SEEN - SE European Bird Migration Network
Wing-formula
Fig. 1. Ascendant numbering of primaries and rectrices. Typical moult directions are shown at the right side of the drawing

Fig. 2. The wing-formula measurement (example used in the text). Note that this is NOT an illustration of the technique of the measurement (see Fig. 3)

Fig. 3. Technique of wing-formula measurement. Clearing the feathers sequence (above) and two variants (A and B - see text) are shown (below)

(feather tips distances method)
The wing-formula includes measurements of distances from the wing point to the tips of the shorter primaries. The primaries from the second to the eighth (ascendantly*) are taken into consideration (Fig. 1); for simplicity the first functional primary is always numbered as second, irrespective of its "evolutionary" number (even in families e.g. Motacillidae, Fringillidae etc., which have lost their first short primary).

Use of the ruler with the zero-stop is not convenient, though possible.
An example wing (Fig. 2): the tip of the win g is formed by primaries 4th and 5th; 3rd    primary tip is by l mm shorter than the wing-tip, 6th - 2 mm, 2nd is equal to the 7th and they are shorter by 6 mm, 8th is 9 mm shorter.
For recording purposes this formula would be spoken as: "four to fifth, zero-one, two,  six-six, nine. The record in subsequent boxes of the form:
| 45 | 01 | 2 | 6 | 6 | 9 |  |
"Zero" (in box 2) is written as an indicator for special processing.
Explanations of spoken recording:
1. in the first box - the numbers of the longest primaries are called out,
2. in the next boxes- distances (in full mm) between the tips of primaries and the tip of the wing.
(1) "fourth to fifth" indicates that primaries 4 and 5 form the tip of the wing (4=5). Other possibilities in this box: (A.) on1y one number (e.g. "third" - means that the tip of the wing is formed by one primary only (the third); (B.) two not consecutive numbers (e.g. "fourth to sixth" means 4=5=6, "third to sixth" - 3=4=5=6).
(2) "zero-one" - the word "zero" indicates that the measurement given is of the distal primary (i.e. placed distally in relation to the longest ones; in this formula the "distals" are the second and third primaries and the "proxima1s"- 6th, 7th and 8th; when the distal primary is equa1 with the proxima1 one the word "zero" is omitted (e.g.” six-six" - 1ater in this formula).
(3) "two" and "nine" - the measurements of the proximal primaries.

Note: if someone would like to measure all primaries - till the 10th - two boxes more should be added into writing shown above.

Technique (Fig. 3)
1. Before measuring spread and extend the left wing to check the state of the feathers for cleanliness, moult, loss or damage and to check that they follow in correct sequence; count the number(s) of the longest primary(ies) when the wing is closed.
2. Fix the closed wing in its natural position (as natural as possible), holding it almost parallel to the body axis (looking from the back side) by holding with the first and second fingers of the right hand near the carpal joint so that the primaries cannot change their position during the measurement procedure.
This is the most difficult and critical part of the technique.
3. Measure the wing-formula with the methods A or B (see below). To measure the distal primaries move the hand with the bird in relation to the fixed ruler position.
A: the butt (the zero-end) of the ruler is placed at the tip of each primary sequentially from the wing tip. After each value has been recorded the ruler's end is moved to the next primary tip.
B: the tip of the wing is put at any centimetre-line of the ruler (convenient for the size of the bird) and the values are taken in the opposite direction from that normally used.
These two methods are equally good. Method A is convenient for rounded (e.g. Chiffchaff) or very long wings (e.g. Jay). Method B is better for pointed wings (e.g. Garden Warbler) and it is far quicker than the method A.
Precision of measurements - 1 mm.

The most common mistakes in measuring -
Mistakes mainly result from inaccurate handling of the bird:
- the head of the bird is pulled back between fingers,
- the wing is extended too much and not firmly fixed between the first and second fingers.
When method B is used the position of the wing tip on the ruler may change causing inaccurate measurements if the ruler is not fixed in relation to the hand holding the bird.

* Using descendant enumeration of primaries (as in moult studies) is much less convenient when talking about wing-formula
Created by Pronetix 2006