Field Notes Journal

Seasonal Analysis and Species Classification

Black Headed Gull

Model Family : Resident detectability

Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK David Walker, Field Notes Journal ( CC BY 4.0 )
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK David Walker, Field Notes Journal ( CC BY 4.0 )
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK David Walker, Field Notes Journal ( CC BY 4.0 )
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK David Walker, Field Notes Journal ( CC BY 4.0 )
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK David Walker, Field Notes Journal ( CC BY 4.0 )
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK
Black-Headed Gull (Chroicocephalus ridibundus), Radley Lakes, UK David Walker, Field Notes Journal ( CC BY 4.0 )

Summary

Black Headed Gull

Resident with summer detectability collapse

Black Headed Gull is classified as resident with summer detectability collapse. The fitted resident detectability target peaks around April and reaches its lowest point around October. The model indicates weak baseline presence, weak spring carry-over, strong pre-summer retention, moderate summer suppression, and strong summer decay acceleration.

Confidence
Medium
Fit score
0.201
Peak detectability
April
Lowest detectability
October

Seasonal wheel

Seasonal wheel for Black Headed Gull Black Headed Gull Peak: April

Calendar strip

Jan 0.11
Feb 0.13
Mar 0.35
Apr 0.62
May 0.34
Jun 0.13
Jul 0.1
Aug 0.04
Sep 0.02
Oct 0.0
Nov 0.0
Dec 0.19

Highlighted months indicate stronger modelled presence or detectability. A ring marks the fitted peak; a hollow mark indicates the trough where available.

Classification evidence

Target peak month
4
Target peak label
April
Target trough month
10
Target trough label
October
Target peak value
0.618
Target trough value
0.0
Target mean value
0.169
Target amplitude
0.618
Baseline to peak ratio
0.068
Autumn to winter weight ratio
0.051
Year end to winter weight ratio
0.344
Decay to growth ratio
1.48

Observed and Simulated Seasonal Patterns

Black-Headed Gull Observed Presence, Thrupp Lake
Black-Headed Gull Observed Presence, Thrupp Lake
Black-Headed Gull Observed Totals, Thrupp Lake
Black-Headed Gull Observed Totals, Thrupp Lake
Black-Headed Gull Simulated Presence, Thrupp Lake
Black-Headed Gull Simulated Presence, Thrupp Lake

Cite this dataset

You are welcome to reuse or reproduce this material under the terms of the Creative Commons CC BY 4.0 licence but please cite it using the reference below, include a link to the licence, and indicate if any changes were made.

Walker, David. Black-Headed Gull. Field Notes Journal. ID FN-WL-SEASONAL. Version 2026.05.26. https://fieldnotesjournal.uk/wildlife/seasonal/thrupp_lake/black_headed_gull.html

Dataset FN-WL-SEASONAL Author David Walker Publisher Field Notes Journal Version 2026.05.26
Reference: Walker, David. Black-Headed Gull. Field Notes Journal. ID FN-WL-SEASONAL. Version 2026.05.26.

BibTeX 
@dataset{fn_wl_seasonal,
  author = {Walker, David},
  title = {Black-Headed Gull},
  year = {2026},
  publisher = {Field Notes Journal},
  version = {2026.05.26},
  url = {https://fieldnotesjournal.uk/wildlife/seasonal/thrupp_lake/black_headed_gull.html}
}