Like all other reptiles, birds have scales. Also, birds lay eggs like other reptiles.
Assuming this is multiple choice, the answer would be "niche". An organism's niche is where that certain organism fits into an ecosystem, or what their part to play is.
Shivering occurs when the core temperature of the body begins to decrease which would threaten normal body function. Shivering is a response by the body to bring back temperature back to homeostasis. Trembling is the continual involuntary contraction of muscles. Muscle activity releases heat that warms up the body. This is the reason why we sweat during physical activities as the body sheds excess heat generated by the muscles in order to maintain the homeostatic body temperatures of 37 degrees centigrade.
