The parents continued to bring home delicious insects everyday for the next few days.
Although the chicks were getting bigger, I noticed that they spent most of the time sleeping and were not very alert even at feeding times. The chicks did not look well to me at all.
A couple of days later, when I woke up one morning, there were only two babies in the nest. One of the nestlings had disappeared over night.
By now, the two remaining nestlings looked unwell too. They didn’t seem to have the energy to take food from their parents.
The following morning, I was so sad to see that another chick was gone. The remaining chick spent the whole day sleeping.
Next morning, I got up early and sadly, the nest was empty. I saw the mother’s grieving face for the last time.
I suspect that the nestlings may have died and been removed by the mother overnight, one by one. After checking online, I found that this kind of behaviour has been documented previously. http://www.birdchick.com/wp/2009/04/interesting-stuff-at-the-nest-cam-site/