Marsworth - Tapes playing and tricky Chiffchaffs

Marsworth
Summary of three sessions in September
03/09/2017 LL, KB, CK
10/09/2017 LL & AM
15/09/2017 LL & AL

We have had three sessions at Marsworth using tape lures, mainly Blackcap and Chiffchaff song with a bit of Willow Warbler, Goldcrest and also tried Redstart (must have been feeling optimistic).
The weather has been quite poor over the last couple of weeks with strong winds and a fair bit of rain but the birds seem to be in good condition. The adults and most of the juveniles have completed moult although we are still getting a few late 3J Wrens and Chiffchaff. With moult mainly over it is starting to get harder to pick out the adults from the juveniles - see below for a couple of photos which show how careful you have to be!
In the latest session today we started to get a few more birds carrying some fat but nothing higher than F3. The Willow Warblers and Reed Warblers are few and far between now but there is no sign yet of any of the autumn migrants such as Goldcrest.
We have been treated to the displays of 4 Hobbies over the ringing site.

Species	Total Summary	unaged	3	3J	adult
Blackcap	94	3	80	4	7
Blue Tit	5		5
Bullfinch	1			1
Chiffchaff	73	1	62	9	1
Dunnock	1				1
Goldcrest	2		2
Great Tit	7		7
Long-tailed Tit	5	5
Reed Bunting	12*				12
Reed Warbler	3		3
Robin	5		4		1
Treecreeper	1		1
Willow Warbler	2		2
Wren	12		6	6
Total	223	9	172	20	22

Here are two photos of known-age Chiffchaffs which show that they are not always easy to age!

This juvenile had quite rounded tail feathers (juvenile tail feathers are usually more pointed than adult tail feathers) but it did have 5 OGC visible which helped to age it as juvenile. It is possible that it had replaced the tail but I don't think so because there is a hint of a fault bar showing in the photograph on the left hand side, and possibly T5 has been replaced on the right . 

The adult Chiffchaff had surprisingly pointed tail feathers - the feathers are quite broad and they have the pale grey edging which seems characteristic of adults but it would be easy for this bird to be misaged as a juvenile if you looked at tail shape alone.

Juvenile Chiffchaff KEA648 15/09/2017 (5OGCs)
Originally ringed 29/08/2017 as 3JP 

Adult Chiffchaff JYV145 15/09/2017
Originally ringed 15/05/2017 as 4(M)