I would think the differences would not be found in the velocities. 1950 - 1959 These years were not long after the war. Everyone was in the same boat regarding availability etc, but the peregrines were far fewer. 1965 - 1975 Again peregrines were fewer, albeit feeding techniques may have started to change. 2005 - 2015 Peregrines were rife. How does this affect velocities. According to your statistics not very much. This means the lead pigeons may be getting through and the tail enders are the prey. If this is correct, then the modern feeding methods of carbs and fats will produce instant acceleration and a maintained speed without calling on the proteins to strip muscle ensuring a faster recovery, ready for next time. The bean / protein fed pigeons may fly at a slower steadier speed and become more susceptible to becoming prey.