Birds : Four species of seabirds bred: red-footed booby 

 (5 pairs), great frigatebird ( I pair), brown noddy (3 pairs), and 

 white tern ( 1 3 pairs). Most conspicuous were white terns, with 

 9 pairs breeding on the 30-m-wide transect swath. One dark 

 morph reef heron fished in the shallows. In summer 1990, 

 sooty terns bred. 



27. EMERALD ISLE (8.34 ha) (Figs. 29,54; Pis. 25,74-76) 



Fifth down the chain, we named Emerald for the richly 

 colored, translucent lagoon waters that fringe its shorelines. 



Physiography : Of thickened crescentic shape, Emerald is 

 330 m long and 240 m wide. Its lagoonside reefs, patch reefs, 

 and coral knolls are irregularly patterned with sandy channels. 

 It is here that the verdure of the lagoon is most intense. 



Vegetation : Emerald Isle has 12 species of plants (5 trees, 

 1 shrub, 6 herbs), 44% ofCaroline's flora. The only introduction 

 is Cocos. Four plant communities, with a fairly high species 

 diversity, are present: the herb mats, covering one-fourth of its 

 land area, are composed almost exclusively of Heliotropium 

 ( 35% cover) with scattered low Tournefortia (30% cover). The 

 Tournefortia scrub and forest attains a maximum height of 8 m 

 and. for a little variety, is mixed about equally with Pandanus 

 over most of its width ( 144 m) on the seaward side. 



The interior forest (to 1 1 m tall) is also mixed, with 

 Pandanus, Tournefortia, Pisonia, and a little Cordia (PI. 75). 

 This condition is similar to the mixed forest on Nake, but 

 because Cocos is absent, it appears more natural. The existence 

 of this 3.20 ha mixed forest, as well as a similar one on Shark, 

 prompted us to suggest that Pandanus may be both native and 

 Polynesian-introduced. Cocos is present as two small groves, 

 complete with coconut crab sign (mounds of shredded fibers, 

 PL 57), beside the east and midwest shores. 



We have been unable to trace the history of Emerald's 

 forests: the presence of Cocos on the west side and fragmented 

 Pisonia suggest past disturbance. 



Birds : Six species of breeding seabirds were present: red- 

 tailed Tropicbird (1 pair), red-footed booby (3 pairs), great 

 frigatebird (230 pairs), brown noddy (7 pairs), black noddy 

 ( 150 pairs), and white tern (83 pairs). 



Although we did not locate any red-tailed tropicbird nests, 

 two adults circled steadily overhead. Two reef herons (one 

 dark morph, one light ) also foraged in the inshore reef shallows. 



28. SHARK ISLET (7.98 ha) (Figs. 29,55; Pis. 29,77) 



We named this islet to commemorate a particularly 

 pugnacious shark who was so anxious to procure a human foot 

 that it charged shoreward and leaped up onto the beach. 



Physiography : Stoutly crescentic. Shark Islet is 280 m 

 long and 310 m wide in the center. The sandy lagoon beach and 

 rubbly seaward beach are each 3 m wide. Beyond high water 

 the seaward reel Hats extend for 280 m. Like Emerald. Shark's 

 reefs and surrounding lagoon waters reflect particularly stunning 

 colors, perfect complements to the sparkling pink coral sand of 

 Caroline's prime beach. 



Vegetation : There are 12 species of plants (5 trees, 

 1 shrub, 6 herbs), 44% of the atoll's flora. Shark has one 

 introduction, Cocos, forming 3 clumps along the lagoon beach 

 ( 1 % of the islet's area). Shark's rings of vegetation approximate 

 the islet's outline. Herb mats dot the fine sand lagoonward. 

 while to seaward they emerge from coarse rubble. The 

 Tournefortia (to 7 m tall) eventually gives way to a 12-m-high 

 Pisonia forest studded with Cordia and Pandanus. Centrally 

 this mixed forest is unnaturally open, suggesting possible past 

 disturbance. 



Birds : Four species of seabirds bred in 1988: great 

 frigatebird (118 pairs), brown noddy (37 pairs), black noddy 

 (125 pairs), and white tern (44 pairs), red-footed boobies were 

 nesting in 1990. The notable colonies of great frigatebirds and 

 black noddies are due in part to the extensive Pisonia forest, 

 covering half of the islet. 



29. SCARLET CRAB ISLET (0.46 ha) (Figs. 28,55) 



This motu was named by the authors in honor of Coenobita 

 perlatus, the scarlet, fist-sized hermit crab that is abundant both 

 here and on the entire atoll. 



Physiography : Scarlet Crab, sixth in the chain and only 

 40 m long by 1 25 m wide, is a young motu shaped like a closed 

 pair of lips. It skirts the southern shore of Shark, separated from 

 it by a channel 1 6 m wide. Because its eastern end points into 

 the lagoon, there is no true lagoon beach. Together with the 

 next three islets. Scarlet Crab's seaward reef flats (480 m) are 

 the most extensive on Caroline's lee side. 



Vegetation : Vegetative cover is slight: less than 1% 

 area coverage of Heliotropium and Laportea, interspersed 

 with 10 small Tournefortia (to 1.5 m). Its species count is 6 

 (1 shrub, 5 herbs), 22% of Caroline's flora. There are no 

 introductions. 



Birds : Although during storms this motu is undoubted!) 

 awash, two species of seabirds were breeding in 1988: brown 

 noddy (one pair, on ground) and white tern (two pairs, in low 

 scrub). 



30. MOTU NAUTONGA "Sea Cucumber Islet- (0.34 ha) 

 (Figs. 28.55) 



We named this motu for the Gilbertese word for the black 

 sea cucumbers or "beche-de-mer" (Ludwigothuria sp. ) that are 

 densely strewn over all ofCaroline's reef shallows (PI. 10). 



Physiography : Semicircular in shape. Nautonga is seventh 

 in the Central Leeward chain, measuring 70 m long and 80 m 

 wide. Situated close to the lagoon, it is one of three small islets 

 that barely protrude above the reef flats. Nautonga' s perimeter 

 beaches are all narrow (2m), and its seaward reef flats are wide 

 (495 mi. 



Vegetation : There are nine indigenous species (three 

 trees, one shrub, five herbs). 33% of the atoll's flora. Though 

 small. Nautonga's vegetation is concentrically zoned, 

 comprising herb mats (10-14 m wide), and a central forest of 

 Tournefortia and Pisonia (84 m wide) up to 10 m high. 



46 



