Hmmm Kelbabe59....
Tell me...is this a basement bathroom...1st or second floor? Where do you live? Snow/frost present?
How many bathrooms in house? If any other bathrooms do they show gurgling?
How about the washing machine???? The sink or dishwasher...look for these things...more detail equals more help.
Any tree branches/leaves above your roof?
Lots of birds in your area...

?? Let me know, then can help better.