walkers and specialist raptor groups under lockdown.
All birds of prey are protected by the Wildlife and Countryside Act (1981).
The Moorland Association (MA), whose members include many shooting estates in England and Wales, said it condemned illegal activity.
The MA's Director, Amanda Anderson, said: "Any confirmed reports of raptor persecution are cause for concern. The incidents specified near Leeds and York in the RSPB release are clearly not on grouse moors, while reports we have from our members in the uplands have suggested that many birds of prey are in fact benefiting from the lock-down restrictions and the subsequent reduction in disturbance from members of the public.
"Estates across the country have reported a number of raptors including peregrine, merlin and hen harriers nesting and living on those landscapes.
"We condemn any illegal activity and Moorland Association members have signed up to a cross-sector zero tolerance approach to wildlife crime. Estates and gamekeepers have been the eyes and ears on the ground during lockdown, reporting suspicious activity. They are also actively working with police authorities in Operation Owl - an initiative to raise awareness of raptor persecution. We always encourage reporting of any suspicious incident."