Question

why birds chirp before the occurrance of an earthquake

Answer 1

according to science, we know that animals can identify the occurrance of natural calamities before the humans.In order to let the other living beings know  they[birds] make(chirp) sounds {since they cant speak }

Answer 2

Many animals and birds have good adaptive senses than humans. When earthquake occurs it creates a miserable shaking and vibrations which are felt by us and after that we can say that earthquake had occurred. But long before an earthquake there are some signs, like some vibrations travel faster and are too small to be detected by the humans but the birds are sensible to these infra sounds. So birds chirp before the occurrence of an earthquake.