The Birds of Yap, Western Caroline Islands 
Harvey I. Fisher 1 
The Yap group of islands, which lies about 
450 miles southwest of Guam and 125 miles 
northeast of the Palaus, is composed of four 
main islands: Rumung, Map, Gagil-Tomil, 
and Yap. There are several islets in the la- 
goon between Yap and Tomil islands. 
The highest elevation (585 feet) is in the 
north-central part of Yap Island (Fig. 1); 
Except for this hilly area, the rest of Yap 
Island is below 200 feet. All of Gagil-Tomil 
is below the 200-foot elevation, and the high- 
est parts of Map and Rumung are from 250 
to 300 feet above sea level. The greatest 
length of the group is about 1.6 miles and 
the greatest width is 6.5 miles. 
Ulithi atoll is the nearest land mass, lying 
about 90 miles to the northeast. To the south- 
west are the Palaus. Thus, Y ap lies in a chain 
of islands from the Palaus in the south to 
the Marianas in the north. None of the is- 
lands in the chain is widely separated from 
the others. Furthermore, to the east is the 
whole group of Caroline Islands. Because 
these islands seem to form a perfect series of 
"stepping stones" for the movement of plants 
and animals from the southwest Pacific to 
the north Pacific through the Marianas and 
eastward through the Carolines to the central 
Pacific Ocean, it was deemed desirable to 
study birds of Yap, especially since the exten- 
sive work of the Whitney-South Seas Expe- 
ditions did not include Yap, and no modern 
collections of birds from this area are known. 
Preliminary investigation and collections 
were made on Yap from July 28 to August 
24, 1946. A total of 148 vertebrate speci- 
mens were taken: 17 amphibians, 28 rep- 
tiles, 9 mammals, and 94 birds. No attempt 
1 Department of Zoology, University of Illinois, 
Urbana. Manuscript received April 28 , 1949 . 
was made to collect large series of any spe 
cies; rather an attempt was made to secure 
representatives of all species present. Records 
of the reptiles and amphibians taken havc- 
been published (Fisher, 1948). 
The University of Hawaii sponsored this 
trip. I wish to acknowledge the aid of the 
United States Navy in furnishing transporta- 
tion and other facilities. In particular, I wish 
to thank Captain O. M. Murphy, United 
States Navy Commander of the Yap Area, 
for use of various facilities at Yaptown and 
for his interest in the project. I also want to 
thank Mr. Eveni Levi of Tutuila, American 
Samoa, who accompanied me from Hono- 
lulu; he helped greatly in many ways. Dr. 
Ernst Mayr has checked the identification of 
all species discussed and has made critical 
taxonomic comments, many of which are 
included in the species accounts. 
It is no longer possible for me to continue 
these studies. Hence, it seems worth while to 
put on record the observations of this brief 
survey. 
As indicated above, the islands are rela- 
tively low. They are almost completely cov- 
ered with vegetation. Yap and Rumung show 
a similar donation of vegetation. On the 
inner side (toward the lagoon) these islands 
have extensive swampy areas, and mangroves 
of two kinds form dense thickets at the 
water’s edge. On the outer side the islands 
have large areas of shallow water inside the 
coral reef. For the most part, these have coral 
and rock substrata with little mud. At the 
upper ends of the tidal swamps on the lagoon 
side are semi-open mudflats. Above these 
swamps or mudflats, or above the narrow 
beach on the sea side, the dense jungle starts 
immediately and continues upward to an 
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