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Monday 22nd December, 2014

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Britain’s Owls
Is The Cup Half Full Or Half Empty?

I’m getting worried. Either my rapidly advancing years are affecting my faculties more than I think, or south-west Cumbria is turning into an owl ‘black hole’! The more I read in ornithological journals and reports, the more I think I am going ‘ga-ga’ (dictionary definition ‘fatuous, senile, slightly crazy’) or else our area is out of synch with the rest of the owling universe in the UK! It’s probably the former as over the years I have many times been accused of being a ‘scare monger’, ‘Job’s comforter’, ‘pathological pessimist’, ‘nutter’, or worse unprintable epithets (!!!) when it comes to the matter of owl population statuses in the UK, especially the long term future for the barn owl in Britain. It all depends on how well people know me! However, the fact is I can only relate what I see and have recorded on a personal level over some 42 years of owl watching between 1965 and 2007.

For instance, between the 1960’s and 1990’s I took tawny owls for granted. They were virtually everywhere in areas holding large trees, and their querulous hoots were a normal accompaniment to my nocturnal wanderings in the late winter and early spring months, especially on my last ‘dog trot’ of the day before I retired to bed (usually about midnight), or while out ‘owling’ in the early hours. At our wildlife hospital at the World Owl Centre we came to expect an annual deluge of ‘rescued’ so-called ‘orphan’ tawny owlets each spring (in what we rather rudely referred to as ‘the silly season’!!!). On average we could expect between 10 – 20 such cases each year, ‘rescued’ by well-meaning people who had found them on the ground or in the road and mistakenly (in most cases) believed they had been abandoned by their parents (the owls I mean, not the rescuers!). Fortunately for us, thanks to the sheer volume of owlets brought in, plus the fact that Muncaster is ideal habitat for tawny owls, we could usually crèche-rear them and return them to the wild where they belong. Only if they had been kept too long as a ‘pet’ and had become imprinted on humans, did we have a problem.

Worryingly, this is no longer the case. In recent years the number of owlets brought in to us has almost dropped to nothing. In 2006 none arrived at all. I would love to think this is because our message of “please leave them alone unless they are in immediate danger” is paying off, but to be honest I suspect this is not the case. The fact is that even here at well wooded Muncaster we are simply not hearing the typical begging calls of wild tawny owlets any more, and it is years since I heard a youngster around my own home at Eskmeals. Adults are certainly still around in the general countryside and I know Sue our Conservation Officer ringed one owlet at Muncaster in June, but sadly it was found dead some weeks later, and despite hearing the territorial hoots of several pairs earlier on, that seems to have been it when it comes to successful breeding. As I have said, I am worried, especially since many of our nest boxes are not being used despite being located in what ostensibly appears to be ideal habitat. On my own ‘patch’ I could normally hear at least three territorial males calling against each other from their regular territories, but in spring 2007 just a single pair briefly visited our garden on three nights, while a single bird arrived for one night in November and again in December – and that was it. The nights remain silent!

Tawny Owlet
Tawny Owlet
Photo © Ian McGuire -

The reason I am worried about all this is that it is a well known fact that tawny owls often fail to breed at all when prey is scarce, and even if they do, only a single youngster or a complete failure results. I am sure many of you watched ‘Springwatch’ on TV this year (presented by our patron Bill Oddie of course!). If you did, you will know that of three tawny owlets filmed in their nest box, one youngster did not make it despite the box being located on a wonderful farm in Devon, and not in sheep-grazed (or should I say ‘razed’?) S/W Cumbria. And when the normally hugely optimistic Chris Sperring, the Hawk & Owl Trust’s Conservation Officer who works in the Mendips and Somerset Levels, also starts expressing concerns I really get worried, for he is usually guaranteed to raise my spirits by telling me his stomping grounds are teeming with voles and owls of all species. Not so in 2006 however, when many areas of Britain suffered one of the biggest vole crashes in recent record, with many owl fieldworkers voicing concerns.

Prior to this, in response to ever-increasing reports of owl declines the British Trust for Ornithology decided to carry out a national owl survey between August 15th – October 15th 2005, with fieldworkers visiting some 2,652 sites across the UK.

For tawny owls the results were reassuring. 63% of the surveyed areas held tawny owls – an almost identical figure to a similar survey carried out in 1989. Only in the English and Scottish uplands and Greater London were tawny owls scarce. A BTO spokesman stated “It is great news that they (tawny owls) are still to be found in most areas in which they were encountered in the previous survey. It may be that with more and more double-glazing in modern houses, we just aren’t hearing them as much as we used to”. Hmmm! Well at least this suggestion is different!!! However, I would urge you not to relax too soon. I certainly don’t walk around in a double-glazed cocoon, and nor I suspect does Chris Sperring or any of the other owl workers who had expressed similar concerns to my own!

At the risk of adding to my reputation as a boring, repetitious, grumpy old misery-guts, let me once again point out that it is not the ‘presence’ of birds which is most important – it is ‘how many surviving youngsters do they produce each year to replace adults which die in the winter months prior to the next breeding season’. Only if this figure equals – or preferably exceeds – mortality, can we breathe a little easier. And of course this applies to all wildlife species, not just owls. It’s not exactly rocket science, but alas, is a crucial point all too often ignored by researchers, especially the ringers who judge ‘success’ by the number of young birds ringed each year rather than the number which survive to join the breeding population the following spring. I would also remind you of the date of the BTO owl survey, i.e. 2005 – one of best owl breeding seasons for many a long year, but alas, the year before the disastrous 2006 ‘vole-crash’. What we now need to ask is “what actually happened in 2006, and what did 2007 bring”? Which brings me conveniently to barn owls!

Readers of these newsletters will need no reminding that I have long railed against the oft-quoted figure of 4,000 breeding pairs of barn owls still being present in the UK (the published results of the last ‘survey’ carried out in the late 1990’s, but which wasn’t in fact a true figure representing ‘actual’ successfully breeding pairs observed at ‘first-hand’). Nor will you need reminding that in our neck of the woods (S/W. Cumbria) breeding barn owl numbers are now but a mere shadow of the numbers present in the 1970’s – late 1990’s, and this is certainly not down to double-glazing!!! It is down to over-grazing and loss of habitat caused by drainage and increased silageing which have destroyed huge swathes of the rough tussocky grasslands needed by both barn owls and their main prey, the short-tailed vole. I know what I used to see and what I see now – and they are not the same – and this is the beautiful ‘wild’ Lake District! Pessimist and grumpy I may be, but blind I am not! I live only fifteen minutes drive from The Owl Centre, and on my way home at the end of the day in the late 1980’s – early 1990’s I could usually rely on seeing between 1 – 3 barn owls (and in the winter the occasional short-eared owl) either hunting in the fields or sitting on fence posts waiting for voles. Not now. Such a sight is a ‘red letter’ entry in my daily diary and a rare event at that. In a bid to keep my favourite species ‘ticking’ at Eskmeals, I have for many years supplementary fed barn owls which come into our garden on a nightly basis for hand-outs – but even with this help, for the past two years only single owlets have been reared by one pair in both 2005 and 2006. We awaited the outcome of 2007 with some trepidation, for although the owls still came in nightly, our searches of the nearby MOD land where this pair breeds (they originated from 4 captive-bred birds we released there in 1972), failed to reveal a breeding site and our nest boxes remained unused. The explanation is simple. Although Jenny and I have bought three small meadows and rent two more in an attempt to re-create good vole (and butterfly) habitat adjacent to our home, this is the first time in 42 years that I have searched suitable habitat for voles and have actually found no trace of them whatsoever! In other words, the voles haven’t recovered from their 2006 ‘crash’ and even with the aid of our ‘soup kitchen’ the birds were not finding enough food to bring them into breeding condition! What a state of affairs!

Now before I go any further, it is important to remember that to get an ‘overall’ view of how things are in Britain as a whole, we must be careful not to become too parochial – and let’s be honest, most of us tend to be just that when we are considering what is happening in the natural world. ‘Our patch’ (rightly) assumes huge importance but might not reflect what is actually happening on a national scale, and I am as guilty as the next man (or woman) in this! So - is the rather miserable picture I am painting only pertinent to S/W. Cumbria? Our North Cumbrian colleagues would certainly say “yes”, for they are forever telling me that I am talking rubbish and that their own nest-box scheme is very successful, and as I have said, Chris Sperring is usually guaranteed to give us good news from the South-West, as is long-standing WOT member and good friend (and ‘twitcher extraordinaire’!) David Rutherford who lives in the barn owl heartland of Norfolk.

It is to answer this question that each year I eagerly await ‘Barn Owl Link’, the newsletter of the Barn Owl Conservation Network in which barn owl ‘guru’ Colin Shawyer invariably gives us a review of the year’s previous breeding season on a national scale. Very useful and sometimes a welcome salve to my own tales of woe!

Barn Owl Tyto alba alba
Barn Owl Tyto alba alba
Photo © Ian McGuire -

Frustratingly, with rumours that in contrast to the record year of 2005, 2006 had been disastrous in many counties, the report was a little late in appearing. But at last it arrived – and as expected, it contained worrying news. Even my old mate Chris reported that for both tawny and barn owls “an over-winter prey shortage had left many adults in poor condition with the result that breeding was at an all time low. As predicted, when food is scarce the marginal pairs seemed to disappear”. However, don’t despair yet, Chris went on to report that “some barn owl pairs made a recovery late in the season and hatched eggs in September, and this upturn, alongside good tawny owl signs this spring gives a promising outlook for 2007”.

In line with this news, Colin Shawyer confirmed that in 2006 many adult female barn owls had been in too poor a condition to lay eggs due to a predicted ‘vole crash’ and the males having to turn to the much smaller common shrew as alternative prey. He went on to say that there had been unusually high levels of owlet mortality, not helped by the wet and cold weather at a crucial time in their development. Nor was it only the owlets which suffered. There were also more adult deaths than normal, especially males at, or near to the nest site. These individuals had apparently succumbed in their vain attempts to bring sufficient food to the brooding females and owlets.

Even the stronghold of Norfolk suffered in 2006, with the North-West Norfolk Ringing Group only ringing about 120 owlets compared with a phenomenal 500 + in 2005. Mind you, we would have been deliriously happy with 120!!! Fortunately, the Norfolk Group remained upbeat, saying that while 2006 certainly wasn’t a good year, it wasn’t disastrous. For example the Hawk & Owl Trust’s fabulous Sculthorpe Moor Reserve (where the habitat is perfect) had two pairs of breeding barn owls which reared 3 and 4 young respectively, with one pair even managing to rear a second brood! Such are the vagaries of barn owl breeding biology!

In neighbouring Lincolnshire too there were differences between locations (akin to Cumbria) with the west of this very large county suffering more than elsewhere. Lincolnshire ‘owl wizard’ Bob Sheppard pointed out that there is a wide variety of prey species in the central grasslands, which means that barn owls are not as reliant on short-tailed voles as they are in most other areas (including Cumbria). Indeed, an early start of 5 barn owl pairs incubating eggs in late March had Bob optimistic for the 2007 season, and evidently things were also looking good in North Oxfordshire, so fingers crossed.

Good news in 2006 also came from Jersey with 60% nest box occupation and 20% + sites successful. In the Galloway Forest area pairs had a late start (mean first egg date 20th May), but with 25 out of 33 monitored sites occupied, and good clutch sizes (mean 5.57 eggs), everyone was happy. In the end 18 sites fledged 54 owlets (average 3 per site), with only 2 certain failures and one unknown result. The other 2006 ‘good news’ areas tended to be in the North, Midlands, and eastern and southern parts of England.

Conversely there was a major shock amongst the ‘bad news’ areas, i.e. most of western England and parts of Scotland and Wales. I have often mentioned the fantastic success of Major Nigel Lewis’s nest box scheme on the Ministry of Defence’s Salisbury Plain Training Area and the Larkhill & Westdown Ranges in Wiltshire, run by the Imber Conservation Group. So successful in fact that it is now possibly the best population of barn owls in the whole of Britain – and this from a starting base of just a single breeding pair in 1987 when Nigel began his campaign to increase the Wiltshire population! Ten years later this figure had risen to no less than 78 pairs in 1997, followed by the following sequence for South Wiltshire : - 1998 – 72 pairs; 1999 – 101; 2000 – 140; 2001 -132; 2002 153; 2003 -166; 2004 – 163; 2005 – 210 (yes, 210!!!); then almost halving to 109 in 2006. On Salisbury Plain itself, the number of breeding pairs was 37, 35, 45, 66, 70, 64, 73, 51, 69 and 26 for the same years, and these reared 87, 51, 151, 140, 144, 130, 178, 83, 231, and 36 owlets respectively. Hence the shock – a drop of almost 200 owlets in 2006! Indeed, Nigel commenced his report with the words “Welcome to the 2006 report (our 23rd) which was the worst year we have had since we started the nest box project! The main reason was the crash of the short-tailed field vole population. This happens every third or fourth year (not reflected in the figures shown above (TW)) and as the vole is the main food source of most owls and kestrels the effect can be serious, but combined as it was with several weeks of freezing weather in late winter the effect was catastrophic”. He went on to describe how the owls were in ‘survival mode’, desperately hunting for food rather than getting into ‘breeding mode’ by consolidating their positions at nesting sites. Some of them were even falling prey to ravenous buzzards which were also in trouble due to the vole crash.

When I tell you that in 2005 Nigel and his team actually ringed an unbelievable total of 671 owlets, while in 2006 they only had 60 to ring, you might well think that he would throw up his hands in disgust and take up golf or something. Not a bit of it. This remarkable man remained amazingly upbeat about the whole situation! He pointed out that “with a minimum of 109 pairs still resident in South Wiltshire (50 on the Training Area) and with an estimated 46 singleton ‘floaters’, there should be enough to cover winter losses and form the bedrock for a good 2007 season”. Colin Shawyer too was equally upbeat when he wrote his report in Spring 2007. Like Nigel he was somewhat scathing about reports in the national press that UK barn owls had experienced a catastrophic decline from 4,000 pairs to just 1,000. In actual fact, this had not been claimed and was down to a typical misquote by the press who had failed to differentiate between a statement by a barn owl organization that ‘possibly as low as only 1,000 pairs might have bred successfully in 2006’ and the totally different ‘possibly only 1,000 breeding pairs now remained’! Colin stated that he and two colleagues had in fact recorded the ‘presence’ of 1,000 breeding pairs of barn owls in just three counties, but didn’t go on to say which counties these were or whether they succeeded in rearing any young (i.e. bred successfully) – which as I have stressed, is the most important factor and the point being made by the barn owl organization.

Also, with due deference to his undoubted expertise in ‘things barn owl’, I am afraid I have to differ from Colin is in his assertion that “the breeding population of barn owls in Britain, although still vulnerable, has not declined overall in the last 20 years and is at the very least stable at 4,000 pairs – the computer generated figure I mentioned earlier. He goes further by stating that most conservationists actively involved in helping the barn owl in Britain have reported a steady increase since the 1990’s and that a figure of 5,000 breeding pairs is now probably a more realistic estimate. I hope he is right, but I’m afraid I still have my doubts that the long term future of this most charismatic of species is assured.

Both Colin and Nigel stressed that short-term fluctuations in the number of young reared, and the absence of adults from their traditional nest sites in some years is a totally natural characteristic feature of the breeding biology of barn owls caused by the regular and predictable changes in the number of field voles, which like Scandinavian and Arctic lemmings, show’ boom and bust’ (aka ‘plague and crash’) fluctuations in population every third or fourth year. However, what really raised my eyebrows was the claim that because these patterns have been recorded for almost 100 years, they were able to predict that 2006 would be a poor breeding year and that 2009 will be the next poor year with 2007 and 2008 being better ones. The problem here is that such fluctuations do not happen on a national scale – they are usually localised, may not even happen at all, or else are brought about by climatic factors such as was certainly the case in 2006 – which did affect many areas of the country including Cumbria. In theory, having ‘crashed’ that year, our vole population should have started to increase again Spring 2007, especially in the balmy month of April which was glorious. They didn’t, and as I have said, for the first time in my life I couldn’t find any evidence of their presence even in perfect habitat. Old age and failing faculties? Maybe, but I don’t think so. They simply weren’t there, having been totally wiped out by flooding and sodden ground during the 2006/7 winter – a scenario which continued throughout May, June, July and mid-August. As I write (New Year’s Day 2008) our own local ‘grassland’ more resembles the Okavango Swamp than barn owl habitat and it doesn’t take a genius to work out what has happened to the vole population which dwelled there! We’ll see what 2008 brings.

Colin also refutes the claim that the absence of breeding pairs at traditional nest sites indicates a massive population crash, stating that this is totally normal behaviour in a poor food availability year due to the birds being unable to achieve breeding condition. In his studies he has evidently found that around three quarters of Britain’s 4,000 (!!!) barn owl pairs do not occupy their breeding sites all year round. If they do not reach breeding condition they simply spend the year roosting nearby, eventually returning to breed successfully the following year. I truly hope this is currently the case, but would ask the pertinent question “If this is what is happening, why don’t we see them still searching for prey in their favoured hunting territories? They still have to eat, so where better than their familiar breeding territory where they know the best prey-rich areas, and where better to roost than in their cosy nest sites with no boisterous kids to pester them! Incidentally, nowadays barn owls invariably nest in man-made boxes – which begs a further question “what will happen if barn owl nest box schemes eventually go out of fashion? How many ‘natural’ sites are actually left?”). These are the long-term points we have to consider, not short-term ‘fixes’.

Another important point I need to raise is the fact that in 2006 Nigel Lewis’s average brood size was just 1.38, a far cry from the necessary 3.2 – 3.5 to maintain/increase the overall population (Iain Taylor 1994). Nigel reported that tawny owls and kestrels were also affected, but little owls fared better since they are not so vole dependent, and of course earthworms, a favourite food of little owls, become more easily available in wet weather. I suspect that such was the case in many other areas.

So, at the end of this marathon, we are left with the question I have used as the title for my article – “is the glass half full or half empty”? Only time will tell, but I leave you with several things to ponder. Was 2006 an entirely predictable cyclic ‘crash’ year for voles, and consequently owls, or was it yet another example of the ‘miner’s canary’ telling us we are in trouble due to global warming causing erratic changes in weather, often severe. Certainly here in West Cumbria it was the latter.

In 2007, after initial euphoria from some owl workers that there were signs of hope for a recovery when some pairs began to nest very early in the glorious weather of April, we had a May which was wetter than normal, followed by a ‘write-off’ summer which was the wettest on record with disastrous floods in Yorkshire, Humberside, Lincolnshire and East Anglia (remember the two latter were ‘good news’ areas in 2006). Conditions in these areas don’t bear thinking about, and if any of our members were victims of these disasters, do please accept the sympathy of all of us at the WOT, we cannot begin to appreciate what you went through and many are still going through. To talk about owls and voles in such circumstances is almost obscene, but I do have to ask you to consider the all-important question – “what happened to the voles, other small mammals and owls in those areas. Even if barn owls have bred successfully in some areas in 2007, what chance have the youngsters got of surviving until next season? The forecasters are predicting more months of rain, violent thunderstorms, tornados, snow, freezing conditions and yet more flooding. Although here in S/W Cumbria we did have some successes, we also had failed barn owl broods and ‘unsaveable’ adult barn owls brought in starving, one weighing just 185 grams (normal healthy weight 310 – 320 grams! Now comes a further worry. The government of Gordon Brown has announced its intentions to build an extra three million homes by 2020, with the number of new properties rising from 185,000 annually to 240,000, some of which, unbelievably, are still to be built on known floodplains! Planning restriction are also to be removed to encourage more development on Green Belt land – including hitherto protected areas such as SSSI’s, nature reserves and ancient woodlands, and even large gardens and allotments etc. are to be re-classed as ‘Brown Field Sites’ subject to Compulsory Purchase Orders to enable them to be built on! Nor will we be able to demand a Public Enquiry into inappropriate Planning Applications. Such decisions will now be made by so-called ‘independent committees’ – and if you believe that you no doubt also believe in fairies! In other words, our once ‘green and pleasant land’ is about to become covered almost entirely in concrete and red brick and transformed into a mass of soulless developments and urban sprawl. Yet we are already one of the most overcrowded countries in Europe and this latest threat strikes me as being an almost fatal blow to the future of what biodiversity we have left – including owls, especially ‘specialist’ owls like the barn owl. (Do I feel another petition coming on?).

However, having made you all thoroughly miserable, I am instructed by Office Manager Jenny Lewin (she’s been on a Course!) that I have to leave you happy, so let me try to put a smile back on your faces by telling you that the BTO report that according to their Nest Record Scheme, in many areas tawny owl, kestrel and barn owl actually ended up having a productive season in 2007 – thanks to a bumper vole harvest!!! Also, Sue Thurley our hard-working Conservation Officer did find some barn owlets to ring this year, and will no doubt be giving you an update on the 2007 season in West Cumbria in due course. On her behalf, and in the light of the above, do please get in touch with her at the office on 01229 717393 or by E-mail here to report how your barn owls and voles fared in 2007 – we really need to know. Such information is vital in the present circumstances – and let me tell you that if you wish to confirm that I truly am a ‘Job’s Comforter’/ ‘grumpy old man’ and all is well, I will be the happiest man on earth to be proved wrong! Here’s to a good 2008!

Tony Warburton

Ref. Taylor, I. (1994). BARN OWLS: Predator-Prey relationships and conservation. Cambridge University Press

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