Anyway, as well as counting the shags (we have 157 nests this year compared with 138 last year and 131 in 2008) we also calculate their productivity. This is a measurement of their breeding success. I do this survey every 7-10 days and in each nest I'm looking to see how many eggs or chicks there are and how close they are to fledging. Most of the species that breed here are very synchronised: individuals lay, hatch and fledge at roughly the same time. Shags, on the other hand, are incredibly spread out. The first chicks fledged on 2nd July but today I saw some chicks that must have hatched within the last few days and there are even some birds that appear to be incubating!