Larus cachinnans in the Netherlands

(last update: August 16, 2020)

Albert de Jong
Merijn Loeve
Roland-Jan Buijs
Leon Kelder
Mars Muusse


Cachinnans x argenteus - nest Lelystad 006

General remarks:

  • Eggs: Volume measured by Stonehouse (1964) and Spaans & Spaans (1975), which make comparison possible with data from Texel (Camphuysen pers comm 16.04.2020).
  • Nest 006 positioned on artificial breakwater 1 at T-split. Location is nest PLDP - 2020 (in 2021, PLDP moved to nest PESV).
  • Certainty on ID in 2021, breeders are male Caspian Gull cachinnans and female Herring Gull argenteus.
location April 16th, 2021: male cach & female teus. May 6th, 2021: male cach & female teus. April 16th, 2021: male cach & female teus.
pulli May 28th, 2021: pullus, likely wrong nest. June 8th, 2021: too many cachinnans! .

Visits and data.

16-04-2021 Two adult at nest, photographed. Nest without eggs. Many Spoonbills breeding here, hampering visits in future.
24-04-2021 Correction on flag code. Now labeled "6". Nest abandoned, no eggs?
26-04-2021 No visit, Camilla is trapping a Spoonbill.
06-05-2021 egg no: width (mm) length (mm) volume (cm3):  water test on May 6th: 3 eggs in nest
  A egg 49,2 68,7 83,73 25 - tip at bottom
  B egg 50,7 71,7 92,80 30 - tip at bottom
  C egg 51,9 71,5 96,97 55 - tip at bottom
      sum nest: 273,50
15-05-2021 2 eggs in nest. Nest located at 'the flat stone' in dense, inaccessible Blackberry complex.
28-05-2021   metal tibia mass (gr) head + bill (mm)
  pullus .5559419 -- -- -- Chick is 1 day old. Only metal ringed. No certianty about species.
  1 egg: just hatching.
  In retrospect: this nest was situated 'too high' at dam 1, likely different nest. Hybrid nest is situated at flat stone, lower and central at dam (see May 15th).
08-06-2021 Sitiuation not clear: several cachinnans and argenteus here guarding 3 large chicks. Favorite place for chicks at the blocks near waterfront, below Blackberry complex.