Hi marghay, , You should not touch the nest leave it as it is and it might get used again, the nest looks like it was made by a Collard Dove to me.
Could also be a Woodpigeons nest
Not sure about the nest, as to who built it or whether to leave it or take it down.
Follow these instructions and hopefully you will be able to post photos along with your text.
At the top of the page, on the right, black bar, go into settings.
Go into the advanced tab, and change the top option (content) to enhanced.
When in your reply box, hit use rich formatting, bottom right.
In this box go into the 7th option along the bar, a little green TV.
Then hit browse and wherever you have photos stored will show, pick an option and then your photo, this will now show in the box. You must have them a certain size. If too big they will not show, I usually change the boxes to 400/500, then hit insert and the photo will be ready post.
Hope this works, good luck.