We now have 80 chicks.  Two nests in zone D which had two eggs in each are gone, presumed to be predated.  I spent some time in that area checking in case any of them had in fact hatched and saw that three little terns have nested well outside the nesting enclosure on the seaside!  I also marked a further two nests inside the enclosure.  These are very late and I hold out very little hope for the nests that are outside.  There are plenty of fledged chicks flying around and there are of course plenty of chicks that have not yet fledged.