Black UFO photographed over Belfast, Ireland

A person has noticed, on a photo taken in Belfast (Northern Ireland) on September 8, 2014, a black and unidentified object. This UFO was probably not visible to naked eye and silent. What is it?

Witness statement:

This picture was taken during a bus tour of Belfast, Northern Ireland. This object was not observed at the time and only after we reviewed our vacation photos, did we notice the object. I have no idea what is depicted, maybe a bug? I zoomed in on the object and it appears to be something flying in the sky. It does not appear to be a bird or a plane.