Last Friday night through to Saturday morning, 13th - 14th May, something quite astonishing happened on the Glaslyn nest.

Ten days after her first touchdown on the Glaslyn nest, Clarach landed again. So, nothing unusual in itself here; the remarkable thing was the way both the Glaslyn breeding ospreys reacted to her. Treating her not as an intruder, but instead as a bird to be tolerated, even close up and despite having two eggs to incubate and protect from harm.

The Glaslyn female continues to incubate her two eggs, completely unmoved by Clarach's presence

Many of you I'm sure witnessed some of this live on the Glaslyn Live Streaming, and judging by the response on our Live Chat, all of you were flabbergasted by what you were seeing as well. I couldn't believe what I was watching and kept pinching myself.

Clarach stayed on the nest for four whole hours before she, of her own volition, decided to depart. Most intruders stay for three nanoseconds on the Dyfi nest before being chased off and long before we've had time to focus in on them. But Clarach wasn't done - she was back the following morning before daybreak and hung around for another four hours.

Here is eight hours of video over two cameras condensed down to five minutes - this ain't no wind-up!

Ain't Bovvered

So, where do we start with this lot? Let's begin first by noting down some of the obvious stuff that we saw:

1. Clarach lands on the Glaslyn nest and is not treated an an intruder as would be 'expected'.

2. The Glaslyn female seems to behave almost as if Clarach isn't there - continues to incubate and food solicit to Aran, despite being trampled on by Clarach.

3. Aran brings two brown trout to the nest - one Friday evening, one Saturday morning. Clarach beats the Glaslyn female to both of them and continues to eat them actually on the nest.

4. Clarach mistakes Aran's foot for the fish.

5. Every time the Glaslyn female gets up to turn the eggs, thereby exposing them momentarily, Clarach moves closer for a better look.

6. Clarach poops on the incubating female - twice.

7. By 8am the following morning, both Glaslyn adults start displaying the behaviours you would expect if there was an 'intruder' around - mantling, chipping etc.

Okay, so these are the main take-aways of what we saw. What questions are generated from what we've seen?

1. Why on earth were both Glaslyn birds so tolerant of another full-adult and breeding-age female being so close to them on their nest?

2. Where has Clarach been for the intervening 10 days between Glaslyn visits?

3. Why didn't the female go bananas when Clarach trampled all over her?

4. Clarach pooped on her twice - was this deliberate?

5. Why did the Glaslyn female not compete with Clarach for the fish to a greater level than she did?

Clarach food solicits on the Glaslyn nest, seemingly uncontested

And the Answer is...

Let's break this down into bits...

Something about (i) Clarach's behaviour and/or (ii) Clarach's recent behaviour in the previous 10 days has reassured the Glaslyn female she is not a threat - has to be. Otherwise any incubating female would staunchly protect her eggs and nest and commence intruder evasive behaviours. The Glaslyn female has successfully protected and produced offspring for the last 12 years on the spin - this girl ain't stupid. What those behaviours and traits are I'm not sure. I don't speak Osprish - but they were clearly there.

Clarach's behaviour on the Glaslyn nest for the two four-hour stints were similar to those of a petulant fledgling. Inquisitiveness, stamping on other birds, mistaking Aran's foot for the fish and those excessive and repeated food soliciting calls. All traits we associate with young juveniles in August and September before they leave on migration. Indeed, Paul WildlifeWriter pointed this out on the DOP Live Chat as we were watching events unfold on Friday night. Paul also commented that Clarach was not attempting to take over the nest (like Blue 24 at the Dyfi say, in 2014 and 2015). She was there for something else - food.

So now we've nailed these seemingly strange behaviours down to one common theme - fish. Now we are in a better position to answer the big question - Clarach is not a juvenile, she's a three-year-old adult osprey looking to breed - so why these seemingly 'strange' set of behaviours?

Clarach has been spending her time on another man-made platform in the Glaslyn for the last 7 - 10 days. A male osprey has been seen with her (almost certainly Aran) and although no fish deliveries have been recorded, he probably has brought her the odd fish or two. These are behaviours that are very similar to those of Monty and Blue 24 over the last few weeks.

Starting to make sense now isn't it? The Glaslyn female would have known exactly where Clarach has been during this time, it only takes a matter of seconds to fly between these other platforms. Another female on another nest is of no consequence to a breeding female, she's not a threat as this was no nest-displacement attempt. This was purely a fish-acquiring exercise.

Clarach knows exactly where the primary Glaslyn nest is, "If the mountain won't come to Muhammad, then Muhammad must go to the mountain", or in this case, Aran's nest. Clarach is following her previous source of (potential) food to his nest - this is exactly what she is predisposed to do at her age: find a nest (platform in this case) and male that will provide her with food. All the other behaviours that were reminiscent of juvenile actions (stamping, pooping, leg pulling etc) are easily explained away by inexperience.

Clarach will not have been in a position of 'living with another bird' or being gifted food from another osprey since Monty last brought her a fish in September 2013 - she's caught all her own food since. Once she finds a mate and starts to breed for herself, she will quickly learn the finer etiquettes of breeding behaviours.

You're pulling my leg, right?

I mentioned in a recent article about the conditions that contribute to polygamous arrangements within osprey populations. We have also been a little unlucky in Wales, which doesn't help.

Clarach is now a three-year-old, one of six 2013 Welsh offspring - all of which were females. The chances of all six birds being female (or all male for for that matter) are 64/1. In 2014, we had 10 offspring from four Welsh nests, again most of these were females (6 ♀ and 4 ♂ - of which Gwynant was one of course). So only a quarter of Welsh offspring in 2013 and 2014 (four out of 16) have been male. These 2014 birds are due back anytime from May onwards two years later. Start looking up!

Over time, these male:female distortions will even themselves out, but for now we, and the young female ospreys, have to sit it out and wait, literally. Blue 24 has had (Monty's) eggs, Blue 5F is sitting on (Aran's) eggs right now with sadly only one inevitable outcome, and now Clarach. Let's hope she does't lay eggs also, thankfully it is getting a bit close to that invisible cut-off point now for egg laying.

What seemed like a puzzling and curious set of events over the weekend that bamboozled all of us, suddenly now starts to make sense. It reminds me of a conversation I had with an elderly Welsh lady in the visitor centre at the Glaslyn Osprey Project in around 2006 (yes, I do people engagement sometimes!) when she accused me of being a sexist pig (in Welsh) for explaining to her that I hoped all three eggs that year would hatch and all three birds would be males, and the next year, and the next year...

We need males to start off with in a recovering osprey population like this because of their high degree of philopatry (come back to the same colony to breed when adults). Believe me, in a few years, once we've reached 10 pairs or so, I will be rooting for the females, as the dynamics will have changed in that direction with a load of males sitting on non-breeding nests.

All photographs and video rights belong to the guys at the Glaslyn: Bywyd Gwyllt Glaslyn Wildlife. I would like to thank them for their time on Saturday when I visited and their consent to use their footage. We work well together, we've now had a Glaslyn offspring land on the Dyfi nest (two in fact - White YC and Blue 80) and they've had one of ours on their nest - Clarach. And long may our close working partnership continue.