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Message: <blockquote data-quote="Steve Dudley" data-source="post: 1709190" data-attributes="member: 5172">I stated my understanding of how this can work but I’m happy for anyone who works with stable isotopes to confirm this or not.QUOTE=jurek;1709033] Many Eagle Owls WERE recorded in Britain, from early historic accounts to recent sightings, but they are not on the list because natural vagrants and escaped birds were unrecognizable. Which is a very different situation from "not occuring in Britain".</blockquote>This is exactly what the Melling et al (2008) paper referred to in my earlier post covers. It reviews the historical literature and known claims of EO in Britain listing all known occurrences from 1678-1990. This paper also covers EO in captivity in Britain (using data from the Independent Bird Register), the likelihood of EOs escaping from captivity, and the likelihood of natural vagrancy to Britain based largely on ringing data from Scandinavia. I repeat my offer to send anyone a PDF of the paper. I just need your email address in a PM.What is your reference for this statement? Eagle Owl has been persecuted across Europe, especially during the 19thC, but it has never been close to extinction (at least I have not seen any literature sources that supports this). Mikkola (1983) estimated the central and north European population as between 4571 - 6472 pairs (total based on 12 countries only, see Mikkola for these). This was about the time the first protection of EOs began and from which the population in some areas has since increased. So I take Mikkola's estimate as the low point at a time when persecution was still exercised and at the time (1983) EO was also a legal hunting quarry in Finland.Persecution, whilst a major cause of decline, is by no means the only reason. Disturbance, habitat change/loss and toxic chemicals (in their prey) have all contributed to the decline and since many of these additional pressures are contemporary, they will have placed an increased (disproportionate?) amount of pressure on declining populations.For those interested in EO diet and in particular other bird species predated by EOs, I suggest you read Mikkola for a fuller account. Mikkola states that depending on available mammal prey, birds can make up to 51% of an EO's diet and to quote Mikkola, included "crows, ducks, grouse, seabirds, and even other raptors and owls" (this from a study of 17,615 prey items from four countries). BWP (Cramp 1985) gives a list of bird species recorded as EO prey and these include "full-grown" Grey Heron, ad male Capercaillie and "full-grown" EOs, and also states that EOs "frequently takes raptors (Accipitriformes and Falconiformes) and other owl species, apparently more often than their abundance warrants." BWP also states that most bird prey is taken "full-grown". Many of these "full-grown" birds will be near-fledged young from nests - Mikkola refers to EOs predating a heronry 4.1 km from their own and a Common Buzzard nest 4.8 km away. EO hunting range is given as 10+ km.My biggest problem with this debate is that people trot out all sorts of 'facts' with no evidence to support their claims. It would be helpful if others were able to provide references in order to substantiate their claims and for others to refer to.RefsCramp, S (Ed). 1985. Handbook of the Birds of Europe the Middle East and North Africa (BWP). OUP, Oxford.Melling, Tim., Dudley, Steve & Doherty, Paul. 2008. The Eagle Owl in Britain. British Birds 101: 478-490.Mikkola, H. 1983. Owls of Europe. T & AD Poyser, Carlton.[/QUOTE]

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