www.gull-research.org

In 2012, first recorded breeding attempt for Larus cachinnans proofed to be successful in the Netherlands.
Credits to PieterGeert Gelderblom who monitored this colony over the last years. The bird has a metal clip ring like the once used in Poland and Ukraine, but still this code has not been read. In 2012 PieterGeert, together with Roland-Jan Buijs tried to trap the bird on the nest to put on a plastic ring but attempts failed. Again in 2013 this bird is paired to the same female Herring Gull (tibia ring white 7C).

Short note (in Dutch):
http://birdingwageningen.blogspot.nl/20 ... -voor.html
http://buijsecoconsult.blogspot.nl/2012 ... meeuw.html

This male cachinnans, with metal clip-ring and paired to female Herring Gull tibia white 7C is not the only cachinnans (hybrid?) breeding at Amerongen sluizencomplex in 2013. This year, a very large female with green ring XKAC also has a nest with 3 eggs, paired with a monsterous male michahellis. Both male michahellis and female cachinnans (hybrid?) have been ringed in 2013. Here some data, which can be used to compare to 'true cachinnans' from Poland and Ukraine.

Measurements taken as in Polish colonies, by Greg. Neubauer (images below are his).
Female cachinnans (hybrid?) green XKAC, now new ring tibia blue SS
Measurements (by Jeroen Nagtegaal / Roland-Jan Buijs / PieterGeert Gelderblom)
Head + Bill = 123.7
BILL1 = 64.1
BILL2 = 53.2
BILL3 = 22.8
BILLD 20.5
G1 = 18.9
G2 = 18.5
G3 = 42.3
LML 78.6
Greyscale wing = 5.0
Greyscale rump = 6.5
Tarsus long = 81.5
Tarsus short = 70.0
Middletoe = 68.6
Wing = 439
W10 = 59
B10 = 39 (59)
Leg colour = 3
Iris speckling = 3
Eye ring = 2.5
Gape = 2.0

Attached images of tibia blue SS (formerly green XKAC). Green XKAC ringed female pullus June 10 2003 at Sedlitzer See, Germany (5133.00N 1417.00E). Autumn 2008 & 2010 & 2012 bird recorded at Waddensea the Netherlands.
Below, attached images of trapped bird at the nest. Pictures by PieterGeert Gelderblom.

This post is about the partner of female cachinnans (hybrid?) tibia blue SS. The partner is michahellis male, now in 2013 ringed at the nest tibia blue JN. Ringed by Roland-Jan Buijs, measurements again by Jeroen Nagtegaal, and images by PieterGeert Gelderblom.

Head+Bill = 128.0
BILL1 = 67.2
BILL2 = 58.7
BILL3 = 21.9
BILLD = 21.8
G1 = 20.0
G2 = 21.1
G3 = 43.8
LML = 83.4
Greyscale wing = 7.0
Greyscale rump = 7.5
Tarsus long = 83.5
Tarsus short = 72.6
Middle toe = 74.5
Wing = 471
W10 = 74
B10 = 162
Clour leg = 5
Iris 3
Orbital ring = 4.0
Gape = 3.0