Which of the following is NOT a nutrient needed to sustain a bird?

Sugar is not considered a necessary nutrient for birds in the same way that oxygen, calcium, and vitamins are. While birds do require carbohydrates as a source of energy, which can include sugars, they can derive these carbohydrates from various sources that are more beneficial for overall health. The primary nutrients necessary for sustaining a bird include oxygen for respiration, calcium for bone health and egg production, and vitamins for metabolic functions and overall well-being. These other nutrients play critical roles in maintaining physiological processes, whereas sugars, while useful for energy, are not an essential nutrient and can be provided through more complex carbohydrate sources found in grains and seeds.