Death of white-tailed eagle on Isle of Wight recorded as ‘uncertain’ as presence of avian flu restricted toxicology tests

In March last year a young, satellite-tagged white-tailed eagle was found dead on the Isle of Wight in what were considered to be suspicious circumstances and a police investigation was launched (see here).

This was the third white-tailed eagle death since October 2021 and all three birds were from the Isle of Wight Reintroduction Project,  a Government-backed five-year project bringing young sea eagles from Scotland and releasing them on the Isle of Wight to re-establish this species in part of its former range.

A young White-tailed eagle. Photo: Garth Peacock

The two other dead eagles found during that period included the one found on the Shaftesbury Estate in Dorset in January 2022, which was confirmed to have been illegally killed by ingesting an extraordinary high quantity of the rat poison Brodifacoum but the subsequent police investigation was botched by Dorset Police (see here); and the eagle found dead on a game shoot in West Sussex in October 2021, confirmed to have been illegally killed by ingesting the poison Bendiocarb and whose death is currently the subject of an on-going police investigation (see here).

A preliminary post-mortem on the eagle found dead on the Isle of Wight revealed it was carrying avian flu, but at that time it was unknown whether avian flu had been the cause of death. Later tests revealed it had not.

The presence of avian flu has important consequences for how the corpse is handled and stored under strict government rules, and unfortunately this impacts on the ability to conduct standard toxicology analyses for other potential causes of death, notably the detection of certain poisons.

Last week Hampshire & Isle of Wight Constabulary issued the following statement about the death of this eagle:

Death of White-tailed Eagle remains uncertain after conclusion of police investigation.

A police investigation into the death of a satellite-tracked White-tailed Eagle on the Isle of Wight has found no evidence of unlawful killing.

It comes after Hampshire Constabulary were called shortly after 5pm on Thursday 24 February 2022 to a report of a dead sea eagle on Bowcombe Road on the Isle of Wight.

The circumstances surrounding the death were investigated by local Country Watch officers, along with the support of various partners including the Animal and Plant Health Agency, DEFRA, Forestry England and the Roy Dennis Wildlife Foundation.

Officers explored all possible lines of enquiry into the death, including; analysis of satellite tracking data, evidential land searches in and around the site where the bird was found deceased, obtaining accounts from witnesses in the local area at the time, comprehensive veterinary x-rays as well as conducting specialist post mortem examinations.

The bird initially tested positive for Avian Influenza (AI), but subsequent post-mortem examination carried out under strict AI protocols concluded that this was not the cause of death.

Standard toxicology testing was not possible due to the AI positive test, but the limited analysis that was undertaken did reveal elevated background levels of two rodenticides, brodifacoum and difenacoum, though not at sufficiently high levels to have caused the death of the bird. As such the post-mortem concluded that the actual cause of death of the White-tailed Eagle remains uncertain.

During the post mortem, there was no evidence of any lesions on the sea eagle to explain the cause of death.

Police Sergeant Stuart Ross of Hampshire Constabulary’s Country Watch team, said: “Hampshire Constabulary has carried out a thorough criminal investigation into the death of the White-tailed Eagle and have found no evidence of unlawful killing from the lines of enquires carried out and evidence gathered by officers.

“As such, we are satisfied that there is no evidence of criminal offences having taken place and that the death of the White-tailed Eagle is being treated as uncertain at this time”.

“The criminal aspect of this investigation has now concluded, but we urge all users of rodenticides, particularly brodifacoum, which is known to be highly toxic to wildlife, to follow all guidelines regarding use. Brodifacoum should only be used in and around buildings.”

The reintroduction of White-tailed Eagles on the Isle of Wight is part of a dedicated scheme run, under a Natural England licence, by Forestry England and the Roy Dennis Wildlife Foundation.


There are no complaints about Hampshire & Isle of Wight Police’s handling of this investigation. They were responsive, thorough and transparent.

The police statement, above, is fairly detailed and informative. However, caution should be applied when interpreting the statement about the presence of ‘elevated background levels of of two rodenticides, brodifacoum and difenacoum, though not at sufficiently high levels to have caused the death of the bird. As such the post-mortem concluded that the actual cause of death of the White-tailed Eagle remains uncertain‘.

Whilst this is factually accurate, and I’m sure not intended to mislead in any way, readers should be aware that the storage of the eagle’s tissues in formalin (as required for AI positive birds) reduces the laboratory’s ability to determine the significance of these rodenticides.

Here is an excerpt from the final lab report:

‘It was suspected that this white-tailed sea eagle had been poisoned, or possibly exposed to anticoagulant rodenticides. Laboratory analysis for some likely pesticides has been undertaken on samples of fixed tissue only, although it is possible that typical abuse pesticides (such as bendiocarb) would not be detected within this sample type. These tests have detected and confirmed a residue of the anticoagulant rodenticides brodifacoum and difenacoum in the fixed liver from this eagle, but the significance of these residues is uncertain given the prior treatment of the sample with formalin. Therefore, the actual cause of death of this white-tailed sea eagle remains uncertain, but this result confirms that it had been exposed prior to death to brodifacoum and difenacoum’. 

Unfortunately we won’t ever now know whether this eagle had ingested high quantities of rodenticides, or whether it had been poisoned with a banned substance such as Bendiocarb, because of the rules on the handling and storing of tissues containing Avian Influenza. And this may prove to be an issue that hampers other investigations if avian flu is detected in a raptor that has died in what are perceived to be suspicious circumstances.

But at least in this case, the police did conduct searches of the land where the eagle was found dead, and have also included a warning in their press statement about the proper use of rodenticides.

To follow news about the reintroduced white-tailed eagles please visit the Roy Dennis Wildlife Foundation website here.

4 thoughts on “Death of white-tailed eagle on Isle of Wight recorded as ‘uncertain’ as presence of avian flu restricted toxicology tests”

  1. Quite possibly ingesting poison when already weakened by AI could have been enough to ultimately kill the eagle.
    However, knowing the handling procedure for birds suffering from AI could be exploited (as you eluded to above) by killers to avoid detection. Therefore where birds of prey are concerned, the handling procedure needs to evolve to give the best chance of identifying with more certainty the cause of death because AI isn’t going away any time soon. And all the time these procedures are being followed, raptor killers could quite literally be getting away with murder.

  2. Echoing Stephen Read’s fears about the opportunities now for potential poisoners, I’m thinking ahead to the gamebird rearing season in 2023.
    Given widespread Avian Flu in France and the UK it will be unthinkable that game eggs or chicks will be allowed to be imported into the UK. What steps are being taken or can be taken to highlight this fear and put legal powers in place?

  3. The way I am reading the police statement, is that following all their enquiries, from the available evidence, and the examination of the eagle, it was impossible to state with any certainty that the cause of death was as a result of a criminal act. However, this lack of evidence pointing to a criminal act does not necessary mean that a criminal act was not committed, and hopefully investigators are keeping an open mind as to what may have happened to this eagle?

    The presence of a residue of the anticoagulant rodenticides brodifacoum and difenacoum in the liver from this eagle suggest the eagle has at some time been exposed to these rodenticides.
    This then raises the question of when, where and how was the eagle exposed to these chemicals?
    It is of note that the police specifically refer to the guidelines regarding the use of rodenticides in their press release. Why would they do this? It could suggest that the police have some suspicion that these chemicals played some part in the death of this eagle.
    From what I understand, the guidelines stipulate that use of these chemicals should be restricted to within or around buildings, and I also understand that any target species killed by these chemicals should be removed quickly to prevent the risk of secondary poisoning to any creature scavenging on the dead carcass.

    This then begs the question, as to whether someone was being negligent or deliberately failed to remove the carcasses of dead target species killed by rodenticides, which the eagle then when on to scavenge, even though the police were unable to find any evidence of this in their investigation?

    Maybe it would be helpful if the authorities started monitoring further unexplained deaths or illness in eagles or other raptors in the area, in order to try and ascertain if there is a spike in the number of deaths or reported sick birds.
    Another indication that something is wrong could be an increase in the number of reports of dead animals such as rats, foxes and crows found in a particular location, which might indicate that someone using these rodenticides is not properly following the guidelines.
    Such evidence might help indicate whether something sinister caused the death of this eagle, even if the scientific testing makes it impossible to state with certainty whether that death was caused by a criminal act.

    I think what took place in nearby Dorset would suggest that there are people in this area who really don’t want to see Sea Eagles return.
    The fact the police have stated that the death of the eagle is being treated as uncertain at this time, might suggest they could reopen the enquiry if more evidence comes to light? Either way, it is encouraging to see Hampshire Police investigate this matter is such a positive manner.

  4. Given the number of birds and other wildlife killed being poisoned by banned pesticides, it paints a picture of the UK countryside as awash with these deadly poisons. I imagine that no charges have been brought against anyone for possession, or use, of the banned substances up to now. Quite what checks are made in areas where banned poisons are responsible for the deaths of raptors, or other animals? Since there are so many incidents where raptors and animals have been killed by poisoning where are these banned poisons being obtained and by whom? This situation should be investigated surely?

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