We always keep the kitchen window open, with a mosquito screen covering it. Whenever we cook, we turn on a small fan to blow the smoke outside.

One day, a bird built a nest right by the window. I often saw the mother bird sitting on the nest, incubating her eggs.

After three or four days, however, the mother bird disappeared and stopped coming back to the nest. At first, I thought she would return the next day, but after two more days had passed, she was still nowhere to be seen.

I became worried that the eggs might die if they were left unattended, so I decided to take them in and try to incubate them myself.

When I shined a light through the eggs to check on them, I discovered that they were infertile—there were no developing embryos inside. That was probably why the mother bird had abandoned the nest in the first place.