The Royal Society for the Protection of Birds was concerned that the investigation into the killing of two threatened hawks had taken place on a royal estate.
Elizabeth's grandson, Prince Harry, has been questioned by police after a member of the public reported the shooting of two hen harriers last week near at the edge of the royal country retreat in Sandringham, about 110 miles (175 kilometers) north of London.
Harry and a friend, who were in the area at the time of alleged shooting, were questioned by police but knew nothing about the incident, according to Buckingham Palace.
Norfolk Constabulary, which is investigating the hawks' deaths, said Wednesday they questioned a total of three people in connection with incident.
The police have refused to identify whom they questioned and no arrests have yet been made, but Britain's media has made the most of the royal link to the investigation. Television crews deployed to the densely wooded estate and Sky News television titled its bulletin: "Harry and the Harrier."
Harry, who is third in line to the British throne, is seldom far from the front pages of Britain's tabloid newspapers. The British media have aggressively covered his party-going lifestyle at glitzy London nightclubs, his frequent gaffes, including his wearing of a Nazi uniform to a costume party, and the decision not to deploy the 23-year-old prince to Iraq.
Conservation officials, meanwhile, were at pains to emphasize that killing the birds was a criminal offense.
Hen harriers are rare in England and classified as globally threatened by the RSPB, which says they enjoy among the strictest protections in Europe. There are only about 20 breeding pairs left in England, and killing the bird can result in a maximum fine of 5,000 pounds (US$10,300; 7,100 EUR) or a six months' prison sentence, the RSPB said.
"This is crime, if you get caught by the police persecuting a hen harrier it is likely that you are going to go to prison nowadays," North Wales Police Chief Constable Richard Brunstrom said in an interview posted to the RSPB's Web site. "The courts have made it fairly clear that (for) these sorts of offenses imprisonment is a reasonable proposition."
Harrier hens are often targeted by hunters because they prey on grouse, a type of game bird.
"It's one of England's rarest birds of prey and it's constantly at risk for illegal killing," said Grahame Madge, a spokesman for RSPB.