Question
We live in front of a lake. For almost 10 days, we hear a fluttering sound, several times per day in the day light as well in the dark (like evening). Can't figure out what it could be. Looked for any whole. Couldn't find any. I saw my neighbor's cat heard the sound and came to inspect. The cat left. We're living here for the last 37 years and have never heard such sound. Any suggestions and/or advice how to resolve this matter. Thank you in advance for you help.

Answer
Noises are very poor indicators of a problem. Like pain, all they tell you (usually) is that there is a problem rather than what the problem is.

I would suggest visiting http://icwdm.org and read our instructions on how to inspect a structure for wildlife problems.

Then when you have scaled down the possibilities we can discuss options.

Just off the cuff, I would be thinking raccoons.