The catch was typical of the time of year, albeit goldcrest numbers remain very low. A few chiffchaffs, eight redwing, our seventh new treecreeper and our eighth new coal tit of the year, a female blackcap and another late autumn Cetti’s warbler were the features.   

The real highlight, however, was a common snipe. We have ringed 125 common snipe (and 34 jack snipe) on the marsh since our first (on 5 November 2014). Subsequently, during the course of winter ringing on the marsh we have recaptured a few ringed birds within winters, showing in one case that individuals appear to remain at Oxwich for several months. However, until now a between-winter recapture had evaded us.

This is of particular importance from two perspectives. Firstly, we want to start to understand more about the snipe using the marsh; is there site fidelity? (we had already recorded a between winter recapture of jack snipe). Secondly, it is difficult confidently ageing snipe without capturing known-aged birds. Plumage differences can be very subtle, adults complete a full post breeding moult (which may be suspended), while post juvenile moult can be extensive; as a result of a lack of certainty, many birds are not specifically aged (age code 2) in the hand. This therefore represented a learning opportunity.

Ageing Snipe

The criteria listed in Baker (2016) for consideration when attempting to age common snipe are:

In addition, it is worth checking for evidence of moult limits in the primaries, as this indicates an adult bird. Main moult can be completed on the breeding grounds or suspended and completed during winter.

There are other criteria listed by Demongin (2016), and there seems to be some disagreement between the standard texts over the typical extent of post juvenile moult. E.g. Baker suggests scapulars are typically moulted, while Demongin notes “PJ moult including body, ….. but perhaps no scapulars.” Demongin also indicates that there is generally a post juvenile moult limit in the median coverts, while Baker notes this is present in “some individuals” suggesting it is less commonly observed.

Other features noted by Demongin include: 

• The shape of the outer tail feather. In young birds this feather is shorter and thinner than in adults, and does not show a distinct notch. (However, this criterion can only be used to help determine first winter birds that have retained their outer tail – some are likely to moult it, but the proportion is unclear). 
• The outer web of (retained) juvenile scapulars have a clear whitish edge (refer to previous text re: scapulars).

A further criteria, listed by Kaczmarek et al (2007) is retained humeral coverts:

• The authors noted this feature was often present in adults which were not actively moulting. Many autumn individuals were recorded as having all fresh plumage other than the humeral coverts. This suggests adult birds moult humeral coverts relatively late; typically at the end of primary and secondary moult. The authors further concluded that humeral covert moult proceeds slowly, and may be suspended or arrested.

The below shows the wing of the known adult snipe. 

With regard to the criteria:

• The bird showed no clear moult limit in the median coverts, which is the feature we tend to look for and give most weight to in ageing. There was no obvious colour change, no feathers that clearly conformed to juvenile pattern and a lot that appeared to conform to adult.
• The primary coverts and outer primaries were indeed relatively rounded (albeit this is pretty subjective), and showed very little wear. There was no moult limit in the primaries, suggesting the bird had completed its moult ahead of migration.
• The outer tail feather showed a clear notch, indicating it had been moulted / was of adult type.
• Two of the humeral coverts appeared to be old (as can be seen from the photograph above). This would indicate an adult that had suspended or arrested moult.
• The only potentially confounding feature was the pale edging to at least one of the scapulars (see photo above). According to Demongin this is a juvenile feather feature.

So, all in all, in the absence of knowing it was a bird we had ringed the previous winter, on the balance of features we would have aged it as an adult (code 4). I certainly don’t think we would have concluded any first winter characteristics were present, but ageing a common snipe as an adult (when moult limits can be very difficult to discern) is a bigger call than ageing a bird as a first winter based on a clear moult limit in the median coverts.

It would be interesting to catch the bird in the later winter, and to to see if the humeral coverts have been replaced.

Hopefully we will see some further between year recaptures during the coming months.

Thanks to Heather Coats, Keith Vaughton, Cedwyn Davies, Richard Dann and Lara Bates-Prior for company and assistance during the session.

Finally thanks to Shalamar for the inspiration for the title of this blog post.

Owain Gabb
02/11/2018

Underwing coverts of snipe (Lara Bates-Prior) – a whole different area to think about!

Snipe to remember (Lara Bates-Prior)