bird) at the wing tip to the nearest 0.5 or 1 mm. The pressures required should
be adequate to flatten the wing onto the rule and straighten the leading edge of
the wing without either pulling the carpal away from the end-stop, or damaging
the wing. Do not try to over-straighten the rounded wings of certain non-passerine
groups, and beware of birds in molt, whose wing tip might not be fully grown.
With a little practice, this measurement becomes highly repeatable (Gosler et al.
1995 a). In multiple-observer studies, it is wise to have all observers measure
a sample of birds to standardize their methods.
An alternative to the “flattened-straightened wing” measure described here, is
to measure just the third outermost primary. This should be done using a stand-
ard rule, available from the Swiss ringing scheme (Vogelwarte Sempach). The
rule has a vertical pin at the tip, which is inserted between the second and third
primaries while the third primary is straightened on the rule and its length read
Size| 105Fig. 4.4Measuring wing length of a small bird using a stopped rule. Note that the
bird’s back is in the palm of the hand, the carpal joint abuts the end-stop, that the
wing is closed and the leading edge of the wing forms a line, as near as possible,
parallel with the edge of the wing rule, and the wing as gently but firmly flattened and
straightened onto the rule. This procedure gives a highly repeatable, and reliable
measure of general body size for many species. This Great Tit has a wing length of
73 mm. (Photo: Andrew G. Gosler)