Do you mean the nuthatch? If so, I’ve observed that they favour certain trees, and with patience you will possibly get lucky. I don’t have that level of patience - one day, perhaps! But even then, as you say, to get the leaves framing the sky round the bird…
While I share the question “Why?” I might hazard a guess that there’s almost an echo of the colours of the Sainsbury’s sign with the colours of the tarmac and its white and yellow lines, or even of the pale blue car and the sky - I could almost imagine a “I like it but I don’t know why” mood.
But then, same poster as “11 miles to the city” two days ago.