Larus cachinnans
(last update:
Greg Neubauer
Marcin Przymencki
Albert de Jong
Mars Muusse
cachinnans plumages
Larus cachinnans hybrid 9CY male, May 2002, Wloclawek Reservoir, Poland. Picture: Magdalena Zagalska-Neubauer.
Presumed hybrid male Herring x Caspian Gull, ringed as a chick in 1994 at Wloclawek Reservoir, Poland. Partial trait score of 10 (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 10, 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) | |
| 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.
