Just added some a Great Crested Grebe section to ‘air’ plus some individual photos to ’other’.  The grebe photos were taken on a Sigma 400mm f5.6, my original long telephoto.  I think it was this session that made me realise that this lens was very good at f8 and above but just not good enough at f5.6.  It was shortly after this that I upgraded to the Nikon equivalent.  A decision I’ve not regretted.