Eagle Owl in Britain (1 Viewer)

KnockerNorton · Mar 1, 2007

Amarillo said:
But eagle owls are part of the same ecosystem as ours on the continent, they interact with the same species as are here in the UK. It can not be compared to the many misguided introductions you mention.

No, our ecosystem is not the same as on the continent, as we have a different blend due to being an island. This is the science of island biogeography. Same as Japan. Or, on a microcosm, Isle of Wight with its red squirrels or Shetlands with their starlings and wrens.

For instance, our water voles have never had to cope with european mink, hence they were quite common here (until yank mink arrived). Similarly, we've never had black woodpecker, so large holes are not available for various species. That means the habitat here has been different. Our ecosystem has fewer species than Europe's, and Ireland has fewer than ours, and Iceland has fewer than Irelands - the effect increases with distance from the continent. That creates different ecosystems. That's why we have different races or various species, often of different sizes and behaviours, as they inhabit different niches. Give them enough time, and they'll turn into new species. Long-term extinctions of predators by man has also created a different ecosystem. A combination of the two means that some species, such as woodland birds, are much more common here than in the 'pristine' forest of Poland/Belarus, which have a full complement of mammal predators.

We have never had a 'full complement' of European predators (least weasel, beech marten, wolverine, various eagles, and eagle owl), so why do people want to put more pressure on species which definately ARE native, just because Roy Dennis likes the look of them?

chris murphy · Mar 1, 2007

IanF said:
Yep! Saw it on Monday around 1:00pm on the NEC building in Exchange Square sat out in the sun warming itself facing onto the railway station. Shame I hadn't my camera with me!

The one in Stewart Park was a week or so before the one in the town centre was found - so it may be the same bird.

There's another Eagle Owl off Thornaby Road, Thornaby by the swimming baths near the allotments - known to be an escapee - maybe they'll meet up

Really? Hadn't heard about the Thornaby one, that's only two minutes from my house! Will have to keep an eye out for it.

Original PaulE · Mar 1, 2007

Poecile said:
The point about welcoming them here because we're ina changing world is a bit spurious. By that token we'd be encouraging anything that managed to escape or was released. Tigers?

I don't think the point is spurious. but the point i was making in my previous post was not about escaped or released birds what i was trying to say, probably not very well, was on the premise of a natural colonisation.
i agree with your other post that the arrival of a top predator like the eagle owl could have a very negative effect on other species however the programme seemed to be saying that these birds were living more or less exclusivley on rabbits which are not as abundant in holland as they are here
i thought the programme also made a good point about buzzards whose numbers have exploded in recent years, we've even got them here in suffolk now hurrah,however unchecked they to will surly start to have a negative effect on the food chain which in turn could damage the birds you are concerned about
the other thing that would be interesting to know which the programme didn't really cover was in holland what overall has been the effect on the barn owl and buzzard populations have they declined? since the eagle owls have arrived and if they have is the blame being placed on the owls

Farnboro John · Mar 2, 2007

PaulE said:
i thought the programme also made a good point about buzzards whose numbers have exploded in recent years, we've even got them here in suffolk now hurrah,however unchecked they to will surly start to have a negative effect on the food chain which in turn could damage the birds you are concerned about

OK, once more with feeling...... in a normal ecosystem predator numbers are controlled by prey numbers and not the other way around. That is what the imbeciles who are going on about Magpies at the moment fail to understand.

Buzzard numbers will NOT rise unchecked for lack of a predator on them, once they reach the maximum that the Rabbit population will support, population growth will stop. And if there is a Rabbit population crash then first of all Buzzard breeding will fail: then there will be some dispersal in search of new prey sources (a la Rough-leg and Owl irruptions in lemming crash years) and finally some losses due to inability to find food. Then the cycle starts again as Rabbit populations begin to recover.

John

lockbreeze926 · Mar 2, 2007

Farnboro John said:
Buzzard numbers will NOT rise unchecked for lack of a predator on them, once they reach the maximum that the Rabbit population will support, population growth will stop.

This (the buzzard/rabbit relationship) has always been my understanding, too, and it hasn't been hard to see the burgeoning rabbit numbers leading fairly directly to the rapid spread of buzzards across the central and eastern UK.

But...several things I've read recently are quite definite that buzzards hardly take rabbits at all. If this is correct, then the expansion argument does not follow, nor would its converse. Is there any recent research that supports the traditional buzzard/rabbit, predator/prey relationship?

STS · Mar 2, 2007

Too right, John.

Brian Stone · Mar 2, 2007

Is it just the greater availability of carrion, i.e. dead bunnies? Or are you saying they don't eat rabbits at all?

Farnboro John · Mar 2, 2007

brianhstone said:
Is it just the greater availability of carrion, i.e. dead bunnies? Or are you saying they don't eat rabbits at all?

My local Buzzards sit up over Rabbit warrens/burrows when hunting from perches and make regular passes when hunting from the air. If they are in fields then they are usually on Rabbit corpses which they may or may not have killed themselves.

However the link between them and Rabbits locally at least, is inescapable.

John

KnockerNorton · Mar 2, 2007

Interesting fact from extensive research on buzzards by Robert Kenward. Around 90% of their diet is composed of....earthworms. They hardly take rabbits at all. When they're sitting around loafing, they're watching for worms or digesting them. John - your birds are probably finding better earthworm hunting on the short turf around warrens, rather than actively hunting rabbits.

Buzzard populations are limited by density, with birds peaking at around 1 pair per sq km. Many of these birds do not breed, however, as only a minority of females are actually producing young.

It's all very well saying that eagle owls only eat rabbits, but rabbit numbers fluctuate with outbreaks of myxi. they're common for a few years, then rare. What do the owls eat then? Also, in Holland there is constant recruitment of things like barn owls and buzzards from the surrounding areas of the continent. In Britian, our birds are much more isolated and recruitment from abroad is minimal - we're a closed system as far as barn owls go.

Steve G · Mar 2, 2007

Buzzards are great generalists & will change foraging behaviour to take advantage of a specific local abundance. At least here in West Fife (which was colonised over the last 10 years) rabbits & rabbit carrion are probably only a modest part of the general diet. Voles, small birds, general roadkill-carrion are all relevant however I suspect that invertebrates form a sizeable part of the diet judging by the hunting strategy of our local birds.

There is certainly now less persecution of Buzzards which perhaps allowed them to move out of their upland strongholds. However, I almost get the impression that UK Buzzards have undergone a 'cultural shift' with resultant dietary diversification (increased intake of worms & other invertebrates, etc) which has allowed them to move into an unoccupied lowland niche -but then again I have no scientific support for making such a statement.

Eagle Owls are also generalists & the debate about the 'appropriateness' of them being in the UK notwithstanding I suspect that if they do become part of our 'regular' UK mainland avifauna they will have no huge effect on other species but will simply use the most abundant food source to hand.

lockbreeze926 · Mar 2, 2007

brianhstone said:
Is it just the greater availability of carrion, i.e. dead bunnies? Or are you saying they don't eat rabbits at all?

Poecile has just answered, I think.

I've seen several pieces of research indicating that Common Buzzards tend to eat mostly worms. Not very noble or mighty, but easier to catch than rabbits.

KnockerNorton · Mar 2, 2007

Steve, I think Eagle Owls will have a disproportionate effect on other owls, regardless of (or perhaps because of) their generalist diet. If there are barn owls in their territory, they are going to get eaten sooner or later. That doesn't meant to say that EO's will only eat barn owls, but it *can* mean that most/all barn owls in the area will be eaten. The EO's can do this, as they have alternative prey once the barn owls have gone, but for the barn owls it's clearly curtains if an EO moves in.

Frenchy · Mar 2, 2007

Poecile said:
Interesting fact from extensive research on buzzards by Robert Kenward. Around 90% of their diet is composed of....earthworms. They hardly take rabbits at all. When they're sitting around loafing, they're watching for worms or digesting them. .

Even in winter?!

Steven Astley · Mar 2, 2007

Frenchy said:
Even in winter?!

Aslong as the ground is frost free, not seaonal like insects. Agree with frenchy and especially poecile who has explained the situation eloquently. The impact of alien species is an ecological nightmare and even if 1 has got here naturally does mean we should let the artificially boosted population go unchecked.

Original PaulE · Mar 2, 2007

Farnboro John said:
OK, once more with feeling...... in a normal ecosystem predator numbers are controlled by prey numbers and not the other way around. That is what the imbeciles who are going on about Magpies at the moment fail to understand.

Buzzard numbers will NOT rise unchecked for lack of a predator on them, once they reach the maximum that the Rabbit population will support, population growth will stop. And if there is a Rabbit population crash then first of all Buzzard breeding will fail: then there will be some dispersal in search of new prey sources (a la Rough-leg and Owl irruptions in lemming crash years) and finally some losses due to inability to find food. Then the cycle starts again as Rabbit populations begin to recover.

John

your point is well made and would surely apply to eagle owls aswell

James Lowther · Mar 2, 2007

PaulE said:
your point is well made and would surely apply to eagle owls aswell

the difference is buzzards are here and always have been....

there are hundreds of examples of extinctions and extirpations caused by non-native predators

don't know if there are any caused by native animals going "unchecked"?

Original PaulE · Mar 2, 2007

James Lowther said:
the difference is buzzards are here and always have been....

there are hundreds of examples of extinctions and extirpations caused by non-native predators

don't know if there are any caused by native animals going "unchecked"?

perhaps because the native predators have never been unchecked whether by gamekeepers pesticides etc
we may now see what effect some native predators sparrowhawks peregrines goshawks etc may have now that there numbers are rising
i as much as anyone enjoy watching barn owls however there numbers are falling it seems they cannot cope with the modern world and without the good work done by the conservation groups would probably be close to disappearing altogether is it right to artifically subsidise these animals that clearly cannot cope in a world of expanding human activity whilst persecuting one that may be able survive alongside humanity
it is interesting to see people on this thread talking about normal or natural ecosystems unfortunately we live in an ecosystem that is far from natural where a large number if not most of the successful animals have either been introduced by man or have had there numbers boosted by mans activities the lemmings/owl situation hardly applies hear when the diets of alot of predators are subsidsed by roadkill or birdtables
it seems that most successful wildlife on our overcrowed island are those that can live with and take advantage of us
i think and hope that animals like barn owls can be protected and i belieive that the work done in this area has been successful in boosting there numbers but with new houses, roads and superstores appearing on almost weekly basis they are simply going to run out of space

Brian Stone · Mar 2, 2007

PaulE said:
perhaps because the native predators have never been unchecked whether by gamekeepers pesticides etc
we may now see what effect some native predators sparrowhawks peregrines goshawks etc may have now that there numbers are rising

Yes, they will be regulated by the availability of habitat and prey rather than the level of persecution.

Amarillo · Mar 5, 2007

James Lowther said:
there are hundreds of examples of extinctions and extirpations caused by non-native predators

but are there any examples of problems caused by predators, which although probably not native, are present in surrounding countries with simlar ecosystems?

I simply cannot see any logical reason why eagle owls will have an adverse effect on other species in Britain.

James Lowther · Mar 5, 2007

poecile's said a few times that the british ecosystem is not comparable to continental europe as it's an island

therefore no way of recruiting extra barn owls when they're eaten by eagle owls etc.

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