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 February and reaches its lowest point around September. The model indicates moderate baseline presence, weak spring carry-over, strong pre-summer retention, moderate summer suppression, and moderate summer decay acceleration.

Confidence
Medium
Fit score
0.224
Peak detectability
February
Lowest detectability
September

Seasonal wheel

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

Calendar strip

Jan 0.63
Feb 0.81
Mar 0.64
Apr 0.42
May 0.36
Jun 0.36
Jul 0.33
Aug 0.24
Sep 0.16
Oct 0.26
Nov 0.31
Dec 0.52

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
2
Target peak label
February
Target trough month
9
Target trough label
September
Target peak value
0.81
Target trough value
0.159
Target mean value
0.42
Target amplitude
0.651
Baseline to peak ratio
0.363
Autumn to winter weight ratio
0.053
Year end to winter weight ratio
0.445
Decay to growth ratio
1.35

Observed and Simulated Seasonal Patterns

Black Headed Gull Observed Presence, Abingdon
Black Headed Gull Observed Presence, Abingdon
Black Headed Gull Observed Totals, Abingdon
Black Headed Gull Observed Totals, Abingdon
Black Headed Gull Simulated Presence, Abingdon
Black Headed Gull Simulated Presence, Abingdon

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/abingdon/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/abingdon/black_headed_gull.html}
}