A typical pose as it ascends  the trunk. Once they get to to the top they will fly to an adjacent  tree, usually at the base and creep up again, never climbing headfirst down the trunk. The only species to do this is a Nuthatch.

Only very infrequently do I have the opportunity to photograph a Treecreeper even though they are one of Britain's common woodland birds but, as the name suggests, they do creep around  and are never still when you see them.  On top of that they usually make it difficult because they quickly climb to the top of the tree and then all you have is a silhouette.  As you can see, I did photograph one today and as well as that I heard it singing and calling which is something that I have heard lots of time before but not been able to put the call to the bird until today.

This picture shows how well they are adappted to their environment and it also shows  the key features of the species.  They have very long claws which they use to hang on to bark as they creep, always  vertically up the tree trunk.  As well as that they have  a stiff, specially adapted tail which they use for stability in the same way that woodpeckers do. If you look at the tail of a woodpecker they also have the same deep "V".  The plumage is cryptic, that is to say it  blends in perfectly to their surroundings.  Their beak is long, thin and pointed.  They use this to feed by probing deep in to bark for insects that other birds, tits for example, can't reach.   Another interesting feature is the white underside which usually  can't be seen as they rarely perch upright on a perch like the other "perching birds".  Quite why they have this snowy white underside is a mystery to me.

As an extra, I took a nice photo of a Chiffchaff again today.

Again note the dark legs….. usually much lighter in a Willow Warbler.