Monday, October 24, 2016

How to age Siberian Accentors?

Siberian Accentors at Muraviovka Park (October): top: juvenile-type, bottom: adult-type
Siberian Accentors Prunella montanella are rather common migrants at Muraviovka Park in Far East Russia. In Europe, however, they occur only as extremely rare vagrants. At least, until October 2016. Right now, there seems to be an influx of Siberian Accentors, with more records in two weeks than during the previous 100 years! You can read the full story here or here (in German).
Their occurrence in Europe fits the phenological pattern of birds ringed at Muraviovka Park, which lies at more or less the same latitude like e.g. Leipzig, Brussels or London. Most birds occur during the first half of October.
Phenology of Siberian Accentors at Muraviovka Park based on standardized bird ringing
(spring 2013,2015,2016; autumn 2011-2015)
Caused by the lack of reference material, determining the age of Siberian Accentors was not covered well in recent literature. It is widely assumed that ageing should be possible based on the criteria used for Dunnocks Prunella modularis. A very nice photo documentation for Dunnocks can be found here in the Ringer´s DigiGuide. 

Since we have ringed more than 400 Siberian Accentors within the Amur Bird Project at Muraviovka Park, we would like to share our impressions about variability and possible criteria for ageing. However, we have to highlight that we never trapped a bird of known age (e.g. a ringed re-trap) - so all the features listed below are only suggestions. We are very happy to read your comments!

three left: juvenile-type; three right: adult-type
Iris colour: juvenile-type olive-brown; adult-type warm reddish-brown

Shape of greater coverts: juvenile-type narrower, edged rufous-brown; adult-type broader, edged grey-brown

Tips of greater coverts: juvenile-type buffish or yellowish, much wider; adult-type whitish, narrower

Shape of tail feathers: juvenile-type worn, more pointed; adult-type rather fresh, broader, more rounded
three left: juvenile-type; three right: adult-type
It seems that many (most?) juveniles retained all juvenile greater coverts, while adult-type birds showed all coverts uniformly edged whitish. However, there have been individuals that did not match the pattern. Please comment - we would like to learn more!

Arend & Wieland Heim

All photo© Arend Heim