It is perfectly normal.
The cere of my hen Stella, when she is not in breeding condition, becomes exactly like Kiwi's for a short time, half brown and half white, then it gets fully white within a few days.
Then, her cere becomes brown again when she is in breeding condition.
I am sure it is the same for Kiwi.
I hope this helps.
Thank you! That's what I figured, but just making sure because it's been staying this two-tone color for a couple days now. She's well under two years old, so this is the first time I've seen it happen.
Please be sure you are doing everything possible to discourage breeding behaviors since Kiwi is now in condition.
Rearranging their cage frequently, and limiting the light they get to 8 hours a day will help tremendously. Please be sure you never put a nest box or anything that could be used as a nesting site in their cage.
When they come into condition, limit the amount of protein in their diet at that time.