guano increases soil fertility and is important for Pisonia 

 growth (Fosberg. 1953). it is of interest that neither black nor 

 brown noddies nested here. 



ft. Deep dips in Fig. 39 (lower graph) correspond to east- 

 west corridors formed from old channels. Vegetation in these 

 relatively infertile, sandy flats is low. similar to that on small 

 developing motus (i.e.. native herbs with scattered Tournefortia 

 <2 in high). One sandy channel (Tr. C; PI. 33) supported a 

 sparse population of Suriana. During the February 1990 

 cyclone, all vegetation was either uprooted, washed away, or 

 smothered with fresh sand and coral gravel along Trs. A and C 

 (personal observation, March 1990). Storm erosion was 

 particularly marked within the channel that almost bisects the 

 island (Tr. A). 



7. Secondary dips mark even older interislet channels 

 ("ancient channels"), visible on aerial photographs (Chapter 

 Frontispiece) but barely recognizable in the field. They are 

 overgrown with Tournefortia and/or Pisonia. 



8. Sharp dips within established forests or herb mats 

 denote relatively recent channels gouged out by storms ("recent 

 storm cuts"). These were also altered during the winter 1990 

 storm. 



Figures 40 and 41 illustrate some differences between the 

 windward and leeward coasts. Transect C (Fig. 40) crosses the 

 north end of Long through an old interislet channel now filled 

 with sand and rubble. Its low profile reflects the simple habitat 

 harboring halophytic herbs and Tournefortia shrubs less than 

 2 m high. Although the shrubs are scattered, the lagoon half of 

 the transect passes through slightly higher ground, which 

 encourages denser Tournefortia. This transverse section is 

 similar to that of a formative motu such as Fishball (Fig. 56). 

 This exposed, scrubby swath, 300 m wide, harbors red-footed 

 boobies, great frigatebirds, and a discrete population of masked 

 boobies. Approximately 127,000 pairs of sooty terns nested in 

 a similar sandy channel 740 m to the south (Tr. A, PI. 59) in 

 1988. 



Transect 8 (Fig. 4 1 ) crossed the islet nearer the southern tip 

 (Fig. 8). This profile departs significantly from the usual 

 parabolic cross-section seen on most of the small motus and 

 which exists further north on Long Island. From east ( windward ) 

 to west, there is first a wide expanse of coarse, unvegetated 

 rubble, followed by rubble dotted with herbs, then Tournefortia 

 scrub increasing to 9 m high. Further inland, a forest of 

 10-m-high Tournefortia. Pisonia. and Cordia continues 

 westward to the lagoon. This leeward margin of Long, extending 

 southward nearly to its tip, is the only location on Caroline 

 where tall, indigenous vegetation overhangs and shelters the 

 lagoon. No herb mat is present. 



In summary. Long contains examples of all major plant 

 communities, as well as two minor ecosystems, Pisonia- 

 Cordia (3.2 ha) and Cocos-Cordia (0.82 ha). Its woodlands 

 total 49.60 ha. Coconut crabs inhabit all areas containing 

 Cocos and Pisonia; our rough estimate of their population is 

 200 crabs. 



Birds : In 1988, Long supported 9 ( 10 in 1965) species of 

 breeding seabirds. as follows (pairs): red-tailed tropicbird (5). 

 masked booby (69), brown booby (12), red-footed booby 

 (659), great frigatebird (808), sooty tern (179,800). brown 



noddy (207), black noddy (986), and white tern (751 ). From 

 1988 through 1990, sooty terns occupied 19 large colony sites 

 (Fig. 11, Subchapter 1.2). 



Comments : Polynesian rats were abundant, especially in 

 Cocos and Pisonia habitats. It was often possible to see 3 or 4 

 simultaneously while conducting daily surveys and 20 or more 

 around camp. At night, their numbers increased substantially. 

 Azure-tailed skinks (Emoia cyanura) were noted. 



Windward Islets 



This chain of 13 islets occupies the southern half of 

 Caroline's east coast. All rest on the same reef flat, separated 

 by surge channels varying in width and depth. They can be 

 waded with care at low tides, but most harbor black-tipped reef 

 sharks: up to four were visible in the shallows within 50 m of 

 an observer. 



The motus range in size from Noddy Rock (0.02 ha) to 

 Windward (1 1.42 ha). They support every major vegetation 

 type, from simple herb mats to magnificent Pisonia forests, 

 21 m tall. Because of their constant exposure to trade winds, 

 the seaward vegetation is wind- and salt-shorn. Though 

 appearing completely natural, all of the Windward Islets were 

 intensively planted with Cocos (Table 13) from 1916-1920 

 (Young, ca. 1922). However, these incipient plantations 

 experienced difficulty and appear to have been abandoned 

 within a few years (see Plant Communities section). 



Flanking the lagoon of the southern motus (Brothers 

 through Tridacna) and extending westward are coral reefs 

 densely studded with giant clams, whose iridescent, 

 multicolored mantles add to Caroline's outstanding natural 

 assets (PI. 26; Subchapter 1.2, Conservation section). 



3. BO'SUN BIRD ISLET (0.86 ha) (Figs. 29,42; PI. 9) 



We named this motu for its red-tailed tropicbirds, 

 commonly called bo' sun birds. The sizeable population is the 

 largest on Caroline. In addition, our 1988 records constituted 

 the first known breeding of this species on the atoll. 



Physiography : Bo'sun Bird Islet, 165 m west of Long's 

 southern tip. is the only motu lying "within" Caroline' s lagoon. 

 It shares the same reef as Long, however, and is not a true 

 "lagoon motu." 



Amoeboid in shape, Bo'sun Bird is greatly affected by the 

 tidal waters that spread across the shallow reef flats and gush 

 through the surge channels that separate Long and Windward. 

 Because it sits near the inner edge of a wide windward reef flat, 

 the layering of sediments around it is complex and transitory; 

 our observations indicate that more rubble was deposited on 

 the islet's western edge since the aerial photos were taken in 

 1985. Its western shoreline rises gradually to a high water 

 mark, and slight changes in water level greatly change its 

 overall size and shape. At high tide its perimeter resembles the 

 shape of Pinocchio' s head — ovoid with a long, expanded nose. 

 The "head" is approximately 70 m wide and 115 m long, while 

 the "nose" is 45 m long and 15 m wide. 



Vegetation and Birds : Bo'sun Bird Islet, composed of 

 coral rubble and sand, supports only natural herb mats 

 (Heliotr opium, Portulaca. Lepturus) and Tournefortia scrub 



37 



