Kent Wildlife Trust are monitoring them (hence the markers) and have counted about 170 in the main area and another 25 or so in another colony nearby. I don't know the last two years' figures, but I understand they were similar to this year, and less than the peak of 500+ in 2008.
While botanising with my eyes on the ground, my attention was occasionally drawn upwards by calling birds - three young Peregrines were following a parent, begging for food, so the adult locked onto a flock of pigeons for a chase - unsuccessful as they were racing pigeons, and fast and maneuverable.
A whooshing sound made me look up again later, and saw four Spoonbills flying over low - camera in the backpack, of course! By the time I'd got it out, they were heading south.
Back at home, a shock.... a White-letter Hairstreak landed in the garden - my first in the UK and only the second ever. It was a mangy looking creature, but very welcome, adding to the Green Hairstreaks seen in the garden in May. The nearest elm, upon which WLHs feed, is nearly a mile away so far as I'm aware, so it was presumably on dispersal.