Total wing length - the distance from the shoulder or "arm pit" to 

 the tip of the longest primary in the extended wing (see Fig. 8). In 

 conjunction with the width, taken across the wing's upper surface at 

 the wrist (see Fig. 8), a ratio of width to length is derived as an 

 index to wing shape, i.e., long and narrow or short and broad. 



Wing length - in a relaxed but folded wing, the distance from the 

 wrist's outer edge to the tip of the longest primary feather (Fig. 4). 

 The wing should be flattened against the ruler. Please note if one of 

 the longest (outer) primary feathers is missing or is only partly re- 

 grown. If one of these feathers is missing, then "wing length" will be 

 shorter than it should be in those species where the outermost primary 

 is longest; the same would be true where the 9th primary is missing in 

 a species where that is the longest feather. 



Figure U. Measuring wing length (wing chord). 



TOP 



UNDERSIDE OF WING 



Nail chord - the straight line distance from the point of the bill 

 tip to where the nail's curvature ends (Fig. 5). For birds in which 

 the bill sheath (outer surface of bill that covers internal bone) is 

 divided into distinct sections, such as petrels, cormorants and skuas 

 (see Plates 3-10, 25), the nail is a distinct section. Some birds, 

 such as alcids and terns, have no nail to speak of. 



