Birds : Five species of seabirds bred in 1988: red-footed 

 booby ( 1 1 pairs), great frigatebird (2 pairs), brown noddy 

 (7 pairs), black noddy (32 pairs), and white tern (10 pairs). 

 Lesser frigatebirds appeared to be preparing to nest in May 

 1 990. One pair of blue-gray noddies, flying toward Azure Isle, 

 was seen by the 1990 expedition in May. 



31. AZURE ISLE (0.20 ha) (Figs. 28,55; PI. 53) 



We named this small, wedge-shaped motu for the striking 

 blue-green of its nearby lagoon. 



Physiography : Eighth from the north, this small, elongated 

 triangle of land is 30 m long and 66 m wide. Its seaward reef 

 flats are wide (512 m). Its surge channels are narrow and 

 shallow. 



Vegetation : Azure has only seven species (one tree, one 

 shrub, five herbs), 26% of Caroline's flora. The Pisonia tree is 

 6 m tall. A young motu. Azure is a superb example of an early 

 stage of biological succession. Its plant cover consists of a 

 single mound of Toumefortia scrub crowned by a single 

 Pisonia tree, growing from rubble only one meter above sea 

 level. Only 45% of its surface is vegetated; the rest, primarily 

 on the ocean side, is coarse rubble. Azure Isle presents what 

 may be the minimum width of vegetation (38 m) in which 

 Pisonia can develop on Caroline. 



Birds : This motu illustrates the speed at which seabirds 

 will utilize newly available habitats. Within its dozen or so 

 Toumefortia shrubs (to 4 m tall), three species of seabirds nest: 

 red-footed booby ( 7 pairs ), great frigatebird ( 2 pairs ), and white 

 tern (2 pairs). A pair of blue-gray noddies were seen in May 

 1990. 



32. REEF-FLAT ISLET (0.09 ha) (Figs. 27,55) 



We named this young motu for its primary characteristic — 

 its reef flats. Ninth in the Central Leeward chain, this curved 

 strip of coarse rubble lies parallel to the surge channels that 

 surround it. It measures about 20 m long and 60 m wide. Only 

 three species of plants are present (one shrub, two herbs), 1 1% 

 of Caroline's flora. They cover less than one-fourth of its area 

 and are distributed so sparsely that not one bird was present. 



33. BIRD ISLET (4.05 ha) (Figs. 29,55) 



This is one of the motus named on Arundel ' s chart ( Fig. 4), 

 probably reflecting the presence of black noddies and/or sooty 

 terns. 



Physiography : Bird is ovoid, measuring 230 m long by 

 200 m wide. It sits close to the inner edge of the lagoon reef, 

 whereas 400 m of seaward reef flats stretch westward. 



Vegetation : There are 12 species of plants (4 trees, 

 2 shrubs, 6 herbs), 44% of Caroline's flora. A small Cocos 

 grove is the only introduction. It is well wooded, with very 

 narrow herb mats (6% of total area). Toumefortia (to 8 m) and 

 Pisonia (to 14 m) each cover 42% of its surface; the rest is 

 rubble. The Pisonia forest is of good quality (90-95% canopy 

 cover), having scattered Mo rinda. Boerhavia. andAchyranthes 



as an understory. One large clump of Suriana (14 x 14 m, 

 2.5 m high) occurred in the islet center (A. Garnett, personal 

 observation). Bird Islet shows very few signs of past disturbance, 

 having prime plant communities, rich in breeding seabirds. 



Birds : Five species of seabirds nested in 1988: red-footed 

 booby (29 pairs), great frigatebird (6 pairs), brown noddy 

 (42 pairs), black noddy (329 pairs), and white tern (48 pairs). 

 In June 1990, many thousands of sooty terns laid on Bird and 

 adjacent Fishball. 



34. FISHBALL ISLET (0.57 ha) (Figs. 28,55,56) 



Eleventh and southernmost in the Central Leeward chain, 

 we named Fishball after discovering a large glass fishing float 

 with a broken bottom, decorously placed in the islet's center 

 within a square of coral slabs. 



Physiography : Paramecium-shaped, Fishball lies close to 

 the lagoon and is separated from Bird by a shallow, rubble- 

 strewn channel 100 m wide. The motu is 45 m long by 144 m 

 wide, with seaward reef flats 595 m in extent. South of the islet, 

 the reef flats — wadable at very low tide — stretch 1 .4 km to the 

 Southern Leeward Islets. 



Vegetation : The number of plant species is eight (one 

 seedling "tree," one shrub, six herbs), 30% of Caroline's flora. 

 Figure 56 depicts an east-west cross-section of Fishball, showing 

 a vertical profile and the relative abundance and distribution of 

 each species. Fishball exemplifies an emerging motu. All 

 plants are low and halophytic; most are herbs. The motu is half- 

 covered with a sparse herb mat of Heliotropium (10% cover), 

 with scattered Laportea. Lepturus , and Portulaca (less than 1% 

 cover each). Small Toumefortia shrubs (to 2 m tall) are 

 scattered in the central sector, while a tiny drift seedling of 

 Morinda, 7 cm high, struggled to gain a foothold in the 

 exposed, salty rubble. 



This motu is a fine example of the initial stages of islet 

 formation and colonization. It demonstrates that sea-dispersed, 

 halophytic herbs first germinate on the coarse rubble, later 

 becoming shaded out by Toumefortia, enabling a greater plant 

 species diversity to establish. It is very unlikely that a water 

 lens is present. 



Birds : Two species of seabirds bred in 1988: red-tailed 

 tropicbird (three pairs) and brown noddy (five pairs). In May 

 1990, many thousands of sooty terns covered the ground and 

 swirled in the air, day and night. On 23 May, no eggs were 

 found, but laying occurred on Fishball and adjacent Bird Islet 

 in June (A. Falconer, personal communication). 



Southern Leeward Islets (Pis. 14, 78) 



This chain of five small motus lies along the southwestern 

 edge of the lagoon. All are built upon piles of rubble about 

 3 m high, oriented in an east-west direction, and are separated 

 by shallow, narrow channels. They range in size from 1 .5 1 to 

 3.67 ha, and their topography, vegetation, and breeding seabirds 

 are similar. Although situated on the leeward side of the atoll, 

 the Southern Leeward Islets exhibit some windward 

 characteristics: they lie opposite and slightly north of a wide 

 break in the windward reef, which allows trade winds to sweep. 



47 



