A music and science lover has revealed that some birds can store and retrieve digital data. Specifically, he converted a PNG sketch of a bird into an audio waveform, then tried to embed it in the song memory of a young starling, ready for later retrieval as an image. Benn Jordan made a video of this feat, sharing it on YouTube, and according to his calculations, the bird-based data transfer system could be capable of around 2 MB/s data speeds.
Why couldn’t you have a likelihood function for the bird?
As a trivial case, you can just say: Does the spectrum look like a bird? Then you’d have a digital channel by your definition for a single bit.
The actual channel bandwidth is obviously higher than that.
Yes you could likely design an optimized modulation scheme to do this, likely some kind of bird specific frequency shift keying. You can also do any kind of quadrature modulation in the audio spectrum (original dialup used acoustic modems).
This person just didn’t do that in this case. It’s still a very cool experiment by YouTube maker standards though.
My point is that it doesn’t have to be optimal to be considered digital. Which in the general case means basically any communication channel can be digital.
If the argument is that they didn’t correctly calculate the bandwidth, then sure.