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 053

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 053 positioned on artificial breakwater dam 1, nest between large blocks. Many Lesser Black-backed Gulls here, and all nests hidden between blocks, invisible from the canoe. Nest is 25 meters east of T-split, approx position of michahellis-outlook. Nest flagged with '053'.
  • Full clutch at early date + pattern on eggs were indication for cachinnans. Both pulli photographed as juveniles raising suspicion towards hybrid ID.
  • ID in 2021 uncertain: probably 2 parents are cachinnans.
location: Nest between blocks, April 16 2021. April 16 2021: Albert plotting nest. April 26 2021: michahellis at look-out.
 
nest: May 15 2021: cachinnans-like 2 eggs. May 15 2021: fuscus-like 3 eggs. May 15 2021: confusing nests at close range.
 
partner 1: May 15 2021: cachinnans is one of the parents? May 15 2021: fuscus-breeder next to 53 flag. .
   
pullus May 28th, 2021 pullus r[F.A]. May 28th, 2021 pullus b[F|=]. .
   
juvenile August 22nd, 2021 juvenile r[F.A]. December 19th, 2021 pullus b[F|=]. .
   

Visits and data.

date:            
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.