Larus cachinnans

(last update: February 16, 2013)

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

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cachinnans plumages

Larus cachinnans hybrid 5CY female PLG DN-? October 06 2009, Pohlsche Heide, Germany. Picture: Armin Deutsch.

5CY Female F2 hybrid Caspian x Herring Gull, Pohlsche Heide, Germany, October 06 2009. Parentage confirmed by microsatellite markers. Both parents were hybrids, trapped at the nest and identified in the hand by phenotype; the female parent had an intermediate genotype. Ringed as a chick in Wloclawek, central Poland, May 11 2005. Unlikely to be separated from Herring Gull with confidence, while pure Caspian can be excluded on the basis of the P10 pattern (very short tongue), the head shape and facial expression (notably the very pale eye). However, signs of Caspian genes include the longish legs, relatively slim bill and nearly all-white head, despite the fact that the moult to winter plumage is more or less finished. Despite it not being possible to calculate a total score for this bird (P4 and P5 patterns not visible), it must have been higher than 12 (this was the partial score without inclusion of P4 and P5). This score reflects the bird’s similarity to Herring (see fig. 6).

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

Here, only 6 traits are visible from the image, score so far is 8, with theoretically another 6 points possible. The caption with this image mentions a partial score of 12 on 7 traits, leaving room for discussion on how to score characters here from the images; e.g. should such legs be scored "moderately long" instead of "long" and, from what we see of the P10 tongue, should it be scored "same shade as mantle" instead of "paler than mantle"? And is the eye ring colour paler orange? If so, these trait scores would sum to the current score, raising it eventually to 12.
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