The dead buzzard was found by a walker on the hills. It was lying on top of a dead pheasant not far from a game bird release pen.
Post mortems on the buzzard and the pheasant showed both had the banned pesticide carbofuran in their bodies.
Carbofuran was once widely used to control insects in a variety of field crops, including potatoes, corn, and soybeans, and is known to be highly toxic to birds with just a single grain causing death.
Police said they believed the pheasant may have been baited to target animals which preyed on game birds, but they were unsure if was left specifically for buzzards.
Together with officials from Natural England, police officers searched the Quantocks earlier this month for any signs of the banned substance and to carry out safety checks on pesticide stores.
Police wildlife crime officer Sgt Andy Whysall said: “The indiscriminate poisoning of wildlife is a serious matter which affects all who use the countryside.
“Pet owners walking on the hills are advised to avoid contact with animal carcasses, suspect baits, pesticides, or pesticide containers.”
Natural England spokesman David Trump said: “Dogs have a tendency to pick things up while walking and some pesticides are fairly quick acting, so sometimes by the time owners realise their pet is unwell it is too late.
“It is also potentially hazardous to children and people in general.
“We want people to be aware and to report anything suspicious to the police.”
Animal Concern charity spokesman John Robins said bird poisonings were often difficult to solve because they took place in remote areas and the birds could fly some distance away from where they took the bait.
Mr Robins said: “We urge people to contact the police immediately and not to touch anything they find because it is evidence and it can be lethal.”
It is a criminal offence carrying a maximum fine of £5,000 to supply, sell, store, or use any non-approved pesticide.
The Wildlife Incident Investigation Scheme investigates deaths of wildlife where there is evidence that pesticide poisoning may be involved and has appealed for information about the buzzard’s death.
Anybody with information should call 0800 321600.
- Our photograph shows the carcass of the buzzard found on the Quantocks. Photo submitted.