Acknowledgement 

It is customary for this particular section to be written at the end of an article. But in this instance, I wish to make it quite clear from the start, that it is only with the encouragement and permission of Hugh Boyd that I am able to complete this document. Hugh is the first author, with Jeffery Harrison and Allan Allison, of 'Duck Wings - A Study of Duck Production'. This supremely useful book was published in 1975 (as a WAGBI Conservation Publication in co-operation with the Wetlands Trust) so it has long been out of print and copies are hard to find. What follows is therefore a summary of the most important and salient points from this book interspersed with my own personal experiences and practical advice. 

Introduction 

Picture the scene. You've had a successful days wildfowling and you sit down to write up a brief resume of the day’s events in your diary. The usual details are included - weather, state of the tide, the location you chose, maybe a brief line about the flora and fauna you noticed in addition to the wildfowl. Almost certainly you'll note down the number of shots you fired as well as specific details about the cartridges you used and how they performed. But above all, you will record the species of duck you bag and perhaps their sex.  

However, before you close the book and sit back to enjoy a glass of your favourite tipple, there remains another piece of information that you can add to the rich tapestry of material you collect. With practice and experience, by careful examination of the size, shape and colour of wings feathers, you can almost always accurately determine the age of ducks. By that I mean either a Juvenile/First Winter bird or an Adult. 

For you as an individual this may become another interesting facet to the sport of wildfowling. Yet when collated at a national level, the resulting information can prove very useful and beneficial to wildfowl conservation. It may be used to determine the abundance of each species, the percentages of duck and drakes and in particular the proportion of young to adult birds. This ratio is used to understand breeding success and mortality rates which together act as a measure of each season productivity. While the BASC maintains a limited study, it is in the US that the analysis of duck wings is undertaken on a massive scale. Each season for the last 40 years, up to 100,000 duck wings are examined at 'wingbees' across the flyways and the resulting data forms an integral part of setting and evaluating hunting seasons. 

Collection and Preservation 

First off, shoot a duck! It is possible to examine wings while still attached to the bird, especially if the features are clear cut, but in most cases manipulation is best achieved by removing them. It is vital that they are kept in the best possible condition since in some cases you may be looking for quite subtle feather differences. To this end, avoid stuffing birds into a game bag or at least ensure that you smooth the wings against the body before carefully packing away. 

For obvious reasons endeavour to pick the best wing from each bird. If both are badly smashed or particularly muddy, you are better off discarding them rather than risk making an incorrect judgement. By all means have a go, but be very cautious about your conclusions. 

Try and cut the wing off neatly at the shoulder (kitchen scissors are very effective) and if possible try and take the fold of skin to which the scapulars are attached (see Figure 1). Inevitably some wings will be wet, bloodstained and muddy, the later being the most problematic and unfortunately not uncommon problem when shooting in an estuary. So once removed, they should be air dried as soon as possible. This is very important because feather shape can be altered in appearance when it is wet. One word of caution, I have found it's best not to place them on a radiator as the consequences of forgetting you've done so can be quite aromatic. When dry, soiling can sometimes be removed using a soft brush making sure you sweep with the lye of the feathers. Remember though, wings and feathers may be quite tough and resilient, but keep handling to a minimum to avoid disrupting important features 

If you are not going to examine or 'read' the wing immediately, the most convenient form of preservation is freezing. Simply pop it into freezer bag, make sure you label it (date, species and sex), and find somewhere in the depths of your freezer that the wife won't object to you using. In this state it is possible to store wings indefinitely and if you collect your best examples for each species, you'll soon have a useful reference collection. Alternatively, you can take photographs and if you have a digital camera and PC store the images in your own virtual gallery but you'll need to take good quality close ups for this to be effective. 

Figure 1 Feather Groups of Duck Wing 

Sequence of Plumage change 

Close study of feather changes between Juveniles and Adults over many years has ensured that for most species the exact sequence is known and can be used to determine age. Juveniles, be they duck or drake, have plumage markings broadly similar to adult females of the species. Often the only clear differences are that juveniles have less defined markings and appear slightly duller. Once fledged the young ducks will undergo a moult into their first winter plumage. 

It is not possible to give a precise timing for this moult, other than to say it will occur some time between September and January. This is due to variables such as the date of hatching, environmental conditions and the physical condition of each bird. For this reason it is likely you'll see all stages of the moult sequence throughout the course of a typical wildfowling season. 

Fortunately though, the majority of juvenile wing feathers are retained until the bird is around one year old. Which means that although it will have undergone a full body moult in this time, it should still be possible to tell it apart from adult birds (more than one year old).  

Perhaps the single most important fact to remember is that the presence of just one of these juvenile feathers is enough evidence that the bird is not yet adult. So once you found one, you need not examine any more, save for your own interest. 

Moult Sequence from Juvenile to First Winter 

Primaries                                  Not Moulted

Secondaries (speculum)            Not Moulted

Primary Coverts                       Not Moulted

Lesser Coverts                         Not Moulted

Middle Coverts                        Not Moulted

Greater Coverts                        Not Moulted

Tertials                                      Moulted

Greater Tertial Coverts              Moulted

Post Humerals                          Moulted

Scapulars                                 Moulted

There are two important caveats to this sequence of events. Firstly, if feathers are damaged and then lost from the wing they may be replaced by feathers of the next sequence ie adult. So it is possible to see adult features that should not have normally moulted on a duck that is very clearly Juvenile/First winter. Secondly, the plumage of adult females that have bred late may become badly worn and as you will see later, feather wear can be indicative of juvenile birds. 

Age Differentiation 

The basis for the examination is to follow a wing 'key' which describes wing features and how they appear dependant upon age. So, with reference to Figure 1, simple work your way down the list checking for the specific identifying characteristics. You will see that although most feather groups are included in each key, they may not necessarily be listed in the same order. This reflects those feathers that are the most practical and give the most definitive diagnosis for each species. While you may only need to refer to a few of these when examining early season birds, as winter progresses and new feathers are grown it will become increasingly necessary to examine all the listed groups. If you are unsure if a listed feature is identical to the one you see, move onto the next one. It is not necessary to get a perfect match for them all, one 'hit' of a juvenile feather is diagnostic. 

Drake Wigeon  

By far the easiest duck to age is the cock Wigeon, which can be readily identified by a single feature. For the sake of completeness though, the whole key is included together with images of Adult and First Winter birds (see Images 1 and 2). 

 ***

The fully white shoulder (lesser and middle coverts) of the adult is usually obtained during the first summer moult. So if present, this is sufficient evidence to classify any drake Wigeon. It has been noted however that the coverts of Juvenile/First Winter birds can become whiter during the season as a result of colour change without moult. But never to the extent that they could be confused with the bright white coverts of an adult. 

Image 1 Adult Drake Wigeon 

Image 2 First Winter Drake Wigeon 

Discussion 

Although the images have been degraded to reduce file size, the differences between some of the feather groups are still clearly visible. The white shoulder of the adult with its grey leading edge contrasts strikingly with that of the juvenile (part 1 of key) which is why this single feature is so useful in distinguishing the two. You can also see the reduced amount of metallic green present on the speculum of the juvenile compared to the adult (part 3 of key). Finally, though it’s not so clear, compare the tertials of the juvenile and adult. You will hopefully see that the tertials of the younger bird are not black and have a narrow white and frayed outer margin (part 4 of key).