An amusing monster with a fun theme. I did notice a few minor hiccups in the stats (a reference to "hellcart" proficiency and to Will saves), but nothing significant.

So I'm not saying its not the perfect training session monster where the wizened old master summons a magical rooster for the student to catch without being burned or killed. I'm not saying it will lead to a story arc where the master and the rooster escaped a evil fire giant living in a volcano with a bunch of fire roster pets and is now after them. You'll probaby have other bizarre thoughts like that too reading something like this. It's awesome!

I like this relatively low powered monster, as an interesting creature that could be used in anumber of ways. Its not-necessarily hostile nature also means it could be more of a role-playing encounter than a lot of monsters, and its firey nature means it could become valuable or sought after.