Phil

I asked a similar question on the forum in May last year under the thread "Hawks and Falcons" - go to page 7 - "General Birding Discussion" section for some very interesting comments - good luck

Google says ......

One difference, which is a key distinguishing factor, is that falcons have a notch on their bills that they use to dispatch prey, whereas 'hawks' do not.
Falcons belong to the family of long-winged hunters, quite a few of which kill birds in flight, whereas hawks tend to take their prey on the ground and are predominantly short-winged for woodland hunting, although there is some overlap in hunting methods between the two types.
The name 'hawk' comes from the days of falconry ('hafoc' or 'havoc') and predominantly referred to the Goshawk (German 'Habicht'), which was the favourite hawk of the country class. They were originally used to obtain food (rabbit etc.) Falcons were classed as more 'aristocratic' species.