It has been a typically slow start to the year at Oxwich. There were no ringing sessions in January (when we focussed on High Pennard), but a spell of settled weather in February has allowed us to get going.
Totals to date are as follows:
|Great Spotted Woodpecker||4||4|
Of note have been:
- A great tit ringed in June 2016 as a juvenile and recaptured periodically since – now in its 8th calendar year.
- A chaffinch ringed in February 2016, as a second calendar year female, and not recaptured again before 4 March 2023.
- A jack snipe and 12 common snipe captured at dawn returning to roost in the Oxwich reedbed (over the course of several sessions). The common snipe included a bird initially ringed in February 2018, recaptured on 24 March 2019, and finally (most recently) on 4 March 2023. Of the 295 snipe captured on the marsh since November 2014, only 14 have been retraps. Most of these recaptures have occurred in the same winter as the birds were ringed. Having a bird of known age was therefore very useful in assessing ageing features; we have found the species is very difficult to age with confidence due to the relative subjectivity of published criteria combined with the extent of post juvenile moult that can occur.
Baker (2016) includes the following ageing features for snipe (to which I have added some notes regarding our previous success applying each feature):
- First winters can retain some inner median coverts. These appear worn compared to fresh adult-type coverts, with the latter also showing a dark shaft streak extending to the tip (whereas the juvenile-type feathers have a whitish unbroken fringe). As both retained first winter and adult feather start to wear, and snipe wings are very visually ‘busy’ , we have found it difficult to assess median coverts.
- The shape of the primary coverts and primary feathers, which are narrower in first winters than in adults. Juvenile primaries would also typically be expected to show a little more wear than those of an adult by March. This feature is also a little subjective without known-age birds, albeit there is an illustration of this and of the tertials in Baker that is helpful.
- Adult tertials show a slight beige edge and irregular V-shaped black stripes; retained juvenile tertials do not have the deep ‘V’ marks. We have possibly given this feature less weight than we should given our experience on 4 March 2023, but this is because first winter birds can moult their tertials (the frequency of this is unclear – it could be that most do). Baker notes that post juvenile moult can be extensive and include most or all wing coverts, scapulars, tertials and tail feathers. It follows that determining an adult with confidence (in late winter) relies heavily on primary shape and wear, whereas a proportion of first winters can be aged with reasonable confidence on a combination of primary characteristics and retained juvenile feathers (if they haven’t completed an extensive post juvenile moult).
We caught two snipe during the 4 March session, the recaptured adult and a first winter. This was very useful. Photos of the two birds are below.
Having applied the features, we reflected on whether, without knowing the age of the recaptured bird, we would have confidently aged it as an adult or concluded it was age unknown. The answer is probably that it depends how brave we were feeling. As we find median coverts a very difficult criteria to apply (and they could all be moulted in a first winter) and adult-type tertials can be found on first winter birds (for the same reason), it depends on how much faith we wanted to put in primary shape and wear. What is certain, however, is that knowing the recaptured bird was an adult enabled us to age the first winter bird with confidence, and that feels like a step forward.
Thanks to Heather Coats, Wayne Morris, Alex McCubbin, Miguel Lurgi, Lucy Rowley, Becky Gibbs, Catrin Ferguson and Kayleigh Bargus for company and assistance during the session.