An adult female Montagu’s Harrier adopted a sunning posture while resting on a favourite sitting post near her nest in the province of Groningen, in July 1994: fully stretching her wings in a slightly drooping fashion, spreading the tail and stretching the neck, bill apparently not opened. She sat with her back towards the sun (Photo 1). A juvenile Goshawk in a revalidation centre was seen adopting the delta wing posture in September 1997 at the very moment that the sun fell on the spot where it was sitting. On 10 October 1998. at 9:08 hr, an adult female Goshawk adopted a low-intensity sunning posture shortly after having landed on an exposed, dead birch on a heath, some 300 m from the nearest woodland. She sat with her back towards the sun, which just emerged from behind the clouds. The Goshawk very slightly opened her wings, which remained in a drooped position. The tail was slightly fanned and cocked, in such a way that it angled at 90° with the sunbeams. She held this position for 65 seconds, until the sun disappeared. Despite intermittent sun breaks in the next 35 minutes, she did not regain a sunning posture. An adult female Sparrowhawk was observed sunning in June 1992 while laying on the ground in heather (central Netherlands); she had just plucked and eaten a prey. She partly stretched her right wing, turning to her side and partly opening her bill. In the left wing, she slightly raised her secondaries, probably a cooling mechanism (Photo 2), This posture took five minutes, after which she uprighted herself and sat for a while on her ankle joints before departing (Photo 3 and 4), In June, July and August 1996, a Common Buzzard was repeatedly observed sunning with outstreched wings and tail while laying in the grass (southern Netherlands). This behaviour only started about 10.30-11.00 hr, when the sun had gathered strength; sunning was never preceded by bathing.

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Rob G. Bijlsma, Bennie van den Brink, Ben Koks, Ron Poschkens, & Petra de Vlaming. (1999). Zon-gedrag van Grauwe Kiekendief Circus pygargus, Havik Accipiter gentilis, Sperwer A. nisus en Buizerd Buteo buteo. De Takkeling, 7(2), 107–112.