It is the adaptation to the limiting factor temperature.
Explanation:
The presence of long ears is the most astonishing characteristic of jackrabbits. These long ears are the jackrabbits' adaptation to their native desert habitat, which helps them to cool down the temperature of their body. The ears allowed them to do so as they are thin and possess an extensive mass of blood vessels. When the temperature of the desert becomes hard to hands, the long ears of jackrabbits allow them to enhance the flow of blood via the ears by dilating its blood vessels. This dilation helps to deflect heat from the body and thus cools the creature.
It would decrease as their prime food source would be taken away. This would result in a decline in population as the birds wouldn’t have sufficient food.
