Now that you mention it, earlier this year I saw a young sparrow huffing & puffing on the lawn, not moving when I got near. At the time, I figured it was a fledgling just getting her “land legs”. Now I’m beginning to wonder.
Birds get a 24 hour “virus”, kind of like a cold.
Their eyes get stuck shut from the discharge and they get snatched by predators while grounded from the temporary blindness.
If you simply take a wet Q tip and clean off the goop, they survive.