Coordinator:
Greg Neubauer
Marcin Przymencki
Albert de Jong
Mars Muusse
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Larus cachinnans hybrid 8CY male 876P May 2004, Wloclawek Reservoir, Poland. Picture: Magdalena Zagalska-Neubauer.
Presumed hybrid male Herring x Caspian Gull, ringed as a chick in 1997 at Wloclawek Reservoir, Poland. Partial trait score of 9 (with a potential 2 points extra in case legs are short); this bird is either on the high end for Caspian but also just in the hybrid zone.
Below, table 1 is repeated to score this bird. Not all traits can be scored (leg length not possible), the partial scores are in italic + bold.
Here, only 8 traits are visible from the image, score so far is 9, scored by Mars Muusse (open for discussion), with theoretically another 2 points possible for (short) leg length.
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; note that the red gonys spot looks pale and this may depend on camera settings |
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) measured 2,74, Mars Muusse from photo |
2 |
intermediate (ratio 2.0-2.39) difficult to measure from this picture, bill slightly angled |
3 |
short and deep, well-marked gonydeal angle (ratio <2.0) |
Leg length |
0 |
long |
1 |
moderately long |
2 |
short |
Fig. 6 below. Sum trait scores for adult Caspian Larus cachinnans and Herring Gulls L argentatus, and hybrids. Scores are calculated by summing individual trait score values. The figure shows the percentage of individuals in the sample with a given sum value. Numbers in parentheses are the minimum and maximum values recorded.
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