Which term is also known as stress marks in a bird's feathers?

The term that is recognized as stress marks in a bird's feathers is fret marks. These marks are typically indicative of stress or other environmental factors that can affect feather development. Fret marks can be observed as variations in the feather's texture, color, or structure, which result from periods of stress that the bird has experienced during its life.

Understanding fret marks is important in falconry, as they can provide insights into a bird's health and well-being. By observing these marks, a falconer can assess whether a bird has experienced significant stress or has been subjected to conditions that may adversely affect its health and performance.

The other terms, although related to birds and feathers, do not specifically denote stress or the conditions that lead to stress marks. Growth marks refer to the normal growth lines present in feathers that indicate age and growth patterns. Color bands are identifiers used on birds, often for tracking, and feather lines generally refer to the natural markings found on feathers that do not suggest stress but rather identify specific species or coloration.