To make a sound like the hoot of an owl, you bring a finger completely off the hole and then put it back on.
It helps to alter the breath so you burst out a little then slow down your exhale too.
The Native American Scale benefits from adding hoots into it, especially slow hoots.
About this exercise#
The owl hoot is an ornament, not a melody note. You lift a finger clear of its hole and drop it straight back, and the pitch dips and returns in a soft, rounded swoop that really does sound like a hoot. The breath does half the work here: push a small burst as the finger leaves, then ease off as it settles back. Start slow. A lazy, drawn-out hoot carries the effect far better than a quick one, and it sits especially well inside the Native American scale, where the open, breathy mood gives each hoot room to land.