There seems to be a long folk tradition that birds do grieve:
“All the birds of the air fell
a-sighing and a-sobbing
when they heard the bell toll
for poor Cock Robin”
See the Wikipedia article on Cock Robin.
Your "grieving bird" is a video of a peregrine falcon (Falco peregrinus) and its (nearly?) dead chick on a hot summer day in Phoenix, Arizona (USA) in 2016.
Photo credit: Arizona Game And Fish Department
The video is from a nest camera webcam set up in the Maricopa County building in Phoenix, Arizona by the Arizona Game and Fish Department.(See this ...