Here at the farm in Denmark, I managed to catch a single yellowhammer (Emberiza citrinella) close to the hedgerow last week. Again I’m attempting to apply my tactic of taking multiple photos of the bird in hand and trying to “work it out” later, with the help of the many on-line resources available (including experienced ringers) which are invaluable!
At first I assumed it was a female, as there was limited yellow visible on the head and the shaft of the feathers was broadly coloured black. However after reading this detailed article (Dunn & Wright, 2009), I was reluctant to decide on a gender for this bird too quickly. (You may have noticed the bird had a small wound on the side of the head above the right eye. Apart from this it appeared in good health.)
According to Jenni & Winkler (1994) the postjuvenile moult involves all lesser, median and greater coverts, putting them out of the question when searching for moult limits, however it is always worth a look! The next step is to search for a moult limit among the tertials, carpal covert, alula and tail feathers which may be partially moulted in some birds during the postjuvenile moult. Adults on the other hand, undergo a complete postbreeding moult, which means it SHOULD be possible to differentiate the two age groups at the moment. A limited prebreeding moult has also been reported in some birds, but this was restricted to the head and upperparts.
Having a closer look at the tertials, the innermost tertial appears to have a darker center and a more clearly defined brown edge compared to the two larger tertials where the border appears more diffuse. According to Dunn & Wright (2009) tertials with a distinct boundary (as seen in the innermost tertial) are typical of first year birds. However the DigiGuide from Ottenby, suggests that this is typical of adult tertials, causing me some confusion. So it is possible a moult limit is present in the tertials, but I’m unsure which feather belongs to which generation. Furthermore looking at the secondaries, they appear notched, or heart shaped at the top, which Dunn & Wright suggested was also typical of first year birds, with adults having a more flat or square appearance. However, I’m still not confident that I am correctly interpreting these subtle differences, if they are even present.
Comparing the photos of the primary coverts, alula and carpel coverts with those in the DigiGuide from Ottenby, I didn’t get very far. To be honest I’m not exactly sure what to look for. The primary coverts don’t appear to be loosly textured, and they are quite glossy, possibly suggesting adult like. The pale yellowish-buff edge on the middle alula appears less green-ish that that of the smallest alula and the carpel covert – but is that just my eyes? or could this be a result of wear with the difference only evident towards the tip of the feather?
From my reading of the literature, the tail and both upper- and under-tail coverts seems to be a good place to look for some reliable clues to ageing and sexing. In general the tips of the tail feathers appeared rounded or with blunt edges, and not pointed or sharply angled, which suggests in this case adult type feathers (Dunne & Wright, 2009). On closer inspection, it appears to me that one tail feather appears more sharply angled at the tip (see yellow arrow). It is also possible that a first year could either accidentally or deliberately moult all tail feathers (or most of them, see David Norman’s blog), resulting in an adult like tail. Hmmm…
The extent of white on the 5th and 6th tail feathers was mentioned in the literature, but I don’t think this bird fits into any of the extremes where it can be used to assist with ageing. However the shaft colour of the upper tail coverts may give us a clue to sexing. In males the shaft of the upper tail coverts is a similar colour to the feather (chestnut brown) whereas in females the shaft is darker, almost black, as seen here.
My conclusion; female yellowhammer – age- to be continued!
Some interesting seed eaters – David Norman Blog
Jenny C. Dunn & Chris Wright (2009) Ageing and sexing the Yellowhammer Emberiza citrinella caliginosa during the non‐breeding season, Ringing & Migration, 24:4, 240-252. Link
Jenni, L. & Winkler, R. (1994): Moult and Ageing of European Passerines. Academic Press, London, UK