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Peris: A Four Day Vacation

Posted: Sunday 18th August 2019 by Emyr MWT

This week Peris returned from a four-day holiday.

He set off at just before 9am on Friday, 9th August, and by Monday morning we had actually put his departure time in our Dyfi Migration Age chart.

This is what it looked like:

 

And here is the chart that plots migration days post-fledging:

Surely Peris was too young to have migrated at 74.2 days?

There are occasional records of British osprey fledglings having migrated at 70-something days old - Rothiemurchus for example, who migrated at around the same age as Peris and successfully returned two years later as an adult - but it's far from common.

Had Peris migrated or come to an ignominious end?

Our questions were answered at 08:40 on the Tuesday morning - four days to the minute almost - when Peris returned.

 

 

Where had Peris Been?

It is fairly uncommon for fledglings to disappear like this for so long and then return several days later; I have certainly not seen this within the Welsh population.

Let's look at some possibilities of where Peris might have been:


1. Migration: He actually started his migration and could well have travelled several hundreds of miles before the weather triggered him to rethink and return; after all, the weather was pretty terrible for migration at the time.

2. Travelling: He had been travelling around the vicinity, possibly visiting other nests. This certainly happens with young fledglings and only this week we saw a young bird from the Snowdonia nest (ON4) land on the Glaslyn nest briefly.

3. Mummy's Boy: He's been down river with Telyn (who was also 'missing' for a couple of days at the same time) who provided him with food, negating the need for him to return to the Dyfi nest.


KC1 - a male fledgling from the nearby ON4 nest visits the Glaslyn nest this week                (©BGGW)


Behavioural Changes

Maybe there are clues here in Peris's behaviour that could help us understand where he has been?

He returned a very different bird to the one that left four days earlier. He was aggressively screaming for food, the likes of which I haven't seen before. He was fiercely defending the nest from his siblings and had gained a level of independence you only really see in adults that are defending their nests from other intruding ospreys.

 

Peris - fiercely independent

 

It was fascinating to watch. It was as if an 'independence switch' had been activated in his brain; gone were the previous traits of sibling sharing, tolerance and patience, replaced by a ruthless streak of autonomy and self-determination. Peris against the world.

Of course, these adult-type behaviours will serve him well when he reaches Africa, he'll need them and then some; we're just not used to seeing such independent characteristics at the stage of life Peris is at right now - one of three siblings sharing a nest, just four weeks after having taken to the air for the first time.

We'll never know for sure, but based on behavioural observations of Peris after his return, I believe that he actually started his migration. That 'independence switch' was indeed triggered and the fact that he was ferociously begging for food upon his return suggests to me that he wasn't just out of sight, down river with Mum supplying him with fish. These were the behaviours of a bird that had not eaten in four days.

The fact that the UK was gripped by 60mph winds at the time lends support to this 'changed my mind' hypothesis.

Did Peris actually start his intended migration at 74 days old?

As I said last week, we will never know everything... every good story needs an element of mystery.

Peris returns, ferociously independent - and hungry...

 

Hyperphagia

Meantime, Berthyn and Hesgyn are doing great and hyperphagia has well and truly kicked in.


We've reached mid August and the final stage of osprey development before they embark on their greatest journey.

Just as we humans stock up on provisions if going away or when bad weather is due, so do the ospreys. Berthyn, Peris and Hesgyn are in full hyperphagia mode, they constantly scream for food despite there being plenty of fish available on the nest. This has nothing to do with daily calorific requirements.

Berthyn and Hesgyn squabble over dinner

This time next week they could well be approaching northern Sahara - they will need every last calorie of energy they can store up now for the lean times ahead. And it's not just geographic challenges they face - none of these birds have caught their own fish yet as far as we can tell. Their success rate will be nowhere near as good as their parents'.

This evolutionary-imposed gluttony is there for a very good reason.

Peris has settled down a bit more by today, but we still see evidence of that newly-gained independence. He's definitely at the top of the pecking order; Berthyn is submissive to him (unusual for a female, and the eldest of the three at that), as is Hesgyn, but his little brother has been seen to push back a little over the weekend. They're amazing to watch.

Family matters - all calm again, for now...

 

Monty's Fish Slap

We're also at that stage of the season where non-osprey intruders appear on the nest.

Monty gets quite irritable when he sees crows in his near-vicinity. This week we saw him doing his usual barking at them, a vocalisation that basically warns the crows to stay away.

One bird, however, probably a youngster, didn't get the message until it was too late.

Here's how Monty dealt with the crows:

We think the crow survived.

 

Intruding ospreys

This week we've also seen adult ospreys intruding onto other nests.

Tegid was seen at the Glaslyn nest again and Rutland's Blue 5F visited the Dyfi briefly on Thursday

5F at the Dyfi

 


And Finally

No osprey season would be complete without the usual August toe-curling event. Only this year, it was Telyn, not Monty, who took the full brunt of a youngster's mis-directed attempt at fish grabbing.

My name is Hesgyn and I have Hyperphagia...

 

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