Spring is the best time to observe a flying or circling European Honey-buzzard (Pernis apivorus) on their breeding grounds. Now is Display time! Since the breeding birds arrive until the middle of May in the breeding area, bird watchers and bird photographers have to hurry-up to take pictures of European Honey-buzzards. This is because oviposition falls on the brink of May/ June. At the end of June / beginning of July, the youngs appear and at to the beginning of August fledging starts.
There are two periods of activity for the adult European Honey-buzzards: display and post-fledging. Display takes place in Germany from mid of May till early June. There is a time lag between spring migration observations and display flights. It seems, that on first arrival in early May the birds are rather lazy perhaps feeding and resting after the long migration. The lazy flight with long periods of effortless floating, interspersed with the very occasional stall or spell of active flapping, occurs over their breeding areas at this time. This can be misinterpreted as migration flight. In this time very impressive and repeated display flights – “butterfly display” – is brief and in rainy springs may not be conspicuous. In “butterfly mode” the European Honey-buzzard shakes its wings above back in rapid succession, usually six or seven times.
A good description you will find here. The author mentions, that Continue reading Display flights of European Honey-buzzards