This is how you can improve the quality of your images on Blogger. As you are composing your post, and have uploaded your image(s), click on the HTML tab (arrowed below).
Now you will see the underlying HTML code (below). All of your written words still appear as you have typed them, but the pictures that you have uploaded appear as code. The code contains numbers that are instructions as to how large, and at what resolution, the picture will appear and where it sits on the page. I have highlighted each of the Corn Bunting pictures with a red box. Everything is identical bar one thing - which I have circled in purple - the 's' figure. Blogger will set this at a bog standard 640 or 400. All you need do is alter this to 1600. It's as simple as that. Your images will now appear sharper.