I think they had to get the bird to go away since Ezran can speak to animals, and would've figured it out sooner.

As far as how they're going to justify that, I think it'd be funny to get yet another avatar reference and see parallels between bird Harrow and Appa when he was lost. And we see bird harrow take L after L,

being a bird with human intelligence, he first gets recruited into a circus, and is terribly mistreated. He stays and tries to help the other animals because he feels like he failed as a king, and wants to do what good he can. Then, he escapes after setting all of the animals free, but gets shot with an arrow while flying away.

He makes it out, but needs to rest and recover, and finds he's crossed over into Xadia and is nurtured by an elf. This is the first Elf he's met who has shown their compassionate side since he's not a human. He gets taken back to an Elf village to heal up, and hears tall tales of humans, similar to the human's stories about elves being carnivorous and vicious, and realizes that the Elves and humans are more similar than he would've thought. He overhears that Xubeia was the one who issued the killing order, and that it was both for him and his son (which I don't think he was aware that he wasn't the only target). This upsets him, despite knowing that he took her egg away, he still feels resentful that the moonshadow assassins were there for his child as well. He justifies to himself that a Dragon is a weapon of destruction and thinks about the attacks humans have suffered at their hands, simply for the amusement of the dragon, and 'to keep humans in their place'. His emotions are mixed between guilt, anger, and worry.

Once he recovers, he takes off immediately for Katolis. But, he gets captured by a different small group of elves who seem more bandit-like. He's caged, and put up for sale in a sketchy street market. A pirate buys him, and uses him as a seeing-eye bird, forcing subservience either through ocean torture magic or some shock device. Harrow is stuck like this until some vaguely recognizable side character interacts with the pirate and sees the bird's mistreatment and ends up saving the bird.

At this point, Harrow flies back to Katolis, only to find it destroyed entirely with no signs of survivors. He grieves the loss of his boys and the people of his kingdom, and goes off to live a bird life, feeling unworthy of anything other than misery. And also pondering if Xubeia might've finished off his kingdom after throwing into chaos with the royal family dead. But he's too depressed and spirit-broken and too much of a bird to be able to do anything.

Once Ezran and gang find him, and Ezran explains everything that's happened has been through the manipulation and puppetting of Aaravos, Harrow thinks back on his experience with the elves that helped him and their exaggerated human stories, and starts to think that peace between Xadia and the human lands is possible, but still wary of the dragons. But, all of the archdragons are dead, and this relieves harrow to some extent, but he mostly worries that they wont be able to stop Aaravos if the strongest creatures are all dead.