Why is it that chickens can/do lay unfertilized or fertilized eggs almost daily and other birds seem

Why is it that chickens can/do lay unfertilized or fertilized eggs almost daily and other birds seem to lay eggs once or twice a year?

Susie Osler, Maberly, Canada

• Chickens will keep laying eggs until they have collected enough for a clutch. If you keep taking the eggs away, their primitive powers of mathematics tells them that they haven't laid enough yet. Leave the eggs there and they will stop laying when they have a clutch of about a dozen eggs. She will then sit on them just as your other birds.

  david roberts, crewe