American Herring Gull (smithsonianus)
(last update: October 30, 2015)
American Herring Gull (smithsonianus) adult.
P5 (figure 10, table 8)
The shape of the black mark (when present) is important, even more so than in P6. The majority of NF smithsonianus in our sample had a complete, uninterrupted black band, while this is less frequently seen in European birds. In those NF smithsonlanus with a complete black band, there are normally three pointed wedges (as in P6), creating a nice symmetrical
’W’-pattern (see figure l0a and percentages below it). In birds in which the black band is interrupted, or entirely confined to the outer web, two very pointed wedges usually remain, creating a forked or ’U'-shaped pattern (figure 10b). In argenteus, the common pattern is that of a thick black spot entirely confined to the outer web - which is only rarely seen in NF smithsonianus (see figure 10e). Of those argenteus with a complete black band in our sample, only a minority showed a distinct ’W'-pattern. In argentatus, black markings are commonly absent altogether (figure 10c), No birds in our sample had a distinct, complete ’W’. In Eastern Baltic Herring Gulls, the pattern on P5 is quite variable.
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| % NF smithsonianus | 70.2 |
16.8 |
5.2 |
2.8 |
2.0 |
| % argenteus | 6.8 |
3.4 |
16.8 |
15.2 |
47.2 |
| % argentatus | 0.0 |
22.2 |
52.8 |
2.8 |
22.2 |
| % E-Baltic Herring Gull | 12.7 |
22.2 |
28.1 |
15.8 |
20.6 |
FIGURE 10 Variation in pattern of P5 in herring gulls (Peter Adriaens). Percentages refer to the combination of shape and extent of the black pattern. Here, for instance, it is stated that 70.2% in our sample of NF smithsonianus had an uninterrupted black band (on both webs), which, in addition, was shaped like an almost symmetrical 'W', as illustrated in figure 10a. (click on image for larger view) |
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| TABLE 8 Amount of black on P5. | |
| P5 | % of birds with
complete black band |
| NF smithsonianus | 73 |
| argenteus | 22 |
| argentatus | 3 |
| Eastern Baltic Herring Gull | 30 |
Note: In a smaller sample of adult NF smithsonianus (n=100), Jonsson & Mactavish (2001) recorded 65% with a complete black band on P5. |
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