Coordinator:
Greg Neubauer
Marcin Przymencki
Albert de Jong
Mars Muusse
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From the Rarities Committee's files - Identification of
Caspian Gull.
Part 2: phenotypic variability and the field characteristics of hybrids, by Chris Gibbins, Grzegorz Neubauer and Brian Small, IN: BB 104/2011.
Fig. 4. Length to depth bill ratios for sample adult birds. The ratio values (0-3) relate to the trait categories described in table 1.
| 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) |
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Larus cachinnans