Eagle Owl- Swedish Findings Proves Crossing Large Bodies of Open Water no Problem.

[singlepic id=174 w=250 h=152 float=left]The Eagle Owl debate continues with new and exciting information coming to light all the time. There has always been a presumption on the part of some individuals (experts) in the UK that eagle owl for some inexplicable reason will not cross large bodies of water. We at Raptor Politics have always regarding this statement as conjecture, rather than based upon any scientific evidence, and such a presumption does seem to be at odd with what we already know about this species.

It is a well known fact that after leaving their nest as fledglings, first year eagle owls are known to migrate hundreds of kilometres form where they were reared. One of the three eagle owl chicks from the 2007 nest in Lancashire’s Forest of Bowland was later recovered dead just below Edinburgh after flying well over 150 kilometres from its natal nest site. There is compelling evidence from the Alps which shows tagged eagle owls have crossed this mountainous region flying up to 300 kilometres. So the idea that eagle owls would never cross large bodies of water like lakes or across the North Sea is difficult to understand or accept.

Observations by Alar Broberg a member of the Swedish Eagle Owl Study Group pointed out in 2008 that based upon his studies in Sweden eagle owls have no problem crossing large open bodies of water and he finds claims made by UK “experts” as very odd indeed. Alar Broberg says that after reintroducing eagle owls into Sweden where they had been almost eliminated by human persecution, eagle owls crossed the Baltic Sea from the Swedish mainland, possibly via the  island of Oland, a distance of approximately 46 Kilometres onto the small island of Gotland where there is now a thriving new population. So based upon the Swedish model, it now seems very probable that the so called UK “experts” may after all be wrong – eagle owls like most migrants would have no problem crossing the North Sea from Europe. 

The significant of this new information published in British Birds in September 2008 is the fact that it appears to have been disregarded in the findings of the FERA Risk Assessment. In fact we are unable to find any referrance to this important data anywhere in the Risk Assesment analysis. The question that now needs to be answered  is why? Much of the argument about whether or not the eagle owl was a alien non native species to the UK was based upon an expert opinion that eagle owls would NOT cross large bodies of water. Isn’t it interesting the very “experts” who were charged with undertaking the Risk Assessment have known since 2008 that this understanding was entirely false but said nothing.

The fact that Swedish ringed Eagle Owls have reached Gotland is mentioned on page 484 of the paper published in British Birds magazine in September 2008. It is available online here :- http://raptorpolitics.org.uk/wp-content/uploads/2010/11/The-Eagle-Owl-in-Britain1.pdf

Gotland Island in the Middle of the Baltic Sea  

29 comments to Eagle Owl- Swedish Findings Proves Crossing Large Bodies of Open Water no Problem.

  • daniel

    Oh dear,that’s the end to the debate then! is it not?

    No one could now can argue all eagle owls in the UK are all either released birds or directly related to them.

    This Swedish evidence should now provide the owls with complete protection under european law if common sense prevails.

  • Paul Doherty

    I have to point out that this news isn’t exactly “new and exciting”. The fact that Swedish ringed Eagle Owls have reached Gotland is mentioned on page 484 of the paper published in British Birds magazine in September 2008. It is available online here :-

    http://thebritishlist.blogspot.com/2010/07/eagle-owls-in-britain.html

    I think mentioning the distance travelled as being over 100 kms is potentially misleading. Any Eagle Owls flying to Gotland are likely to travel via Oland which reduces the over water distance to about 46 kms.

    I must also challenge the statement that “It is a well known fact that after leaving their nest as fledglings, first year eagle owls are known to migrate hundreds of kilometres form (sic) where they were reared.”

    Young Eagle Owls do indeed disperse from their natal area (it would be surprising if they didn’t), but neither they nor the adults are migratory. Nor indeed are they nomadic or irruptive in the style of other European owls such as the Hawk Owl.

    Recent ringing information from 8 European countries and involving 957 ringing recoveries showed an average distance travelled of 57 kms which confirms that the Eagle Owl is indeed one of the more sedentary European owls.

    I can supply further evidence (not conjecture) which supports the idea that Eagle Owls are reluctant to cross large bodies of water, but in the interests of brevity I will leave it at that for now.

    • admin

      Hi Paul,

      Many thanks for this important information, we have now amended the distance based upon your advice and have added the link to the paper you so kindly provided.

      At least this research, not referred to in the FERA Rist Assesment, does prove eagle owls do cross large bodies of water. 46 Km is 29 miles, Raptor Politics would class this distance as important to this on going debate.

  • skydancer

    The RSPB and NE will come up with their own ideas on this and will probably dismiss it anyway as they are determined to cull these birds despite this compelling evidence.

  • E. Felton

    I’m afraid I can’t help but agree with skydancer. The facts and figures don’t mean a great deal if a species is not welcome in any given environment.

  • admin

    Raptor Politics has been asked by a reader of this web site to add his comment below. We have kept his identity confidential.

    Dear Sir, I have just read with interest your correspondence with Richard Benyon MP (Raptor Politics Website).

    I must say it makes interesting reading not too good for such a majestic bird as the eagle owl. Politicians never answer a straight question do they and I am really surprised by their lack of knowledge on UK Law. The Wildlife and Countryside Act 1981 does not transpose the EC bird directive into English Law. They are two seperate entities.

    Certain sections of W & C Act are used to implement Birds Directive whilst other sections are implemented by Conservation(Natural Habitats & c.)Regulations 2010 (as ammended). On the whole European Law supercedes British Law.

    As you say the eagle Owl is protected in EU member states by the Birds Directive so why should it be different here.

    No one comments about the provenance of other legally reintroduced species i.e. red kites from spain and sea eagles from Norway all of which arrived on planes (Dont get me wrong I am not complaining about these species and I am a firm supporter of reintroductions) we also dont call for a cull of goshawks which ‘probably’ originate from captive stock for the majority of the UK.

    My personal view is that the government are under extreme pressure from the shooting fraternity to outlaw the eagle owl –
    I also have a view that whilst I admit it is a predator of a large number of species of birds it also eats foxes etc that could potentially pose a threat to ground nesting birds like the harrier hence they do well in Bowland.

    David xxxxxxxxxxx

  • John Miles

    With so many species now giving the BOU the run around there is no surprise that the BOU are helping the shooting estates on this one. The case of the Middle spotted Woodpecker has shown that the experts can no longer predict which species may turn up in the UK. The Dutch birders are now predicting that this could be the next species to come to the UK when one turned up on an island [not supposed to cross water!!] this year the same distance from Calais to Dover.

  • Thank you David for your comments which I agree with wholeheartedly the government will side with who ever lines their pockets and without a doubt these are landowners and the shooting fraternity. As for the BOU, The BTO and Natural England they will sit on their backsides and while we are searching for any evidence to help the Eagle Owl, and in fact doing their jobs for them, they will be hoping that no proof is forthcoming because they do not want the EO here and also if we do find proof they will all look very stupid and have to admit their errors which will not sit well with any of them.

    It is a good job that there are dedicated people out there with a love for these owls who are prepared to stand up and be counted in their quest to stop these organisations getting rid of such a magnificent bird that is doing little harm, If any and as you say is more British than the Red Kites and Sea Eagles that are being reintroduced into this country. The Sea Eagle is a magnificent bird but I am of a mind to think it could do far more damage than any Eagle Owl ever will.

  • DEAN

    Good morning,

    I’ve missed some of this debate over the various threads but seem to recall the RSPB had on this site, made it quite clear that they did not support an EO cull. Has their position changed?

    @David,I think the point that was being made was that there was no compelling evidence that EO’s had ever existed here and that therefore differentiated them from reintroduced species. Apologies but I can’t understand the point you are trying to make in your last sentence can you explain further?

  • Paul,

    Forget -“in the interests of brevity”. Brevity doesn’t come into it (as I continually prove!) If you have ‘firm evidence'(sic)that Eagle Owls “are reluctant to cross large water bodies” then it is incumbent on you to provide that evidence – but please do not simply quote from the paper you co-authored with Melling abd Dudley in 2008 – this is full of ‘conjecture’ on your parts (and, yes, I can quote examples if you wish!). What we are after are first-hand observations of Eagle Owls being faced with a large body of water and saying to itself “whoops, I’m not flying over that” and turning back. At the same time, if you are so set against ‘conjecture’ please tell us how you are so sure that all the Eagle Owls now on Gotland ‘are likely’ to have travelled via Oland. Is this because Alar Broburg mentioned it, or do you again have ‘firm evidence’ to prove that your comment too is not ‘conjecture’? Even if they did go via Oland, do you not consider 46km of the Baltic ‘a large body of water’? If “no”, then do please enlighten us as to what you consider does qualify for this description. Did you see the powerful 100ft+ high flight of one of this year’s Bowland owlets on ‘Countryfile’ last Sunday? If you did, do you still consider this species incapable of crossing the North Sea?

    Finally, let me quote from an old 1952 book about the Eagle Owl in Sweden ‘Eyes in the Night’ by Bengt Berg who studied the Eagle Owls nesting on the various islands off the Swedish mainland. There are many such islands off the east coast of Sweden which in the 1950’s, some of which evidently still held breeding Eagle Owls (to quote Berg “Of course I had heard the Eagle Owls calling from the island forests during the first cool weeks of April”), and these are true islands in the sense of being surrounded by water! He records one particular male visiting an island where a pair of White-tailed Sea Eagles bred, then crossing back over the water to return to its own island where it had a mate on eggs – on an island which Berg describes as “a long way off” (p.28).

    I look forward to reading your response.

    Tony Warburton

  • Andy

    DEAN

    Don’t think the RSPB’s position has changed. Their official position has never been as anti as the BOU or Natural England, but they do seem to talk negatively about the presence of EO’s. Possibly by saying they are not in favour of a cull might still mean that they want to remove them, just that they would favour capturing rather than shooting?

    Does anyone know when a decision is due? If as suspected the decision was made to cull them before the risk assessment was even started, why the delay?

    Is it because they are worried it will be a PR disaster or in these times of cost cuts do they not have the money?

  • More like the former Dean.

    Tony Warburton

  • Re.the confidential letter received yesterday, could any of Natural England, RSPB (Mark Avery???) or the BTO answer this one once and for all. Are we correct or wrong about thinking the EU Laws supersede the UK W.& amp; C. Act? If the former is correct, then it means our Minister for the Environment doesn’t know the laws – and he’s the one making the final decision! If the latter, we should be even more worried.

    Tony Warburton

  • John Miles

    In the Cumberland News this week one of the headlines ‘EU law threatens free entry to the museum for city residents’. The complaint being that any one outside Carlisle should also have free entry! This goes against the British Government and how it uses its Bird laws. All birds are protected in the breeding season under EU law. But in the UK that does not apply as so called vermin like Carrion Crow, Jays, Magpies and many others can be killed if thought to be doing damage. Therefore when it comes to WANT to bide by EU law it has not to upset the shooting estates!!!

  • paul williams

    Why not designate the whole of the Forest of Bowland into a National Park for the people and for wildlife, and take it away from those who are hell bent on destroying our National Heritage for their own pleasure?

  • Hi All. Sorry to be a kill joy. But this is important. Almost word for word you have lifted Alar Brobergs comments from my facebook account. I must point out it his comment and not research. If others get hold of the fact you have said research when its comment it won’t do the EEO UK cause any good at all. Might be a good idea to remove it quickly. If you want to approach Swedish workers themselves then fine, but please let me know in future prior if you want to use my facebook postings from my friends in EU.

    I’m with you all and supporting you all in many different ways as Tony Warburton knows well.

    Best wishes

    Chris

    • admin

      Hi Chris thanks for your update on this very important subject.

      Are you saying that what the Swedish Raptor Worker reported is not true, or are you saying the fact that at last someone has proved eagle owls can and do cross large bodies of water is embarrassing? After adding the post Raptor Politics was able to confirm the information used had already been enclosed in a Scientific Journal published by British Birds in September 2008 and was in our view therefore research.

      The important point Raptor Politics was trying to make was for some strange reason this very significant research was not highlighted within the FERA Risk Assessment.

      If Scientists like Alar Broberg are saying he finds claims made by UK eagle owl “experts” as very odd, this is very significant. Alar Broberg is a raptor worker with extensive first hand knowledge of eagle owls in Sweden. The fact that his findings/research prove eagle owls have no problem crossing large bodies of water appears to undermine claims to the contrary which have been made by so called British experts.

      One last thought, if any eagle owl from the continent had already arrived in the UK unknown to anyone, European Scientists like Alar Broberg would not be too happy to learn that these birds, possibly even from Sweden, had then been culled in the UK along with all the rest.

    • I was under the impression that the Forest of Bowlsnd was already declared, or is at least a ‘candidate’, SPA (Special PROTECTION Area) for Hen Harriers. In addition I believe much of the area is SSSI but I’m not sure what the criteria for declaration were but whatever there is plenty of legal ‘protection’ for the land, its habitats and their wildlife. Those who own/manage it should be accountable for any actions they or their staff do to the land/habitats/wildlfe that are illegal, the same as you or I would if we, or our business, would if we were to break any laws.

      • admin

        You are correct the Forest of Bowland is designated as a Special Protected Area (SPA) and SSSI. Unfortunately this has so far failed to halt the decline of the hen harrier in this area. Under the SPA designation, moorland habitat within Bowland should be managed with a due regard for the many protected species of wildlife that share this upland region, including hen harriers.

        There have been far too many instances where shooting estates have made successful applications to English Nature, now Natural England for approval to install shooting tracks which for some curious reason have been allowed to cross prime hen harrier breeding habitats, net result no more hen harriers within these locations. On several of the region’s shooting estates peregrine eyries have also been adversly affected by poor estate management planning; for instance installing boundary fences alongside a ground nesting peregrine site on the day the four eggs began to hatch. The gamekeeper of course claimed he knew nothing about any peregrine nest in that location while forgetting to mention he visited the same location every 24 hours to check his vermin traps.

  • Re.the confidential letter received yesterday, could any of Natural England, RSPB (Mark Avery???) or the BTO answer this one once and for all. Are we correct or wrong about thinking the EU Laws supersede the UK W.& C. Act? If the former is correct, then it means our Minister for the Environment doesn’t know the laws – and he’s the one making the final decision! If the latter, we should be even more worried.

    Tony Warburton

  • Having failed to get any reply to my query of November 12 I have spent today delving through the wording of the EU Birds Directive and the UK Wildlife & Countryside Act 1981 and I am sorry to say that it would appear that Richard Benyon is correct. The W & C Act does indeed transpose the EU Birds Directive, and Section 16 of the UK Act does provide powers to derogate from the set protections if a licence is issued by the appropriate authority (DEFRA of Natural England?) for a variety of reasons – including bird protection. You will now understand why the ‘anti- Eagle Owl’ lobby has attempted to make such play on the surmised threat of Eagle Owl presence on breeding Hen Harriers. Keep your powder dry!

  • paul williams

    LALOWS, You are correct, land owners and their staff should be made accountable for their illegal persecution of all birds of prey, all wildlife and their habitat, however, when Natural England personnel (STEVE MURPHY) openly admitted to having tea and biscuits with private estate gamekeepers. Is it any wonder why there is only one Hen Harrier nest site on the vastness of private estates making up the Forest of Bowland outside those few pairs allowed to breed on the United Utilities estate, just 5 pairs this year. It is obvious to me the dialogue Natural England are using is not working.

  • John Miles

    Can some one please explain how one law applied to UK citizens is EU law, while another is British law? See my last post.

    If the people of Carlisle no longer have the right to free access to their museum, which they are paying for via their council tax because EU law claims they can not, how the hell can birds which migrate from one European country to another European country be held under a law which is only for one particular European country!!

    It would also give Malta or any other European country the free right to make their own bird laws so they can kill birds regardless of European law. No wonder that this country is run by crooks making their own laws.

  • Paul Doherty

    Tony

    Thanks for the comments. Firstly I suspect we may have to agree to disagree if you regard “first-hand observations of Eagle Owls being faced with a large body of water and saying to itself “whoops, I’m not flying over that”” as firm evidence, because it seems to me that would be anecdotal evidence.

    When looking for evidence I was thinking more in terms of :-

    Ringing recoveries
    Radio and satellite tracking
    Records from islands where Eagle Owls aren’t normally seen

    Ringing recoveries

    Earlier this year I contacted the ringing offices of the eleven countries closest to the UK and asked for up to date ringing information on Eagle Owls. To date seven have replied. I specifically asked for ringing recoveries which demonstrated or suggested the birds had crossed large bodies of water. None of the seven had a single record suggestive of this to add to the small number listed in the 2008 Melling et al paper.

    Information received prompted me to list both the average and the maximum distances moved by European owls as revealed by ringing recoveries

    Ranking from most sedentary to most migratory (data primarily from BWP).

    Based on average distance moved by ringed birds

    Tawny Owl – 15 km
    Little Owl – 15 km
    Ural Owl – 30 km
    Eagle Owl – 57 km
    Great Grey Owl – 100 km
    Barn Owl – 110 km
    Pygmy Owl – 150 km
    Tengmalm’s Owl – irruptive movements of over 1000 km noted
    Snowy Owl – 830 km
    Hawk Owl – few figures, but recoveries are long distance (eg Sweden to Russia). One moved 1860 km.
    Long-eared Owl – Migratory in parts of its range with movements of over 2000 km recorded.
    Short-eared Owl – Migratory and nomadic. One movement of 3345 km.
    Scops Owl – Few figures, but wholly or partially migratory and eastern birds travel 7000–8000 km to their wintering areas.

    Based on longest recorded movement

    Ural Owl – 200 km
    Pygmy Owl – 300 km
    Great Grey Owl – 490 km
    Eagle Owl – 528 km
    Little Owl – 600 km
    Tawny Owl – 745 km
    Tengmalm’s Owl – 1350 km
    Snowy Owl – 1380 km
    Barn Owl – 1650 km
    Hawk Owl – 1860 km
    Long-eared Owl – 2300 km
    Short-eared Owl – 3345 km
    Scops Owl – 7000 km

    As you can see whichever way you measure it the Eagle Owl comes out as one of the more sedentary European owls. I know some people look at these sort of figures and say that if Eagle Owls can do 528 km overland then the shortest part of the North Sea won’t be a problem for them. The obvious counter argument is that a Tawny Owl has done 745 km overland, but Tawny Owls have never even occurred in Ireland never mind colonised it and there is general agreement that is because the relatively modest 20 km crossing of the Irish Sea is too much for them.

    Sweden to Denmark ringing recoveries

    Up to the end of 2008 the Swedes had ringed 8282 Eagle Owls and had 2285 recoveries. Not one had made the sea crossing to Denmark despite it being less than 20 km at several places (and at one point it’s only 4 km). Of course that does not prove that no Swedish Eagle Owl has ever crossed to Denmark, but it does surely indicate that even a short crossing can be a barrier to them. Nor did any of the 46 ringing recoveries from the Danish ringing scheme involve an Eagle Owl making a sea crossing to Sweden.

    Radio and satellite tracking

    None of the information I have seen from radio and satellite tracking in France, Holland, Italy, Spain, Sweden and Switzerland includes any evidence indicative of crossing large bodies of water.

    Records from islands where Eagle Owls aren’t normally seen

    I haven’t been able to find any records of Eagle Owls on islands where they aren’t normally seen. However my research did lead me to Gatkes book, The Birds of Helgoland. This was published in 1895 and describes the results of over 50 years observations. The totals Gatke recorded were:-

    Tawny Owl 1
    Little Owl 1
    Tengmalm’s Owl 30
    Long-eared Owl well known, up to 4 in a day in autumn.
    Short-eared Owl common migrant in spring, very common in autumn.
    Scops Owl 1
    Snowy Owl 1
    Hawk Owl 1
    Eagle Owl 0

    In over 50 years on an island noted for its migratory birds and just 40 km off the German coast he recorded a host of rare birds, but not a single Eagle Owl. Helgoland now has a bird observatory, but over 100 years since Gatke’s book Eagle Owl still hasn’t occurred on Helgoland.

    In fact the owl numbers Gatke recorded are entirely compatible with the information from more recent ringing recoveries as detailed above. These (and other studies) confirm that Eagle Owls are not migratory, irruptive or nomadic. They do of course disperse, as all animals do (they’d suffer terribly through in-breeding if they didn’t) but the average distance is a relatively modest 57 km.

    Please note that we have never said that Eagle Owls do not/will not cross water. I agree that 46 km is a large body of water, but the lack of over-water recoveries from anywhere other than Gotland surely indicates that the Gotland record can’t be taken as typical.

    Even at its narrowest point the North Sea is significantly wider (150 km in fact). The Channel is narrower (only 35 km), but there are no breeding Eagle Owls in Northern France, and the Channel has certainly proved to be a significant barrier to the Little Owl (and Crested Lark and various other species).

    It’s a combination of all this information which leads to my belief that the Gotland Eagle Owl travelled via Oland. It’s a much safer and easier route than travelling twice that distance over the sea.

    With regard to the information in the book by Bengt Berg then I think you have to accept that “a long way off” is a bit vague. Does he mean 5, 10, 25, 50 km? It would be interesting to know which islands are involved, as the overwhelming majority of Swedish (and Norwegian) islands are within a few kilometres of the mainland or another island.

    I genuinely don’t have an axe to grind and if new or overlooked evidence becomes available and shows that Eagle Owls are happy to cross large bodies of water then that’s fine by me. However there are thousands of ringing recoveries spanning over fifty years and it seems unwise to ignore or discount them. Certainly they seem to me to be a more reliable, more objective measure than the TV clip you find so convincing, and I cannot accept that a single, brief TV clip of an Eagle Owl flying across a valley is persuasive evidence that they are willing to fly across the North Sea.

    Incidentally I can’t find anything about Eagle Owls on Countryfile on Sunday 7th November and I assume you’re actually referring to the item on The One Show on BBC1 on Monday 8th November (and as noted above I have seen that).

  • John Miles

    I think it is clear that Britain is now facing its worst crisis in Bird laws. If this Eagle Owl cull goes ahead every raptor on a shooting estate no longer has any protection as the same old story will be told ‘we are protecting our stock just as you were when you killed the Eagle Owl’. Not only that other European countries will be free to shoot what they want when they want as well.

  • Andy

    Agree with that John. I’ve debated this issue at great length and in some ways I can see the argument for removing them as regardless of the possibilities of some birds arriving naturally, the population is from escaped birds.

    BUT in a real world situation rather than a textbook one, the negative effects of a cull will be far greater than even the worst-case-scenario potential negative effects of eagle owls. For this reason it makes sense to just accept that although they probably derive from escaped stock, they are basically European birds so lets protect them and accept that they are a part of our fauna – just as we did for Goshawks, which also probably (re)colonised from escaped stock, which no-one cares about now.

    The arguments of people like Steve Dudley at the BOU are sound arguments from an ecological point of view, but their weakness is that they are unable to seperate the textbook from the real world.

    • admin

      Beginning in the early 1960’s members of the British Falconers Club, unofficially, began an unapproved scheme to reintroduce the goshawk in large numbers back into England, and possibly even parts of Wales. Since that time many more have been lost having been imported from Germany, Holland, Finland, Sweden, Norway, Russia and the Czech Republic to name but a few donor countries.

      We are also aware that as many as 12 imported goshawks from Czechoslovakia were lost by a single falconer in the Holmfirth region between 1959 – 1966. It is now accepted these birds began breeding in the late 1950’s in the Derwent valley Derbyshire, where their descendants are still located today.

  • Paul,

    Many thanks for your detailed reply. Much appreciated. You have obviously done a great deal of very useful research on this matter and I have every respect for you for this. Also I would like to thank you for putting your data in print for general viewing; this is exactly what is needed if we are to ever get a universally acceptable answer to this controversial subject and I hope others will follow your example rather than repeating unsubstantiated anecdotal comments such as “all records of Eagle Owls in Britain, either now or in the past, are believed (probably) to be escaped or deliberately released individuals or their progeny”.

    I hope you will agree that such a claim is unprovable one way or another. What we are all waiting for is firm proof of natural immigration, either from Fennoscandia or Europe (probaly Holland or Belgium). In the meantime the fact is, all owlets born in Britain, are classed as ‘wild’ no matter what the provenance of their parents is, proven or unproven. Can we at least agree on that one?

    To answer some of your specific points: –

    Ringing recoveries.

    While your data makes very interesting reading, the use of figures for non-migratory short winged woodland/forest-dwelling species (e.g. your reference to Tawny Owls not crossing over to Ireland)as comparisons with the powerful long-winged Eagle Owl is not really a valid exercise. This was the reason for my mention of the TV clip (and of course you are right, I did get my wires crossed – it was ‘The One Show’ and not ‘Countryfile’). Nevertheless, this ably demonstrated the gliding ability of the Eagle Owl and I don’t think you will ever live to see a Tawny Owl doing that! I wasn’t inferring that this footage proved that Eagle Owls are willing to fly across the North Sea. I was simply trying to convince you that they are certainly capable of doing so.

    Nor am I claiming the Eagle Owl is migratory/irruptive or nomadic. What I am claiming is that while many breeding pairs are undoubtedly largely sedentary, it has been shown that immature birds (i.e. <4 years old) are known to travel over large distances (100km – 200km+ – not the average 57 km you quote) before settling into their own breeding territories (Glutz & Bauer (1980); Mebs (1992); & Aebischer (2009)). I fully realise that these movements were recorded over land, but it surely puts to rest the trotted out claim that the Eagle Owl as a species is basically sedentary? Breeding pairs are; immatures are not.

    Heligoland.

    Sorry Paul, but the likelihood of an Eagle Owl landing up on Heligoland is unlikely in the extreme – and please note, the known irruptive/nomadic Snowy Owl (now recognised as another 'Bubo') was only recorded once on Heligoland by Gatke despite the figures you quote of average distance movements of 830 km and longest distances of 1380 km. Nor will you need me to remind you that Snowy Owls turn up in Britain with regularity nowadays – and cross large water bodies to do so!

    Similarly, the flat pastoral landscape of Denmark would be unlikely to pursuade an Eagle Owl to stay around for long, and unlike the flat Netherlands, so far as I am aware, Denmark does not have quarries to attract this species. Nor so far as I am aware are there any records of Snowy Owls arriving in Denmark, despite this country being well within its southern limits as a vagrant. So again my apologies Paul, I cannot accept this data as indicating that 'even a short crossing (of water) can be a barrier to them (Eagle Owls)'. Nobody is trying to claim that natural immigration of Eagle Owls via long sea crossings is 'typical' behaviour for this species, or even common. We are simply saying that it is perfectly feasible from time to time. It always puzzles me that no-one ever queries it when a Scops Owl turns up in someone's British garden, but this too is not 'typical' behaviour for this species. I really do believe there is a strong 'size-phobia' in the UK when it comes to Eagle Owls – and of course the media love to 'jazz up' this aspect. So we will just have to disagree on that one – but hey, what a dull world this would be if everybody agreed with each other! No doubt we will get some firm answers to all these disagreements one of these days.

    By the way, I had to smile at your comment "I haven't been able to find any records of Eagle Owls on islands where they aren't normally seen". I can name one – Britain! Or should I say "used to be not normally seen"!

    I'm afraid Bengt Berg didn't name any of the islands he referred to, the eastern Swedish archipelago has hundreds. But I am quite prepared to concede that "a long way off" is vague. I just wanted to stress that crossing over water didn't faze this particular bird, nor evidently birds resident on other islands.

    Being mischievous (and with tongue in cheek) – with regard to the Gotland record referring to a bird taking the Oland route because "it's a much safer and easier route than travelling twice the distance over the sea", I have to say that I wasn't aware that Eagle Owls possessed GPS's to plan their routes!!! Doesn't this represent 'conjecture' too?

    Anyway Paul, I honestly do appreciate the trouble you have taken to answer my posting in a thoroughly polite and professional manner. We do not agree on some points, but at least we can discuss our differences in a civil way.

  • Paul Doherty

    Tony

    Thanks for the prompt and helpful reply and apologies for the delay in replying, but I was away for a couple of days. Hopefully by discussing the points we disagree on we can both learn something, even if at the end of the day we may have to agree to disagree.

    Whether owlets born in the wild are “wild” birds is a legal question and I’m not much of a lawyer, so I’ll leave that for people more informed in that area to comment.

    For what it’s worth I started out thinking that the British Eagle Owls were probably wild birds, but having taken some video footage of the Bowland birds I did a bit of research and it soon became obvious that the British population didn’t have much to do with Continental immigrants, but a lot to do with escapes and illegal releases. Three years on and a fair bit of research later I’ve seen nothing to make me alter that view (just the reverse in fact).

    Specific Points :-

    One Show footage

    I really can’t see how a brief TV clip of an Eagle Owl flying across a valley is any use in understanding whether Eagle Owls are capable of making a long sea crossing. Are you genuinely saying that this clip is convincing evidence that they are “certainly capable of doing so”?

    Ringing Recoveries

    I don’t have copies of Glutz & Bauer (1980) or Mebs (1992), but information from both of them is included in BWP which I do have. The average (mean) distance between ringing site and recovery site I detailed of 57 km is entirely compatible with the information in Aebischer (2009). Here are two quotes from Aebischer (2009) :-

    “The area where young Eagle Owls first settled was, on average, 46 km from nest. Our results on settlement distances confirm previous ring recoveries.”

    “The maximum dispersal distance (distance between the nest and the furthermost roosting place that we were able to record) was, on average, 57.8 ± 27.7 km (12–105 km, n = 28 birds).
    The average settlement distance was 46.1 ± 31.9 km (range: 3–95 km, n = 18)”.

    Where I suspect the confusion arises is because Aebischer also says :-

    “The total distance (sum of night distances) covered by the birds which were tracked precisely during dispersal was, on average, 102 ± 66 km (range: 20–230 km, n = 13 birds).”

    As the maps on page 5 of Aebischer (2009) confirm, Eagle Owls dispersing from their natal area don’t move in a straight line (hardly surprising), so the “maximum dispersal distance” is significantly less than the “total distance (sum of night distances)”.

    In fact Aebischer’s average maximum dispersal distance of 57.8 km is uncannily similar to the figure of 57 kms I detailed.

    I don’t think you have any option but to accept the fact that the average (mean) recovery distance I detailed of 57 km is correct. On the list I compiled that places the Eagle Owl as the fourth most sedentary of the thirteen European owls listed (and that ranking is confirmed by the identical ranking for Eagle Owl if you rate them according to maximum distance moved (not average)).

    I should stress that I’m not saying they are completely sedentary and I’m happy to acknowledge that dispersing youngsters move further than territorial adults (but that’s true of most owls). However the evidence (not conjecture) shows that they are one of the more sedentary owls. If they were one of the more sedentary members of a highly migratory group, then it wouldn’t matter so much, as their vagrancy potential could still be quite high. But it’s widely acknowledged that Eagle Owls aren’t migratory, nomadic or irruptive, so their vagrancy potential is low.

    We can debate exactly how low their vagrancy potential is, but it is definitely low.

    Helgoland

    You’ve been quite definite that Eagle Owls from Scandinavia and the Low Countries could reach Britain, but you virtually dismiss the idea that one would occur on Helgoland.

    You say that Eagle Owls are “unlikely in the extreme” to make the 40 km crossing to Helgoland; if that is the case, then isn’t a minimum crossing of 350 km (Scandinavia) or 150 km (Low Countries) significantly less likely than “unlikely in the extreme” or have I missed something?

    Incidentally the fact that Gatke only recorded one Snowy Owl isn’t a surprise – Helgoland is over 1000 km from their normal breeding range, whereas they have bred in N Scotland.

    Denmark

    It’s interesting that you rejected my data about lack of Eagle Owl movements between Sweden and Denmark on the grounds that the habitat in Denmark is unsuitable for Eagle Owls, and you also pointed out Snowy Owls don’t occur there as further evidence of the lack of suitable habitat.

    The habitat can’t be so unsuitable because Eagle Owls breed in Denmark – they re-colonised in the 1980s as a result of the arrival of birds from the German reintroduction scheme.

    Snowy Owls do occur as vagrants in Denmark – they’re less than annual, but in irruption years there can be multiple occurrences.

    Care to reconsider that rejection?

    Size-phobia

    There is no size-phobia. People don’t have any problem with the idea of Scops Owls as a vagrant to Britain because this is a long distance migrant with a history of vagrancy outside its breeding range. The fact is that sedentary birds are much less likely to stray than birds which are migrants, and long distance migrants are more likely to stray than short distance migrants.

    Note how neatly it ties in with the list of owls Gatke recorded on Helgoland. He’s got Scops Owl on his list, but no Eagle Owls, even though the breeding range of Eagle Owl is much closer to Helgoland than the breeding range of Scops Owl.

    On page 14 of your report published in Feb 2010 you comment about the inclusion of Scops, Tengmalm’s, Hawk and Snowy Owls on the British List. However their inclusion is not at all surprising when you consider that ringing recoveries and other information show that they have significantly higher vagrancy potential than the Eagle Owl (see the lists in my comment on the 14th November).

    Again note that it all ties up neatly – those four species all appear on the list of species Gatke recorded on Helgoland (and for all four that’s despite the fact that their breeding range is much further from Helgoland than the breeding range of the Eagle Owl).

    I noticed you seem puzzled that Tengmalm’s Owl has been accepted as a genuine immigrant, whilst Eagle Owl hasn’t, and you suggest this is because of the Eagle Owls size and prowess as a hunter.

    In fact a Norwegian ringed Tengmalm’s Owl has been recovered in Britain and the irruptive habits of this small owl give them an obvious potential for vagrancy; Gatke recorded 30 of them on Helgoland!

    There is no size-phobia; it’s just that Eagle Owls are less prone to vagrancy than most other European owls (and the reason for that is because they are relatively sedentary birds which normally avoid lengthy sea crossings).

    I hope these points are reasonably clear and apologies for going on at such length, but you did say that brevity wasn’t necessary.

    I’ve got ringing data from seven European countries involving over 3000 recoveries and there is just one which involves a significant sea crossing. Having looked at this and other evidence and bearing in mind that the report by Melling et al (2008) includes evidence that there are thousands in captivity in Britain and that escapes occur at the rate of about 65 per year, the only reasonable conclusion I can come to is that the current British population is derived from escapes, illegal releases and their offspring, and the input of wild birds from the continent is either zero or so close to zero that it is effectively zero.