Columb headings:
A: No.
B: Wing
C: Tail
D: Difference: Longest and shortest tail feather
E: Exposed culmen
F: Tarsus
===================+===+=========+=========+=======+==========+==========
LOCALITY | A | B | C | D | E | F
-------------------+---+---------+---------+-------+----------+----------
_S. s. sumatrana_ | | | | | |
Micronesia | 13| 221 | 127 | 65 | 37 | 20.5
| | 211-225 | 117-138 | 54-79 | 35-39 | 20.0-21.0
| | | | | |
Phoenix and Union| 5| 228 | 113 | 66 | 37 | 19.5
| | | | | 36-38 | 18.5-20.0
| | | | | |
Fiji, Samoa, | 29| 221 | 131 | 63 | 38 | 20.0
Tonga | | 218-229 | 122-142 | 51-74 | 36-41 | 18.0-21.0
| | | | | |
New Caledonia, | 8| 224 | 141 | 72 | 39 | 19.5
Loyalty, New | | 221-230 | 135-148 | 68-81 | 37-41 | 18.5-20.0
Hebrides | | | | | |
| | | | | |
Queensland, | 4| 229 | 142 | 78 | 38 | 19.5
Torres Straits | | | 139-148 | 71-83 | 36-40 | 18.5-20.0
| | | | | |
Solomons | 52| 227 | 144 | 77 | 36 | 19.0
| | 220-232 | 129-162 | 66-95 | 34.0-38.5| 18.5-20.5
| | | | | |
New Guinea, | 10| 224 | 143 | 76 | 34 | 19.5
Bismarcks | | 219-231 | 135-146 | 67-81 | 32.0-36.5| 18.5-20.0
| | | | | |
Malay area | 49| 228 | 141 | 74 | 34 | 20.0
| | 220-234 | 125-153 | 63-84 | 32.0-37.0| 19.0-20.5
| | | | | |
China coast, | 21| 223 | 144 | 77 | 35 | 19.5
Riu Kiu | | 212-234 | 130-151 | 67-85 | 31.5-38.0| 19.0-20.0
| | | | | |
_S. S.mathewsi_ | | | | | |
Indian Ocean: | 10| 220 | 125 | 71 | 38 | 19.0
Aldabra, | | | | | 35.0-40.0| 18.0-20.0
Providence | | | | | |
-------------------+---+---------+---------+-------+----------+----------
The differences in the length of the exposed culmen of these terns shows
that birds from islands more remotely oceanic possess longer bills than
do those from islands closer to the Asiatic continent. Murphy (1938:538)
has written that this phenomenon is characteristic among some species
which have both continental and insular populations (or subspecies).
Figure 10 shows the southeastern part of the range of the subspecies,
_Sterna s. sumatrana_, and gives the average measurements of the exposed
culmen of birds from several localities. These localities are given in
table 19. Terns with longer bills (37-39) were taken in Micronesia, in
the Polynesian islands, and in northern Australia. Terns with shorter
bills (34-36) were taken in Melanesia, Malaysia, and the coastal region
of China, but there appears to be no abrupt line of demarkation between
them. Further evidence of this tendency may be obtained from the
literature. Kuroda (1925:191) gives the measurements of the exposed
culmen of seven males and five females from the Riu Kius as averaging 35
mm. (range 31-40.5). It is also of interest to note that the length of
the exposed culmen of the males averages one to two mm. longer than that
of the females. The status of _Sterna sumatrana mathewsi_ may be
questioned. I find no characters separating my series of mostly poor
specimens. The systematic position of this subspecies from the Indian
Ocean (and likewise the status of subspecies of other sea birds which
range into the Indian Ocean) may not be known with certainty until
additional material is obtained.
[Illustration: FIG. 10. Geographic variation in the average length of
the exposed culmen of _Sterna sumatrana sumatrana_.]
=Sterna lunata= Peale