I agree completely with Stuart and Eduardo, the picture shows a male Sparrowhawk chasing a female Sparrowhawk:
-the hand is broad compared with the arm, on a Goshawk the hand is clearly narrower than the arm (with the bulging secondaries creating almost oval shaped wings, compare with the Goshawk in post #14)
-the wings look relatively short
-the neck looks relatively short
-the sides of the throat and the barring on the underside including the underwing coverts is rufous (should be mid-brown or greyish brown on a Goshawk)
-the base of the tail is narrow
Size:
-according to the Collins guide, a male Sparrowhawk is 29-34 cm, a female Sparrowhawk 35-41 cm and a male Goshawk 49-56 cm
-an average male Sparrowhawk (31.5 cm) is thus about 80% as long as an average female Sparrowhawk (38 cm)
-a large male Sparrowhawk (34 cm) is about 70% as long as a small male Goshawk (49 cm)
-the larger bird in the picture is about 80% as long as the male Sparrowhawk, i.e. this is consistent with the average size difference between a male and female Sparrowhawk (as the birds are chasing each other it can be assumed that they are equally distant to the camera)
