======================================+=====+=========+=========+========
| | | | Exposed
LOCATION | No. | Wing | Tail | culmen
--------------------------------------+-----+---------+---------+--------
_Anoüs stolidus ridgwayi_ | 18 | 278 | 158 | 41
Isabella, Cocos, Clipperton Islands | | 260-295 | 147-166 | 38-42
| | | |
_Anoüs stolidus galapagensis_ | 11 | 277 | 151 | 40
Galapagos Islands | | 274-282 | 142-160 | 38-42
| | | |
_Anoüs stolidus pileatus_ | 35 | 281 | 162 | 42
Hawaiian Islands: Nihoa to Midway | | 268-299 | 149-176 | 38-40
| | | |
Wake Islands | 8 | 278 | 159 | 41
| | 273-285 | 152-170 | 39-43
| | | |
Mariana Islands: Guam, Rota | 12 | 280 | 167 | 41
| | 275-288 | 159-187 | 39-43
| | | |
Palau Islands | 9 | 278 | 161 | 41
| | 268-283 | 155-166 | 39-42
| | | |
Caroline Islands | 41 | 282 | 164 | 42
| | 270-291 | 150-173 | 39-45
| | | |
Marshall Islands | 3 | 282 | 164 | 42
| | 270-289 | 154-174 | 41-43
| | | |
Ellice, Phoenix, Danger, Suvarov | 27 | 284 | 162 | 41
Islands | | 265-295 | 152-174 | 39-44
| | | |
Christmas Island | 13 | 287 | 162 | 43
| | 280-292 | 152-174 | 40-46
| | | |
Marquesas Islands | 19 | 282 | 163 | 42
| | 275-291 | 155-170 | 40-43
| | | |
Tuamotu Archipelago | 38 | 287 | 165 | 42
| | 277-299 | 154-173 | 39-46
| | | |
Society, Austral, Cook, Rapa | 16 | 290 | 290 | 43
Islands | | 280-301 | 155-173 | 40-45
| | | |
Oeno, Henderson, Ducie, Easter | 6 | 293 | 164 | 44
Islands | | 154-175 | 154-175 | 41-45
| | | |
Samoa, Fiji, Tonga | 19 | 285 | 164 | 42
| | 153-173 | 153-173 | 39-44
| | | |
Kermadecs, Norfolk | 23 | 276 | 158 | 41
| | 269-289 | 148-173 | 38-43
| | | |
New Hebrides, Solomons, New Guinea | 31 | 278 | 158 | 41
area | | 265-287 | 150-172 | 3 -44
| | | |
Northwest Australia | 9 | 263 | 145 | 40
| | 258-267 | 138-152 | 38-42
| | | |
South China Sea area, Strait of | 4 | 271 | 153 | 39
Malacca | | 262-278 | 148-257 | 37-40
| | | |
Riu Kius, Japan | 5 | 268 | 148 | 39
| | 259-275 | 143-155 | 37-40
| | | |
Indian Ocean area: Seychelles, | 20 | 276 | 154 | 41
Aldebra, Providence, Somaliland | | 270-286 | 146-164 | 39-42
--------------------------------------+-----+---------+---------+--------
_Geographic range._--Islands in the Indian Ocean east to tropical
parts of western and central Pacific. In Micronesia: Mariana
Islands--Agrihan, Asuncion, Saipan, Rota, Guam; Palau
Islands--Kayangel, Babelthuap, Koror, Urukthapel, Ngabad, Peleliu,
Angaur; Caroline Islands--Ulithi, Truk, Wolea, Mortlock, Lukunor,
Nukuoro, Ponapé, Kusaie; Marshall Islands--Jaluit, Mille, Aurh,
Wotze, Bikini, Kwajalein.
_Characters._--Adult: A large, dark-brown tern with grayish crown
and whitish forehead; line above eye white; crescent of white on
lower eyelid; lores blackish; bill black; feet brownish, iris
dark.
Immature: Resembles adult, but lighter and browner and top of head
grayish-brown.
_A. s. pileatus_ resembles _A. s. ridgwayi_, but darker and less
brownish, although not so dark as _A. s. galapagensis_; forehead
and crown usually duller; length of wing and tail average larger
(282 and 161) than in _A. s. ridgwayi_ (278 and 158) and _A. s.
galapagensis_ (277 and 151).
_Measurements._--Measurements of the Common Noddy of the Pacific
area are listed in table 21.
_Weights._--In 1948 (1948:56) I listed the weights of specimens
from Guam and Rota as follows: four adult males 187-204 (197);
three adult females 177-203 (189).
_Specimens examined._--Total number, 92 (43 males, 39 females, 10
unsexed), as follows: Mariana Islands, USNM--Guam, 7 (May 24, June
15, July 6, 21)--Rota, 3 (Oct. 18, 24); AMNH--Guam, 4 (April 21,
27, Aug. 18)--Asuncion, 1 (Jan. 18); Palau Islands, USNM--Peleliu,
2 (Sept. 1)--Ngabad, 1 (Sept. 11); AMNH--exact locality not given,
6 (Nov. 3, 8); Caroline Islands, USNM--Ulithi, 3 (Aug. 15)--Kusaie,
1 (Feb. 8); AMNH--Truk, 15 (Feb. 1, 8, 25, March 10, May 6, June
12, 13, Nov. 25, Dec. 25)--Ponapé, 20 (Dec. 3, 5, 8, 12,
15)--Kusaie, 24 (Jan., March 10-30, April 1-10); Marshall Islands,
USNM--Bikini, 5 (Feb. 28, March 2, 19).
_Nesting._--Murphy (1936:1152) writes that the Atlantic subspecies,
_A. s. stolidus_, breeds in tropical localities every month of the
year, although there may be a part of the resident population away
at sea at any given time. In the Pacific area, Kirby (1925:187)
found nests "on platforms of sticks built on tufts of grass" at
Christmas Island in August. In Micronesia, Coultas obtained young
birds at Kusaie in January and April and commented (field notes)
that they probably nest "spasmodically at all times of the year."
At Ponapé, Coultas observed nests in high trees in December, and
birds obtained by him in that month had enlarged gonads. At Bikini,
Morrison obtained eggs on March 2 and 19, and young on March 19. At
Palau, Coultas took one female tern in postnatal molt on November
8. Adults obtained by him in that month had enlarged gonads. At
Ulithi, the NAMRU2 party recorded one nest containing a single egg
on August 21. At the same atoll the NAMRU2 party received reports
of a large colony of nesting noddys in May to July, 1945. In the
following August few noddies were seen by the NAMRU2 party. McElroy
found nests on cliffs and in coconut trees at Truk in December,
1945. Hartert (1900:10) reports on eggs taken at Truk in the period
from March to July 1. The NAMRU2 party observed birds carrying nest
materials at Peleliu on August 28 but failed to find the nests. At
Guam, the writer found terns in numbers varying from 4 to 75 in May
to July, 1945, along the rocky cliffs but no evidence of nesting
activity was obtained. Strophlet (1946:537) reports that nests may
have been present on Orote Peninsula at Guam on December 13, 1945.
Coultas (field notes) is of the opinion that the birds do not nest
at Guam but do nest farther north in the Marianas. Borror
(1947:417) found two colonies at Agrihan on August 10, 1945. Thus,
there are records of nesting in nine months of the year in
Micronesia; although I suspect that the larger flocks of terns have
more regular breeding habits correlated with their pelagic feeding
activities. "Stragglers" probably nest irregularly.
_Food habits._--The author (1948:56) records small fish and
crustaceans in stomachs of terns taken at Ulithi and Peleliu. At
Ypao Point, Guam, birds were seen to fly back and forth in the day
from their roosts on the sea-cliffs. On one occasion I saw these
birds feeding approximately a half mile from shore.
_Parasites._--Wharton (1946:174) and Wharton and Hardcastle
(1946:292, 296, 306) list the following species of chiggers
(Acarina) from the Common Noddy from Guam and Ulithi:
_Neoschöngastia bougainvillensis_, _N. americana solomonis_, _N.
egretta_, _Acariscus pluvius_, and _A. anous_. Uchida (1918:484,
488) found the bird louse (Mallophaga), _Nirmus separatus_, on
terms at Palau and at Ponapé he found _Colpocephalum milleri_ on
the bird. Bequaert (_in litt._) has identified a fly
(Hippoboscidae) as _Olfersia aenescens_ from a tern from Rota.
_Remarks._--Of the Common Noddy Tern of the Pacific area, three
subspecies are recognized by Peters (1934:346-347). _Anoüs stolidus
ridgwayi_ is known from islands off the western coast of Mexico and
Central America; _A. s. galapagensis_ is recorded from the Galapagos
Archipelago; and _A. s. pileatus_ is found on tropical islands
throughout the Pacific and west to Madagascar and the African coast in
the Indian Ocean. These subspecies differ from one another principally
in color, as noted by Ridgway (1919:545); _A. s. galapagensis_ is the
darkest form, _A. s. ridgwayi_ is less blackish and more brownish in
color of body, and _A. s. pileatus_ is between the two in coloring. _A.
s. pileatus_ averages larger in length of wing and tail, but these
measurements do not appear to be significant from a taxonomic
standpoint.
As shown in table 21, measurements of length of wing for specimens from
throughout most of the Pacific area are almost the same. Length of tail
is correspondingly uniform. There is a gradual increase in size of birds
in the Tuamotus and Societies and east to Easter Island. In this region
the average measurement for length of wing is 293 millimeters. The
lengths of wing and tails are shorter in specimens from the Kermadecs
and Norfolk Island, which may indicate relationships with the smaller
birds of the Australian area, Western Melanesia and possibly Malaysia
and the Riu Kiu Islands. I am unable to determine the subspecific status
of the birds from the Kermadecs and Norfolk Island, because of the lack
of sufficient material from the Australian region and Malaysia. Possibly
Mathews' name, _A. s. gilberti_, is valid for the noddys of Australia
and also for the birds at Norfolk and the Kermadecs. The small-sized
birds of the Riu Kiu Islands have been designated as _A. s. pullus_ by
Bangs. When specimens from the type locality of _A. s. pileatus_ in the
Philippine Islands are available, the true relationships of the
populations from Micronesia and the other areas in the Pacific can be
ascertained.
The tern found in the Hawaiians has the palest body and the most
chalky-white forehead of any of the birds of the Pacific. Bryan
(1903:101) found terns from Marcus Island to agree with specimens from
Guam and to be "slightly darker" than birds from Midway and Laysan in
the Hawaiian chain. The birds from the Riu Kius are darker and thus
similar to the few specimens seen from Malaysia. Birds from Polynesia
and Melanesia possess the most sooty underparts while those from
Micronesia are only slightly less pale. This condition also seems to be
true for the birds in the Australian area and for specimens seen from
islands in the Indian Ocean. With fading, or wear, or both, there is a
change from dusky black to dusky brown in the plumage; effort was made
by me to compare specimens with relatively similar conditions of
plumage. In summary, the systematic position of the Common Noddy Terns
of the Pacific seemingly depends on the characteristics of specimens
from the type locality in the Philippines. When topotypes are available
for study, they may be found to be nearer the darker forms of Malaysia
or may tend toward the paler, oceanic forms. The Hawaiian population
probably is distinct.
In Micronesia the Common Noddy Tern is not a conspicuous bird except
during its breeding period. Probably it spends most of its life at sea,
being unlike _Gygis alba_ in this respect. Large flocks seem less wary
of man than are small groups and singles, which are often easily
disturbed. Birds of this species appear to prefer the low atolls and
offshore islets where both tall vegetation and bare ground are utilized
for nesting or roosting. At Ponapé, Coultas (field notes) observed the
birds to fly to sea at daybreak and to begin to return to their roosts
by 4:00 pm. Wallace (field notes) observed similar activities at
Kwajalein in May, 1944, where he saw approximately forty individuals in
a flock with _Gygis alba_.
_Anoüs stolidus_ is divided naturally into an Atlantic subspecies, which
is distinguished by its browner color, and into several subspecies which
are distinguished by their blacker color in the Pacific and Indian
oceans. Whether the genus and species evolved in the Atlantic or in the
Pacific region is not known. If it were the Pacific region, the center
of differentiation may very well have been the islands of Oceania.
There, relatively little variation is observable within populations
covering a large area. To the eastward, birds along the American coast
are darker or lighter, to the northward, the birds of Hawaii are paler,
to the southward and southwestward, the birds are smaller and to the
westward, the birds are smaller and darker. The virtual absence of
ground-living, predatory animals which might prey on nesting colonies
has probably been a reason for the lack of discrimination by this tern
in selecting breeding sites. This is probably true of other birds which
nest in colonies.
=Anous tenuirostris marcusi= (Bryan)