Larus cachinnans in the Netherlands

(last update: August 16, 2020)

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


Hybrid Caspian Gull cachinnans F|= 1CY-2CY, May 2021 - June 2022, the Netherlands & U.K. Picture: Thijs Horst, Albert de Jong, Roland-Jan Buijs, Mars Muusse & Miles Cluff.

Pullus which may belong to Caspian Gull cachinnans nest 53, but uncertain (may belong to adjacent LBBG nest).
Brother/sister is r-F.A.

Visits and data.

16-04-2021 Nest checked. 3 eggs.
  egg no: width (mm): length (mm): volume (cm3):  water test on April 24th: laying date:
  A 49,2 70 85,32 30 - tip bottom  
  B 50,6 67,1 86,50 15 - tip bottom  
  C 50,3 70,1 89,30 35 - tip bottom  
sum nest: 261,12
24-04-2021 Michahellis present.
26-04-2021 Michahellis present, but is this the exact location of nest 53? Flag has fallen down.
06-05-2021 2 cachinnans at this location, but flag has fallen down, no exact position determined from water.
13-05-2021 No visit, Camilla is trapping a Spoonbill.
15-05-2021 3 eggs in nest near flag, with brownish pattern, resembling LBBG-eggs. Was this measured on May 6th? 1,5 meters east another nest, 2 bluish eggs, more like cachinnans.
  Landing adult cachinnans at this nest photographed; LBBG near flag 53 photographed.
28-05-2021 Two pulli ringed.
    metal ring darvic ring head + bill age
  pullus .5559425 b-F|= 52,8 age: 2 / 3 days old
  pullus .5559426 r-F.A 50,8 age: 2 / 3 days old
  egg: just hatching.
8-6-2021 No visit.

Tibia B-F|= and metal NLA 5.559.425, ringed as pullus Larus cachinnans on May 28 2021 at Lelystad (Bataviahaven), Holland (5230.00 N 525.00 E) - ringer Roland-Jan Buijs.

19-12-2021 Netherfield (Vuiloverslag), Nottinghamshire, ENGELAND 5.257,00 N 103,00 W colourring read Miles Cluff.

below: Hybrid Caspian Gull cachinnans x Herring Gull argenteus F|= 2CY, June 30 2022, Almere, the Netherlands. Picture: Thijs Horst.

below: Hybrid Caspian Gull cachinnans F|= 1CY, December 19 2021, Netherfield - Nottinghamshire, U.K. Picture: Miles Cluff.

Pro cachinnans are the nice dark outer webs on inner primaries, the dark centred outer GC, and pale tipped tertials.
However, coarsely marked head and bold anchor patterns on 2nd gen scaps are more in line with argentatus.

below: Hybrid Caspian Gull cachinnans F|= 1CY, May 28 2021, Lelystad, the Netherlands. Picture: Albert de Jong, Roland-Jan Buijs & Mars Muusse.

Rather dark brown chick.