I’ve noticed for years that cardinals have a constant tweeting sound when on the ground and often on a perch. I’ve even seen a female or male sitting on a fence tweeting while the other ate at a feeder. The whole concept of making all this noise on the ground struck me as counterintuitive for survival purposes. One would think that the noise would attract predators.
Then recently I read an article in New Scientists about a man who could navigate using clicking noises. This was not unique to him. He could also teach others. A salient point in the article was how detailed his perception could be. He and his students could detect sidewalks vs lawns, fences vs hedges, and various sizes of bowls. Higher pitches allow more detailed detection at the price of only detecting things that are near.
It occurred to me that the cardinal’s incessant tweeting would be helpful for survival if they used it for echolocation and to detect predators without necessarily seeing them. The perception would not have to be detailed since any change in environment would signify potential danger.
They may also use it for echolocation while flying. I’ve noted that cardinals are the last birds to go home to nest in the evening. They are the last birds to leave our feeder at twilight.
None of this is proof that cardinals use their tweeting for the purposes mentioned, but it does suggest an area for research.