BIJLSMA RG (1986) Occurrence and breeding biology of the Honey Buzzard Pernis apivorus on the SW.Veluwe and in the SE.Achterhoek. LIMOSA 59 (2): 61-66.

European Honey Buzzard Pernis apivorus The occurrence and breeding biology of Honey Buzzards Pernis apivorus on the SW. Veluwe (11 447 ha) and t?e SE. Achterhoek (16 600 ha) during 1973-83 is d~s~nbed. Full de~aIls are supplied with respect to the difficultIes m locatmg nests of the species. Of 90 p~irs on the SW. Veluwe (1974-83) 58% nested m mIXed woods, 32% in coniferous woods and 10% i.n deciduous woods, which suggests a prefe;ence for mixed woods (only 25% of the woods consists of mixed forests). Of 27 well-known territories 15 were used six times, or more during the ten years under consldera~ lOn: Seven nests were used two times (not necessanly m consecutive years), one nest three times and another nest eight times. The majority of nests found m the SE. Achterhoek were situated in mixed forest with a large percentage of deciduous trees which is the dominant forest type in this part of th~ country. .In both areas, the numbers of pairs fluctuated only slightly between 1973 and 1983 (fig. 2). On the SW. V~luwe 9-17 pairs. were found each year (0.08-0.15 paIrS/lOO ha) and m the SE. Achterhoek 10-15 pairs per year (0.06-0.09 pairs/IOO ha). Inter-nest distances varied between 1-2 km, but could be as small as 470 m. A substantial increase in breeding numbers of Buzzard and Goshawk during the study period did not negatively affect the population of Honey Buzzards in the study areas (fig. 2). Of 79 pairs on the SW. Veluwe the onset of egglaymg was kn?wn within 5-day-periods. Start of egglaymg was highly synchronized within 10-16 days (range 8-22, x = 14). The ten years combined, however, showed a remarkable spread in the onset of egglaymg: fro~ 16 May up to and including 23 June (fig. 3). Clutch size was determined in 21 pairs: 20x 2 and Ix 3 eggs. Of 43 eggs, 41 hatched and 36 fledged (84%). Seventy-two out of 90 pairs succeeded in raising at least one young. In sum, 104 young fledged (41 xI, 30 x 2, 1x 3: 1.16 young/pair or 1.44 young/ successful pair). The majority of young fledged during August; the last date of fledging found was 4 September (fig. 3). In the SE. Achterhoek 14 pairs raised 19 young (9x 1, 5x 2: 1.36 young/successful pair). A comparison of the breeding densities .in six different areas in the Netherlands is given in tab.!.

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