Birds Eggs Identification

[cacher]

The kids found some pieces of egg shell on a walk across fields today and want to know what laid them. 1st was 4-5cm hig and pale green colour, no spots or markings. 2nd was same size but fawn/pale brown colour, again no spots or markings. 3rd was smaller, 4cm, pale browm/fawn but with tiny darker brown spots and a few larger brown flecks. 4th was largest at a full 5cm high, biege, maybe a hint of green, some slight shodows but no spots or flecks. 6th was also 5cm high and white, no markings.