No no, they land again at dawn, but towards the east so that they enhance the movement of the earth, and indeed sometimes cause small earthquakes.

>Birds take off at sunrise. On the opposite side of the world, they are landing at sunset. This causes the earth to spin on its axis.

Bats take off at sunset and thus, to some degree, counteract the effect of the birds. The fluctuating bat population is what causes the different amounts of sunshine during the year.