8 Size of Movement
Any figure placed on the size is going to be at best a guesstimate. We are going to quantify a number of statements in this paper:
The UK movement involved raw totals of 196 birds on 13/9 and 215 on 14/9, giving a total of 411 birds. There will be duplicates but many birds are likely to have been missed in the early start and there are indications that juvenile Honey-buzzard are routinely misidentified as Common Buzzard by a number of observers. The actual number moving from 13/9-14/9 could be as high as 600-800 birds.
The proportion of the birds noted in Benelux that were of British origin was 80-90%, only 10-20% arriving from Jutland to the E.
The estimated passage in Benelux was 285 on 13/9 and 539 on 14/9, derived from grand totals of 981 on 13/9 and 862 on 14/9. The estimated passage from 13/9-14/9 is therefore 824 birds.
The total recorded earlier in Denmark from 5/9-11/9, was 2945 with 274 in Jutland and 2671 in E Denmark. As the reports came from many stations, there are likely to be many duplicates. The largest single movement was 524 birds on 11/9 over Nordsjælland in E Denmark. Perhaps 1500 birds were involved over the whole period in the country as a whole.
The total recorded in SW France from 12/9-14/9 was 814 birds and from 15/9-20/9 was 710 birds.
The exceptional movement over Malta of 700 birds occurred on 19/9 with a further 100 birds on 18/9.
The Honey-buzzard exiting Britain (600-800 birds, 13/9-14/9) mainly moved through Benelux (824 birds, 13/9-14/9) before travelling through France to the SW area in the Pyrenees (710 birds, 15/9-20/9). The Honey-buzzard exiting Denmark (1500 birds, 5/9-11/9) moved initially broadly SW through France to the SW area in the Pyrenees (814 birds, 12/9-14/9) and later broadly S through Italy to Malta (800 birds, 18/9-19/9). The numbers support the mapped routes given earlier but obviously nothing is actually proved.
The Honey-buzzard movement in Britain was remarkable for how long it lasted. From 1/9-12/9 35 migrants were noted, from 15/9-21/9 368 were seen and from 22/9-30/9 98 were noted, giving a monthly total of 1100-1300 birds. With 31 in August and 19 in October, this gives an annual autumn passage of 1150-1350 birds. To estimate the number of breeding pairs it is necessary to know the proportion of juveniles. This is not known but it is safe to say that the total indicates 400-500 pairs (1/3 birds are juveniles, productivity 1 young/pair) up to 750-900 pairs (2/3 birds are juveniles, productivity 1 young/pair) with of course other permutations possible.
8.1 Summary
Looking at the overall totals: the Honey-buzzard exiting Britain (600-800 birds, 13/9-14/9) mainly moved through Benelux (824 birds, 13/9-14/9) before travelling through France to the SW area in the Pyrenees (710 birds, 15/9-20/9). The Honey-buzzard exiting Denmark (1500 birds, 5/9-11/9) moved initially broadly SW through France to the SW area in the Pyrenees (814 birds, 12/9-14/9) and later broadly S through Italy to Malta (800 birds, 18/9-19/9). The numbers support the mapped routes given earlier but obviously nothing is actually proved.
