Results of Honey-buzzard Breeding Survey 2000
Preliminary Results
Reference: Batten, L A, European Honey-buzzard Survey 2000 and 2001: preliminary results and requests for further surveys, British Birds 94(3): 143-144 (2001).
With a total of 61 breeding pairs reported (29 confirmed), the recorded population of Honey-buzzard in 2000 is the highest on record. Further only 16 out of 35 co-ordinators have reported so far so the final reported total is likely to be higher even though most outstanding are likely to be negative returns. Apparently some areas known to hold Honey-buzzards have still to report.
The outcome of last year's survey with regards to the likely source of the movement in autumn 2000 is on the face of it inconclusive. Enough birds have been found to indicate that a significant movement of British-bred juveniles must occur. Not enough have been counted to explain the numbers seen in September and early October 2000.
The editorial (Riddington, R, British Birds 94(3) p.102 (2001)) in the same issue appears to take a very conservative view of population trends which appears unjustified in view of the figures obtained with comments such as "This survey is an important step towards improving our knowledge of the small, but possibly increasing British population of the European Honey-buzzard" and "it is still an extremely rare ... breeding species".
First Official Results
Reference: Ogilvie, M, Rare Breeding Birds in the United Kingdom, British Birds 95(11) p.554 (2002).
Surprisingly this showed a decrease from the preliminary results with 51 pairs found (30 confirmed). The regional distribution was given as: England 43 (24 confirmed), Wales 4(4), Scotland 4(2). Breeding productivity was indicated by a total of 15 pairs raising 2 young, ten one and five none. The overall productivity was thus 40 young from 30 pairs or 1.33 young/pair.
Corrected Results
Reference: Ogilvie, M A, European Honey-buzzards in the UK -- correction to breeding totals, British Birds 96 (3) p.145 (2003).
This showed the expected increase from the preliminary results with a total of 69 pairs (33 confirmed). The regional distribution was given as: England 45 (24 confirmed), Wales 10(5), Scotland 14(4). Clearly the first official results omitted some significant records from Wales and Scotland.
The comment is made that "The total number of confirmed pairs is well in excess of any previous total reported to the Panel and confirms the belief that this species has been considerably under-reported in the past".
Prospects for 2001
The decision to run the survey again in 2001 reflected incomplete coverage in 2000, some of which resulted from the sheer area of habitat which needs to be covered and some from the related problem of insufficient time and effort spent on each wood. The Foot-and-Mouth epidemic delayed any re-run until 2002.
Comments (NR)
Personally I think this is a species whose breeding population cannot be assessed accurately by counting occupied sites 1,2,3,... across Britain (See census difficulties). Clearly, the basis of the census must remain the fieldwork and the collection of details for habitat, altitude and geographical region for sites found. However, two improvements can be suggested. Firstly the latter details should also be collected for negative returns. Secondly some extrapolation of the results should be made to allow for areas poorly covered using the results from areas where intensive fieldwork has been carried out by observers experienced with the species. This extrapolation will clearly be based on area and suitability for the species in terms of habitat, altitude and geographical location. These techniques provide a scientific basis for delivering a reasonable estimate of the population of Honey-buzzards. Such an estimate is likely to give a better idea of the British breeding population than the strictly minimal counts obtained in the fieldwork. All other European countries appear to use extrapolation techniques to calculate their populations of Honey-buzzards.
The decision to go for a further year's survey in 2001 is to be very much welcomed as it will raise the quality of the base data which can then be extrapolated with narrower confidence limits.
