COMMON CAUSE

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“When you have eliminated the impossible, whatever remains, however improbable, must be the truth”
        Arthur Conan Doyle The Sign Of The Four (1890)

Strange things have been occurring at several of the monitored osprey sites, this season. Unaccountable, worrying things that seem - on the face of it - to be so far removed from the usual that they defy explanation.

17.7.2016 Fledgling Z0 “Ceri"

falls from a perch at MWT Cors
Dyfi and sustains serious injuries
(Infra-red illumination)
[Montgomeryshire WT]

Fledgling birds have been falling from their perches. Youngsters have appeared to have difficulty in walking, holding their legs or talons at strange angles. Some have flown and failed to return; others have gone off their food, seemingly ill, only to recover later. One chick (at MWT Cors Dyfi) has been so badly hurt that she went into circulatory shock and died. And on social media and the forums, everyone has been asking:-

What the hell is going on? 

These are wild creatures and every moment of their lives is at hazard. Bad things can and do happen to individuals, whether they are under observation or not. It's Nature. Flying is an instinctive ability, but the judgement of speed, distance and timing are not: these are acquired skills and they have to be learned and practised. Young inexperienced birds sometimes have accidents, and the outcome depends very much on chance and circumstances. Usually, they get away with it unharmed – but not always. 

We on the other hand are not wild birds. We are human beings and one of our less-rational habits is to search for patterns in isolated events, where often none exist. Psychologists even have a term for it: “apophenia”. Scientists are trained to recognise this trait in their own day-to day work, and to eliminate it in favour of objectivity and rigour.

There's an app for that...

Statistical mathematics include a set of tools that can tell us whether the frequency of an event (or series of events) is higher, lower, or the same as might be expected to occur by chance. Numbers were crunched and the answer came back: it was higher. Not by much, but detectable.

30.7.2016 Osprey W7 sustains

apparent grazing impact injury.
Close-up of bruising and
swollen leg joint.
[BGGW Glaslyn Wildlife]

This begged the next question: could there be some underlying factor that was affecting some of these birds but not others, even though the incidents were happening in widely-separated nest locations and at different times? Powerful minds (much more powerful than mine) applied themselves to the problem. The 'usual suspects' were rounded up: provisioning rates, environmental pollutants, fungal toxins... one by one, they were eliminated from the inquiry. Exotic diseases were invoked: could it be bird flu? Avian malaria? Trichomonosis? Any of these can affect lower body function but they have other symptoms, too, none of which seemed to be present.

The leg rings themselves were checked on, and checked on again. But all were the same rings as had been used in previous years, made from the same materials and fitted by the same teams. It wasn't the rings.

Other theories were suggested, from the mildly unlikely to the just-plain-bonkers. Recessive gene mutations? Nope. Calcium deficiency causing paralysis? Can't be. Short term variations in the Earth's magnetic field? Gimme a break.

Perhaps there IS no answer. Alternatively (and it's just another theory) the answer might have been staring us in the face, all the time...

Kielder osprey Y0 fledged on 15^th July, out of

view from the nest cameras. She did not return

to the nest after fledging. Current whereabouts

unknown. [Img: Paul McMichael]

I was chatting with young Damien the other day. Damien is one of the guys on the local red squirrel conservation survey, and he gets the job of installing the higher-level trail cameras and bait trays. Part biology student and part gibbon - with vocalizations to match – Damien is not a happy arborealist these days.

“Duuude... real gnarly climbing up there... like, slippy and slidey, y'know... maaad dangerous...”  

And this is a bloke who will happily hang from a branch by the crook of one elbow while thumbing tweets into his mobile with the other hand. The boy's prehensile. If Damien thinks that working up in the trees has suddenly become “mad dangerous”, then something is amiss.

My UK readers will have noticed that, in 2016, the notorious British Summer has been even less summery than usual. Rainfall - markedly in the west and north - has produced totals for June that were 30% higher than the moving average. The figures for July are not likely to be much better. Cloud cover has been over 90% for almost 90% of the days. These unsettled conditions have featured blustery winds, variable in direction and gust strength. In technical terms, it's been rubbish.

What effect might such unseasonably poor weather over such an extended period have on the environment?
 
Wet and humid conditions are ideal for growing the algae and moss that has

been troubling our Damien. Branches of deadwood trees (exactly the ones that are favoured by ospreys for perching) never get the chance to dry out, making them slippery and even liable to breakages. Cloud cover makes for poorer visibility, more difficult judgement of distance, while gusting winds are the last thing that any fledgling bird needs to encounter on its first experimental flights.

Any one of these factors could cause a problem on its own – but put them all together and they stack: generating a persistent and cumulative rise in the accident rate that we start to notice.

And so we mustn't give in to that seditious inclination of ours: that everything that happens must have a single identifiable cause and agent, so that we can hold someone or something “responsible” before dashing off in pursuit of the next conspiracy. I find no mysterious or even sinister forces at work here. There's an underlying rough-and-tumble to any wild fledging season - and the rougher it gets, the more tumbles it produces. In certain isolated years, all the adverse factors combine in one relentless stream of bad luck and unhappy accidents.

I blame the weather – but the weather didn't mean it. All these incidents are still just Nature, doing that stuff She does.

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The views expressed in this article are those of the author himself, and are not intended to be representative of any other organization or group.