Preface

Ringers' DigiGuide is based on photographs of birds caught in the ringing program at Ottenby Bird Observatory, SE Sweden. Each image is accompanied by a caption in which a number is given within square brackets. This number refers to the unique number of the ring that was applied to that specific bird and was included here to give the reader an opportunity to separate and to refer to different individuals. Additionally, the number makes it possible for us to track biometrics, moult score and other data collected during the ringing. In a few cases we have used dead birds (found dead under the nearby light-house) in order to complete the photographic samples. When dead birds are shown, the number has been exchanged to the term 'specimen'.

Ringers' DigiGuide was opened to the public in February 2015. By then, the collection of digital photographs at Ottenby contained close to 70.000 images of 3.900 individuals representing more than 230 species. When released, the guide contained 34 species, but new additions are made continuously (a few species each month during the first year) and eventually we hope to be able to reach c. 100 species, shown with complete sets of images of all age and sex categories during both autumn and spring.

The birds caught at Ottenby are on migration, and we rarely handle birds where we have 'tangible proof' of the age or the sex (e.g. recaptures or breeding pairs). Hence, the age and sex given to the birds in this guide reflect our interpretation of present knowledge, but should be regarded as open for discussion. 

Moult terminology 
We have chosen to use the following terms and definitions which we believe are easy to understand for new ringers and (with some simplifications) are rather practical to apply to passerines of northern Europe. 
 
  • Post-juvenile moult: Conducted by the young (1cy) bird soon after fledging (often close to the breeding grounds) and is generally completed before, or during the early stages of, the autumn migration.
  • Pre-breeding moult: Conducted sometime between the autumn migration and the spring migration, generally on the wintering grounds.
  • Post-breeding moult: Conducted by the adult (2cy+) bird during late summer by the end of, and soon after, the breeding period (often close to the breeding grounds) and is generally completed before, or during the early stages of, the autumn migration.
  • Arrested moult: A moult of flight-feathers that stops before it is completed, and is not resumed later on.
  • Suspended moult: A moult of flight-feathers that stops before it is completed, but is resumed later on.
     
Each of the three basic moults mentioned above may be complete (involving the whole plumage) or partial (involving parts of the plumage, often the body contour feathers and some wing-coverts, but usually no primaries, primary coverts or secondaries). A partial moult results in a moult contrast which is a rather central term for a bird ringer, meaning a contrast between different generations of feathers. Careful study of the plumage, combined with knowledge of the species' moult pattern, is the base for ageing birds. This is the reason why each species-chapter in this guide starts with a short, but important, presentation of the moult pattern - both as a moult-key, and in more detailed (but still easy to understand) text. In the moult-key we use single letter abbreviations for summer (S or s), winter (W or w), complete (C) and partial (p). The codes 'sp' and 'WC' should thus be read as 'summer partial moult' and 'winter complete moult' respectively.

The iris
The colour of the birds' irises undergo a general development during the first years of living. The general rule (with exceptions of course) is that young birds show a dull and rather cold greyish iris that turns warmer brownish during the first year. During autumn, the difference is often readily apprehended through an eyepiece in good light conditions, but already during their first spring most species have developed a colour that is more difficult to tell from adults (3cy+). Thorough and long term studies of birds of known ages (i.e. recaptures) may give experience enough to, for some species, separate three age categories (which is only exceptionally done on passerines when ageing is based on plumage), but our advice is to be cautious in this respect. We suggest that logged ages should primarily be based on the assessment of the plumage and that the colour of the iris (or any other soft part) is treated as a supplementary character to add to the general impression. In this guide we have included photographs of irises rather irregularly, and this is mainly because of the difficulties to depict the character under studio conditions. 

The photo lab
The photographs in this guide have been shot with a Nikon D300 (up to spring 2015) and a Canon 7D Mark II (from autumn 2015 and onwards). The studio flashes have gone through some changes over the years, and that's why we suffer from some variations in the light conditions in the images. The levels have been carefully corrected in Photoshop, but clear variations are still seen. In other words - some photos are good and some are bad, and the latter ones will be replaced as soon as better options are available. During autumn 2014 we installed a professional set with two Elinchrom flashes and the white-balance was fixed according to the 12% grey background. Because of this we have reasons to hope for better (and much more uniform) photos in the near future.
 
Acknowledgements
3.900 birds are not photographed without A LOT of hard work. We would like to express our deep gratefulness to our (voluntary based) staff that have worked with us during the years! We love you! Really! Further, we would also like to thank Gabriel Norevik for technical support in the photo lab as well as for developing our standard manual for handling and photo-views. Gabriel, together with Aron Edman and Simon S. Christiansen have also been invaluable discussion partners during much of the writing of this guide, and their deep knowledge on the subjects have been crucial. Finally, it must be acknowledged that Lars Svenssons' Identification Guide to European Passerines together with Lukas Jennis' & Raffael Winklers' Moult and ageing of European Passerines are important sources for anyone learning the art of ringing, and much of what today is considered as 'common knowledge' originates from these two references.

 
Enjoy the birds!
 
/Magnus Hellström, head of Ottenby Bird Observatory
 
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