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Strange Osprey Behaviour

Posted: Saturday 2nd May 2020 by Emyr MWT

A few days ago Idris had a 'funny five-minutes'.

Both Telyn and Idris have been bonding well, everything looks ultra normal, then - out of the blue - we witnessed a series of behaviours that looked completely out of place.

Idris is incubating the eggs whilst Telyn is away having a bath in the Dyfi River. Completely normal.

When she returns, however, this happens...


We've had plenty of intruders recently - did Idris think Telyn was an intruder?

Here's the most recent intruder from yesterday morning - a Cumbrian three-year old male..

Let's try and piece together what exactly was going on here and come up with some explanations as to why we saw this (what seems to us) strange behaviour.

Here are a few hypotheses:


1. Intruder

So, Telyn comes back from the river, she has wet plumage, Idris thinks it's not her.

Makes sense, right? Idris had only been here 19 days up to this point, the missus comes back with wet hair, mistaken identity.

Case solved.


2. Imprinting Imbalance

If indeed Idris has bred before at another nest - maybe for several years - his old partner would still be imprinted in his brain.

Did Idris, for a few moments, 'forget' that he had a new partner and react accordingly when he realised that the female landing on the perch was not his previous mate?

Wouldn't that explain the hostile reaction, which only subsided a few minutes later when he finally realised that he now has a new partner?

3. Sex

The third egg was laid on 22nd April. Idris' 'funny five-minutes' happened three days later on the 25th.

By that time the clutch was complete and Telyn was becoming less receptive to his mating attempts. Isn't this a simple case of testosterone-triggered male hostility in response to reduced copulation?


And Finally

I don't think any of the above explanations are correct.

For either the intruder or imprinting imbalance hypotheses to be correct, the requisite and reciprocal behaviours are not present. Look at the intruder video above - did you see any of the behaviours that Idris displayed to a 'real' intruder in the Telyn video?

The main give-away here as to whether Idris thought Telyn was another bird is the complete lack of vocalisations. He would have been chipping away like Harry Ramsden if he thought this bird was anyone other than Telyn. The almost complete silence throughout the sequence of behaviours is a big clue.

Idris with plenty of fish, but not a chip in sight

The sex theory is also dead in the water before it's taken its first swimming lesson. If true, we would see these behaviours all over the place, all the time. We don't.

As a Behavioural Ecologist, one thing stood out to me like a sore talon when I saw this - Redirected Behaviour.

Those of you that have been following for many years will have heard me talk about displacement and redirected behaviours before. To me, this is absolutely 'Classic' redirected behaviour.


What is Redirected Behaviour?

These are behaviours that are triggered by a stimulus, but manifest themselves in a context not directly associated with the trigger - in other words, they are redirected.

Redirected behaviours occur when some course of action is thwarted or inhibited, leading to frustration.

Frustration is associated with stress which often results in aggressive or hostile behaviours; I believe this is what we saw here. 

Telyn was away in the river, Idris 'confined' to incubation duties. Whatever behaviours he wanted to express during this time had to be delayed, leading to frustration/stress.

Redirected behaviours are mostly (but not always) associated with aggression - like we saw here. What the trigger for the frustration or stress was, we may never know. The clue in trying to figure out the trigger is always to look back in time, before the event.

Expressed aggression

Was there a lack of food, were there predators around, other ospreys in the vicinity? After all, we've had plenty of intruders recently. We may never know.

These things are usually extremely subtle and only an osprey will be able to pick up on them.

The final clue to understanding this as redirected behaviour is the complete return to 'normality' soon afterwards. Things reverted back to breeding-behavioural equilibrium as quickly as they started, in just an instant - another classic sign of a redirected behaviour episode.

We may have de-coded Idris' 'funny five-minutes', but they are extremely fascinating nonetheless. We should be set for a very interesing summer...

And.... relax

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