---------------------------+-----+---------+--------+---------+-------
| | | | Exposed |
| No. | Wing | Tail | culmen | Tarsus
---------------------------+-----+---------+--------+---------+-------
Marianas: Asuncion, Guam | 6 | 264 | 107 | 47 | 21
| | 256-287 | 97-117 | 44-50 | 20-21
| | | | |
Palaus: Peleliu | 11 | 257 | 108 | 45 | 21
| | 242-270 | 98-122 | 40-49 | 19-21
| | | | |
Carolines: Ponapé, Kusaie | 11 | 261 | 105 | 47 | 21
| | 252-271 | 97-114 | 44-49 | 21-22
+-----+---------+--------+---------+-------
Total: Micronesia | 28 | 260 | 107 | 46 | 21
| | 242-287 | 97-122 | 40-50 | 19-22
---------------------------+-----+---------+--------+---------+-------
_Specimens examined._--Total number, 37 (22 males, 10 females, 5
unsexed), as follows: Mariana Islands, USNM--Guam, 5 (June 11, July
21); AMNH--Asuncion, 1 (June?); Palau Islands, USNM--Peleliu, 5
(Aug. 29, 31, Sept. 5, 6); AMNH--exact locality not given, 7 (Oct.
13, 26, Nov. 15, 23, Dec. 18); Caroline Islands, AMNH--Ponapé, 9
(Dec. 8, 9, undated)--Kusaie, 10 (March 1-8, April).
_Nesting._--The NAMRU2 party observed nests of the White-tailed
Tropic Bird at Peleliu in August and September, 1945. Several
nests were seen in hollows of the Australian pine (_Casuarina
equisetifolia_) between 20 and 30 feet above the ground. Birds
could be seen in the nest hollows because the plumes of their long
tail usually extended well out of the entrance. One nest was found
in a dead tree in a battle-cleared area; others were observed in
jungle habitat. Coultas observed nesting at Ponapé between
November 1 and December 30, 1930, and found nests in the tops of
trees and in hollow trees; a few were observed in holes in cliffs.
Yamashina (1932a:407) records the taking of one egg at Ponapé on
August 18, 1931. At Guam the NAMRU2 party found birds along the
high cliffs which edge the beach. There was no evidence that they
were nesting from May to July; nevertheless males taken in June
had enlarged gonads. The bird is known to breed at Namorik in the
Marshall Islands, according to the Hand-list of Japanese Birds
(Hachisuka _et al._, 1942:209).
_Food habits._--The NAMRU2 party found small fish in the stomachs
of these birds taken at Peleliu.
_Parasites._--Uchida (1918:489, 492) records the bird lice
(Mallophaga), _Colpocephalum epiphanes_ and _Menopon eulasius_,
from the White-tailed Tropic Bird from Palau.
_Remarks._--Birds taken in Micronesia differ only slightly from those
from other areas in Oceania. Within Micronesia (see table 15) the birds
from the Palaus have the shortest wing and shortest exposed culmen.
The White-tailed Tropic Bird appears more numerously in western and
northern Micronesia than in the Marshall Islands. This distribution may
be correlated with a preference for the "high" islands; especially those
which have rocky cliffs, including Guam, Rota, Peleliu, Angaur, and
Truk. Reports were received in 1945 that the birds were only
infrequently seen at Ulithi, a low atoll. Stott (1947:524) observed
birds flying into rocky crevices at Saipan on December 18. Gleise
(1945:221) also recorded the bird in the vicinity of Saipan. Borror
(1947:416) reports seeing birds at Agrigan on July 29, August 5 and 6,
1945. Coultas (field notes) found tropic birds common at Ponapé in
November and December, 1930, in forested regions and along the cliffs.
He made similar observations at Kusaie and Palau. At Ponapé and Palau,
Coultas noted the use of the eggs, young and adults as food by the
natives. At Palau the plumes are used in headdresses worn by the
natives, the birds being taken with the blowgun.
Murphy (1936:807) states that the principal enemy of the White-tailed
Tropic Bird at Bermuda is the introduced rat (_Rattus rattus_).
Introduced rats, particularly _Rattus mindanensis_ on Guam, may prey on
the nesting birds. Baker (1946c:404) writes that this rat is a good
climber and may spend considerable time in trees. The rat was trapped
also in rough coral jungle at the edge of the cliffs, where tropic
birds, Micronesian Starlings and other species, may have been nesting.
Little has been recorded concerning the post-breeding season wanderings
of these tropic birds in Micronesia. They seemingly spend considerable
time at sea, but whether they move as far from their breeding areas as
do birds in the Atlantic, as reported by Murphy (1936:803), Baker
(1947a:253) and others, is not known.
Murphy (1936:796) notes that the northward distribution of the tropic
birds in the Atlantic is dependent on the warm currents of water. In the
western Atlantic, the poleward-flowing, warm currents of the Gulf Stream
allow for the northern extension of the range of these birds to Bermuda.
In the eastern Atlantic, cool currents flowing toward the equator
restrict the northern range. The same condition prevails in the eastern
Pacific where warm current flowing toward the pole enable the birds to
range north to the Bonins and other islands.
The three species of tropic birds known from Micronesia overlap very
little in their ranges in this area. The White-tailed Tropic Bird has
become firmly established in the western part of Micronesia, but there
are only a few records from the extreme eastern part. The Red-tailed
Tropic Bird appears to be resident only in the northern Marianas
although it has been recorded in the Carolines and Marshalls.
Interspecific competition may prevent considerable intermingling of
breeding populations in Micronesia, or it may be that each species
requires different ecologic conditions.
=Sula dactylatra personata= Gould