As the song goes …
‘When the red, red robin comes bob, bob, bobbin’ along, along
There’ll be no more sobbin’ when he starts throbbin’ his old sweet song….’
~ Harry Woods, ‘When the red red robin comes bob bob bobbin’ along’, 1926

Woods was writing about an American Robin (Turdus migratorius), which is a very different bird from the British Robin (Erithacus rubecula), but the bobbing still applies. And this juvenile Robin, which is just moulting into its adult plumage, was bobbing very well for me during yesterday’s exercise walk.