Dr Jamie McKaughan, our Conservation and Research Coordinator, cracks open the myth surrounding Kestrels and how they hunt their prey, separating fact from fiction and revealing what the science is really telling us…

When better evidence comes along, it should update our knowledge and our thinking, but sometimes our collective memory does not always keep pace, or perhaps the new evidence does not get the public spotlight it should – another discussion for another time perhaps!

Nonetheless, ideas that have never been properly demonstrated, tested or proven can become so deeply embedded in popular understanding that years of repetition give them an authority they never earned, sometimes even allowing them to survive a robust scientific study that has directly challenged or disproved them. The result is a strange inversion: common belief being more persistent than empirical evidence. Even if you ask an AI system, it is likely these very same inherited assumptions are confidently repeated rather than any reflection or credence given to the robustly tested published research that overturned it…

So, where am I going with all this?! There are many examples of this scenario regarding wildlife, but a prime example comes in the form of Kestrels, and the idea that they use urine trails to help them hunt their prey – 100 percent, right? Wrong! A piece of research by Olle Lind and team set about testing this theory properly, with their comprehensive results published in 2013, coming up on 15 years ago now…

This myth originated from two circumstantial pieces of information being put together with an assumption they were related without ever being tested… Point Number One – birds’ vision is sensitive to UV light and point Number Two – a finding from Finland that urine of Finish voles reflects UV light.

Let’s break those two points down… are they even true and are they actually related?

Let’s start, logically, with point Number One – birds’ vision is sensitive to UV light. We widely accept that many birds are what are called tetrachromats, where they possess a fourth specialised cone type in their eyes that detects ultraviolet or violet wavelengths of light. For comparison, humans are trichromats, possessing only three types of colour-receptive cones in our eyes (blue, green and red). The extra colour-receptive cone that many birds have allows them to experience a world of colour humans cannot perceive. As the feather structures of many bird species also reflect light in the ultraviolet or violet range and because many birds can discriminate this greater variety of colours than humans it is likely that birds will appear quite differently to each other than they do to us. So, part one of our myth, thus far, is giving truth vibes… However, that is just part of the tale…

The 2013 study that disproves this entire myth tested the specific wavelengths of light that actually make it to the retinas of several species of raptor. Before light hits the retina, it is filtered through the cornea, the lens and the fluids in the eye, all of which could impact what amount and/or wavelengths of UV actually reach the retina – something their research showed to be true. They found that a lot of UV light was filtered out, with only much higher wavelengths reaching the retina. As such, in order for Kestrels to be hunting voles by following their urine trails they would need the vole urine to be reflecting the higher wavelengths of UV light…

So, what wavelengths might vole urine be reflecting if any?…

To address point Number Two – that urine of voles reflects UV light – the same 2013 study tested the amount of UV light that vole urine reflected. In a contrast to the idea from many years before that Finish vole urine reflects UV light, their findings showed there was very little if any UV light reflected, with many other studies also studying mammalian urine and finding no UV is reflected, with it effectively appearing the same as water would – pretty robust and conclusive! If there is no UV being reflected by vole urine (which there isn’t!), Kestrels cannot be using it as a means to hunt said voles!

So, despite the long-standing claim that Kestrels use vole urine trails to locate their prey being a compelling ecological story that has persisted in popular and even scientific discourse for decades, and a narrative that still seems to remain, it is not true! Now we just need to dispel this commonplace myth more widely… If you hear someone saying that the Kestrel’s superpower is hunting voles by following their UV-reflecting urine trails, be sure to let them know this is not true… science says so!

My final reflection is about how we perceive species and their ‘value’… I often hear Kestrels being hailed as awesome because of this mythical hunting superpower, and it strikes me as curious that we would think their achievements are more awesome because of this supposed ability than without it. If anything, I think they become even more wondrous by being able to hunt successfully in the way they do in the absence of this ‘special ability’ in their arsenal… They are super enough as they are and that is just one reason we are working so hard to conserve them!

If you’ve ever spent time watching owls, be that in the wild or in human care, in the UK or overseas, one of the things you’ll no doubt notice is just how different their eyes can be. At the Hawk Conservancy Trust, we have some wonderful examples. Sweeney Todd, our Snowy Owl, has striking bright yellow eyes that seem to glow against her white feathers. Molly, our Eurasian Eagle-Owl, stares out with vivid orange eyes, while Troy, our Tawny Owl, has deep, dark brown eyes.

So why are they so different?

For years, one of the most common explanations has been that an owl’s eye colour reflects when it is most active. The theory suggests that owls with yellow eyes are adapted for brighter conditions and tend to hunt during the day, orange-eyed species are most active at dawn and dusk (crepuscular), and dark brown or black-eyed owls are specialised for hunting at night because their eyes absorb more light.

It sounds neat and tidy, but nature rarely is.

The truth is that we don’t actually know for certain why different owl species have different eye colours. While the popular theory has some appeal, there are simply too many exceptions for it to be considered a definitive explanation.

For example, one study found that almost 60% of owl species considered strictly nocturnal have dark irises. That might seem to support the theory, but it also means that more than 40% of nocturnal owls don’t fit the pattern. Likewise, nearly 30% of owl species that are active during the day or at dawn and dusk also have dark eyes.

It’s a bit like the old spelling rule many of us learnt at primary school: “I before E except after C.” It’s a useful guideline until you discover there are so many exceptions that it quickly falls apart. Owl eye colour appears to be much the same – perhaps an interesting trend, but far from a universal rule.

That said, there may be some evolutionary clues.

Researchers have suggested that changes in an owl’s activity pattern over evolutionary time may have influenced changes in iris colour. This idea appears to hold up a little better when looking at the two main owl families.

Willow the Barn Owl

The Tytonidae family, which includes Barn Owls and Bay Owls, consists almost entirely of nocturnal species, and they all have dark eyes. In contrast, the much larger Strigidae family, which includes almost every other owl species, displays a remarkable variety of eye colours alongside a wide range of activity patterns.

Even within the UK’s owl species, however, there are exceptions. Tawny Owls and Long-eared Owls are both predominantly nocturnal, yet Tawny Owls have dark eyes while Long-eared Owls have bright orange eyes. Then there’s the Little Owl, with its pale yellow eyes, which seems to fit the traditional theory by being partly active during the day, but it is also perfectly capable of hunting at night.

Mozzarella the Little Owl

So, if activity patterns don’t tell the whole story, what else might explain these colourful eyes?

Across birds in general, eye colour is often thought to have evolved for one of two main reasons: to improve survival or to communicate information to other birds.

The activity-pattern theory falls into the first category, suggesting eye colour provides an advantage in different lighting conditions. Another possibility belongs in the second category.

Walter the Great Grey Owl

In some owl species, scientists have suggested the pigments responsible for yellow and orange eye colours are influenced by compounds obtained through their diet. If that’s the case, the richness of an owl’s eye colour could potentially reflect its health or, in breeding birds, a parent’s ability to find enough food to raise its young successfully.

However, once again, this is unlikely to be a universal explanation. It may apply to some species, but certainly not to all.

In the end, owl eye colour remains something of a mystery. While researchers continue to investigate the role of evolution, behaviour and diet, there is still no single explanation that works for every species.

So next time you meet Sweeney Todd, Molly or Troy, take a moment to appreciate their remarkable eyes. They may be different shades, but each one is a reminder that nature often refuses to fit into the neat little boxes we’d like to create.

If you want to hear more then check out this episode of the Trust’s Nature’s a Hoot podcast, hosted by Tom Morath, investigating more about owls, their head turning and their eyes!

As ever, July brought with it Global BirdFair, and we went along, joining thousands of fellow bird enthusiasts to celebrate and discuss all things birds!

As an international bird of prey conservation charity, we couldn’t miss the opportunity to share the work we’re doing around the world. Our Conservation and Research Coordinator, Dr Jamie McKaughan, gave two talks over the weekend. The first highlighted the status of vultures in Pakistan and the conservation challenges they face, reflecting on nearly 30 years of our work in the country. The second explored the challenges falcon conservation faces from the illegal wildlife trade, drawing on our recent publication on digital trade (watch this space for more on that!).

We caught up with Jamie when he was back…

“It was great being back at Global BirdFair this year. One of the best things about BirdFair is catching up with friends from around the country, and sometimes the world, and often making new friends there too – the joy of being surrounded by so many like-minded individuals with similar passions can be infectious. It was also great to catch some members of the Trust there again, whose support of the Trust generally, but also attendance at my talks and the live podcast episode we recorded was greatly appreciated as always!

Jamie talking at Global BirdFair 2026

Catching up with others is not just good for the soul in a conservation world that can be disheartening if you think about it too long, but it also gives an opportunity to check in with the bigger picture. Last year for example, everyone I spoke to in the proverbial raptor nest box game(!) was experiencing terrible nesting numbers and success rates countrywide. While that was not a positive for the species we are striving to conserve – it is valuable information and context when it comes to these types of occasions and trends, and allows us to broaden our questions or considerations to reasons beyond the borders of our own study areas. Thankfully this year, that scenario has been turned on its head and cavity nesting birds of prey appear to be doing extremely well in many parts of the country, so long may that continue!

This year we were lucky to have colleagues from SAVE (Saving Asian Vultures from Extinction) at the event, some of which had travelled from India to be there, so it was really great to see them and catch up with them in person. Having long been part of the SAVE consortium to help conserve and recover vultures across South Asia, it is great to have such opportunities to touch base in person with some fellow vulture lovers! It was especially well-timed too, given my talk on day one was on the progress and challenges of vulture conservation in Pakistan!

On that topic, BirdFair also provides a great opportunity to talk about the conservation work we are doing to an audience that we may not always reach. We do a good job of communicating our work to our members and visitors, but it can be more difficult to share those stories more widely with people who may be less familiar with who we are and the impact of our work. We often let the work speak for itself, but events like BirdFair give us the chance to showcase the longevity of our commitment to what we do and the difference our conservation efforts are making.  It also helps to raise awareness of the challenges and successes across the countries and species we work with, and engage with people who could become future supporters, partners or advocates for birds of prey and our conservation work. Ultimately, broadening that awareness helps strengthen support for our conservation ambitions and enables us to achieve even more for birds of prey in the years ahead.”

Jamie also joined Tom Morath, host of the Hawk Conservancy Trust’s Nature’s a Hoot podcast, for a live episode in front of an audience of fellow bird lovers drawing in the audience with some myth-busting fun and games!

Nature’s a Hoot live from Global BirdFair 2026

“As part of the myth busting, we talked about owl eye colour, bird of prey vision and the nuances of some long-spoken myths! For example, it is likely that many hawks have similar vision to ours, but also some are very different to us and to each other, like Harris’ Hawks, Red-tailed Hawks and Cooper’s Hawks, that vary in their visual acuity despite all being hawks – being hawk-eyed means different things depending on the hawk! Meanwhile, a similarly nuanced topic is owl eye colour, myths of which we also busted… to a degree anyway! For more on that, check out our recent blog too. We at least had one thing that was more categorical – Kestrels hunting voles using the UV light reflected from their urine… debunked pretty robustly by a study in 2013, and supported by several other studies since – but I will let you catch the full explanation of that, along with all the other podcast fun I had with Tom, in the Live at Global BirdFair podcast episode coming soon!”

Some readers might be aware that 2025 was a very poor year for cavity-nesting birds of prey such as Barn Owl, Tawny Owl, and Kestrels. Only 132 young birds were ringed from project boxes in 2025, which is considerably lower than in previous years. 2013 was the last time we recorded as few in the nest boxes. A lack of small mammal prey is one of the likely reasons for the poor season, along with unfavourable weather conditions. The Small Mammal Project, a project within the British Raptor Programme, focuses on monitoring abundance and diversity of small mammal species in the local area to the Trust that overlap with locations of our nest boxes. In 2025, only after six weeks of surveying did we find the first Field Vole of the year! Field Voles, also known as Short-tailed voles are one of the primary prey species for Kestrels. The low capture rate across the Small Mammal Project combined with poor reports from the nest boxes raised alarm bells. This year, however, things have bounced back and the nest box monitoring has felt busier than ever.

General observations from the wider Raptor Nest Box Project in 2026 include birds nesting earlier in the season and larger clutch sizes; a record of 9 eggs were found in a Barn Owl box this Spring! It has been a welcome change to the previous year when we had just over 10 confirmed Barn Owl fledglings in total. As of the end of June, we have already ringed more than 250 Kestrels, 200 Barn Owls and 100 Tawny Owls across our project area. This surpasses the 2025 total of 132 quite considerably and given the early nesting of Barn Owls this year, there is even a possibility of second nesting attempts later in the year. The Small Mammal Project has also been reflecting the success from the boxes, with 37 field voles being caught in six weeks of surveying and 150 captures of a variety of small mammal species to date.

Other positive news includes achieving our target fundraiser back in 2025; ‘£60k for Kestrels’. Thank you! As a result of the many generous donations, the Conservation and Research Department bought several GPS tags for Kestrels. These solar-powered GPS tags can record fine-scale movements of these birds over the course of the breeding season. This is key for understanding what habitats they use, how far they travel from the nest box and how frequently they provision to their chicks. This year, we have successfully fitted four Kestrels with these tags in the Hampshire area; two females and two males. This project is ‘growing wings’, and we hope to deploy a few more of these tags in 2027 and see what data we can retrieve from the birds tagged this year.

With the increased productivity of the nest boxes, 2026 has been a ‘record year’ for the Kestrel Colour Ring Project. Under a BTO licence, Dr Matt Stevens has been fitting these rings as part of the British Raptor Programme since 2015. With a previous record of 140 kestrel colour rings in a season, over 200 colour rings have been used in 2026 already, with more expected. Quite the year for Kestrels! These rings are bright blue and marked with a white unique code variation; i.e. “A H 7”. The codes can be read at distance with binoculars or telescopes and reported back to us

If you notice a colour ring on a Kestrel, please let us know by emailing Matt@hawkconservancy.org with the location, date and time you spotted the bird. If you can take a photo of the Kestrel with the tag, that would be ideal, but we know this is easier said than done! This information is incredibly valuable and helps us to understand more about the movements and dispersal of Kestrel fledglings from our boxes.

Finally, we couldn’t do all the in-depth monitoring work for Kestrels without the nest boxes. An expansion to our group of dedicated and hardworking nest box Volunteers in late 2025 has meant that over 130 new boxes have been built for the British Raptor Programme. This new nest box building team has been a fantastic addition to the Conservation and Research Department; their time and skills have helped us to build up a good stock of boxes in preparation for replacing damaged or worn nest boxes, installing new boxes in the Autumn of 2026 and will set us up to provide even more for Kestrels in 2027!

We are delighted to embark on a new conservation partnership between the Hawk Conservancy Trust and Kynren – The Storied Lands.  The partnership will support the development of conservation and research work focused on birds of prey across the North East of England, expanding knowledge about bird of prey populations in the region and contributing to wider national research efforts.

The same methodologies used for the Trust’s Raptor Nest Box Project (RNBP) and Raptor Survey Project will be applied to the project in the North East. Field surveys, habitat analysis and a variety of other conservation monitoring approaches will be used to help strengthen the understanding of status of birds of prey populations in northern England. Centred on County Durham and surrounding areas, the project will be developed in collaboration with other organisations and interested parties to complement ongoing ornithological research in the North East.

By bringing together data, observations and expertise from a range of sources, the project with Kynren hopes to operate on a larger scale than previously seen, building a clearer picture of how bird of prey populations are faring and identifying opportunities to support their long-term conservation.

A central focus will be the Kestrel, one of Britain’s most recognisable birds of prey that is now Amber listed as a species of conservation concern, with populations declining in many areas of the UK for reasons that are not yet fully understood.

The Trust’s long-term Kestrel research programme in southern England, has been running for more than a decade to investigate these trends and through the new partnership, similar research will begin in the North of England, allowing findings from different parts of the country to be compared and contribute valuable information to the national picture.

Dr Matt Stevens, British Projects Manager at the Trust, is working closely with staff from Kynren who will work alongside volunteers to play an important role in the programme.  This will create new opportunities for people with an interest in wildlife and conservation to become directly involved in research and fieldwork.

Kynren – The Storied Lands opens this summer in Bishop Auckland, County Durham as the UK’s first live-action daytime park, featuring five spectacular shows and immersive experiences inspired by history, myth and legend. Set within the wider park, The Lost Feather sees more than 250 birds take to the skies in an awe-inspiring story of flight and conservation.

Penny Smout, CEO of the Hawk Conservancy Trust, said: “We are pleased to be working with Kynren and The Lost Feather to extend our research and conservation efforts into another part of the country.

“Partnerships like this help build knowledge over time and encourage people to engage with the conservation of birds of prey in their own communities.”

Jimmy Robinson, Curator of Birds and Conservation at The Lost Feather, said: “This partnership gives us the opportunity to contribute to the wider understanding of birds of prey in the North East while working alongside other organisations and individuals who already care deeply about these species.

“By sharing data, experience and expertise we can help strengthen the evidence base th  at supports long term conservation.” As well as Kestrels, the nest box programme will also support Barn Owls, Tawny Owls and Little Owls. The aim being to increase the nesting opportunities for these species across a landscape where the availability of natural cavities and other traditional nest sites may have declined.  Data generated from the Raptor Survey Project will help us to identify the current status of raptor species across the North East and help in targeting future conservation actions.

The research programme will begin this year and is intended to develop over the coming years as further partnerships, volunteers and research opportunities emerge.