PEREGRINE (Falco peregrinus, 游隼) is not a common bird in Beijing. I have sometimes seen one or two on passage in autumn and spring and occasionally it’s seen in winter. I suspect it breeds in the mountains in small numbers (I have seen juveniles at Wulingshan, just over the border in Hebei, in July).
Most of the birds we see in Beijing look like pretty standard Peregrines, most likely of the subspecies peregrinus or japonensis. However, occasionally, we see one that looks small with rufous underparts, reminiscent of Shaheen Falcon (ssp peregrinator). One such bird was seen on 1 September 2013 at Miyun (photos below).

And on Friday this week, Paul Holt and I saw another that we suspected could be a Shaheen. Although it was very distant, I was able to record some video of this bird.
According to literature, ssp peregrinator breeds in India and across to Vietnam and southern China and is non-migratory. It shouldn’t be anywhere near Beijing. A range map of the various subspecies of Peregrine can be seen here. I’d love to hear views from those familiar with ssp peregrinator as to whether they think this bird is of this subspecies.
I have seen one flying around Balizhuang in the last month. I wasn’t close enough to identify the markings, but it was definitely a peregrine.