Maybe not only birds.

Today, I drove home from Las Vegas to Portola Valley. I went 95->6->120 over Tioga pass, then home.

I've driven this route over several decades. My recollection (corroborated by a few Kodachrome slides) is that my windshield would be smeared with bug impacts by the time I got to Lee Vining, necessitating a stop at the humongously overpriced gas station so I could use their window cleaners. Since about 15 years ago, not so much.

I had a total of three bugs at Lee Vining today. I bypassed the gas station and window cleaning, went over Tioga.

If we're really missing the quantities of bugs my anecdote may illustrate, it's no wonder the birds are missing, too.