An inquiry has discovered their efforts have been disjointed, badly resourced or mismanaged.
A joint review by the police and prosecution inspectorates in Scotland has accused some forces of down-grading the significance of crimes against protected species and breaching their own guidelines.
The inquiry was ordered by Scottish executive ministers after an outcry over the death of a female golden eagle, poisoned on a grouse moor near Peebles, in the Borders, last year.
No one was charged for the crime – the 36th case of raptor poisoning in Scotland last year – and conviction rates for such crimes are extremely low.
Other crimes include clearing forests of rare snowdrops and native bluebells for sale to garden centres, stealing rare bird eggs, and trapping finches or siskins to cross-breed with canaries.
The inspectorates urged chief constables and prosecutors to introduce national minimum standards for investigations and asked all eight forces to appoint senior officers and full-time wildlife crime officers.
Among 24 recommendations, the Crown Office, which runs Scotland’s prosecution system, was told it had to improve its use of specialist wildlife crime prosecutors and ensure they worked more closely with the police and other agencies.
It said: “Too frequently in dealing with wildlife crime, the police had allowed their considerable body of professional knowledge and practice to be set aside… there were times when even high-profile wildlife crime matters had not been managed well, causing disappointment, frustration and tension.”
The Crown Office has instructed a senior prosecutor to introduce a national action plan, said the solicitor general, Frank Mulholland QC. The review’s recommendations, he said, would be implemented in full.
The RSPB is expected to press environment ministers in London to introduce a review in England and Wales, arguing that policing and enforcement in wildlife crime is often comparatively weak.