Len Kersley writes: There is an excellent book, The Starling, by Christopher Feare published in 1984. He quotes a study carried out in Cornwall in 1929 where the maximum distance travelled from roost to feeding area was only 38km/24 miles, but also mentions work from North America in 1969 where the distance was up to 80km/50 miles. Radar studies of starling flocks departing from roosts have measured an average speed in winter of about 70km per hour/45mph so that the birds in the latter case must have flown for more than an hour. At what point is the energy value of the food souce a poor return for the flight effort? Elfyn's suggestion of up to 100 miles, more than 2 hours flying time, would seem to be very high.
I believe that Peter Walters Davies and Tony Cross published a paper on the Aberystwyth starlings in the 1990s. Unfortunately, I do not have a copy, but perhaps it contains some of the answers.
(Len, they did indeed and their paper was in the 1999 Ceredigion Bird Report but it focuses on their migration to Aberystwyth from their northern European breeding areas. JAD)