The wind was blowing and an owl hooted in a tree above me.
This indicates that the wind was blowing throughout the period being described, or repeatedly, and that the owl hooted once (or gave a series of hoots in quick succession). The hoot took place at a particular point of time, whereas the wind blew continuously or repeatedly over a period of time.
The wind was blowing and an owl was hooting in a tree above me.
This probably means that the owl hooted multiple times over the period, and it suggests that the period of time when you were aware of the wind blowing and the period in which you heard the owl hooting were roughly the same period.
If the narrative is very fast-moving - for example, you were running from place to place - it's also possible that the owl only hooted once (or performed one series of closely connected hoots). Because things were fast-moving, your perception was that the wind-blowing and hooting took place within the same short period.