What is the most common bird on earth?

The most common bird in the world is the domestic chicken (Gallus gallus domesticus). In 2018 it was estimated that there were around 23.7 billion chickens in the world, up from 14.38 billion in the year 2000. Chickens are mainly kept for egg-laying and meat with China alone producing 529 billion eggs in 2017. The world’s second leading egg producer, the United States, produced 106.7 billion eggs in the same year and 19.71 million metric tons of meat in 2019.

Source: Bird Spot