With regard to poisoning of raptors:
There were two ways raptor numbers were affected by poisoning. The first and most obvious is to purposely lace a carcass with poison to kill the bird directly with an immediate overdose of a toxic substance.
The second way was unintentional as a result of mankind's endless meddling without thinking it through via pesticides/pollution. This works for toxins that do not break down and accumulate inthe bodies of animals such as DDT and heavy metals like lead and mercury. As each stage in the food web is reached there is a gradual concentration of levels in the food eaten at each stage. I'm assuming the basic principle of a food web is understood here (google is your friend). This means that in effect the apex predator is eating the equivalent of several thousand invertebrates by the time it eats the song thrush. So every time it eats one thrush it has taken on the whole food web below it's intake of the poison. Meanwhile, the single thrush only eats its own share and each snail it eats only ingests its own share but it eats thirty snails a week. The snail in turn eats many leaves which each only had their own share. The animals lower down the food web often show no ill effects because they don't ingest sufficient poison before dying of natural causes or being eaten. Meanwhile, our Sparrowhawk, after eating ten thrushes is feeling very poorly indeed....
Yes, I understand the basic principle of the slow accumulation of ingested toxins in the food chain, our Peregrine populations were particularly devastated in this manner - (but thanks anyway!)
However, none of this is directly relevant to a situation where a raptor (rarely I presume since apparently no or few people have witnessed it) takes a
live raptor as in my hypothetical case of the Female Sprawk taking a male that has itself ingested poison.
So in answer to, does our Sparrowhawk eating a bird that was poisoned itself in turn become poisoned: it depends on a few factors:
Does the toxin used break down in the very action of being toxic and is therefore used up? Is the toxin stored in the tissues of the dead animal or excreted/stored in the gut? Is it the actual toxin stored in the tissues or the residue of the toxin after taking effect - and is this, in itself, toxic?
Well this was the actual question I raised but which you answer with more questions in fact those I wanted answered when posing the question!
It doesn't always follow that a purposely poisoned animal is itself toxic to eat, though experimental eating would be unwise to try.
I'm not sure I understand that comment
The levels of toxin in the poisoned animal will likely be far lower than in the poisoned bait
Well that probably stands to reason but again doesn't answer my question as to whether a Sparrowhawk will be (fatally? seriously?) poisoned by eating
one Sparrowhawk that itself had fed on poisoned bait (a baited Spar or otherwise).
Your problem with Owls scavenging poisoned rodents is that they may well ingest a large number of them if a poisoning campaign is particularly vigorous and successful, thereby concentrating the poison.
Again more relevant to the scenario of a BoP eating poisoned bait
directly and/or accumulation by quantity of poisoned bait being digested over a period of time. Obviously s Sparrowhawk's main diet isn't other Sparrowhawks, so slow accumulation through the food chain by
secondary poisoning in the form of other Sparrowhawks who've eaten baited prey (baited Spars or otherwise) is probably irrelevant to the scenario I outlined.
My question followed on from the comments Nirofo made regarding BoP being used as bait and whether a Sparrowhawk taking another Sparrowhawk which itself had fed on a deliberately baited Sparrowhawk
and had survived long enough to have been taken as live prey itself. Which brings me back to the original question and the point of the link in the first post/ Ian Newton's comments:
That is: Whether anyone has actually witnessed a Sparrowhawk taking
live Sparrowhawks as prey?
I agree 'google' can be 'your friend' but whatever snippets found need still to be put together in a way that's logical and relevant to the question being asked