31/05 Thatcham Marsh LNR

Location: Thatcham Marsh LNR CES 2026.04

Session:   31/05/2026 06:00 to 11:00hrs

Present:   JHW, IW, RAD, JL, JA.

Weather: bright sunny, calm, hot.

Nets: 198M Reed Ride (site A) + 1 x12M separate rides set in scrub (site B) up from 06:30 to 10:30hrs.

Lures (none): 

Notes: The first cooler day after a very hot period. As can be seen below the total for visit CES 2026.04 is a little better than the 2025.04 visit, particularly for Reed Warbler. However, for the time of year the reed bed still seems quieter than usual - fewer Reed and Sedge Warblers singing and very few other species seem to be venturing onto the reed bed than in the recent past. To test these perceptions below are a couple of charts that plot the totals for most years the group has been in existence.

Provisors are:

·       In the early days until the 1980s ringing on the marsh was less structured, the number of nets erected or there locations not recorded.

·    Site names were general for much of the marsh until the 1980s when specific areas ringed were recorded including the number and location of nets erected.

·     Ringing was less regular and was alternated with other sites such as Hambridge Lake and at Thatcham south of the railway. On occasions this meant that ringing was at best sporadic and some years few visits were made due to poor weather and the alternation.

·      The number of active ringers (effort) has also been a factor; numbers peaked in the early 1970s at 18 members then dropping to four in the early 1980s before peaking at again in 2010 at 14 active members – currently there are usually between four and six ringers in attendance.

·    All records still in existence for Thatcham Marsh have been added to the data system back to 1973 prior to this there are gaps due to data not yet being entered or no longer in existence and which may account for the lower numbers for this period.

·    In the mid-1980s ringing on the Thatcham LNR was prioritised from April until the last warblers left late Oct – Early Nov and on every visit each net ride was recorded including species encountered therein. In 1993 were joined the British Trust for Ornithology’s Constant Effort Site (CES) scheme that runs from late Apr to early Sep when 12 “official” visit limited to the reed bed ride of 198metres of net are made. Ringing in between and outside these visits also follows this structure including any peripheral nets rides erected.

The first chart shows the yearly totals for the primary species ringed Reed Warbler and Sedge Warbler. From 1989 numbers (with exceptions) become more consistent as we adopted CES type ringing methods. With some exceptional years it shows a steady decline in numbers of both species from 1990 and as perceived by us

The next chart indications species diversity, again the overall trend is downwards. Some account for this may be due to the number of nets erected at any one time and  their location also the loss of reed beds due to gravel extraction etc, and the steady encroachment of scrub into the reed habitat over the period. Prior to the mid-1960s passing stream trains would sometimes throw their fires. Setting fire to the nearby phragmites reed that would spread over the reed beds and curtail the encroachment of scrub growth. This probably accounts for the survival of the extensive reed habitat along the Kennet valley to the late1960s when steam power was replaced.

Session Capture details.

Recaptures: (13)

Blue Tit ringed: 23/05/2026

Cetti’s Warbler ringed:11/08/2024, 29/06/2025

Chiffchaff ringed 02/04/2023

Reed Warbler   ringed: 03/07/2022, 11/06/2023 03/05/2025, 10/05/2025x2, 02/08/2025, 18/05/2025, 26/04/2026, 02/05/2026

Sightings: Less activity this session, still some species singing but some have gone quiet – Garden Warbler? The juvenile Robins and Blue Tits  also a couple of tit families in the scrub towards the end of the session show that species are now fledging including some summer migrants – Blackcaps etc. The change in the weather to unsettled meant that fewer insects were out and about and for the first time this year more Banded Demoiselles than Beautiful Demoiselles seen.

23rd May CES visit 2026.03

Location: Thatcham Marsh LNR CES 2026.03

Session:   23/05/2026 06:00 to 11:00hrs

Present:   JHW, RAD, IW, JL, CMD.

Weather: bright sunny, calm, hot.

Nets: 198M Reed Ride (site A) + 2 x12M separate rides set in scrub (site B) up from 06:30 to 10:30hrs.

Lures (none):

Notes: It was quite hot this session even early morning. Some have the impression that we are not ringing as many Reed and Sedge Warblers as in the past, however looking at the last nine years 2017 to 2026 (we were not able to ring in 2020 due to covid restrictions) our total for CES visit 3 this year is about average over the period. 21 Reed Warblers in 2021 after a pause of a year is interesting but probably a coincidense! Sedge Warbler numbers have been dropping for some years now; it is a species moving its range north due to global warming - Willow Warbler similarly is moving north for the same reason. We have been regularly ringing this site since the 1960s although visits were not as structured as they are for CES ringing. However, both species numbers have reduced, also Reed Bunting were once found here in good numbers but are at just one pair in the vicinity of the reed bed net ride so far this year. Reed beds at Thatcham Marsh have much reduced since 1967 when the group formed. Many (most) former extensive reed beds are now angling pits following gravel extraction, and most others are overgrown with scrub with fragmented areas of reed. So a reduction in numbers is not unexpected.

Totals for CES visit 03 (2017 to 2026)    

For reference the average for May per decade since the CES started in 1993 is:

Recaptures: (21)

Blue Tit ringed: 10/05/2026

Cetti’s Warbler ringed: 26/04/2026

Chiffchaff ringed 17/04/2026, 02/05/2026

Dunnock ringed: 09/10/2024.

Reed Warbler   ringed: 03/06/2023, 11/05/2024, 10/05/2025x2, 18/05/2025, 21/06/2025, 23/08/2025, 26/07/2025, 26/04/2026x3, 05/05/2026,

Sedge Warbler ringed: 26/04/2026, 02/05/2026, 10/05/026, 26/06/2026

Sightings: Some gulls feeding high on (invisible to us) flying insect - probably small dragonflies or similar. The male Kestrel was again hunting over the former waste tip hill and flying over SSW towards the escarpment woodland below Greenham & Crookham Common sometimes carrying small prey. Goldcrest were singing again after being relatively quiet for the last two visits. Otherwise much as expected though few hirundine and no Chaffinch detected.

 

17/05 Thatcham Marsh LNR

 Location: Thatcham Marsh LNR non-CES

Session:   17/05/2026 07:00 to 11:00hrs

Present:   JHW, IW, JL.

Weather: bright sunny early clouding over later, cool, calm.

Nets: 36M of scrub net in 3x12M separate rides set in scrub (site B) up from 08:00 to 11:00hrs.

Lures (none): 

Notes: It was a non-Constant Effort Site weekend so the three of us each put a 12M net up in the scrub east of the track to the angling pits and the main reed bed. We had to clear two of the rides, one was an old ride not used for some years, the others were along the west side perimeter of the lake; one we often erect when doing the CES visits. Our expectations were fairly low and so it proved – just eight birds in 3 hours; three from one net on the first round. two from the same net on the second round, further rounds produced no bird until nets down when two were in the net that produced the five earlier birds and one from another net. It was even quieter than we expected as very few birds were moving in and around the scrub or coming off the reed bed etc.

Recaptures: (05)

Blackcap ringed: 14/09/2025.

Blue Tit ringed: 29/06/2025.

Goldcrest ringed: 14/09/2025, 12/10/2025.

Wren ringed: 06/08/2023. 

Sightings: More than usual few large gulls seen occasionally over, including a 8+ flock of mostly Lesser black-backed Gulls high up probably feed on insects. Several gull sighting were of high up of apparent feeding birds. More than the odd swift was present with up to six seen occasionally through the session. The male Kestrel spent much of the morning hovering over the old rubbish tip hill to the north. We think it has a nest somewhere to the south as it flew in that direction once or twice including carrying prey on at least one occasion. The only members of the finch family detected being Goldfinch; the single local Chaffinch usually heard has gone quiet!

10/05 Thatcham Marsh LNR CES 2026.02

Location: Thatcham Marsh LNR CES Visit 2026.02

Session:   10/05/2026 06:00 to 11:00hrs

Present:   JHW, IW, JL, CMD, IQ.

Weather: mostly cloudy, some sunny periods, windy, cool.

Nets: one 198M long line of reed bed nets plus a 12m scrub net up from 06:30 to 10:30hrs.

Lures (none):

Today’s adult Jay that was not in breeding condition – probably a non-breeding wanderer. 

The local Jays that have been quite active during the last two sessions here were notably absent today.

Notes: Not an ideal day to ring due to the very strong easterly wind. About half the Reed Bed nets had some shelter, but all were significantly affected by the wind particularly during the gusting periods. The reed bed still seems quieter bird-wise than memory says it should be. The Greenham Common 2024 Chiffchaff is a good re-encounter.

Recaptures: (14)
Cetti’s Warbler ringed: 26/04/2024.
Chiffchaff ringed: 19/07/2024 ringed at the Western Enclosure, Greenham & Crookham Common.
Great Tit ringed: 29/06/2025.
Reed Warbler ringed: 03/05/2025, 02/08/2025, 26/04/2026x2, 02/05/2026x2.
Sedge Warbler ringed: 18/05/2025, 26/04/2026x2, 02/05/2026.

Sightings: Quite a few birds about given the weather, a few Swifts and hirundines occasionally drifted over  northeast-ish during the session – possibly missed a few. The Cuckoo arrived mid-session calling but did not stay long. Water Rail young called a few times and still at least two Reed Bunting about.

Birds: 47 Species

02/05 Thatcham Marsh LNR CES visit 2026/01

Location: Thatcham Marsh LNR CES Visit 2026.01

Session:   02/05/2026 06:00 to 11:00hrs

Present:   JHW, JL, IW, RAD, NC.

Weather: misty early, bright and sunny for most of the session, warm, calm.

Nets: one 198M long line of reed bed nets plus a 12m scrub net up from 06:30 to 10:30hrs.

Lures (none):

Notes:  Since last Sunday’s session somebody has stolen one of the insitu guy ropes and peg. Can’t think what use a length of some dirty weathered cord and a grubby wooden peg would be to them; I suppose they took them because they could - fortunately we had some spares with us. A good start to the Constant Effort Site season included a Garden Warbler as above. Many of the migrant species have yet to come into breeding condition, some are probably on their way through to sites elsewhere. Notable for the time of year are a few more Dunnocks than we usually get on the reed bed also the  Great Tits that included a July 2022 ringed individual.

Recaptures: (19)

Cetti’s Warbler ringed: 21/06/2025, 12/07/2025, 28/09/2025, 12/10/2025, 26/04/2024.

Chiffchaff ringed: 26/06/2025.

Great Tit ringed: 03/07/2022, 30/06/2024, 29/06/2025.

Reed Warbler ringed: 03/06/2023, 18/05/2025, .26/04/2026x2

Sedge Warbler ringed: 26/04/2026x3. 

Sightings: It was a little quite bird-wise apart from some noisy Jays foraging in the scrub. A few Swift detected high up drifting about and no hirundines seen for the second week running. Two Common Terns flew over towards Lower Farm calling, and a group of three Little Egrets flew northeast from the direction of Lower Farm. The Bank Vole ran across the track near our ringing station and the Muntjac ran down the edge of the scrub quite close to us; use to humans being about it seemed. A female Mallard with about five quite mature ducklings in tow ran across the track; fewer surviving ducklings than last week.