Whooping sound - Bigfoot in the Netherlands?

Описание: Hello again!

It's been a while since our first two uploads about possible Bigfoot structures in our country, the Netherlands.
As stated before, we are new to the bigfoot world. We've watched a lot of videos on the subject here on Youtube and got fascinated by it.
Fascinated enough to stay open to the possibillity that this mighty creature does exist.

It was after this that we began to notice similar "structures" - as the ones seen on many videos - in the woods of our country.
This is the reason of our first two uploaded videos, find out how big - or small - the possibillity of Bigfoot in the Netherlands could be, from people more knowledgable on the subject than us.

The same goes for this upload as well!

We don't go about looking for these kind of things, we just come across them, and this happened again a couple of days ago.
This time it is not just tree structures, but a whooping like sound, that occurred just once.
It was around 20:30 and no one else was there.
We are not experts in forest animal sounds, still this sound was to us out of the ordinary.
We've searched the internet for animal and bird sounds - especially owls - but could not find one that matched...

Please let us know in the comments bellow what you think this sound could be.