I'm reading the Harry Potter series for the first time and I'm on book 3! I'm having trouble understanding why Sirius is able to ride Buckbeak; wouldn't he have had to bow and wait for a bow back from Buckbeak before being able to mount and ride him without issue? I understand Sirius mounts Buckbeak for the first time behind Harry and Hermione - two people that the Hippogriff trusts - but a minute or two later, Sirius mounts and rides away on Buckbeak alone. I don't understand how this is possible. I'd be very grateful if someone can explain this to me! Thank you!
It doesn’t seem to be a requirement to bow, just highly advised.
In Fantastic Beasts and Where to Find Them, Newt writes that bowing to the Hippogriff shows good intentions, but he doesn’t say it’s an absolute requirement to tame or ride on one. It’s likely that by not bowing, the person who doesn’t risks being attacked like Draco if the Hippogriff doesn’t like them. By bowing, they can tell in advance if it’s safe to approach. Not doing it is risky, but it’s not shown to be strictly necessary. Hagrid has his students do it because he wants to keep them safe.
The Hippogriff is native to Europe, though now found worldwide. It has the head of a giant eagle and the body of a horse. It can be tamed, though this should be attempted only by experts. Eye contact should be maintained when approaching a Hippogriff. Bowing shows good intentions. If the Hippogriff returns the greeting, it is safe to draw closer.
- Fantastic Beasts and Where to Find Them
Hermione also got on Buckbeak without bowing to him first, and although Harry was there as well and had already earned Buckbeak’s trust for himself, she went first before he did, he helped her up.
“Hermione put her hands on Buckbeak’s back and Harry gave her a leg up. Then he placed his foot on one of the lower branches of the bush and climbed up in front of her. He pulled Buckbeak’s rope back over his neck and tied it to the other side of his collar like reins.”
- Harry Potter and the Prisoner of Azkaban, Chapter 21 (Hermione’s Secret)
She also didn’t bow to Buckbeak during Hagrid’s class, she bowed to a different Hippogriff.
“Hagrid untied the Hippogriffs one by one, and soon people were bowing nervously, all over the paddock. Neville ran repeatedly backwards from his, which didn’t seem to want to bend its knees. Ron and Hermione practised on the chestnut, while Harry watched.”
- Harry Potter and the Prisoner of Azkaban, Chapter 6 (Talons and Tea Leaves)
So, she’d also rode on Buckbeak without having bowed to him first. Her circumstance is a bit different than Sirius’s since Harry’s always close by and she’s never alone with Buckbeak, but he did let her get on his back without trying to attack her in any way or throw her off.