Unknown nocturnal sound

Observation - Unknown nocturnal sound. Description: At night I am hearing a whoop noise that goes up in pitch. It happens about every 30 seconds. The habitat is farmland with ponds and woodland though the sound I am hearing is near the cottage which has fields and trees around it. I have checked the

At night I am hearing a whoop noise that goes up in pitch. It happens about every 30 seconds.

The habitat is farmland with ponds and woodland though the sound I am hearing is near the cottage which has fields and trees around it.

I have checked the RSPC sound files for owls and game birds as there are pheasants and partridges on the farm but it is a different sound. I can't get a photo