Government sanctions cormorant cull to appease anglers (1 Viewer)

[alcedo.atthis]

"Please can we keep this thread to the issues."

Yes Robin, it's getting a little out of control. Are the mod's birding??

The attack story is about as factual as this:
Did you know ... ?
A cormorant can eat 30,000 tons of fish a year - that's over 82 tons a day!
(Source: The Independent, July 28, photo caption)
Journalistic lisence or what!!

For a few facts :-

http://www.gnn.gov.uk/content/detail.asp?ReleaseID=129833&NewsAreaID=2&NavigatedFromSearch=True

http://www.defra.gov.uk/wildlife-countryside/vertebrates/reports/cormorant-licence.pdf

http://www.defra.gov.uk/wildlife-countryside/vertebrates/reports/cormorant-removal.pdf

Regards

Malky.

 

[godwit]

Citing 6 detailed studies Birds of the Western Palearctic states:

Daily consumption varies between 425–700 g.

This is what is known as a FACT

Dave

 

[Edward woodwood]

The story is factual - I heard it on Radio 4. Whether Bradshaw was actually given a bit of jip by a cormorant is a different matter

perhaps not!!! the point being made is Bradshaw doesn't know a Cormorant

 

[godwit]

Please can we keep this thread to the issues. Playing the "man" is not acceptable.

Robin, if you can be bothered to highlight (via a PM) any comments I have made that are unnacceptable in this debate I will happily go back and edit them out so long as the obvious falsehood spread by others are also removed. This will allow those who wish to examine this thread to do so in such a way as to be properly informed which I assume is their reason for reading it.

It is rather frustrating trying to debate things with people who just make things up.

Dave

 

[Edward woodwood]

I agree Dave

but maybe best to leave up some of the 'facts' for posterity

atb
Come on you Rams! B

 

[robinm]

Please can we keep this thread to the issues. Playing the "man" is not acceptable.

Robin, if you can be bothered to highlight (via a PM) any comments I have made that are unnacceptable in this debate I will happily go back and edit them out so long as the obvious falsehood spread by others are also removed. This will allow those who wish to examine this thread to do so in such a way as to be properly informed which I assume is their reason for reading it.

It is rather frustrating trying to debate things with people who just make things up.

Dave

As I have said in the "Complaining about postings" thread it is not the mods job to rule on what is or is not fact. It is (part of) our job to control personal abuse.

If you or any other poster wants to remove any personal comments about other members then I will leave it at that.

 

[Steve Lister]

two days away from my computer so I have missed this thread up to now. as I read through it I paused to PM several contributors to correct statements they had made, but in the end I decided to contribute.

I am one of the relatively few birders that actually look at Cormorants, mainly at Rutland Water, and I know how to tell [sinensis and carbo apart. There were 640 Cormorants at RW yesterday, and most were carbo. Sinensis are very much in the minority, and are out-numbered by intergrades. To say that all inland Cormorants are sinensis is clearly wrong. There is evidence that new inland tree-nesting colonies are initially established by sinensis birds but the colonies quickly attract carbo birds. Sinensis is regarded as a more migratory race so they should be less numerous in winter. Whether they originate in southern Germany I do not know. Ringed birds that I have recorded have come from Denmark and Holland (as well as Wales, Scotland, Ireland, Essex, and Nottinghamshire, far out-numbering foreign sources).

Anyone controlling Cormorants will not be bothered about the niceties of sub-specific identification, and the legislation does not expect them to. Oddly, I read recently on a Cormorant discussion group that the Spanish government has also introduced a cull, but only of sinensis, which is the breeding form in Spain; how they will prevent carbo being shot too I do not know.

I do not want to get involved either for or against the increase in the culling levels, but I do want people to be clearer about the birds involved.

Steve

 

[godwit]

"To say that all inland Cormorants are sinensis is clearly wrong."

This is surely dependant on the reliability of the identification criteria you use, none of which has been properly tested. In an earlier post it was pointed out that:

"The UK inland birds have been proved to be continental sinensis birds because they were DNA tested by my old uni mate Stuart Piertney"

Think I'll go with the hard evidence. I'm not disputing that some carbo could appear inland and even intergrade with tree nesting sinensis on occasion but this has yet to be proven. If the carbo population were properly able to utilise inland waters they would have done so countless generations ago, the truth is they are marine and specialise on bottom feeding coastal fish such as flounders and have presumably always found it difficult to adapt to feeding on freshwater species.

"Anyone controlling Cormorants will not be bothered about the niceties of sub-specific identification, and the legislation does not expect them to."

No, of course not, the only reason the point was raised is because of iritatingly persistent suggestions that carbo has been forced inland by overfishing in the sea. it has not.

Dave

 

[Steve Lister]

"To say that all inland Cormorants are sinensis is clearly wrong."

This is surely dependant on the reliability of the identification criteria you use, none of which has been properly tested. In an earlier post it was pointed out that:

"The UK inland birds have been proved to be continental sinensis birds because they were DNA tested by my old uni mate Stuart Piertney"

Think I'll go with the hard evidence. I'm not disputing that some carbo could appear inland and even intergrade with tree nesting sinensis on occasion but this has yet to be proven. Dave

Hi Dave

I identify the sub-species by the shape of the rear of the gular skin; as far as I am aware this is reliable, but I would obviously be interested to know if it has been shown to be wrong. This method needs good views but is the only one that has not been found to be lacking. Interestingly, the reference to Spain that I mentioned still referred to 'white heads'.

There has been DNA work on inland breeding Cormorants that supports what I said in my earlier posting - there is a mix of the two sub-species and they do inter-breed, including at Rutland Water. I have copies of some of the research papers if you really want to see them.

Cheers
Steve

 

[alcedo.atthis]

"Citing 6 detailed studies Birds of the Western Palearctic states:

Daily consumption varies between 425–700 g.

This is what is known as a FACT"??????

Dave, I take it that the above generalisation regarding consumption is based on guesswork. How else can one tell what the daily consumption is. If one looks at exercion of the individual bird, the temperature of surroundings, the body temperature loss due to wind-chill and water temp -v- time spent in the individual medium, the mass of the bird, the digestive tract efficency, the protein levels of the prey species, the fat level of the species, etc, etc, how can you, or anyone else quantify or qualify the statements,

Daily consumption varies between 425–700 g.

This is what is known as a FACT.

The only fact, is that these figures are written elsewhere.

Regards

Malky

 

[Edward woodwood]

Malky

cant speak for Dave but

I would fully expect account to be taken of these factors and the sample size to be sufficiently large to make the effects of temperature, illness, etc staistically insigificant.

and come on, they aren't 'generalisations'; if you're gonna knock people who have done the studies and come up with the figures we may as well just start every post with 'well I reckon.....'

Six studies quoted in BWP are reasonable references to quote - only wish more people would do it.

 

[godwit]

"I identify the sub-species by the shape of the rear of the gular skin; as far as I am aware this is reliable, but I would obviously be interested to know if it has been shown to be wrong."

I believe, but would need to check this again, that the classic sinensis pattern is only found in sinensis but that the classic carbo pattern, and intermediate patterns, are found throughout the range of sinensis. Because the emphasis in Britain has always been to locate sinensis there has been little attention paid to those sinensis that are not diagnosible.

"There has been DNA work on inland breeding Cormorants that supports what I said in my earlier posting - there is a mix of the two sub-species and they do inter-breed, including at Rutland Water. I have copies of some of the research papers if you really want to see them."

Thanks for the offer but I'll happily take your word for the fact that some carbo genes are present in inland populations now, though I'd be interested to now whether the research actually shows that birds with carbo genes are actually carbo or intergrades and the numbers involved. It seems counter intuitive that carbo would only have begun to utilise inland waters coincidental with the reappearance of large numbers of sinensis in Britain after ignoring an empty niche for milliennia. There has been no discernible decrease in numbers at the coast, or increase in productivity there, at least as far as I know) that would account for large numbers having moved inland.

With regard to Malky's bizarre post (110): that signals my abandonment of this thread for, what I hope, are obvious reasons!

Dave

 

[alcedo.atthis]

"Six studies quoted in BWP are reasonable references to quote "

"Six studies" or data from one study quoted six times. How can you measure the consumption. Are you doing it on the basis of what Cormorants catch, then recover the caught fish, like the Chinese Cormorant fishermen. If so, then the figures have to be a guesstimation, as you are removing the fish, therefore leaving the bird devoid of nutrition. If so, then you are back to square one. Again the bird requires nutrition, it feeds again. You remove the food to weigh it. The bird is still hungry, and so it goes on and on. Are they doing this under controlled parameters. Keeping Cormorants in a controlled environment, supplying food at known weights, calculating what the individual bird has consumed. How can anyone do this. This is not how a wild, free-flying bird would react with available resources on a daily basis. It still guesstimation. The influencing factors make the signifiance to the actual consumption, therefore data cannot be accurate.

Regards

Malky.

 

[Katy Penland]

I'm going to let the bird experts answer your question specifically about cormorant consumption, but *in general* energy requirements of any organism can be calculated fairly accurately based on that organism's mass, metabolic rate, fat reserves, etc., and the energy-density of the prey being consumed. Then there are seasonal variations to these calculations, as during breeding or migration, that require additional energy and so caloric intake must increase.

I.e., you don't have to sit there and count the number of prey being caught to determine what any organism needs to survive if not thrive.

 

[Bluetail]

"To say that all inland Cormorants are sinensis is clearly wrong."

This is surely dependant on the reliability of the identification criteria you use, none of which has been properly tested. In an earlier post it was pointed out that:

"The UK inland birds have been proved to be continental sinensis birds because they were DNA tested by my old uni mate Stuart Piertney"

Think I'll go with the hard evidence. I'm not disputing that some carbo could appear inland and even intergrade with tree nesting sinensis on occasion but this has yet to be proven. If the carbo population were properly able to utilise inland waters they would have done so countless generations ago, the truth is they are marine and specialise on bottom feeding coastal fish such as flounders and have presumably always found it difficult to adapt to feeding on freshwater species.

I don't know enough to comment on the issues raised in this thread (and muct confess I've not been following it very deeply), but I did a quick google on Stuart Piertney and the first thing that came up was this:

http://www.abdn.ac.uk/zoology/piertney/cormorant.htm

Bit puzzled and wondering how it squares with the above. Seems to imply Ian might have overstated the case a bit?

 

[Edward woodwood]

"Six studies quoted in BWP are reasonable references to quote "

"Six studies" or data from one study quoted six times. How can you measure the consumption. Are you doing it on the basis of what Cormorants catch, then recover the caught fish, like the Chinese Cormorant fishermen. If so, then the figures have to be a guesstimation, as you are removing the fish, therefore leaving the bird devoid of nutrition. If so, then you are back to square one. Again the bird requires nutrition, it feeds again. You remove the food to weigh it. The bird is still hungry, and so it goes on and on. Are they doing this under controlled parameters. Keeping Cormorants in a controlled environment, supplying food at known weights, calculating what the individual bird has consumed. How can anyone do this. This is not how a wild, free-flying bird would react with available resources on a daily basis. It still guesstimation. The influencing factors make the signifiance to the actual consumption, therefore data cannot be accurate.

Regards

Malky.

I too am giving up with this thread

Look, I don't know the methodology these people used. Ask them. As it was published data it will have been refereed/peer-reveiwed (as we do at OBC with papers we get) - any old numbers and unsubstantiated theories are not published on a whim. Maybe you should write into a journal pointing out how they have got it all wrong? Funny how no-one ever takes this option?

 

[alcedo.atthis]

"but *in general* energy requirements of any organism can be calculated fairly accurately based on that organism's mass, metabolic rate, fat reserves, etc., and the energy-density of the prey being consumed. Then there are seasonal variations to these calculations, as during breeding or migration, that require additional energy and so caloric intake must increase."

Exactly Katy,
"organism's mass" Were each of the study birds weighed, and the difference between flesh mass and feather mass taken into consideration.
"metabolic rate" Were each of the birds exertions measured in output of carorific value, and was heat loss, or (over)heat exertion and dispersion taken into consideration.
"fat reserves" Was original fat reserves measured, not calculated, and was ongoing loss and gains of fat reserves constantly measured. Metabolic rate would control losses and gains, where there is insufficient, or a glut of resources, and would be influenced by ongoing exertions, heat retention, heat loss, digestive efforts, core temperature, flying in the cold or warmth, or flying against prevailing winds, distance to travel to available resources etc etc.
"energy-density of the prey" Was this done on an individual prey species basis. Each prey would be different. Each prey would have a different carorific value per gram and differential digestive time within the actual and individual Cormorant would take place again affecting metabolic rate.
"seasonal variations" Was the data from each sex kept apart, or was it lumped all togther? Was the data from the females different from the males, and if so, by how much.
To all of the above, I don't think so.

Regards

Malky.

 

[alcedo.atthis]

One thing that has crossed my mind.
The individual species of naturally occuring species of Cormorant
Great Cormorant Phalacrocorax carbo + Phalacrocorax carbo sinensis
Double-crested Cormorant* Phalacrocorax auritus
which are on the British list.
Are they all now under threat??
What if any of the other transatlantic rarer species puts in an appearance.
I hope the birders get there before the guns.

Dave "With regard to Malky's bizarre post (110): that signals my abandonment of this thread for, what I hope, are obvious reasons!"

"Bizarre" Hmmmm!! I take it that you are now devoid of meaningfull discussion""

Regards

Malky.

 

[David Bryant]

at least as far as I know [/COLOR] that would account for large numbers having moved inland.

With regard to Malky's bizarre post (110): that signals my abandonment of this thread for, what I hope, are obvious reasons!

Dave

LOL!
Thought we were dealing in FACTS not opinions!

 

[godwit]

"LOL!
Thought we were dealing in FACTS not opinions!"

I was going to refrain from commenting further but unfortunately (sorry everyone) I can't resist this one.

Re: facts, theories and opinions.

A FACT (demonstrated by some form of objective measurement) is something that you wouldn't recognise if it jumped up and bit you on the ****, you may well form an OPINION (subjective, not measured) about this and, if you put your mind to it, you might come up with a THEORY (an idea that might be tested through measurement) about how or why it happened.

It is quite right to deal in facts when you have the evidence (measured) to support the view that they are facts. if you don't have this information you can still make an assertion or a suggestion (an opinion or a theory) but it is disingenuous to pretend that you know it is a fact. There is no guarantee that a fact will always remain the same, it might change as new evidence is introduced or when something changes. I.e, It was a fact that this thread interested (measured by my level of interest in contributing to it), given that some of the contributors are not up to the task of dealing in facts (and were actually just making stuff up) it is now a fact that I am not interested in this thread (measured by the fact that I will not be contributing anything further).

All the best,

Dave