I have found a part shell of a bird's egg in my drive, below a creeper-covered wall. It's all-white, not very big. Anyone any ideas what kind of bird lays all-white eggs? Cannot find any pics of birds' eggs on Google.
The size will help. Yvonne has given you Collared Dove. This egg is smooth, glossy and measures 31mm x 24mm.
Another possibility is the House Martin which can have broods up until September. This egg is a lot smaller at 19mm x 13mm and although white like the CD is smooth, but non-glossy.