D1 Field Morphometry

Topic

Before a bird's flight system can be described using any other model, the system must be measured as a physical object; this is the purpose of the morphometric measurements taken on a bird held in the hand—whether it has been captured, banded, or is undergoing rehabilitation. These morphometric measurements do not rely on observing the bird in flight from a distance but rather on a standard biometry protocol applied directly to the bird's body, aiming to characterize its wing system as a measurable physical object.

The standard biometry protocol begins with a handful of raw measurements taken directly from the bird in hand, such as folded wing length and body weight. Using these raw measurements, the model applies a set of equations to link them to aerodynamic variables derived from the wing system: wingspan, wing area, and body mass are the three measurements that determine—in turn—aspect ratio, wing loading, Reynolds number, and the bird's power curve. Without knowing the wingspan, wing area, and mass, none of these derived aerodynamic variables can be calculated.

These aerodynamic variables—derived from wingspan, wing area, and mass—extend beyond the standard biometry protocol itself; they serve as the input parameters for all other models of the bird's flight system, describing both its normal functioning and any functional failures. No other model can calculate the aspect ratio, wing loading, Reynolds number, or power curve of a specific bird without first having access to the wingspan, wing area, and mass data obtained through this standard biometry protocol. Based on these same raw measurements and derived aerodynamic variables, the standard biometry protocol also defines condition indices that summarize the physical state of the captured bird. One condition index—comparing the bird's actual weight against the weight expected for its wingspan and wing area—allows for the detection of abnormal excess body weight, the kind that imposes a pathological wing loading; another index—comparing the folded wing lengths of the left and right sides—allows for the detection of wing asymmetry caused by a bone fracture.

Thus, this set of morphometric measurements taken from a bird in hand serves as the gateway to the complete flight system simulator: no other model—whether describing the bird's healthy functioning or any of its impairments—can be applied to a specific individual until that individual has been characterized using this same standard biometry protocol, measuring its wingspan, wing area, mass, and condition indices.

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