Mogelijke vervanging van mannetje Wespendief Pernis apivorus tijdens de jongenfase

Prolonged stays in tree tops in July were used to detect prey-transporting Honey Buzzards, in the hope to locate their nest via triangulation. On 19 July 2017 (duration of watch: 4.15 h), a male Honey Buzzard was observed that possibly belonged to a nest that was found at a later date. During the same day I saw the female twice, on both occasions giving alarm calls above the nesting site. During the second day (5.00 h of observation) her departure from the nest site was recorded three times, apparently heading for feeding areas; the return with prey was observed once. On the morning of 21 July, after a night with heavy rain, the soaking-wet female was drying her plumage in a larch in the edge of a small heath close to the nesting site when a male (1) in dry plumage landed nearby. After 20 minutes the female departed and headed for the nest. At the same time another male (2, of much lighter plumage than the first male) emerged from the same section of the forest, flew towards male (1) and disappeared under the canopy nearby, followed immediately by male (1). A visit to the nest site (nest easily located based on previous clues) showed a fresh plucking of an adult male on the forest floor underneath the nest, probably killed by a Goshawk (a female had been seen previously, searching the forest near the nest of the Honey Buzzard). The nest contained a single chick of 12 days old; the female alarm-called during the nest visit and she was accompanied by male (2). The chick was in good condition. At this age the male normally provides all the food to the nest, whereas the female broods or stays in close vicinity (Holstein 1942, van Manen 2011). The frequent foraging flights of the female recorded on 22 July suggests that the plucked male under the nest may have been her partner. If so, it is remarkable that already the day after the male’s depredation, two other males were present, apparently attempting to take-over the breeding territory of the widowed female. The latter observation is relevant to the behaviour of non-breeding male Honeybuzzards. Non-breeding birds form a large and consistent (over the years) part of the breeding population, amounting to some 50% of all Honey-buzzards present. In contrast to floaters in other raptor populations (which live a low profile life), non-breeding Honey-buzzards show high profile behaviour, spending a considerable amount of time soaring and wing-clapping at great heights. These flights overlap with the largely discrete territories of breeding Honey-buzzards. Advertising whilst roaming around may serve to permanently check on the fortitudes of breeding pairs in combination with showing individual quality by wing-clapping series.