19/05 Thatcham Marsh LNR

Location: Thatcham March LNR CES v 2024.03.

Session: 19/05/2024 05:50 to 11:15

Notes: A seemingly quiet session today with few birds, this brought about a discussion of there being many more birds about on the reed bed in the past. As a result, I did a check of the birds processed for CES visit 3 since 1993 when we joined the BTO Constant Effort Scheme. The oddities such as Mute Swan etc should be ignored. The only regularly processed species are Reed Warbler and Sedge Warbler and there is some indication that numbers may be dropping for Reed Warbler but not at the level perceived, at least not for the last 31 years (2020 was abandoned due to covid restrictions). Sedge Warbler show a decline in numbers in line with the national data that indicates Sedge Warbler to be moving its range north as a result of global warming. Comparison over a longer period is not safe as ringing on this site was irregular and there is no record of the duration, or the number of nets erected each session. For both species there is no doubt that numbers over the whole of Thatcham Marsh are much reduced due to the loss of reed bed to gravel pits, also the increasing intrusion of Willow Scrub. The other species perceived to have all but disappeared is Reed Bunting, but this species had declined nationally before the 30+year period for reasons that are unclear. On the  plus side we have gained Cetti’s Warbler that first bred adjacent the reed bed net ride in 1993.

Present: IW,JHW,DL,RAD,JL.

Weather: overcast sunny periods late in session, calm, cool.

Nets: 198metres in one reed bed ride 06:30 to 10:30hrs

Lures: None

Recaptures:(12)

Blackcap            ringed: 04/05/2024.

Reed Warbler    ringed: 23/05/2021, 10/07/2022, 11/06/2023, 04/05/2024x3, 11/05/2024x2

Sedge Warbler  ringed: 04/05/2024x3

CES VISIT 3 SPECIES TOTALS BY YEAR 1993 to 2024

Sighting: Mostly IW’s list, I was not able to get to site until mid-session. A few swifts drifted about high up for much of the morning and two Swallow over, otherwise as might be expected for this time of the year.