What factor may cause a bird's flight weight to vary?

The reason temperature can cause a bird's flight weight to vary is rooted in the bird's metabolic processes and energy requirements. When the temperature changes, a bird may need to alter its weight to adapt to thermal conditions. For instance, cooler temperatures can lead to increased energy expenditure as birds may need to generate more body heat, which influences their ideal weight for efficient flight.

Additionally, birds naturally adjust their weight based on environmental conditions to maintain optimal performance and energy efficiency. During warmer temperatures, they might lose weight to reduce energy needs due to less heat loss, while in colder conditions, they may gain weight to provide insulation and energy reserves.

Maintaining a consistent flight weight is essential for a bird's health and performance in falconry, and it can be affected by several external factors, among which temperature is significant.