Aside from late in the afternoon and early morning, this is the pattern.
Bird A bird lands on the feeder with his head on a swivel.
Then you see the look which means
Bird M flies in like an F/A-18 Super Hornet narrowly missing Bird A.
Bird M’s Lookout
For perspective, this branch is maybe 30 feet from the feeder.
Lather, rinse, repeat. There seems to be a bit of a break early in the morning and later in the afternoon and early evening. Bird M seems to take a break from his protective duty.