30/08 Thatcham Marsh LNR

Location: Thatcham Marsh LNR CES Visit 2026.12

Session:   30/08/2026 06:00 to 11:00hrs

Present:   IW, JL, RAD, JHW, IQ.

Weather: Overcast early clearing to sunny, returning to low cloud at end of session.

Nets: 192M net along the reed bed ride (net lengths 1A & 2A) up from 06:30 to 10:30hrs.

Lures:   (none)

Grasshopper Warbler – fledge this year.

Notes: The Grasshopper Warbler was an unexpected find in the net. We last had one here in 2023 and before that 2017. Willow Warber here is also unusal this decade. We regularly ringed a few (latterly on passage only) each year in diminishing numbers until 2016, after their occurance on this site spring and autumn has become sparadic; the last ringed here before today being a single in 2022. Mostly the changing habitat from low and scattered scrub in the dryer areas to mature trees and woodland is a major factor. Comparison with 2025 matching visit 12 in the table below highlights the lack of juvenile Reed Warblers, an indication of a poor breeding outcome. As can be seen in the following chart it is not the  lowest juvenile total though 2007 was also a poor year. 

Note we started the Constant Effort Site regime in 1993 and except for the 2020 covid year we have carried out all 12 of the required visits and the chart below indicates reed warblers encountered on those visits only.

CES visit 2026.12 Recaptures: (04)

Cetti’s warbler ringed: 12/07/2025, 21/06/2026.

Wren ringed: 25/07/2026, 22/08/2026. 

Sightings: A passage Spotted Flycatcher was the highlight of the morning with the Grasshopper Warbler and Willow Warbler all on passage. Heard a Water Rail calling near the reed bed ride; we have not detected them on the last one or two visits.