Larus cachinnans in the Netherlands

(last update: August 16, 2020)

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

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Cachinnans - nest Lelystad 041

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 041 positioned at breakwater 2, close to large code "17" marked on block.
  • This pair has a complicated history. Main problem: whole month of April a group of adults were guarding a nest together on blocks, close to each other. Group included Herring Gull 4CY, Caspian Gull with intense yellow legs, and Yellow-legged Gull ( type) adult. April 16th, 2021 nest 17 contained 2 eggs and parentage was unknown, but on April 24th the nest was empty.
  • By May, the group had split and May 15th, 2021 the yellow legged female Caspian Gull and male Yellow-legged Gull (hybrid) started their own nest, 6 meters east from old nest 17.
  • Herring Gull from the group started also a new nest in May, only 1 meter away from old location (see nest 17 season 2021 data).
  • ID 2021 certain, parents are female Caspian Gull cachinnans, and male Yellow-legged Gull michahellis or hybrid bird with michahellis blood.
location March 30th, 2021 guarding group. April 26th, 2021. Nest May 15th, 2021: 3 eggs clutch.
 
partner 1 April 26th, 2021: male michahellis (-type). April 26th, 2021. April 26th, 2021.
 
partner 2 April 26th, 2021: female yellow legged cachinnans. June 8th, 2021. June 8th, 2021.
 

Visits and data.

date:            
16-4-2021 2 eggs in nest 17, size and pattern okay for cachinnans. Several adults present as small group. Parentage of eggs unknown.
    egg no: width (mm) length (mm) volume (cm3):  water test on April 16th: 
    A 53,5 71,5 103,04 20 - flat on bottom
    B 52,3 68,9 94,89 25 - flat on bottom
         
26-4-2021 Nest 17 is empty.      
  Guarding in group: Herring Gull type 4CY, Caspian Gull with intense yellow legs, and Yellow-legged Gull ( type) adult.
  2 meters west of old nest is a nest with 2 eggs: new nest 17 (parents probably Caspian and Herring Gull). For data, see NEST 17 from this date on.
  6 meters east of old nest 17 are two adults: female Caspian Gull cachinnans, and male Yellow-legged Gull michahellis or hybrid bird with michahellis blood. They have no eggs.
             
15-5-2021 Herring Gull is obvious parent of nest NEW 17, other parent remains uncertain. There is always a guarding adult cachinnans at the blocks though. For data, see NEST 17.
  female Caspian Gull cachinnans and male Yellow-legged Gull michahellis also have nest with 3 eggs.
  3 eggs: egg no: width (mm) length (mm) volume (cm3):  water test: No
    A 51,4 72,0 95,78 --
    B 52,5 72,6 100,75 --
    C 50,9 70,1 91,44 --
  sum nest: 287,97
         
28-5-2021 2 eggs.      
         
08-6-2021 2 parents at nest.    
         
28-6-2021 No birds, no activity, no eggs.