A lot of people believe that birds aren't real
Birds are real things but the concept of they not being real has some real evidence and that's what causes more people to believe it. There's something in particular that some do believe and that's the bird poop actually being a tracking fluid. It sounds crazy to say that but with how technology is currently going it's not too crazy any more.
Smart Dust is actually a thing. They are tiny sensors that you can hide in liquids. Once they land on something, they will send information back. They have the ability to sense light, vibrations, God knows what else, but the point is they exist. The government has used chemical tags for decades. There is invisible paint for cars that can only be seen by special scanners. You could be driving around and someone could be following you and you wouldn't even know it. All looking like conspiracies but sometimes it's what they want you to think.
Today normal companies use DNA tracers. These are liquids with codes in them that you can't wash off. So you can see how they could track products in different continents, it works.
So, when you think about all that, it is not science fiction anymore to say you can use liquid to mark and track someone. Infact just maybe, it was never science fiction in the first place. Old CIA documents show their interest in this type of tracking goes back many years.
I'm not saying that every bird you see pooping is government drone poopin gel for surveillance but just know that liquids can be used to track you is not conspiracy any longer, that is just what they have created unknowingly and never questioned.
Some sources as evidence I was reading,
Smart Dust: What Actually Works (2026)
DNA-Based Traceability Technology
CIA Historical Collections on Intelligence Methods
I hope this is enough evidence to back my arguments and it's all opinions I'm giving not facts but that also doesn't mean they're wrong too.