From: <GeoffDobbs@aol.com>
To: <nrossiter@supanet.com>; <owner-ukbirdnet@dcs.bbk.ac.uk>
Subject: Re: [UKBN] Honey Buzzard Movement Autumn 2000
Date: 04 November 2000 04:16
>Nick
>I will leave the statistics to others, but I will (somewhat reluctantly as I feel I am wasting my time) respond to your [comments]
>In a number of points made in reply to mine, I believe you suggest or imply >that:
>1. Any accompanying Common Buzzards were British
There is no evidence that Scandinavian Common Buzzards ever reach Britain (see Ringing Data for Raptors ) . When local knowledge contradicts data from ringing recoveries, questions do need to be asked. Only one foreign-ringed Common Buzzard (from Belgium) has been recovered in Britain to date. It is much more likely that Common Buzzards moving through eastern Britain are British, reflecting the exploding populations of Common Buzzards in some parts of eastern Britain.
>2. Past evidence of Honey Buzzards arriving in-off on SE winds is inconclusive as to origin as the sample size is too small, and there is no definite proof.
>3. That there was some contradiction in my description of the "rules" (not my term) that govern raptor passage at Spurn, relating to wind directions favourable for raptor passage and the presumed origin of these raptors.
>4. There wasn't a big enough fall of Continental passerines on the coast to support Continental origin of Honey Buzzards
This is surely true. See Accompanying Species .
>5. Some (or many?) of these passerines were therefore British.
It's difficult to prove otherwise for those species that breed in Britain.
>6. No reference was made to the appararent lack of breeding Honey Buzzards in Yorkshire (although this may be too sensitive an issue to discuss on UKBN if Nick knows of breeding pairs hitherto unreported to the County Recorder).
No, I'm hiding nothing. I did though hear of a fairly well-watched site on Forestry Enterprise land in Yorkshire a few years back. So there is potential. Yorkshire does seem to still have worryingly high levels of persecution of raptors. Indeed Clements in his BB paper on the spread of Common Buzzards identified the disappointing lack of progress there compared to nearly every other county in eastern Britain. However, there is some excellent habitat for HBs, particularly the North Yorkshire Moors and some of the Dales. Some observers are extremely reluctant to reveal information on HBs - this secrecy is bedevilling the current debate because of weaknesses in the base data. It is difficult to get accurate census data.
Geoff, I've not commented on the further points below, because the ringing data seems to be compulsive. Regards .. Nick
******************************
>Geoff, thanks very much for the information. We can only rely on records where the identification (of Buzzard species) is confirmed.
True - I am of course collecting descriptions, but the point I was making was
that there was a much bigger "buzzard" arrival on the coast on the 20th than
reported on the pagers, even if descriptions to species may never be received
for many seen by non-birders. It is accepted that a small proportion were
Common Buzzard, as some Common Buzzards were seen by birders. You seem to
suggest that these were British Common Buzzards rather than Continental
Common Buzzards. Common Buzzard is a rare bird in East Yorkshire, with
perhaps only 2 breeding pairs. All Common Buzzard sightings are therefore
submitted to me as a matter of routine.
e.g. 1997 (OK the population has increased slightly since)
"The only autumn records on the coast were one at Spurn on 9th August and
one at Flamborough on 22nd November" YNU 1997 Report in prep.
Therefore there was a possible unprecedented migration of British Common
Buzzards in Yorkshire due to....? .. but no accompanying Kestrels and
Sparrowhawks?
>Can you make a rule from these observations? Your past samples seem very
small. The actual instances quoted seem to involve an ambitious labelling as
British or continental.
The past observations I quoted were of 2, possibly 3 Honey Buzzards coming in
off the sea from the last 3 years...(I could have trawled through all past
YNU Reports) ......The samples are admittedly small in number because Honey
Buzzard (whatever its origin) is normally a rare migrant in Yorkshire. Do you
need to trap one with a ring on to make it a "rule", or can you draw the
conclusion that in-off Honey Buzzards with easterly winds behind them have,
in the past, with a high degree of probability, crossed the North Sea? How
ambitious is such a conclusion? Other species are also seen coming in off the
sea, e.g. Short-eared Owl (not always on pager messages) in similar
conditions on the same days. Birders on the Yorkshire Coast do draw the
conclusion that these birds arriving during the day on
easterly/South-easterly winds are from the continent... remember the recent
in-off Demoiselle Crane (debated as presumed escape from the Continent)
around the same date in September in not too disimilar conditions? Are we all
wrong ?
I'm not sure what I put in my first private draft that contradicts my UKBN
posting with regard to "rules" for judging the probable origin of migrant
Honey Buzzards, despite re-reading it several times. It was clumsily
expressed but here it is
"British raptors only pass down the coast in Autumn on North-Westerlies, with
Marsh Harrier, Kestrel and Sparrowhawk far out-numbering Honey Buzzards, but
with the best passage on dry days. Presumed Continental Honey Buzzards arrive
on South-Easterlies, and usually no other raptors accompany them apart from
the occasional Buzzard or early Rough-leg. If the winds were from the west
with a front offshore, then the British Honey Buzzard theory has some
credence, but one would expect a supporting cast of other British raptors
like Sparrowhawks on 18th-20th, even in reduced numbers because of the poor
weather. If the winds were south-easterly on 19th then I would favour
Continental birds making landfall late in the day."
Perhaps you can explain the contradiction to me.
Yes we do make predictions: that there will be a (British or previously
arrived migrant?) raptor passage at Spurn when the winds are North-West in
September, with a passage of Sparrowhawks and Kestrels, and a small
supporting cast of larger raptors, with the recent increase in Marsh Harriers
and Buzzards clearly reflecting the expanding British populations, and these
would be the ideal conditions for British Honey Buzzards, but Honey Buzzard
sightings in these conditions are very rare and no comparable increase has
been noted.
>It's pretty routine for September on the east coast
It's routine in so far as it shows a typical fall of Continental migrants
occurred on the 20th, associated with south-easterly winds. Massive falls are
rare but can apply to some species one year more than others. I'm not sure
why you suggest that an unprecedented influx of Continental Honey Buzzards
would be accompanied by a massive influx of passerines, as the first would
migrate by day and the latter by night, therefore experiencing at least
slightly different departure conditions?
(I'm not yet convinced by the argument that there was a continuous arrival of
Honey Buzzards after 22nd, as there was little evidence of any on the
Yorkshire coast after 22nd).
I trust you are not suggesting that the birds seen at Flamborough are
normally present throughout September on the Yorkshire coast no matter what
direction the wind is from? The suggestion that some of the passerine
migrants on the coast on the 20th and subsequently could be British is
supposition, and there may be evidence from ringing controls to
support/refute this supposition.
Rough-legged Buzzard somehow came in to the argument, with regard to them not
moving inland (to support the argument that the Honey Buzzards were not seen
moving inland and were therefore British).
<< But the Winter Atlas (Lack 1986) shows a marked eastern bias with many on
or
near the east coast. Lack says "there is little outward movement following
an autumn arrival". >>
The following extract from 1998-99 YNU Report in prep (G. Dobbs) suggests
almost as many in the west as the east, with birds in the west wintering and
birds in the east migrating.
ROUGH-LEGGED BUZZARD Buteo lagopus
Scarce migrant and winter visitor
1998: 2 were regularly seen on the North York Moors from January to early
March, being reported from Bransdale and Sleddale. One showed well in
Derwentdale at Howden Res. from 10th January and was seen at Midhope Moor on
28th March, Pike Low on 5th April (SG: JWa) and Ewden Heights on 23rd April.
One was reported from the Gouthwaite area from 7th January (PJC) to March,
including at Barden Scale on 5th March (NCD et al). In the east of the
county, one was reported from Millington Pastures near Pocklington on 23rd
February. One flew north-west at Spurn on 3rd May (LJD: PKG), with one at
Sammy's Point, Easington on 24th (AA: DJS), with probably the same bird
flying south at Beacon Ponds and Spurn on 1st June (MJP et al).
In autumn, one flew south at Spurn on 30th September, one was at Coatham
Marsh, Redcar on 3rd October, and one was at Skeffling and later Grimston on
11th, 12th and 17th October (TI). One was in Sleddale again from 18th to 25th
and another at Leighton Res. on 25th. Further sightings included a first
winter in the Kildale/Commondale area in November, and singles at Scaling Dam
on 3rd, Dallowgill on 12th (PKB, DVB), and Bransdale on 19th December.
1999: Reports of wintering birds were of singles in early February at
Scaling Dam Res. and Bransdale on the North York Moors, with further singles
reported from Leighton and Gouthwaite on 15th and 20th. One flew south-west
over Buckton on 28th March. In April, one flew over Allerton Bywater,
Fairburn Ings and Fryston on 2nd (JB: CW: JG: SW). Possibly the same bird was
seen over Sammy's Point, Easington on 4th, U-turning over Spurn before
heading towards Skeffling on 5th, and finally passing south at Spurn on 6th
(GED: LJD et al). One flew south-east over Thwing near Bridlington on 6th
April.
In autumn, one at Cloughton on 18th October, one at Spurn on 25th flew off
south-east after resting in the dunes (NAB et al) and possibly a different
bird flew low west then north over Kilnsea on 26th (IF). One was in Sleddale
on 27th-28th November (MC: JLS).