Police have launched an investigation after vandals killed four chicks from a rare bird of prey in North Yorkshire.

North Yorkshire Police suspect that a nest of Hen Harrier chicks, found dead earlier this year, was deliberately destroyed by human activity, and are calling for anyone with information to come forward.

The Hen Harrier nest, near Whernside in the Yorkshire Dales National Park, was being monitored by Natural England fieldworkers as part of their routine Hen Harrier monitoring.

The nest was progressing well, and by 10 May 2022 there were four chicks, aged approximately 8 to 12 days old. The parent female was satellite-tagged "Susie", who was tagged in Cumbria in 2020.

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Natural England staff became concerned on 20 June when "Susie" was unexpectedly and abruptly shown tracking approximately 35km away from her nest. An adult female should be attentive and close to her nest during this period. Her sudden exit from the nest area was worrying.

For this reason, on 21 June, Natural England field staff acting under licence checked the nest - and made the grim discovery of three dead Hen Harrier chicks.

There were no clear signs that the chicks had been killed by a predator. The situation was suspicious and so the Police were informed.

Natural England staff retrieved nest camera footage which confirmed that there were four chicks in the nest before the incident, that they were well fed and provisioned by the parents, and looked fit and well.

After dark, at 9.54pm on 15 June, the camera showed the nest site appeared normal with "Susie" settled in the nest with chicks. However, at 9.59pm a sudden irregular 'whiteout' of the camera occurred, blinding the camera.

The camera used is movement-activated, and it was not triggered again until the following morning when footage captured apparently dead chicks in the nest and "Susie" attempting to feed them.

She can then be seen removing her dead chicks from the nest. Three of these were found just outside the nest, and it is not known where she deposited the fourth.

A 'whiteout' has not occurred with a Natural England nest camera before, and the camera itself continued to operate normally since then, and once "Susie" returned to her nest the following morning her movement triggered further recording of images.

There was no trace on the ground that a vehicle had driven over the nest, nor did the nest camera footage indicate that this had happened.

There was, however, a footmark impression in the vegetation at the nest site, strongly indicating that a person had approached the nest. Natural England staff are careful to approach using known routes - the footprint observed was believed to be recent, and not made by Natural England staff.

Post-mortem examinations of the three chicks were subsequently conducted and showed that each suffered with multiple fractured bones including humerus in one chick, both femurs in the second chick, and in the third chick, the humerus and a crushed skull. The fractures were complete and showed a considerable trauma had taken place for each chick.

Although avian flu H5N1 virus was detected in one of the chicks, the post-mortem examinations also showed that the birds had been eating up until their deaths. This implies that deaths were sudden rather than a result of a chronic disease process.

North Yorkshire Police have considered all the evidence, and strongly suspect that someone approached the nest after dark and deliberately killed the chicks.

A predator would normally be expected to return and remove the dead chicks. Stoats can kill without rendering much obvious damage, but as the chicks were within the nest, it would be reasonable to expect nest camera footage of a predation or other event.

The living status of the chicks, followed by a 'whiteout' of the nest camera (possibly by a bright lamp, or something placed in front of the camera) – followed by all chicks being lifeless on the next footage – together with the post-mortem results showing broken bones in all the chicks and a crushed skull, suggests human illegal persecution activity.

The Hen Harrier is listed on Schedule 1 of the Wildlife and Countryside Act 1981 and is protected under Annex 1 of the EU Birds Directive (2009/147/EC) as it is considered vulnerable within Europe. It is on the red-list of birds of conservation concern in the UK.

A North Yorkshire Police spokesperson said: "Despite there being encouraging news this spring regarding the numbers of successful Hen Harrier nests this year, we sadly continue to be regularly called upon to investigate cases of illegal persecution of Hen Harriers and other birds of prey. There is no place for the selfish and illegal killing of our wildlife in our countryside."

Paul Cantwell, Investigative Support Officer with the Police UK National Wildlife Crime Unit, said: "This incident unfortunately shows that despite more recent breeding success in Hen Harriers, people still appear to be determined to cause harm to this vulnerable species through cruel criminal acts.

"We urge anyone with information about this matter to report it to the Police or Crimestoppers."

John Holmes, Natural England Strategy Director, said: "The evidence points to this being one of the most clear-cut and brutal cases of Hen Harrier persecution we've ever found, and we would urge anyone with information to come forward.

"We were diligently monitoring this nest and moved quickly to ensure collection of forensic and other evidence to support a police investigation as soon as persecution was suspected.

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"We have recently seen welcome increases in Hen Harrier numbers, but despite our best efforts there are still those who are set on disrupting this progress. We will continue to work to monitor Hen Harrier nests, to increase understanding of Hen Harriers and to support our enforcement and forensic partners where foul play is suspected, following every evidential lead possible.

"We call for all landowners and managers to help police identify and prosecute anyone who commits these horrific crimes against birds of prey."

Anyone with any information regarding this incident is asked to contact North Yorkshire Police on 101 and quote incident reference number 12220107140, online via the North Yorkshire Police website, or contact Crimestoppers anonymously on 0800 555 111.