A post-mortem examination has revealed a golden eagle found dead near Fort William was poisoned.
The bird was found dead near Morar, Lochaber, Fort William in March.
It is the third known eagle poisoning incident in the area over the last ten years, with two white-tailed eagles previous victims.
Northern Constabulary said the post-mortem revealed the bird had been poisoned with banned pesticides.
A joint investigation is now being carried involving Northern Constabulary, the National Wildlife Crime Unit and RSPB Scotland.
Chief inspector Matthew Reiss, Northern Constabulary's wildlife crime co-ordinator said: "Wildlife tourism is an increasingly significant income generator in the highland economy, and particularly so in the West Lochaber area of the Highlands.
"Poisoning is indiscriminate, it could be your pet dog, or even a human, that could be killed simply by contact with such illegal poisons. This is a completely unacceptable and illegal practice.
"People who use illegal poisons are threatening the economy by killing the very wildlife that people visit the area to enjoy viewing. These visitors are contributing significant spending in the area, so crimes such as this are also threatening the jobs of people directly and indirectly reliant on the income derived from wildlife tourism."
The eagle was fitted with a satellite transmitter in 2010 prior to fledging from a nest in a habitat management area created by Scottish Power Renewables beside Beinn an Tuirc wind farm on the Kintyre peninsula.
Peter Robson, an ecologist at Scottish Power Renewables, said: "We were saddened and disappointed to find out that one of the Golden Eagles from Beinn an Tuirc had been poisoned. The habitat restoration project at the wind farm has been a great success, producing four healthy golden eagle chicks in a short period of time following a long run of barren years.
"The data from the tracking device was providing experts with a unique insight into the movement patterns of golden eagles during their early years. It is a sad loss, and a setback for all those involved in the conservation of Golden Eagles in Scotland."
Anyone with information relating to this case is urged to contact Crimestoppers on 0800 555 111 or Northern Constabulary on 01463 715555.
