I have a pair of lovebirds. In May the female laid 4 eggs and after 27th days she threw it out of the nesting box.After 2 weeks she laid one egg and in 2 days she threw it out of the nesting box.Any idea why is my bird behaving this way.Please help.

Sounds like the eggs were duds. In other words, they either weren't fertilized, or they weren't growing.

Birds are pretty amazing. They know what an egg is a dud, and they'll get rid of it to make room for an egg that will actually hatch.

Are you intending to breed?

If so, I would suggest that you read up on it to be better informed. There's more to it then just getting a male and female bird.