Monday, 18 August 2025

Mist netting 15th August

After having had several successful catches in the vicinity of the Discovery Hut, four of us ventured down to Colyford Common to ring in the 'crop field', which hasn't been used for crops in quite some time & is now actually a scrubby field. We set six nets, and had a hot, tiring but successful morning, catching 55 birds of 16 species.

As is usual for this time of the year, the bulk of the catch consisted of juvenile birds, and most of the few adults we did catch were undergoing a main moult including wings & tail (moult code M). Much discussion was had during the morning regarding the age & moult code of various birds. 

All Blackcaps in their original nest-grown plumage have brown heads, and only gain their black caps (males) & chestnut caps (females) during their post-juvenile moult. It can sometimes be difficult to determine if the brown cap is that of a bird in completely juvenile plumage before moulting has begun (age code 3J, moult code J), or a female.

The bird shown below was determined to be a 3J J ie hatched this year and as yet to start its post-juvenile moult. The very pointed tail, with growth bars that lined up (not really visible in the photo) strongly suggest this is a young bird, and the bare belly is very pink & smooth, again suggesting a juvenile bird. 

Blackcap with no active moult....female or 3J J?

Completely bare belly....3J J or adult with brood patch?

Very pointed tail...a juvenile feature (although there is a lot of overlap)

A second Blackcap was with the first, which was slightly further ahead in development & was undergoing its post-juvenile moult, which included the growth of feathers on the head. These were showing tiny brown tufts from the end of the feather sheaths, indicating that this was a female.  The bird was still largely in its juvenile plumage so was still age code 3J, but with moult code of 'P' which is used to show that a bird is undergoing its post-juvenile moult.

Female Blackcap (age code 3J, moult code P)

We caught 13 House Sparrows, a bird that we seldom catch around the Discovery Hut. House Sparrows are one of only a few species in the UK in which both the adults & juveniles both undergo a full moult as a post-breeding or post-juvenile moult respectively. This can make aging tricky as the usual premise, that a bird undergoing a main moult of wings & tail is an adult, doesn't apply. However, looking at the wear of the feathers & the presence of a brood patch can help. An adult House Sparrow would have grown its wing feathers last year & they would therefore be more worn  & tatty than a bird hatched this year which has only had a few months of wear. Of the 13 House Sparrows caught, only one was an adult.

Adult female House Sparrow (age code 4)

Wing of adult House Sparrow

Feathering-over brood patch of adult House Sparrow

Juvenile House Sparrow (age code 3)

Wing of juvenile House Sparrow showing less worn old Primaries

This Blackbird was undergoing its post-juvenile moult:

Juvenile Blackbird 

Growing feathers are black, showing that this is a male.

This Blue Tit was also undergoing its post-juvenile moult:

3J P Blue Tit (juvenile undergoing post-juvenile moult)

Moult contrast between replaced Greater Coverts & juvenile Primary Coverts

Moult limit in tail between old greenish juvenile feathers & new blue central feathers

Juvenile Garden Warbler (age code 3)

The Team




Ringed

Blackbird

2

Blackcap

2

Blue Tit

6

Cetti’s Warbler

1

Chiffchaff

3

Dunnock

5

Garden Warbler

1

Goldfinch

2

Great Tit

3

Greenfinch

1

House Sparrow

13

Reed Bunting

1

Reed Warbler

3

Robin

1

WillowWarbler

7

Wren

4


55




Saturday, 16 August 2025

Mist netting 14th August

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

Saturday, 9 August 2025

A bumper catch on 3/8/25

What a day! We started early, meeting at the Discovery Hut at 0430hrs for our 3rd attempt to catch Sand Martins in front of the Sand Martin bank. Unlike on the previous sessions, as we walked the nets out in front of the bank, very few birds emerged from the holes into the nets. As it was so quiet & there were seven of us (the most for years!), we decided to set some nets in the reed bed where we'd caught well a few days earlier. 

We planned to set six nets in the reeds, but after one quiet round, numbers started to increase & we never managed to put up the sixth net. Meanwhile, the Sand Martin catch also improved, with plenty of re-traps. 

The team in full flow...minus Doug who was watching the Sand Martin net

As usual, we didn't leave the Sand Martin net up for too long to minimise disturbance. Despite the quiet start, with only five or six birds as we walked in, we ended up with a total of 52 birds from the bank net, 35 adults & 17 of this year's young, all re-trapped birds apart from one adult & one juvenile.  Presumably the youngster had come in to roost from another colony as we're pretty sure we've ringed all the young hatched in the wall. Later in the day we also ringed one brood of four pulli (nestlings), things are definitely slowing down in the wall!.

The young birds caught that had been ringed as pulli in the nest had been ringed between 6/7/25 & 17/7/25, so quite a short window.  It was interesting that some of the young were captured together with their siblings, presumably as they were leaving a nest hole as they were extracted from the wall side of the net. Unless there's a reason to suspect that the young from a nest box haven't fledged, when completing nest records, an empty box is usually shown as a successful outcome. It was particularly nice therefore to catch APC2977-APC2980 together, which is the whole brood ringed (by me!) from box G28 on 13th July, proof that that particular brood had indeed fledged successfully.  At least two of the young were still using the nest box on 24th July, but had fledged by 31st July. Interesting to see that they are staying together & roosting in the bank, although we can't say for sure that they're still using G28. 

The brood in G28 on the day of ringing (13/7/25)

Two of the brood still present 24/7/25

We've also had our first Sand Martin that was ringed as a pulli re-trapped elsewhere. Although this was some time ago, it doesn't seem to have made it onto any previous blog post. The bird was ringed on 22/6/25 & caught at Dungeness Bird Observatory on 21/7/25.

From the Dungeness Bird Observatory X feed

Two other birds were caught in the Sand Martin nets, a Sedge Warbler & a Kingfisher. As Doug was constantly monitoring the nets, he saw the Kingfisher fly across the pond & into the net. His description: "it came in like a bullet & almost looked like it was heading for one of the holes!". A quick check on Google revealed that although not common, Kingfishers are known to predate Sand Martin nests, taking eggs & young. We have had a couple of missing eggs & young from the wall, so maybe a Kingfisher was responsible, although probably not this one as it was a youngster....unless it had learned the trick from its parents having been fed them as a chick!

Kingfisher....dark breast band & dark tops of its feet indicate a young bird (age code 3)

Lack of pale area on lower mandible indicates a male

Meanwhile, the nets in the reed beds were getting very busy, with plenty of Sedge & Reed Warblers & Chiffchaffs migrating through, plus a good variety of other species, mostly young birds hatched this year. The juveniles included two more un-ringed Sand Martins, like the one from the wall, presumably a visitor from another colony. 

At first glance this Chaffinch looks like a female, which is duller than the male. However, a closer inspection shows some brighter pink feathers appearing on the breast, growing as part of the post-juvenile moult, when the bird replaces the feathers grown in the nest with the adult type.

Chaffinch, a young male (age code 3J...still mostly in juvenile plumage)

Brighter pink breast feathers indicating this is a male Chaffinch. 

We also caught a young Robin moulting into its adult red breast. It had also moulted its juvenile inner Greater Coverts & was replacing them with the adult type which at the moment are just small tufts emerging from the feather sheaths, otherwise known as being 'in pin'. Often the juvenile Greater Coverts have distinct orange coloured 'thorns' along the shaft (see post on 26/9/24). However, this bird only has a very small amount of orange at the tip, so the background colour of the feathers will be more important for aging this bird once it's finished its post-juvenile moult. 

Robin undergoing post-juvenile moult, changing mottled feathers for red ones


Juvenile Robin wing

We also caught several young Goldcrests. The one pictured below was still mostly in juvenile plumage but was starting to grow its crest...which looks orange indicating that it's a male. 

Goldcrest growing its crest

We also caught three 'controls' ie birds ringed elsewhere.
  • A juvenile Sedge Warbler ringed at Teifi Marshes in Ceredigion Wales on 9/7/25. 
  • A Chiffchaff that had been ringed further up the Axe Valley at Colyton Sewage works by Mike Tyler on 22/7/25.  
  • A juvenile Reed Warbler ringed at Oxwich Marsh, Swansea , Wales on 10/7/25
Also, one of our juvenile Sedge Warblers that was ringed on site on 1/8/25 & re-trapped on 3/8/25 was then caught by the Swale Ringing Group at Spitend Marshes, Kent on 6/8/25. 

One unusual incident of note occurred mid morning. Two Roe Deer were seen running into the reed bed. On reaching the far net, it was found lying flat on the ground, with a guy & peg stuck high up in a tree on the far side of a stream. A large deer-sized hole was also found in the bottom shelf. Luckily the few birds in the net survived unscathed. 

It had been a long, exhausting & productive session. Although we'd started with seven of us, numbers gradually dwindled as people had to leave, and for the last few hours it was just Neil, Jan & myself, catching the last birds at 1500hrs & finally leaving the Wetlands at about 1600hrs having processed 217 birds!

The weary die-hards! Seemed silly to stop whilst we were still catching!

Results for the reed bed:


Ringed

Re-trapped

Control

Blackbird


3


Blue Tit

6

3


Cetti’s Warbler

3

1


Chaffinch

3



Chiffchaff

13

2

1

Dunnock

2

1


Garden Warbler

1



Goldcrest

3



Goldfinch

5



Greenfinch

9



House Sparrow

5



Kingfisher 

1



Reed Bunting 

2



Reed Warbler

33

5

1

Robin

2



Sand Martin

2



Sedge Warbler

31

6

1

Song Thrush

1



Whitethroat

1



Willow Warbler

6

1


Wren

5

1



134

23

3