Chil is a kite -- a family of old world raptors.
In some US editions of the Jungle Book, you'll find Rann the kite instead of Chil.
Both Mang and Chil appear in the opening "Mowgli's Brothers":
Now Chil the Kite brings home the nightBoth Mang and Chil assisted in the rescue of Mowgli from the Bandar-log by alerting Bagheera, Baloo, and Kaa to his kidnapping.
That Mang the Bat sets free--
The herds are shut in byre and hut
For loosed till dawn are we.
This is the hour of pride and power,
Talon and tush and claw.
Oh, hear the call!--Good hunting all
That keep the Jungle Law!
Night-Song in the Jungle
The Jungle Book is also available online for free from Project Gutenberg (It's a US edition).
One of my pet peeves with the Disney movie was the way they changed Kaa's character.