Larus cachinnans in the Netherlands

(last update: August 16, 2020)

Coordinators:
Albert de Jong
Leon Kelder
Roland-Jan Buijs
Thijs Horst
Merijn Loeve
Mars Muusse

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Caspian Gull cachinnans hybrid 6.Z 1CY, May 30 2022, Lelystad, the Netherlands. Picture: Mars Muusse.

Red tibia ring r[6.Z] and metal NLA 5.625.138, ringed as pullus Larus cachinnans hybrid at nest 18 on May 30 2022 in colony Lelystad, the Netherlands. Ringer: Roland-Jan Buijs ringing team.
ID certain in 2022: one parent is adult cachinnans, other parent is adult argentatus.

Visits and data 2022:
Estimation egg laying: A-egg = April 17 2022. Estimating hatching = May 15 2022.
   
29-04-2022 Nest located and eggs measured.
  One parent is female Herring Gull. Other parent is aggressive male Caspian Gull.
  egg no: width (mm) length (mm) volume (cm3):  water test on May 6th:  3 eggs in nest.
  A 48,6 72,9 -- floating - halfway.      
  B 47,8 70,5 -- 90 - tip bottom.      
  C 48,7 71,4 -- 90 - tip bottom.      
   
17-05-2022   metal NLA colour age        
  pullus .5625137 - <2 days old        
  pullus .5625138 - <2 days old        
  egg just hatching.      
   
30-05-2022   metal NLA colour age mass wing H+B Bill
  pullus .5625138 r-6Z <2 days old 444 91 80,2 34,3
  pullus .5625177 r-60 <2 days old 327 60 74,7 27,1
  egg just hatching.      

below: Caspian Gull cachinnans hybrid 6.Z 1CY, May 30 2022, Lelystad, the Netherlands. Picture: Mars Muusse.

r[6.Z] hybrid cachinnans from nest 18 (226). Picture: May 30th, 2022.
Ringed on May 30th. No observations since. Same for sibling r[6.0]. Sibling NLA5625137 ringed on May 17th. No observations since for this one either.