The bird of prey was found dead on a hillside on the Invercauld Estate, in the heart of the Cairngorms, near Crathie and the Balmoral estate on March 19 after being illegally targeted with a toxic substance.
Police Scotland said officers searched a number of properties on the estate on Tuesday as they continue carrying out inquiries. No arrests have been made.
Detective Chief Superintendent Gary Cunningham, the force’s wildlife crime lead, said: “Scotland’s rich, rare and diverse wildlife and landscapes are among its biggest attractions.
“We cannot allow the indiscriminate use of poisons and pesticides to threaten our natural heritage.
“Police Scotland, working with our key partners, is committed to protecting our wildlife habitats and to bringing those who seek to destroy or harm it to justice.”
The Royal Society for the Protection of Birds (RSPB) reported last October that dozens of birds of prey were shot, trapped and poisoned in the UK in 2019.
There were 85 confirmed incidents of bird of prey persecution, involving buzzards, red kites, peregrine falcons, golden eagles and hen harriers.
The highest concentrations of crimes were in the north of England and Scotland, with North Yorkshire the worst spot, and half the confirmed incidents occurred within protected landscapes, the conservation charity said.
Ian Thomson, RSPB Scotland’s head of investigations, said: “Raptor persecution crimes on grouse moors in this area happen regularly.
“In 2019, a young eagle was photographed caught in a trap less than two miles from here, and in 2016, a line of illegal traps targeting birds of prey was found set across the hill less than three miles away.
“The perpetrators of these crimes don’t just threaten wildlife, but put at risk the reputation of the area and the jobs dependent on the associated tourist industry.”
The RSPB has said its data, peer-reviewed science and population surveys showed persecution was concentrated on and near grouse moors, and called for tougher action on the industry to end the killing of protected species.
It also said a growing number of satellite-tagged birds of prey such as hen harriers are vanishing in suspicious circumstances – leading conservationists to believe they had been illegally killed.