From: John Cantelo <cantelo@zetnet.co.uk>
To: <ukbirdnet@dcs.bbk.ac.uk>
Subject: [UKBN] Re: Honey Buzzard Movement Autumn 2000
Date: 04 November 2000 11:22
The message <3A029B0B.00108B.00211@baldrick.mybriefcase.net>
from simon nichols <nomis1@mybriefcase.net> contains these words:
> Nick R Droned on !!!
> > If you did a similar exercise for Kent you
> > would get very different figures
> > with 2000 not being anything like so
> > exceptional. We need to consider
> > national figures not local ones. The particular
> > exit points chosen in any
> > one year will obviously vary. Should we not be
> > less parochial. It's good to
> > keep a national perspective on a national
> > birdnet!
> Can we have someone from Kent commenting on this - the people I have spoken to , who live in Kent - Say that this is the best year ever BY FAR !!
>I can't give chapter and verse on this issue, but as far as I can >make out it rather depends upon where you were in Kent.
Yes, Birdline South East shows that numbers were low in east Kent and high in west Kent.
>At Bockhill (nr Dover) the total HBs (5?) was pretty much 'average'
>which, given events elsewhere, was both very disappointing and rather
>surprising. The meagre total of 2 Common Buzzard was very much down
>on recent totals. I heard of a few on Thanet and 5 at Pegwell Bay,
>but better numbers towards the west of the county (eg Cliffe) and
>certainly more seem to have been 'picked up' in odd parts of the
>county. I'd guess that the overall total then will be well up on the
>average, but nowhere like the striking totals recorded in Sussex.
>This is suggestive of the HB influx being of birds pushed westwards &
>then reorientating southwards.
>Being mathematically challenged I can't comment on Richard Fairbank's
>statistical analysis, but base my attitude to the claim that the
>movement involved British bred birds on the fairly simple basis of
>credibility. My logic goes something like this:-
>a) Population of HB's on the continent to our north & east - BIG;
>population in UK not big - in fact bloody small. Even if the
>potential 200 pairs posulated (but discounted) in the recent 'BB'
>paper were true,
The 200 pairs was not discounted. However, it was felt that a larger sample size was needed: hence the census this year.
>then it remains very small compared to the population in Scandinavia & Germany
True! But we are looking for an adequate source consistent with the capabilities in migration of broad-winged raptors, not the largest.
>b) Strong airflow from the continent (cf that German baloon) at relvant time strongly indicates that the origin of the migrant is precisely what we'd expect.
So the facts, that a) in almost 200 years nothing like this has happened before and b) that the winds on the continent were not that strong, do not trouble you. See Unprecedented in Almost 200 Years . The balloon incident is irrelevant from an ornithological perspective -- it tells us nothing that we do not know already from the weather maps: there was a force 6 SE wind at the altitude the balloon was travelling over north-west Germany, Holland and the North Sea.
>c) For the movement to be fueled by UK bred birds (even accepting a speculatively high population) then they would have to have been co-ordination (i.e. birds 'agreeing' to exit en masse) that would have made a synchronised swimmer green with envy.
Concentrations very often occur in raptor movements. See (Fågelobsar i Skåne, http://www.skof.se/obs/index.html , click on Rovfågelsträcket, then Se Diagram in turn for Pernis apivorus and Buteo buteo) to see very concentrated movements of Honey and Common Buzzards over Falsterbo.
>d) Although supposedly rooted in imperical observation & deduction, concensus is very important in science.
So we do now worry about evidence!
>No, it's not a popularity contest, but if all your peers take a contrary view then it requires exemplary rigor and convincing factual support to overturn such a concensus.
All my peers? I've had quite a few messages of support.
>This is singularly lacking.
On the contrary, John. With the addition of the Danish movements and the ringing data to my pages, the case for a continental origin now looks very weak indeed.
>Hence we come to our dear friend Occam and his razor - and the argument that the birds were UK bred falls.
Occam's razor is applied to reduce a collection of equivalent theories to one all-encompassing theory. It cannot be applied to conflicting theories.
>If more convincing argument to the contrary can be produced then I for one would celebrate - HBs are superb birds and it'd be wonderful to have such a healthy population.
But you're not even waiting for the results and interpretation of the HB census. I see what you mean above about evidence not being important! However, I am delighted to see that you would celebrate a healthy British HB population, just like the one you reported on in north-west France (see Cross Channel Birding (http://members.aol.com/berksbirds/calais.htm , now at http://www.birdtours.co.uk/tripreports/france/calaise/calais.htm ).
Cheers ... Nick
>John C
>P.S. I am tempted to speculate that the recent strong passage of
>Storm Petrels through the Channel from the west indicates that
>Atlantis is still out there somewhere, but that would be s(c)illy, wouldn't it?
