Assistant Investigations Officer – Jack Ashton-Booth – from the Hen Harrier LIFE Project, talks us through the secret to uncovering a hen harrier’s history.

The seasons have turned, and the autumn skies have grown big, blue and crisp. As our hen harriers settle into their roosts, traversing the landscape, you might have been fortunate enough to see one for yourself against the backdrop of the blustery sky.

But did you know that hen harriers carry colour rings on their legs that could be the key to finding out more about this bird? Never fear, we’re here to talk you through how to identify the code that reveals a hen harrier’s history.

This species is of great conservation significance and is treasured by the birding community, yet it suffering a significant population decline across the UK. An overwhelming body of independent scientific evidence shows that the main reason for the decline is illegal killing associated with intensive management of moorlands for grouse shooting. The most recent study found that 72% of satellite tagged hen harriers were either confirmed or likely to have been illegally killed and are ten times more likely to die over areas of land being managed as grouse moor than land with no grouse moor.

If you’re a keen naturalist, bird watcher or photographer you might have been lucky enough to catch a glimpse of a rare hen harrier, or maybe you even managed to get a photograph as one danced over the moorland. To learn more about how far these birds disperse nationally and internationally, how long they live, as well as where they nest and roost during the winter, we have fitted nestlings with a lightweight and hard-wearing colour ring.

The ring is fitted on the bird’s leg, and each colour ring gives a unique code. Each ring is carefully fitted by an individual wo has been fully trained, under license by the BTO, and is sealed carefully to ensure that nothing can get caught in the opening where the ring is closed. These rings will also hopefully allow us one day to carry out additional survival analyses too.

As part of the Hen Harrier LIFE Project, we use satellite tagging technology which provides live tracking data that allows us to follow where hen harriers are and their outcomes. However, the cost involved in this process, from the cost of the individual tag, to the data downloads, to the time invested in fitting these tags to fledgling birds, means that using colour rings gives us information about the wider population of the species. This is a fantastic and cost-effective solution that provides a combination of tools to analyse the population more completely.

What to look for:

A black colour ring with a white inscription on the bird’s left leg. The rings are inscribed with two digits (usually a number and a letter).

How to read the ring:

When you are reading the colour ring, the trick is to read from the top to the bottom – knee to foot. We’ve included an example for you to look at.


What have these rings told us so far?

When out and about as part of my role as Assistant Investigations Officer for the Hen Harrier LIFE Project, I am lucky enough to see hen harrier in the uplands. I recently photographed a male hen harrier and upon closer inspection the photographs revealed the two-letter code that allowed me to find out more about these birds by submitting  my sighting to the project.

The first was a breeding male I had seen at the nest, and the colour ring data tells us that the bird was born in 2014, making it 5 years old. As that male was seen helping to raise a brood of chicks, it’s exciting to think about the life of this bird. His chicks were colour ringed this year too, so you may spot them if you’re out and about!

Another colour ringed male hen harrier was seen roosting in the reedbeds at RSPB Blacktoft Sands in East Yorkshire and was photographed by Graham Catley. From his excellent photos we could see the bird’s colour ring on its left leg and again the original ringing records told us that this bird was ringed as a chick in Scotland and was born in 2016.

Working with hen harriers on this project, we receive a lot of bad news and lose many birds before their time, so it is wonderful to see male hen harriers surviving well in the wild. It reminds us that everyone should have the opportunity to see these birds.

Are the colour rings only used in the UK?

Colour ringing isn’t just carried out across the UK, but worldwide, and has been a useful tool to shed light on the movements of the harriers on the near continent.

Staff at the Dutch Montagu’s Harrier Foundation observed a hen harrier they had tagged crossing the North Sea to spend the winter in the UK. This further highlights the importance of maintaining good quality roost sites in the UK for hen harriers across Europe, and how critical it is to protect these migrating birds across the whole of their range.

We also know the birds from the UK visit the Netherlands. In April 2019, a hen harrier chick who was colour ringed on Hoy, in the Orkney Islands by the Scottish Raptor Study Group in 2018 was photographed by one of the Dutch Montagu’s Harrier Foundations volunteers in the north of the Netherlands. Less than a handful of records of Scottish birds have been observed there. Like us, they need your help to look for colour ringed birds and are hoping more birds are discovered moving between the UK and continental Europe in the future.

This season Dutch birds have been fitted with orange colour rings with a black inscription with one number and one letter on the bird’s right leg. H3 below is one of the Dutch colour ringed adult females who is a remarkable 9 years old (ringed in 2011 as a chick) and again her offspring were also colour ringed, one of whom is shown in the image below.

Colour ringing is a vital technique to help us uncover more about the journeys our hen harriers are making, how long they are living, and the places they are visiting.


Please do help us out by taking photos of any hen harriers you see and checking if they have colour rings fitted. You can report them to our hen harrier hotline by calling us on: 08454 600 131 (calls charged at local rates) or email us at with information on what it looked like, where it was (grid reference if possible) and what it was doing (eg. flying North, hunting, carrying nesting material). You might learn something remarkable about your encounter!

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