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Yes, satellite tags can fail – that doesn't mean their failure is always "suspicious"

In July 2019, a hen harrier named Colin was tagged with a satellite transmitter at his nest in Northumberland. A year later, in August 2020, his tag was again recorded as transmitting from Northumberland – but it was interesting to read a report from the The Hen Harrier Protection Partnership in Northumberland that: “Colin’s tag has ceased to work but careful surveillance work by Natural England staff identified him with his tag still in place but unoperational.”

It is excellent news that Colin has been found healthy and thriving. But the question is: how many other tagged birds have been reported missing due to a failure with their tag? This is important for two reasons. Firstly, as hen harrier numbers are under such close observation due to their scarcity – although as we have seen this breeding season, numbers are on the rise – and the public attention placed on them through campaigns such as Chris Packham’s Hen Harrier Day.

And secondly, due to the fact that whenever a tagged hen harrier goes missing, the finger of blame is often pointed directly at estates where there are grouse moors – or estate workers directly.

Just a quick look at the lines fed to the public by the likes of Luke Steele and even the RSPB demonstrates exactly why moor owners are so nervous about satellite tagging failures. In April, for example a piece in the Yorkshire Post announced that a young female named Yarrow had disappeared “in suspicious circumstances”. What made the circumstances suspicious? Mark Thomas of the RSPB was quoted as saying that:

After her tag ‘checked in’ over Stockton-on-Tees, which turned out to be the last known location we received, we expected a further transmission the next day showing that Yarrow had reached the North York Moors but that never came. Sadly, it is highly likely that Yarrow was killed and the tag destroyed in a matter of hours after its last fix was recorded, based on our extensive knowledge of these tags and the patterns of disappearance of hen harriers.

What, exactly is suspicious about that? The simple fact that her tag stopped working – there is nothing to say that this bird is dead – near the North York Moors is enough to blame grouse moor owner and workers for her disappearance. The piece goes further, stating that the disappearance of two other hen harriers – Tarras and Dryad – were also “suspicious” as they had been living on or near grouse moors.

The admission that satellite tags do sometimes fail is at least a step in the right direction to accepting that grouse moors are not necessarily to blame simply because a hen harrier’s tag stops transmitting. That is not to say that incidents have never happened, and along with many other Countryside Organisations, we would like to be very clear that we have zero tolerance for any form of raptor persecution.

However, to paint all tag transmission failures as “suspicious” is both unfair and untrue. As has been shown by the successful breeding rates of hen harriers in the uplands in general, and grouse moors specifically, in 2021, landowners and keepers are working hard to encourage these birds to make their homes on the moors; to thrive and to raise their young there. The acceptance that tags do sometimes fail is something we all need to bear in mind when embracing this modern technology.


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