Thursday 14th August saw seven members & a prospective member assembling for a relatively late start of 6am for our fourth attempt to catch Sand Martins in front of the Sand Martin cliff. We'd started at 430am on the previous attempt, but as very few birds were caught very early, we decided on a more civilised hour.
As there were so many of us & we weren't expecting a large Sand Martin catch, we divided into two groups, one to set nets for the Sand Martins, & one to set five nets in the reed bed behind the Discovery Hut where we've recently had several successful sessions.
A total of 20 Sand Martins were caught, three adults (age code 4) & 17 juveniles (age code 3). Interestingly the three adults were all caught first thing. There were only two new birds, both juveniles, which presumably had been roosting in the cliff overnight having come from another colony.
Initially the ringing base was the picnic table below the Discovery Hut, but we moved into the hut when it started to drizzle. However, the drizzle was only minor & very brief, so there was no need to close the reed bed nets, and the Sand Martin nets had already been taken down.
The reed bed nets caught 55 birds of eight species, with the bulk of the catch being Sedge & Reed Warblers, most of which were juveniles. There were a few adults though, which are usually obvious to spot.
The wing of the Sedge Warbler adult is usually much more tatty than in the juvenile as the bird will have grown the feathers over the winter in Africa & then flown back & bred, causing wear & bleaching. The Tertials & Greater Coverts in particular look tatty with a whitish edges, whereas the juveniles have fresh new feathers, with the Tertials & Greater Coverts having nice dark centres and buff edges. Juvenile Sedge Warblers also has a spotty 'necklace', although this is not always obvious, and black spots on the tongue.
 |
| Difference between adult (L) & Juvenile (R) wing of Sedge Warbler |
 |
| Tatty pale-edged adult Sedge Warbler (L) & fresh, more colourful juvenile (R) |
One of the basic rules of ringing a bird is that if you can't identify the species, then you can't ring the bird. The identity of a Chiffchaff /Willow Warbler in the hand can only be confirmed by careful examination of the wing, using the shape of the outer vein of the 6th Primary feather. A Chiffchaff will be emarginated to the 6th feather (ie it will narrow towards the tip), whereas a Willow Warbler will only be emarginated to the 5th feather. After breeding, adult Chiffchaffs & Willow Warblers undergo a main moult of all of their feathers, including their Primaries.
We caught a very tatty looking bird undergoing its main moult. On checking the wing to ascertain if it was a Chiffchaff or Willow Warbler, I found that the 6th Primary feather was only just starting to grow, and there wan't enough length of feather to determine if it was emarginated, & therefore to confirm the species. The bird looked like a Chiffchaff, but without the 6th Primary, I would be unable to ring the bird.
 |
| A moulting Chiffchaff/Willow Warbler |
 |
| Right wing of Chiffchaff/Willow Warbler |
Luckily Ian was on hand to point out that the bird had two wings.....and maybe the moult may not be symmetrical. And that did turn out to be the case, as the bird had yet to drop the 6th primary on the Left wing. I was therefore able to confirm that the bird was indeed a Chiffchaff, and ring it!
 |
| Left wing of the CHIFFCHAFF! |
 |
| Most of the Team! |
Ringed | Re-trapped | |
Blackbird | 1 | 1 |
Blue Tit | 3 | |
Cetti’s Warbler | 1 | |
Chiffchaff | 5 | 1 |
Goldcrest | 1 | |
Reed Warbler | 16 | 2 |
Sand Martin | 2 | 18 |
Sedge Warbler | 18 | 3 |
Wren | 2 | 1 |
48 | 27 |
