Honey Buzzard Movement 2008, View of Birdwatch Magazine
Reference: various pages (as given below) in issue 197, November 2008.
Verbatim:
Monthly highlights [National] p.61
13th was lucky for some with a Zitting Cisticola in Kent and an Eleonora's Falcon in Essex, while at the same time there was a huge arrival of Honey Buzzards, with at least 18 over Minsmere.
South-West [England] p.64
The biggest influx of Honey Buzzards since 2000 had birders all over the country looking skywards. The South-West had its fair share, with about 60 logged, The Weymouth/Portland area had by far the largest number, with at least 25 noted. Portland also hosted a juvenile Woodchat Shrike from 10th-12th.
South-East [England] p.65
The big raptor news concerned Honey Buzzards: the species was seen daily, with double-figure totals on several days and birds clearly moving on a broad front. Four drifted over Brighton, East Sussex, on 8th; at least 31 were seen in the region on 14th, with three together over Fareham, Hants; eight passed over Potters Bar, Herts, on 16th; and a minimum of 32 were seen on on 20th-21st, including three over Ramsgate, Kent. A Black Kite was reported flying north over Hill Head, Herts, on 25th. Thirteen Common Buzzard over Rainham Marshes RSPB on 20th was also a highly unusual record.
East Anglia p.66
Large numbers of Honey Buzzards were reported at numerous localities around Norfolk on 13-14th. Many continued south to Suffolk, resulting in record counts at Minsmere RSPB – the largest count was 18 on 13th, while Welney WWT logged eight on 14th.
Midlands p.67
September's highlight was the significant number of migrant Honey Buzzards, of which at least 54 were reported across 11 counties, with Bedfordshire accounting for just over 20 per cent of these. The majority occurred as fly-overs mid-month as part of a national influx, arriving on an easterly airstream from the Continent.
North-East [England] p.68
It was the raptors, though, that captured the imagination, as large numbers of Ospreys and Honey Buzzards were swept across the North Sea. Approximately 210 Honey Buzzards were recorded in the region in the second half of the month. The main arrival took place over the weekend of 13-14th. Some 70 Honey Buzzards were reported on 13th alone, with a concentration of 16 recorded on Teesside, 11 in Durham, 14 in Northumberland and 25 in Yorkshire. Only four made it into Lincolnshire, but the following day the county recorded over 30 birds, this total included 16 the passed over Gibraltar Point before breakfast.
High pressure over the following weekend of 20-21st produced a further onward movement, with most birds being reported inland from Durham and Yorkshire. This influx mirrored a similar invasion that took place in September 2008. As then, high pressure from Russia extended into Scandinavia, drifting birds westwards. Low pressure over Britain squeezed under the high brought easterly winds, on which the buzzards continued westwards towards the east coast.
North-West [England] p.69
The Isle of Man also hosted a Turtle Dove on the Calf on 3rd and a Honey Buzzard flew over on 24th. As part of the national invasion, upwards of 30 further Honey Buzzards were recorded in the region, with the peak count being three at Bowland Knotts, Lancs, on 21st.
Scotland p.70
... and there were good showings by both Hobby and Honey Buzzard, with 14 of the former reported, mainly juveniles, and including up to seven in Lothian. A total of 38 Honey Buzzards was reported, including five from Fife from 14th onwards and nine in Aberdeens, including four reported over Collieston on 14th.
Wales p.71
A further taste of Scandinavia was brought to Wales in September, a a few stragglers from the massive Honey Buzzard invasion were recorded over Gronant Dunes, Denbighshire, on 17th, Rumney Great Wharf, Glamorgan, and Parc Bryn Beach, near Merthyr Tydfil, on the Glamorgan-Gwent border, on 24th.
Northern Ireland p.72
no reports apparently
Republic of Ireland p.73
no reports apparently
Comments by NR: blue font indicates statements made without justification or evidence. That such a remarkable movement should warrant no in-depth treatment is somewhat surprising. Since it is this magazine that invented the phrase Once in a Lifetime in 2000, a sequel would have been expected such as Twice in a Lifetime! Or maybe not! There are some rather vague claims on the weather above, indicating some of the writers support the Spiral or the N Model as an act of faith. This is particularly true for the writer for North-East England where of course tensions on this species are slightly raised! However, rather pointedly no origin is given for the birds by the authors of the Scotland, East Anglia and South-East England accounts. Some detailed research shows that a continental origin is most unlikely. We consider two models here. A description of these models can be found here.
The N Model: Origin Holland
Let's hypothesise on the N Model. This supposes the birds leave the Continent around Holland and move NE to the north-east coast of England or possibly further south. To be plausible we would expect the birds to leave Holland in daylight hours on Friday, 12th September, probably in the afternoon, and cross the North Sea at night, arriving in time for breakfast the next day on Saturday, 13th September, rather like a North Sea ferry! It's 450km from Amsterdam to Newcastle and 200km from Amsterdam to the Norfolk coast. So assuming a steady flight speed of 35km/hour it would take 13 hours to get to Newcastle and 6 hours to Norfolk.
So the birds should arrive around dawn in Newcastle and well before dawn in Norfolk but of course they may be disorientated, spiralling around in endless circles! Any broad-winged raptor is going to find such a flight, and particularly the one to Newcastle, a major challenge and not all birds would survive, ending up at oil rigs, in the sea or in a distressed condition on the land.
So you would expect some very serious weather conditions to cause such a movement, particularly as we went through every year in the 20th century before 2000 without any significant movement at all. Two weather charts are shown here: a forecast for 12th September at 12:00 and the actual situation at 13:00 on 13th September. The first shows W winds over the southern North Sea with E winds further north. The second shows E winds over the southern North Sea and E winds further north turning S on the coast. The situation on 12th looks rather finely balanced so let's look at the actual weather in Amsterdam using Weather Underground. This table, showing the weather hour by hour for 12th, reveals that the wind was light E in the morning, turning W 31.5km/hour about 13:00 with rain through to about 19:30. The wind slowly declined to 14.8km/hour W by 19:30 and continued W up to midnight. On 13th the table from Weather Underground shows that the wind was still basically W until about 08:30, moving to a constant ENE from 10:00 for the rest of the day.
So it was wet with W winds in the southern North Sea at the critical time for any exodus towards the W or NW from Holland. So the hypothesis looks very weak from the Amsterdam weather point of view. Of course the times above for crossing the North Sea are based on calm weather; with a headwind all calculations are much worse for the safety of the birds.
We can virtually rule out an Amsterdam origin by looking at the maps for Honey Buzzard migration through Belgium and the Netherlands (Benelux) on Trektellen. These show for Wespendief (wasp killer!) that 58 passed on 12th, 981 on 13th and 862 on 14th. Better quality maps than these screen dumps 12/09 13/09 14/09 can be easily obtained directly from the Trektellen site. Since the circles are close together, there will be some duplication of birds but it is clear that large numbers are on the move, generally keeping well inland and moving steadily S just as expected. There is no indication of birds moving to the west over Friesland or over the coast to the south.
It looks as if the more clued-up birders in south-east England and East Anglia reporting above have already looked at the weather information and wisely ruled out a simple transfer from the near continent.
The Spiral Model: Denmark
The advocates of the Spiral Model may claim it is infinitely flexible, I think even the keenest advocate would say the birds were over the North Sea on Friday, 12th September, arriving in time for breakfast on Saturday, 13th September. If there had been an exodus over the North Sea further N, then there was surely some sign of this in Denmark. The winds were basically E over Copenhagen, Denmark, from 12/9-21/9, thus facilitating drift migration to the W. Looking at Weather Underground from 12/9-21/9 we see winds were E/ENE from 12/9-17/9, NE from 18/9-19/9, W on 20/9 and NE on 21/9. But the winds were not strong, declining steadily from 26km/hour on 12/9 to 16km/hour by 17/9 and only 8km/hour on 19/9. Of course there is no evidence from its movements anywhere in Europe that the Honey Buzzard is a drift migrant, allowing itself to be drifted across the North Sea, like a warbler. But to check a detailed examination was made of all the records available in Denmark for Honey Buzzard throughout September and a comparison of Danish totals was made with those in Benelux and the UK. This research does not support at all a case for immigration from the continent with migration there progressing as normal, relatively few birds on the North Sea coasts and a very late migration in the UK not matching records elsewhere by any standards.
The Spiral Model: Birds too high to be seen
Of course the keenest advocates of the Spiral Model would retort: the birds were flying so high that nobody saw them.
This view is very weak from the physics point of view. There are no thermals over water in the same way as over land, so the Honey Buzzard would have to abandon soar-glide and flap all the way at low altitude. So they should be seen at North Sea oil rigs or boats in the North Sea. Certainly by 2000 there had only been a single record of a Honey Buzzard at an oil rig in the North Sea. There are no reports either in September 2008 and a comment on the BirdGuides webzine showed also that none had been seen on a research vessel in the North Sea at the critical time from 12/9-15/9.
If the Honey Buzzard were a drift migrant across the North Sea we would also expect ringing recoveries of continental birds in the UK. Populations on the continent were high throughout the 20th century so there has been a long period for birds carrying rings to be recovered. But by 2003. there had only been one Scandinavian Honey Buzzard carrying a ring recovered in the UK. Even in the large movement in 2000, no recoveries of continental birds were made. No recoveries of continental Honey Buzzard have been reported to date in 2008.
Conclusion
Neither the N Model nor the Spiral Model accounts for the movement of Honey Buzzard in the UK in September 2008. There is no evidence at all for the movement having originated from the continent. The authors from Scotland, East Anglia and South-East England are congratulated on their judgement.
