Awkward lighting, but I wanted to show and explain behaviour.
Fred took another one yesterday, you should be able to see the tail hanging down. I've now worked out why Fred, and maybe other Sparrowhawks, given the choice, prefer Mice to Birds.
I've seen male Sparrowhawks eat every bird from Blue Tit to Collared Dove (very rarely), and I've seen it from attack to just a pile of feathers. A Sparrow takes at least 15 minutes to eat, a Blackbird 30 minutes plus. There's plenty of waste; mostly feathers, but often bones left in the pile.
Mice are different. I watched Fred eat the Mouse from start to finish yesterday. There was nothing left, no bones or fur, not even the tail. It took less than 7 minutes. I'd guess a similar amount of nutrition to a Sparrow, but only half the time taken to eat it. After cleaning his bill and talons, Fred was watching for another Mouse within a minute of finishing eating.
Camera Maker: SONY
Camera Model: SLT-A58
Lens: 75-300mm F4.5-5.6
Image Date: 2015-04-01 11:02:56 (no TZ)
Focal Length: 300.0mm (35mm equivalent: 450mm)
Exposure Time: 0.020 s (1/50)
ISO equiv: 400
Exposure Bias: none
Metering Mode: Matrix
Exposure: program (Auto)
White Balance: Auto
Flash Fired: No (enforced)
Color Space: sRGB
GPS Coordinate: undefined, undefined
Copyright: 2015 Chris K