Larus cachinnans

(last update: February 16, 2013)

Peter Adriaens (Belgium)
Ies Meulmeester (Netherlands)


cachinnans plumages

Larus cachinnans adult 47P3
April 30 2008, Włocławek Reservoir, central Poland. Picture: Magdalena Zagalska-Neubauer.

September 17 2008, Boulogne-sur-Mer, NW France, Picture: Jean-Michel Sauvage.

Bird trapped at the nest, as breeding adult cachinnans in Poland.

Anneau de métal: Gdansk DN 22158
Anneau de couleur: vert 47P3
Espèce: Larus cachinnans
Âge: adultes
Situation: élevage
Date: 30/04/2008
Lieu: Wloclawek réservoir, la Vistule, la Pologne, 52.39N, 19.08E
Ringer: Grzegorz Neubauer

espèce. Larus cachinnans.
Age : adulte
Bague verte (green) code 47P3
Observé le 17.09.2008 à :
Le-Portel (beach)
Coordonnées: 50.42N 01.34E
De nouveau observé sur le port de Boulogne sur mer ce 30.01.2010.

below: photo when the bird was trapped.

Larus cachinnans adult female 47P3 April 30 2008, Włocławek Reservoir, central Poland. Picture: Magdalena Zagalska-Neubauer.

Female 47P3, 30 April 2008, Wloclawek - Vistula river, Poland. Bird to show variation of wing-tip of adult Caspian Gulls at the mixed colony at Włocławek Reservoir, central Poland. Birds are included only if all characters are within known cachinnans variation, to ensure that influence of argentatus (possible hybrids etc.) is minimal or lacking. All birds were trapped at nests during incubation. If there are photos of the same bird from different years, they are presented side by side.

Below, table 1 is repeated to score this bird. Not all traits can be scored, the partial scores are in italic + bold.

Here, all 9 traits are visible from the image, score so far is 6, which is perfect for pure cachinnans.
Trait Score Description
P10 overall pattern: white to black ratio 0 less black than white
1 approximately equal black and white
2 more black than white
P10: white tip 0 clear white, no signs of black
1 small dark spots on one or both webs
2 incomplete subterminal bar (two large black spots, one on each web or an unconnected bar, broken in the middle)
3 complete subterminal bar
P10: tongue 0 white or whitish
1 paler than mantle
2 same shade as mantle
P5: extent of black 0 black on both webs connected, forming band, black of equal depth on each web
1 black on both webs connected, forming band, black on outer web deeper than inner
2 black on both webs, but isolated spots (= incomplete bar)
3 black on outer web only
4 no black
P4: extent of black 0 black on both webs
1 black on one web only
2 no black
Iris peppering 0 dark-looking, >50% covered by dark spotting/peppering
1 moderately dark, with 10-50% of the area spotted
2 single or very few dark spots (area < 10%)
3 no dark spotting on iris
Eye-ring colour 0 dark/deep orange to red 
1 pale to moderately orange 
2 yellow
Bill shape 0 very long and slim, with little/no visible gonydeal angle (L:D ratio >2.8) measured 2,82, but head not completely in profile
1 slim, slight gonydeal angle (ratio 2.4-2.79) 
2 intermediate (ratio 2.0-2.39) 
3 short and deep, well-marked gonydeal angle (ratio <2.0) 
Leg length 0 long
1 moderately long 
2 short