It appears that this male Anna’s hummingbird is singing but not a sound came out when he opened his beak wide. It’s a behavior I have observed in Bobo, my Red Lored Amazon Parrot and I have always assumed it is something stuck in her craw when she does this. I guess this hummer must have had something stuck in his craw—a gnat perhaps?
Focal Length 400mm; ISO 640; f/5.6; 1/250
