James Emerson
Norwich Birder
I would be very surprised if the BTO did not have data about the number of casualties directly caused by ringing at CES sites, and one of the reasons for running them is to monitor increases and decreases in populations (separating out the causes of a change is more difficult).
Whilst accepting that part of the reason for raising your concerns here is to see what other people think, have you directed some of your concerns directly to the BTO? They might be able to put your mind at ease by providing some of the data that you mention? Without doing that much of the response here will at best be anecdote, and otherwise just "what if" type suggestions.
Regards,
James
Whilst accepting that part of the reason for raising your concerns here is to see what other people think, have you directed some of your concerns directly to the BTO? They might be able to put your mind at ease by providing some of the data that you mention? Without doing that much of the response here will at best be anecdote, and otherwise just "what if" type suggestions.
Regards,
James
Hi John,
I'm really talking about the rise and fall, at the constant effort site, affecting the quality of the data. You are not factoring in the unknown net casualties, plus the disruptive effect. and physical presence of the nets, tending to aid predators like Sparrowhawk in their particular hunting style. This temporary but regular netting (In my view) is more than enough to increase the density of that predator visiting the site, in the short term, and in the long term in much the same way as a farmer's field of wasted maize will sustain a higher than normal Corvid population, until they move out of that area with a taste for fresh eggs in spring. I agree that over a larger area, the arms race would tend to keep in balance. But at the sites, the songbirds would gradually decrease. I would think that by now, there should be enough data from constant effort sites, to prove or disprove this theory?
Colin