Lancs Eagle Owls (1 Viewer)

[Farnboro John]

what utter rubbish. Weasels are taken by any mammalian predator that can catch them (e.g. Wildcats, Pine Martens). Tigers habitually eat leopards. Wolves habitually eat (and limit the numbers of) foxes. Humans from Africa to China eat all manner of predators.

There are plenty of recorded instances of Wolves eating their own after a fatal leadership exchange fight. Very little consumable protein goes to waste in the natural world.

John

 

[Nightranger]

what utter rubbish. Weasels are taken by any mammalian predator that can catch them (e.g. Wildcats, Pine Martens). Tigers habitually eat leopards. Wolves habitually eat (and limit the numbers of) foxes. Humans from Africa to China eat all manner of predators.

Why use the words what rubbish'? I clearly indicated that I was not convinced the idea works for every case. The point I have been trying to discuss is that predation of predators may not always be stimulated solely by the need for food. At the same time, it seems strange that the creature killed is sometimes not eaten given the effort (or risk of injury) that the killing may or may not have taken. Weasels are not a bad example because I have heard accounts that suggest they are sometimes rejected when taken back to the den for young. As I mentioned elsewhere, (most) birds have a relatively poor sense of taste compared to mammals so it would make more sense that predators on predator incidents would be more common than in mammals, particularly in relation to subsequent feeding. In other words, are the EOs setting out to deliberately eat hen harriers because they can? Or is it utilisation of food killed when actually eliminating a rival or danger?

 

[Nightranger]

Is nt there more day based activity if the owls have chicks? From what is known about eagle owls they are pretty hard to detect for their large size. This dunsop pair appearsto have been around for a few years.

Indeed, but the location was deliberately suppressed despite being alluded to in a Natural World programme around four years previous to the Roy Dennis version. I am not sure why this happens but some bird watchers build a 'I know something that you don't know' attitude and I suspect this has pervaded the EO situation more than it has done for any other species for reasons that are not clear to me (anyone got any ideas?). I know there was the issue over a second golden eagle nest in the Lake District that I mentioned, which never existed (at least not for many decades). There were quite strong rumours about a pair of EOs in Nottinghamshire a few years ago but this morphed into possibly being in Lincolnshire with no more specifics. Without knowing the origin of the rumour, it is difficult to know whether there was any real substance to it.

Having said that, there seems to be an idea that relatively high breeding numbers would possibly indicate natural colonisation and I am not sure this works. If 50 pairs were present it is more likely to infer that some of the offspring produced by breeding escaped birds have survived. This effectively becomes an accidental introduction so we are back to the idea of whether EOs were formerly a UK bird or whether natural colonisation is inevitable in the future.

 

[KnockerNorton]

Why use the words what rubbish'?

because you typed these words: "this would better read mammalian predators do not (generally) eat other mammalian predators."

They "generally" do.

 

[KnockerNorton]

At the same time, it seems strange that the creature killed is sometimes not eaten given the effort (or risk of injury) that the killing may or may not have taken. Weasels are not a bad example because I have heard accounts that suggest they are sometimes rejected when taken back to the den for young.

have you ever looked in a raptor nest? They are littered with uneaten prey of all kinds. So by your logic, peregrines find pigeons distasteful, because "I have head accounts that suggest they are sometimes rejected" when taken back to the nest.

Having said that, there seems to be an idea that relatively high breeding numbers would possibly indicate natural colonisation and I am not sure this works. If 50 pairs were present it is more likely to infer that some of the offspring produced by breeding escaped birds have survived. This effectively becomes an accidental introduction so we are back to the idea of whether EOs were formerly a UK bird or whether natural colonisation is inevitable in the future.

Nobody has even shown that these birds are pure Eurasian Eagle owls yet.

 

[Nightranger]

have you ever looked in a raptor nest? They are littered with uneaten prey of all kinds. So by your logic, peregrines find pigeons distasteful, because "I have head accounts that suggest they are sometimes rejected" when taken back to the nest.

I am not sure I am saying what you think here. As I have said, birds mostly have a poorly developed sense of taste whereas mammals are supposed to have a better ability (if you can call it that). To get back to the point, it makes sense that BoPs would utilise victims killed for other reasons. As Farnboro John said, it is rare for a protein source to be wasted in nature but it does happen for a number of reasons although the end result can be masked when scavengers are around (eg, vultures scavenging a hyena killed and discarded by lions). The original point I was trying to make was that EOs may not be systematically preying on hen harriers (as the case tends to infer) as a food source but are opportunistically eliminating a potential rival. I am not in any way defending EOs becaue I don't think we have all the information we need but you have to agree it has been a fascinating discussion and it is great to see all the examples that have been given here.

Nobody has even shown that these birds are pure Eurasian Eagle owls yet.

Absolutely, it is one of the points that gets lost in the 'are they genuine or not' debate.

 

[Nightranger]

because you typed these words: "this would better read mammalian predators do not (generally) eat other mammalian predators."

They "generally" do.

I thought I made clear that I was discussing common assertions made on wildlife programmes, if not then I apologise. Nevertheless, to centre in on one part of a sentence out of context is a bit pedantic don't you think?

 

[rob stoff]

IThe original point I was trying to make was that EOs may not be systematically preying on hen harriers (as the case tends to infer) as a food source but are opportunistically eliminating a potential rival.

why they are killing them is utterly irrelevant

Rob

 

[KnockerNorton]

why they are killing them is utterly irrelevant

Rob

Indeed. When people talk about the number of rabbits and the number of Hen harriers killed, and whether they're actively looking for them or just being opportunistic, it completely misses the point. The EO diet could well be 99.999% rabbits and 0.001% hen harriers, but if there are 5,000 rabbits and 4 hen harriers in the vicinity then the predation rate is disproportionate. If 1 hen harrier is killed then that's 25% of the population, whereas 500 rabbits is only 10%. Rabbits can also dive in a hole, which a harrier can't, so the chances of being predated are also different.

What EO's are 'mostly' eating, and what % of their diet is rabbits or birds, is irrelevant, it's the proportion of local birds that are being predated that matters. And where you have low-density rare birds like hen harriers, then predation can be disproportionate and have a real impact on them. The rabbits may actually reinforce this by propping up the EO diet and filling in the large gaps between e.g. Hen harrier snacks.

 

[Nightranger]

Indeed. When people talk about the number of rabbits and the number of Hen harriers killed, and whether they're actively looking for them or just being opportunistic, it completely misses the point. The EO diet could well be 99.999% rabbits and 0.001% hen harriers, but if there are 5,000 rabbits and 4 hen harriers in the vicinity then the predation rate is disproportionate. If 1 hen harrier is killed then that's 25% of the population, whereas 500 rabbits is only 10%. Rabbits can also dive in a hole, which a harrier can't, so the chances of being predated are also different.

What EO's are 'mostly' eating, and what % of their diet is rabbits or birds, is irrelevant, it's the proportion of local birds that are being predated that matters. And where you have low-density rare birds like hen harriers, then predation can be disproportionate and have a real impact on them. The rabbits may actually reinforce this by propping up the EO diet and filling in the large gaps between e.g. Hen harrier snacks.

Absolutely (acknowledgement to Rob too). The only rider I would add to this is that whatever (maybe even, whether) EOs are killing hen harriers for is a fringe issue despite the discussion we have been involved in (not least, me) but it becomes fundamentally important in deciding what (if anything) to do next.

Scenario 1: The EOs are genuine colonists, then we cannot justify (ahem!) controls even on conservation grounds. Apart from anything else, it would not achieve much more than a short-term solution and is a dangerous area to convince the general public over given a slightly weak position.

Scenario 2: The EOs are undoubtedly all escapees, then it is essential that action is taken whether this involves a concerted effort at recapture or (ahem! ahem!) culling.

IMO, there is not enough effort going in to determine the status of these birds and believe me, I am no fan of introduced species (excepting reintroductions with certain reservations).

 

[rob stoff]

Absolutely (acknowledgement to Rob too). The only rider I would add to this is that whatever (maybe even, whether) EOs are killing hen harriers for is a fringe issue despite the discussion we have been involved in (not least, me) but it becomes fundamentally important in deciding what (if anything) to do next.

Scenario 1: The EOs are genuine colonists, then we cannot justify (ahem!) controls even on conservation grounds. Apart from anything else, it would not achieve much more than a short-term solution and is a dangerous area to convince the general public over given a slightly weak position.

Scenario 2: The EOs are undoubtedly all escapees, then it is essential that action is taken whether this involves a concerted effort at recapture or (ahem! ahem!) culling.

IMO, there is not enough effort going in to determine the status of these birds and believe me, I am no fan of introduced species (excepting reintroductions with certain reservations).

what 'effort' do you suggest that would confirm their status?

Rob

 

[KnockerNorton]

Indeed. We've already been through all this (see the earlier Poecile post re the 4 options, a few weeks ago).

The BOU has looked at status, twice, and found it quite clear that there is no good evidence for wild colonisation, or even a single wild vagrant.

We also know that several hundred EO (of various sub/species) escape/are released every year (these figs are available from the falconry groups who reunite owners with recovered lost birds).

It's only people like Roy Dennis who think that it's plausible to suggest that these escapes are adding little to the feral population and the tiny naturalized population on the continent is adding the bulk, despite all of the BOU's work. The precedent of Little Owls (all breeding birds being introduced) seems to elude him.

 

[Farnboro John]

Indeed. When people talk about the number of rabbits and the number of Hen harriers killed, and whether they're actively looking for them or just being opportunistic, it completely misses the point. The EO diet could well be 99.999% rabbits and 0.001% hen harriers, but if there are 5,000 rabbits and 4 hen harriers in the vicinity then the predation rate is disproportionate. If 1 hen harrier is killed then that's 25% of the population, whereas 500 rabbits is only 10%. Rabbits can also dive in a hole, which a harrier can't, so the chances of being predated are also different.

What EO's are 'mostly' eating, and what % of their diet is rabbits or birds, is irrelevant, it's the proportion of local birds that are being predated that matters. And where you have low-density rare birds like hen harriers, then predation can be disproportionate and have a real impact on them. The rabbits may actually reinforce this by propping up the EO diet and filling in the large gaps between e.g. Hen harrier snacks.

Rabbits are introduced too, perhaps we'd better get rid of them.

John

 

[KnockerNorton]

Rabbits are introduced too, perhaps we'd better get rid of them.

John

Too expensive, there's 60 million of them. There are, however, only a few hundred Eagle owls, so we should allow them the same protection as the rabbits (zero) and get rid of them while we still can.

 

[Amarillo]

It's only people like Roy Dennis who think that it's plausible to suggest that these escapes are adding little to the feral population and the tiny naturalized population on the continent is adding the bulk, despite all of the BOU's work.

That isn't what Roy dennis or anyone else who broadly shares his views thinks.

Everyone with any knowledge on the subject knows that the vast majority of EO's in Britain are escapees and that there is no hard evidence for natural colonists.

People like Roy dennis accept the possiblity of natural colonists in addition to the escapees and that possibility leads them to reach different opinions regarding EO establishment in britain.

I'm not getting into this debate again, its been done to death - but don't twist peoples arguments

 

[rob stoff]

That isn't what Roy dennis or anyone else who broadly shares his views thinks.

Everyone with any knowledge on the subject knows that the vast majority of EO's in Britain are escapees and that there is no hard evidence for natural colonists.

People like Roy dennis accept the possiblity of natural colonists in addition to the escapees and that possibility leads them to reach different opinions regarding EO establishment in britain.

I'm not getting into this debate again, its been done to death - but don't twist peoples arguments

do you believe, like Roy Dennis, that EO's were once present here but were hunted to extinction, this seems extremely improbable to me

Rob

 

[Amarillo]

do you believe, like Roy Dennis, that EO's were once present here but were hunted to extinction, this seems extremely improbable to me

Rob

I believe that they were probably present here at some point - they range right across Europe and Asia so until our landscape was extensively deforested it seems likely to me that they were here. Why is it improbable?

 

[KnockerNorton]

I believe that they were probably present here at some point - they range right across Europe and Asia so until our landscape was extensively deforested it seems likely to me that they were here. Why is it improbable?

Yaaaaaaaaaaaaaaawn. Crested Lark, Black Woodpecker, Zitting Cisticola, Little Owl, Black Kite, Purple Heron, Black Stork, Hazel Grouse, Scops owl, Teng owl, Hoopoe, Grey-headed pecker, Tawny Pipit, Bluethroat, Melodious/Icterine warbler, island biogeography, land bridges, post-glaciation, yaaaaaaaaaaaaaaaaawn.

Nobody even knows what the forest looked like - whether it was closed canopy or savannah. So your hunch of what lived in it isn't very meaningful.

 

[Amarillo]

Yaaaaaaaaaaaaaaawn. Crested Lark, Black Woodpecker, Zitting Cisticola, Little Owl, Black Kite, Purple Heron, Black Stork, Hazel Grouse, Scops owl, Teng owl, Hoopoe, Grey-headed pecker, Tawny Pipit, Bluethroat, Melodious/Icterine warbler, island biogeography, land bridges, post-glaciation, yaaaaaaaaaaaaaaaaawn.

Nobody even knows what the forest looked like - whether it was closed canopy or savannah. So your hunch of what lived in it isn't very meaningful.

Most of those have limited ranges due to climatic factors. EO's are found in almost any habitat across different climate zones.

My hunch is just that - a hunch based on the above logic. Why are you so adamant that there were no eagle owls here?!

edit: sorry just realised its you, Poecile. Think we've probably covered this already! although despite considerable debate you still seem to have difficulty grasping what my argument (and Roy dennis's) is - see your post saying that he thinks most EO's are natural colonists. Your argument is good and has caused me to rethink slightly, so I don't see why you feel the need to twist what the other side says.

 

[KnockerNorton]

I'm not twisting. Roy Dennis argument (and yours - are you he?!) seems to be that just because there is a theoretical chance that even a single EO may have reached the UK, that means that the feral population should be treated as if they were a native species. This is like saying that we should treat the Edinburgh Zoo free-flying Night Herons as if they were a native breeding species. And is is beside the point when the BOU has found no evidence that EO has EVER been here as a vagrant. they are nothing if not thorough.

It's romantic codswallop. I don't believe in basing policy on hunches, I believe in assessing the evidence. And there is no good hard evidence that they're native (2 post glacial bones from human settlements mean little - we have more post-glacial lion remains than that from Tower of London moat), and a very large yawning chasm in the British archaeological record that puts them in the same bracket as unicorns and yetis.