218 



BERQER 



shade for it. Chicks also seek the shade of vegetation 

 when available. 



Unfortunately, little precise Information Is available on 

 the nesting activities of the birds of Enewetak Atoll. No 

 definitive studies have been made on any of the 12 species 

 of breeding birds; still awaited Is proof of nesting by the 

 four species of "possible breeders." 



More has been written about the distribution and nest- 

 ing of the sooty tern on Enewetak than on all other species 

 together. There now app>ears to be either one or two nest- 

 ing colonies of sooty terns at Enewetak, and there is con- 

 siderable historical evidence that the birds shift their nest- 

 ing sites from island to island. For example, Richardson 

 (MS) observed a colony of sooty terns on Aej (Olive) dur- 

 ing February 1959, but none was found at that Islet during 

 the summer of 1965. Carpenter et al. (1968) estimated a 

 colony of 16,000 terns on Lujor (Pearl) in 1966, but a 

 year later the colony was found on Luoj (Daisy) more than 

 10 miles away. Berger found the only large colony of 

 sooty terns on Janet Island during the third week of July 

 1971. 



Temme (1979) reports that in November 1977, there 

 were about 10,000 sooty terns nesting on Aomon (Sally) 

 in an area cleared only a short time before; when crowded, 

 the nests are closely packed with 25 to 30 eggs per 

 square meter. The following March an estimated 5000 

 adult and Immature birds were there, with a few nests con- 

 taining eggs. During Temme's visit only a few hundred 

 additional sooty terns were observed on the 14 other 

 islands visited. However, during November 1978, an 

 estimated 29,000 adults, 7800 chicks, and 6700 eggs 

 were present on Boken (Irene). 



In the Hawaiian Islands, William Y. Brown determined 

 an incubation time of between 28 and 31 days. The young 

 terns first fly when they are about 57 days old, usually 

 leaving the island during the day but returning to it to be 

 fed by the adults at night (Berger, 1981). 



Because no data are available for consecutive 

 12-month periods and for several consecutive years, only 

 problems for study — rather than conclusions — can be sug- 

 gested. The shift of nesting jxjpulations of sooty terns from 

 island to island in different years apparently is partly a 

 function of vegetation removal and/or rcgrowth. This tern 

 nests on the ground in open areas, often where scattered 

 patches of grasses and other low-growing vegetation are 

 interspersed with open sand or coral. 



In the Hawaiian Islands, the brown noddy nests on the 

 ground; at Enewetak, however, this noddy also often 

 builds a nest in scrub vegetation (e.g., Scaevola, Pisonia, 

 Toumefortia) or even in coconut trees. According to 

 Robert K. Bastian (MS), the nest of the brown noddy at 

 Enewetak contains sticks, leaves, grasses, feathers, drift- 

 wood, gravel, algae, sponge, and, characteristically, coral 

 and shell fragments. 



In most parts of its range, the black noddy builds a 

 bracket-like nest in shrubs and trees, but Atlantic Ocean 

 populations usually nest on cliff ledges and offshore stacks, 

 where the birds are safe from mammalian predators. At 



Enewetak nests usually are built in trees (especially 

 Toumefortia and Pisonia). The nests lack the coral and 

 shell fragments of the brown noddy and usually are com- 

 posed largely of seaweed and accumulations of feathers 

 and guano. 



A great deal needs to be learned about the breeding 

 seasons for each species and for the apparent variation in 

 nesting seasons, especially for the sooty tern. Carpenter et 

 al. (1968) noted that: "The 1959 and 1962 colonies were 

 breeding In the March to May period; the 1966 colony was 

 breeding In the July to September period; In 1967, in June 

 and July. A satisfactory reason for the apparent variation 

 on Eniwetok does not seem to exist, though food supply, 

 precipitation, or even vegetational appearance may be fac- 

 tors." A thorough study of the sooty tern at Enewetak 

 would be revealing; in other parts of its range, the sooty 

 tern nests at 6-, 9-, or 12-month intervals (Ashmole, 1965; 

 Kikkawa, 1976). An intensive study of banded birds will 

 be needed to determine the pattern at Enewetak. 



The white tern is one of the most Interesting species at 

 Enewetak and one that occurs on most of the Islets of the 

 atoll. This tern does not build a nest and usually lays its 

 single elliptical egg on a bare, horizontal branch of a tree 

 or shrub, sometimes in the deserted nest of a noddy tern 

 (Figs. 1 and 2). Carpenter et al. (1968) estimated the 

 population of white terns to be about 1400 birds for 

 Enewetak Atoll in 1966; they found the largest concentra- 

 tion on Liblron Islet. I found the densest populations on 

 James (Libiron) and Irwin islets during the third week of 

 July 1971. Many adults were incubating eggs, but there 

 also were young birds ranging from newly hatched to those 

 just capable of flight. 



THE REEF HERON 



The reef heron (Egretta sacra) has a wide range that 

 includes Korea, Japan, Malaysia, Australia, Melanisia, 

 Polynesia, and Micronesia. It Is the only heron found at 

 Enewetak. It occurs In three color phases: white, gray, and 

 mottled. Most immature birds have the mottled plumage. 

 Of 57 herons observed by Carpenter et al. (1968), 48% 

 were white, 28% were gray, and 24% were mottled. Pear- 

 son and Knudsen (1967) reported a 20:30:50 ratio. Slater 

 (1971) notes that the "white phase predominates In the 

 centre of Its range and the grey phase on the periphery." 



The reef heron nests on many of the islets of 

 Enewetak, on or near the ground. The birds apparently 

 nest singly, with a clutch of three eggs. Carpenter et al. 

 (1968) found "all stages from eggs to fledgling young" 

 during June. These herons feed largely on fish and crabs. 

 Carpenter notes that "the preferred feeding location was 

 the reef and abandoned landing craft." 



REGULAR MIGRANTS AND ACCIDENTALS 



Many shorebirds that nest in Alaska and Siberia winter 

 on islands In the Pacific Ocean. At least 17 species have 

 been recorded at Enewetak. Some of these have been dis- 



