Hiding in plain sight

The male black cap sings beautifully, but is surprisingly difficult to spot.  His grey colouring and dark black cap seem to merge into the shadowed canopy of whichever tree or shrub he's sitting in and it often takes a bit of time to find him, despite the fabulous cascade of trills he's issuing.

It reminds me of a puzzle book that I was given as a child one Christmas, which had a picture of a tree with lots of leaves.  Some of the leaves were birds, they were bird shaped and had an eye, but were otherwise identically coloured to the leaves.  The puzzle required you to find all the birds.  Now that I think back I realise that my parents were probably looking for something that would keep me occupied and out of trouble.  It certainly managed the former :-)