Thursday, 14 January 2010

Norfolk Eagle Owls!!

Some 'interesting' discussion about Eagle Owls in Norfolk!!
Cut and pasted from UK400 Club (hope that it is alright!)

Original Post by LGRE:
An autopsy and isotope analysis of a EURASIAN EAGLE OWL picked up dead as a road casualty in Thetford Forest has apparently proved positive in terms of comparison with the clades of birds resident in Continental Europe and Scandinavia, indicating that the small population in East Anglia is perhaps of natural origin rather than of introduced or escaped birds.

As there has been a recent application made by Fera and other organisations to destroy up to 44 pairs of this species breeding in the wild from Scotland and Wales south to Sussex and Kent, on the basis that the birds are illegal releases and may sway the natural swing of the food chain in this country, this new information is perhaps more than ever pertinent and testament to the fact that the birds should be left well and alone.

Furthermore, a recently-published paper by Aebischer and others on juvenile dispersion of Eurasian Eagle Owls on the Continent has provided an insight into the actual movements of this species.

Response from Alex Lees:
Any more information on these molecular chemistry results? Why would escaped birds not be of Continental stock? The abstract of the paper you mention is available here: if anyone wants a PDF then PM me.

Although juvenile dispersal is an important life history component, it remains one of the less understood ecological processes regulating the dynamics of animal populations. Lack of information about patterns of dispersal hampers the estimation of the actual status and demographic trajectory of populations, and can preclude the development of sound conservation strategies. The Eagle Owl Bubo bubo is an endangered bird species in the European Alps. Many breeding sites have been abandoned in the twentieth century, although some recovery has been reported lately. Moreover, the occupancy of traditional breeding sites across years in well-monitored Alpine populations varies a lot, this despite a relatively high breeding success at the population level. This raises concern about the long-term persistence of Alpine populations. Using conventional and satellite radiotracking, we investigated the spatio-temporal dispersal of 41 juvenile Eagle Owls originating from a population in the southwestern Swiss Alps. Our main goal was to determine dispersal distances, places and times of post-dispersal settlement. Juveniles left their parents between mid-August and mid-November. They covered, on average, 12.7 km per night (linear distance between two consecutive day roosts), often crossing high mountain ranges (up to 3,000 m altitude). The mean total distance covered by an individual during dispersal was 102 km (sum of night movements), with a maximum of 230 km. Settlement places were, on average, 46 km distant from the birth place. Our study establishes long-distance dispersal in juvenile Eagle Owls, even in a complex topography, suggesting the existence of a wide-scale metapopulation system across the northwestern Alps. This metapopulation dimension should be accounted for in conservation plans.

Norfolk Bird Info to:
Mobile: 07749779149

Norfolk 364 BOU, 376 UK400, Year 105, Route 69, Sp 25, SM 47, SF 32


  1. Hi David

    Hope all is well. The isotope analysis is from a forthcoming paper in British Birds. Presumably a follow up to the Baikal Teal one:

    Kelly, A, Leighton, K. and Newton J. (in press)
    Using stable isotopes to investigate the provenance of a Eurasian Eagle Owl (Bubo bubo) found in Norfolk, England. British Birds.

    As Alex says though, I don't see why this rules out captive birds of contintal stock, but will wait to see the paper.



  2. Dave can you post your Norfolk list on Bubo please. My 371 is there. Corncrake included melodious warbler is not! Perhaps the rest of the difference goes back well into the nineties.


  3. David Norgate aka Ruralchill15 January 2010 at 21:05

    Ilya, thanks for the message.
    I have to agree that, even if of Continental 'stock', as stated elsewhere, this does not definitely mean it has made it here naturally. I would be interested in knowing how many Eagle Owls are still imported and where from. Also, how many generations stable isotopes would show provenence (or whether it is permanent!)

    Anyway, I would still like to see the birds, if the opportunity ever presented itself!