How many Greylags are there in Pembs?

Before dusk this evening between c. 1730 and 1745, we watched to separate skeins of grey geese (c. 50 in the first and c. 70-80 in the second) fly over from somewhere to the east of Martletwy area probably towards Sprinkle Pill.  From size, colour and call (but not seen through bins) the first group all appeared to be greylags and at least 70 of the second group also appeared to be greylags with possibly a small number of Canada Geese with them. We concluded that there must have been somewhere between 100 and 120 grey geese in total - all most likely to be greylags. We presume that they had been feeding in stubble fields in the area during the day and were heading back to feed/roost on the estuary.