Uk Peregrine Population Limit? (1 Viewer)

[London Birder]

apologies for not being clearer ... 228 in response to 227

 

[Jane Turner]

Over rest of British mainland, feral C. livia made up 25% of total prey, thrushes and S. vulgaris 45·9%, waders 8·7%, and L. lagopus 3·8% (Ratcliffe 1963). In northern Ireland, feral C. livia constituted 61% of total items, 68% on sub-coastal districts and 35·2% on coast, where gulls and auks (Alcidae) accounted for 42% (McKelvie 1973).

In Finland, waders main food (30·5%); ducks 21·4%, and thrushes and S. vulgaris 16·3%. If prey assessed by weight rather than numbers, ducks 40·5%, waders 21·6%, and thrushes and S. vulgaris only 3·0% (Sulkava 1968). In Dovre mountains (Norway), corvids (especially Hooded Crows Corvus corone) most frequent prey (29% of total items), ducks 10·5%, gamebirds 12·1%, waders 13·7%, and thrushes and S. vulgaris 12·1% (Hagen 1952a; Sulkava 1968). Maritime Peregrines in Finland, as in Britain, take high proportion of gulls (Bergman 1961). In many German areas, feral C. livia commonest prey: 20·7% of total (Busse 1972), 21·5% (Rockenbauch 1971), 34·2% (Schnurre 1966), 35·2% (Uttendörfer 1952); in coastal areas, ducks and gulls have increased importance (Schnurre 1973). F.*p. brookei concentrated on doves, larks (Alauda, Melanocorypha, Calandrella, and Galerida), S. vulgaris, and Cuckoos Cuculus canorus in Spain (Diaz del Campo 1974), and on corvids in Corsica (Thiollay 1967c). Individual pairs and local breeding groups may develop high degree of specialization for locally abundant prey, e.g. Common Gulls Larus canus (Robein 1930; Stadie 1936), Black-headed Gulls L. ridibundus (Fischer 1967a), Jackdaws Corvus monedula (Löhrl 1936), Rooks C. frugilegus (Dementiev and Gladkov 1951a).


In short Peregrines eat what they find around them. Whatever the commonest allsort is. If there are insufficient sweeties they move on

 

[CBB]

An interesting comment - but no more than that. It would be much more meaningful to know the identity of the top 5 species on the list, together with the percentage of the Peregrine Falcon's total diet each one represents. Can you (or anyone else) enlighten me, please?

Anthony[/QUOTE]




Hi Anthony,
D.Radcliffe says domestic pigeons form 41% of the peregrine diet.(by number-not weight). Obviously I realised this may be slightly out of date so did some 'surfing'. Pigeon numbers taken differ widely depending on the area (as we well know) However, a rough average of 40% would seem fair. Being a P***** R***** yourself and knowing what we all know about animals targeting the weakest prey in the group, is it not fair to say that peregrines are more likely to take 'poor' quality racing pigeons? The ones who return are then better to breed, being faster and stronger. This must be better for pigeon people?

Chris

 

[Jane Turner]

Thought this might be of interest - particularly point 5. Not only are C.livia frequently abundant, they also have had their vulnerablility raptors increased by (in)breeding.

Predator hunting behaviour and prey vulnerability
J. L. Quinn and Will Cresswell†

Summary
1. Game theoretic models of how animals manage predation risk have begun to describe predator responses to prey behaviour relatively recently. This is partly because our understanding of how terrestrial predators select vertebrate prey is often limited to numerical and functional responses to measures of prey abundance. Prey vulnerability, however, may improve our understanding of predation because predators could maximize foraging success by selecting prey on this basis.

2. We tested the hypothesis that sparrowhawks (Accipiter nisus L.), a typical generalist predator, hunt redshanks (Tringa totanus L.), a favoured prey species on coastal shores, primarily on the basis of their vulnerability rather than their abundance.

3. Five direct measures or indicators of redshank behaviour predicted sparrowhawk attack success in a multipredictor statistical model and therefore serve as measures of redshank vulnerability.

4. These and other vulnerability measures influenced whether sparrowhawks decided to hunt redshanks on saltmarsh habitat. A model that included most of these measures predicted correctly whether sparrowhawks hunted redshanks (attack decision) 90% of the time and accounted for up to 75% of variation. Prey abundance accounted for no additional variation.

5. Thus the hunting behaviour of some predators can only be predicted well by several highly dynamic and interacting factors related to prey vulnerability. These results mean that, theoretically at least, the management of prey populations may sometimes be achieved best by manipulating prey vulnerability, rather than by culling their predators.


Journal of Animal Ecology (2004) 73, 143–154

 

[Jane Turner]

Ecography
Volume 24 Page 359 - June 2001
doi:10.1034/j.1600-0587.2001.d01-634.x
Volume 24 Issue 3


Prey availability influences habitat tolerance: an explanation for the rarity of peregrine falcons in the tropics
The density and productivity of peregrine falcon Falco peregrinus populations correlate positively with distance from the Equator, while habitat specificity increases with proximity to the Equator. Low peregrine densities in the tropics may be a result of competition with similar congeners (e.g. the lanner falcon F. biarmicus in Africa), which replace them in many areas. Alternatively, tropical peregrines may be limited by resource deficiencies that do not affect their close relatives. Data from peregrine and lanner populations in South Africa support the resource deficiency hypothesis, and there is no evidence to suggest direct competition between the two species. In areas where prey are not spatially or temporally concentrated, or otherwise particularly vulnerable to attack, morphological and behavioural specializations of peregrines probably restrict them to optimal foraging conditions. The relative dynamics of Arctic and temperate vs tropical prey populations is suggested as an important factor determining peregrine distribution globally. Populations of other widespread but particularly specialized avian predators (e.g. osprey Pandion haliaetus) may be similarly controlled. Food limitation (in terms of a dearth of particularly vulnerable prey) in the tropics has resulted in specialization and rarity in peregrines and generalization and relative abundance in similar congeners.

 

[colonelboris]

I think the two posts above make a good point that only fastest and cleverest pigeons are getting through. Natural selection helping the p***** f*****.

 

[Jane Turner]

I think the two posts above make a good point that only fastest and cleverest pigeons are getting through. Natural selection helping the p***** f*****.

....and as we know RPs are not particularly quick and they certainly are not clever, even by pigeon standards!

 

[Collster]

....and as we know RPs are not particularly quick and they certainly are not clever, even by pigeon standards!

Also doesnt help when their owners house them under crags containing breeding Perrys , start exercising them just as the Perrys are getting into condition to breed, get lorry loads of relatives( RP) to visit said areas enmasse and then have the nerve to moan because the Perry wants a piece of the action. Do you think the owners are as blunt as their pigeons o

 

[Jane Turner]

Do you think the owners are as blunt as their pigeons

You might think that. I couldn't possibly comment!

 

[nirofo]

Also doesnt help when their owners house them under crags containing breeding Perrys , start exercising them just as the Perrys are getting into condition to breed, get lorry loads of relatives( RP) to visit said areas enmasse and then have the nerve to moan because the Perry wants a piece of the action. Do you think the owners are as blunt as their pigeons o

It almost makes you think that the PF's have got a death wish for their RP's doesn't it, or maybe they just want an excuse to persecute Peregrines.

As for their owners being as blunt as their pigeons, NAH! The pigeons know where their going, don't they?

nirofo.

 

[Anthony Morton]

Time Out!

I see that we are already up to 250 postings on this thread but sadly far too many of them, including some replies, have little or nothing to do with the question I posed at the beginning. It seems that some are only interested in trying to antagonise or belittle other interests they either do not understand, or do not want to understand. Rather than bringing the two sides closer together by examining the common ground, this will only serve to drive them further apart.

So perhaps while we catch our breath we should all read 'Grousemore's' Post #86 again, and in particular the second paragraph which I have highlighted. In the meantime, I will try to answer a few more of the outstanding comments and/or suggestions as and when time allows.

...Certainly not that I've read and I wholly agree with your points about fines; but zealots are on the loose with a 'worthy' cause, so it doesn't matter.

The very worst of Birdforum has been exhibited on this (and a similar) Thread, in that facts and proof are irrelevant when faced with an opportunity to have a go at those whose hobbies we don't share.

You asked earlier about how many 'PF's' have been convicted; the lack of any response speaks volumes to me.

 

[London Birder]

in answer to your original question Anthony, who knows ...

 

[Anthony Morton]

Another myth!

I think the two posts above make a good point that only fastest and cleverest pigeons are getting through. Natural selection helping the p***** f*****.

This is another myth put out by the pro-raptor lobby. When a Peregrine Falcon attacks pigeons during a race, it goes for the first ones it sees which are the leaders. In other words the fastest (best) birds are attacked first and either killed or scattered, while the slower ones following on behind get through.

So the only 'natural selection' possible as a result of predation by Peregrine Falcons is to ultimately reduce the pigeon's racing ability, not improve it!

 

[London Birder]

can you source that Anthony?

reason I ask because that's not always the case in my experience, they equally take the birds which stand out the most, i.e. pigeons with more white in the plumage than average ... why are you on about racing pigeons again, the Peregrine doesn't differentiate between racers or local ferals ...

 

[Anthony Morton]

Anthony, the fanciers down this way were predominantly old miners, unfortunately due to a shorter life expectancy through working in the pit most of these people are expired. There isnt generally much of a take up of the hobby by the younger element so i think this is why the numbers have dropped.As for them giving up because they can't stop the carnage that aint true- they just started killing Perrys to even it up

You really must learn to stop making these unsubstantiated accusations linking each and every Peregrine Falcon death to pigeon fanciers. All it achieves is to widen the gulf between the two sides.

How many times and in how many ways must I tell you this?

 

[Jane Turner]

My observations of Peregrines taking out Pigeons are the complete opposite. In about 400 observed kills the victim has always been a straggler or a lone bird

 

[London Birder]

I think the gulf is wide enough down to your fellow hobbyists judging by the inane nonsense on the various websites ... nonsense like up to 10 pigeons per day at an eyrie, something which I've asked you about but you seem not willing to address, despite the empirical evidence of those who've actively watched eyries ... if there's a gulf that's down to the fanciers, no birder I know is anti-pigeon racing

 

[Jane Turner]

Clearly a new breed of Peregrine is evolving - one that hoardes scores of dead pigeons in cliff top refrigerators. That would explain Anthony's "take out the leader" observation too. No more of this "just take the easiest bird to catch" shinnanegins

 

[stuart scott]

I'd be interested to know why you think the first pigeons a peregrine would see are 'leaders'. You state it like its a fact. The chances are it could see any pigeon, and choose to strike which ever one it feels it has a chance of getting.
I admit I've seen little of pigeons racing other than groups exercising around the local area of an enthusiasts loft, where they are grouped. Surely in races the birds are much more scattered so there is no obvious 'leader'.

Incidentally I no part of any 'pro-raptor lobby'. Just someone who thinks that there should be no negative interference with wildlife from any enthusiasts who has a little hobby ( how ever much time and money they spend on it ).
Pigeon racers should accept losses from raptors the same as losing birds from vehicle hits, diseases, or bad weather.

 

[colonelboris]

I think the two posts above make a good point that only fastest and cleverest pigeons are getting through. Natural selection helping the p***** f*****.

This is another myth put out by the pro-raptor lobby. When a Peregrine Falcon attacks pigeons during a race, it goes for the first ones it sees which are the leaders. In other words the fastest (best) birds are attacked first and either killed or scattered, while the slower ones following on behind get through.

So the only 'natural selection' possible as a result of predation by Peregrine Falcons is to ultimately reduce the pigeon's racing ability, not improve it!

I've not read anything by either side - that was just reasoning.
In nature, though it doesn't make sense to go for the strongest. You have to put in more energy and there is risk more risk of injury. Linons, tigers, wolves, sharks and almost any other carnivore I can think of use this tactic. I don't know if it's true for birds, but I'd find it surprising if it was the case.