Tristis and colybita Chiffchaffs

I managed to photograph at least one "tristis" AKA Siberian Chiffchaff today. It's hard to separate tristis from the colybita birds though, colybita is the nominate species and the birds that we are familiar with. On my session today, at first I saw, heard and then photographed a colybita bird, in fact there were several, (having said that this is a bird that takes a bit of looking for and finding in the winter). I was pleased to see them but expected to see at least one Siberian bird as I had seen them here on my previous visit. I decided to play a trisits taped call to see what reaction I got and almost immediately another bird appeared and instantly I could tell that it was subtly different although the photographs that I took are not as dramatic.  (See photos above and below, both depicting a tristis Siberian bird based on their reaction to the  "tristis" call).

In the next photographs I include photographs of a "colybita" Chiffchaff,  there is more colour in the beak and legs and I heard the bird calling in the normal, familiar Chiffchaff way.

This next one is a bird that I am not sure of but it appears to be darker than the others so could perhaps indicate a "tristis" and it's inclusion proves how hard this subject is.