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Merin and Tegid Return

Posted: Friday 25th May 2018 by Emyr MWT

Q. What could be better than news of a Dyfi chick returning as an adult?

A. Two birds returning of course.

And so it was last week. Welsh osprey ringer Tony Cross messaged me early Wednesday morning to say that a Blue W1 (Merin - a male chick from the 2015 brood) was nesting in Denmark.


Some other countries do use blue rings as we do in the UK, so before telling everyone about the potential great news, I though it best to carry out some 'extra checks', just in case. Once incorrect information is out there, you cannot pull it back.

Another 24 hours was enough to provide all the information we needed - and more. Photographer Vagn Donskov sent me the most amazing images you could wish for from Denmark - it was Merin alright, no question. His was a Darvic ring used only in the UK.

Here are some of Vagn's photographs of Merin

All ©Vagn Donskov

Merin is breeding with an unringed female and they've been incubating eggs since around 11th May. Their nest is built by the ospreys themselves on top of a pine tree.

It doesn't look the strongest nest in the world, let's hope it can survive for the next three months. The conservation guys over there are currently planning to strengthen the nest during the winter if all goes well.

It barely feels like three years ago since we ringed Merin and his siblings - here is the ringing video...

Merin is not the first British osprey to favour a more continental lifestyle. A Cumbrian osprey has been doing the northern European rounds, including Denmark, for a while. A Rutland male, another three-year-old like Merin, is currently in the Netherlands - his second year there.

No 14 from the Lake District Osprey Project 


Jutland and Philopatry

Merin's nest in north-west Jutland, Denmark, is around 560 miles (900 km) away from his natal Welsh nest.

So, what about this 'philopatry' male ospreys tend to exhibit, returning fairly close to their ancestral nest when it's their time to breed?

Philopatric behaviour is a real and tangible breeding dispersal behaviour of many animals, particularly some long-distance migratory birds including ospreys. Of course, there are always individuals that will buck the trend, but on the whole, on average, male ospreys (Pandion haliaetus haliaetus) choose a nest site that is relatively close to their ancestral nest; this is called 'natal dispersion'.

This has been observed and recorded in numerous European and American osprey populations and indeed for the Rutland population, for which there is very precise and accurate data; the Rutland male/female natal dispersion numbers are as follows:

Males: Breeding nest distance from natal nest = 6.8 miles (11km, 12 birds recorded)

Females: Breeding nest distance from natal nest = 60 miles (96km, 10 birds recorded)

Below is an extract from Alan Poole's excellent book "Ospreys: A Natural and Unatural History' page 138.

In long-term studies of north American ospreys, three-quarters of males (33 birds studied) chose a nest location within six miles (10km) of their natal nests. In a similar Swedish study, three-quarters (32 birds studied) chose to breed within 30 miles (50 km) of their natal nests.

© Alan Poole

Of all the Welsh offspring that have returned to date that have either bred, or made serious attempts to, none of them are nearer than 100 miles (160km) from their natal nest.

Returning Welsh offspring that are/have breeding

So what's going on? Are all these Welsh birds bucking the trend, are they all behavioural non-conformers, or is there an underlying cause to this seemingly lack of close natal dispersal behaviour - philopatry?

I'll write a blog in the autumn/winter and try and answer this question.

It matters not where Merin is nesting. What is important is that he has survived the first three years of his life into adulthood and is making a fair shot at producing his own offspring.

Denmark, like most north-western European countries, has a small osprey population that is in a fragile state of recovery. At the start of this century there were practically no ospreys breeding in England, Wales, Denmark, Belgium, Netherlands, northern France. Less than two decades later all these regions have small populations; in years to come and as osprey numbers increase, all these colonies will merge into one large osprey population, eventually connecting up with the larger populations in Germany, Scandinavia and central France. That's the hope anyway.

As I said in the Glesni tribute, birds couldn't give a hoot about borders, passports and visas. Neither do they care about BREXIT, although Merin could quite possibly be the first Welsh bird ever to have voted ;-)

Merin on the Dyfi in 2015, just before he started his first migration southwards


Barely had we had time to recover, gather our thoughts and drank the last dregs of apple juice following the momentous news that the first Dyfi male offspring was breeding, along came another burst of euphoric news - and this time a bit closer to home.

Last Saturday afternoon I was in the 360 Observatory talking to Alwyn when the phone went - it was Janine ringing from the office 600m away. "Are you sat down" she said. This can mean just one of two things - extremely bad news, or extremely good news.

Heather, Project Manager at the Glaslyn project, had just rang DOP in an extremely excitable state. Janine explained that she was so excited, in fact, she was barely understandable and would probably have burst something if she had carried on much longer.

(In a Wolverhampton accent:) "Intrruder maile, jwst landed on the Pont Crawseor nest, Oi can see a ring... Oi ffink it's's Tegid...blwoody bostin...etc, etc"

Moments later Heather had managed to calm herself enough to send over a photograph. We had confirmation of another Dyfi offspring returned just three days after the Merin news. Bostin indeed.

Tegid - the first photograph of him as an adult                 ©BGGW - thanks Heather


Tegid didn't stay on the Pont Croesor platform long. It's inside Aran's (the Glaslyn male) territory, so just like Gwynant and all other males before him, Tegid was met with hostility and swiftly ushered away.

A few days later we spotted him on the Dyfi nest - Tegid is the first Dyfi offspring to have actually visited his natal nest. Others may well have come close, but never landed on the nest or the near-by perch.

Here's a video of Tegid back in Wales:

Eye Colour

So, what about that perennial question everybody keeps asking... do Monty's kids have darker eyes, just like their Dad?

Here's a collection of offspring. What do you think?

Dai Dot on the far left for comparision to a more normal adult yellow eye colour

For what it's worth, I think all of the three returning boys have a darker eye colour than usual. Gwynant has only slightly darker eyes than usual, Tegid quite a bit darker and Merin's are so dark, his eyes are almost as amber-brown as his father's.

Merin - Monty's doppelgänger!                 ©Vagn Donskov

I had a chat with our geneticist volunteer Dr. Helen yesterday during her people engagement shift. She is now seriously looking into this! We may well be on the verge of a breakthrough, after all, we have DNA for most of these returning birds.

Clarach as an adult - darker than usual eyes?              BGGW

The brightly coloured yellow eyes of most ospreys result from the presence of pigments, such as pteridines, purines, and carotenoids. Maybe Monty has a gene(s) that prevents one or all of these becoming fully active, ensuring that the dark orange colour that all young ospreys have as chicks never progresses beyond this colour? A bit like leaf colour - the chlorophyll's green color dominates and masks out the colors of any other pigments that may be present in the leaf. Thus, the leaves of summer are characteristically green until the point where all the chlorophyll is used up and the other pigments come to the fore resulting is the leaf's colour change to yellow then brown.

It certainly makes sense and almost certainly eliminates an 'acquired' theory for Monty's dark eyes (i.e any factors he's experienced during his life that could account for eye colour such as variation in sunlight, shade, disease etc)

Watch this space, Dr. Helen is on it.

A Hat-trick of Boys

In three weeks we've had news of three Dyfi boys returning as adults. I can't tell you how happy we are.

We don't do this for the money nor for any other reason other than osprey conservation. Returning ospreys as adults is our currency - this feels like winning the lottery I guess.

We've seen Tegid one more time on the Dyfi this week and we hope, naturally, that he stays in Wales to breed, and that goes for Gwynant too. We've been crying out for more males in Wales for years, then two arrive within days of each other.

Going back to the Glesni tribute again, I said at the end "Glesni mothered 11 young ospreys to migration age, two of which have already returned as adults: Clarach - her first ever offspring from 2013 and Gwynant, her first male offspring from 2014. There are others out there, make no mistake. Glesni will live on and as the years pass by her legacy will become clear for all to see."

Little did I or anyone else appreciate how soon we would realise Glesni's legacy.

For the first four years she was with us, one chick from each of those four years has already made it back, two of them are already breeding - Clarach and Merin. That's four out of eight chicks back - a 50% return rate. That's practically unheard of.

Four of Glesni's offspring have already returned as adults (thick black border)

There will be some stiff necks come next May when Aeron, Menai and Eitha are due back.

And Finally

I think it's fair to say that we took some serious stick from a small minority of people two years ago for not 'intervening' to try and save Ceri, who had injured herself following a fall just after fledging.

Ceri was capable of flight and would have almost certainly bolted off the nest as we approached, probably never to be seen again. If she had been the only chick in the nest that year, our decision may have been different - but she wasn't.

Her brother, Tegid, hadn't fledged when Ceri injured herself - we had to think about him too. Approaching the nest would have caused him to prematurely fledge and again, there's a risk that he may have never returned. We would have lost both of them.

As it turned out, Ceri didn't make it, but her brother did.

Tegid looks on as his sister, Ceri, lies dead beside him

These are awful decisions to have to make under extreme pressure, but we have to remain calm and ensure that we make the correct decisions for the ospreys. Nobody gets all the decisions right, but I believed in 2016, as I do now, we made the right call.

A group of children were looking through binoculars in the Ceri Hide on Tuesday afternoon, trying to spot whether there were any nests in the floating raft we had placed on the lagoon in early spring. Ceri is buried near-by and as I thought of those horrible few days back in 2016 and the decisions we took, sadness soon gave way to joy when I turned my thoughts to seeing Tegid once again this week, flying high over the reserve.

Just as Glesni's is, Ceri's legacy is very much alive and well - in her brother, Tegid.

His sister's demise meant that as the sole surviving chick in 2016, Tegid had all the fish he could ever want for the next six weeks of his life. As he grew stronger by the day, his chances of succeeding and returning as an adult also grew stronger. Ceri had inadvertantly given her brother the best start in life he could have had. Tegid shares 50% of Ceri's genes, she lives on in him.

If there's a better feeling in the world than seeing an osprey again, flying high above you having returned as an adult from the nest you watched him hatch and grown up in, I have yet to experience it.



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