Larus cachinnans

(last update: February 16, 2013)

Coordinator:
Peter Adriaens (Belgium)
Ies Meulmeester (Netherlands)

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cachinnans plumages

Larus cachinnans hybrid 6CY May 2011, Vistula, near Warsaw, Poland. Picture: Marcin Sidelnik/Michal Rycak.

6CY F2 or backcross hybrid Caspian x Herring Gull, Vistula, near Warsaw, Poland, May 2011. Mother known as hybrid, father unknown. Ringed as chick on May 08 2006 in Wloclawek, central Poland. This bird is actually very Herring-like, as all trait scores correspond to Herring Gull (e.g. unmarked eye, strong bill and the P10 pattern (more black than white). The Caspian influence is barely detectable  - if at all.

Below, table 1 is repeated to score this bird. The partial scores are in italic + bold.

Here, only 8 traits are visible from the images (not leg length), score so far is 16, with theoretically another 2 points possible.
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) 
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