[Evelina]

Today Joker has been with me for 20 days! While I was giving him an antibiotic this morning I noticed his beak looks different, like twopartite...

It seems lighter yellow on one end, and darker near the cere, it also has some tiny cracks...

Should I be worried?

 

[Jonah]

The outside edges and tip of the beak have no blood flow through them and often are lighter in color because of that. Do you have anything in the cage for him to work his beak on like a hard mineral block or stone ? Shredding/chew toy's are also good for them...

 

[FaeryBee]

The new growth on Joker's beak looks quite healthy.
Think of the beak as growing outward from the cere similar to the way a fingernail grows. The tip of the beak is the oldest portion.
As Randy indicated, the tip does not have blood flow.

Ensuring Joker has a cuttlebone, mineral block and a beak buffer will help him to keep his beak in peak condition.

I'd also suggest you add ACV to his water if you don't already do so.

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If the beak seems unusually dry near the tip (as it may since you indicated it has some cracks in it) you can massage a drop of olive oil into it being careful not to get any into his nares.

If the beak becomes too long, you'll want to take Joker to an Avian Vet for it to be trimmed.