Answer: To attract a Mate
Explanation: In competition, males use feather color to warn potential rivals that they occupy a piece of territory. When it's time to mate, male birds show off their plumage to attract a mate. In experiments, female birds prefer males with more fanciful feathers, or brighter colors.
The biome that exist closest to the Earth's poles are descibed as polar
Weather conditions, temperature, and Food availability
The answer is; concentration of oxygen and/or total atmospheric pressure is lower at high altitudes
This means that at high altitude, due to the low pressure, every breath has a lower oxygen content than at a lower altitude. This, therefore, necessitates the body to increase the erythrocyte numbers in the blood to maximize the uptake of oxygen from the thinner air.