He is a rattlesnake, since his tail has a rattle on it which makes a loud rattling sound as he shakes it around.
In "Watch the Birdies", he is the main antagonist. He first appears sleeping in his underground burrow before Courage pulls him out by the tail mistaking it to be a worm after he dropped Eustace's bucket of fish bait worms. Courage then stored the snake right into the worm bucket and took it to the baby birds' home tree, before realizing too late he brought up a snake into the bird nest. The snake first started complaining at Courage but then he beamed at seeing three baby birds, particularly man-sized ones and remarked he loves babies. He sarcastically named them "Breakfast", "Lunch" and "Dinner" then asked them to come play with his rattle.
Muriel in a panic came to the baby birds' defense, while Courage grabbed a bee hive (which the baby birds were playing with earlier) and threw it at the snake, but thanks to his poor aim it ends up hitting Eustace instead. Because this fails, Courage then resorted to shoving himself into the Snake's mouth to keep it open so that he can't eat the babies. The hive then covered Eustace in honey, and the honey made Eustace get sticky with the birds' mother's thick black feathers. The Snake then saw Eustace and mistook him to be the babies' mother, and deciding "she" will make more of a meal than her three babies, the Snake chased after "her".
It is unknown what happened to the Snake afterwards.