foraged on herb mats close to the beach scrub. The total 

 population was approximately 40 birds. Those few birds heard 

 were all H. incanum. We saw six tattlers in March 1990 and 

 several in May of the same year. 



Ruddy Turnstone ( Arenaria interpres) 



One turnstone w as found on the windward beach of Motu 

 Mannikiba in September 1988. and five on atoll beaches in 

 March 1990. The Caroline population probably does not 

 exceed 1 5 birds. 



Bristle-thighed Curlew (Numenius tahitiensis) 

 (Subchapter 1.1, PI. 23) 



The bristle-thighed curlew, common in the Line and 

 Phoenix Groups, is a widespread migrant to the low atolls of the 

 central and South Pacific during the boreal winter (Pratt el ai, 

 1987). One of the world's least-studied shorebirds, the species 

 is considered rare throughout its range (Johnsgard, 1981; 

 Marks et ai, 1990) and is a candidate for the US Fish & 

 Wildlife Service Endangered Species List (Gill. 1990). Clapp 

 & Sibley! 197 la) estimated 20 birds for Caroline in June 1965. 



We counted 83 birds on 12 of Caroline's islets in 1988. 

 including the 3 large islands (Nake. Long, South) and motus in 

 the Windwards, Central Leewards, and Southern Leewards. 

 In March 1990, we saw 20 curlews on 10 islets during 

 incidental observations throughout the atoll, bringing the total 

 number of islets on which they have been recorded to 16. On 

 our return trip (May 1990) we only saw three curlews (only 

 eight islets visited). Undoubtedly, curlews occur on all islets, 

 utilizing essentially all plant communities. Although they are 

 most conspicuous on the beaches and reef flats, higher numbers 

 may actually forage in the forests during the day. The Falconers 

 (personal communication) note that small numbers of curlews 

 remain all year. They are least common between April and 

 August and most abundant after September/October. This 

 correlates with preliminary information from Rangiroa Atoll. 

 Tuamotu Archipelago (Gill. 1990; Gill & Redmond, in prep.). 



Perimeter Habitats : On a complete perimeter count of 

 South Island in 1988, we found 29 curlews. Twenty-one were 

 foraging and loitering on the windward east coast, principally 

 above the beach crest on coral rubble interspersed with herb 

 mat. Similarly. 14 of 20 curlews found on Long and the 

 Windward Islets foraged along the windward beach crest, with 

 only 6 birds found on the lagoonward shores. Curlews were 

 equally common on windward and leeward shores in the 

 leeward islets, occupying habitats composed of coral rubble 

 and sand. While the numbers indicate that curlews showed a 

 preference tor windward shores, they may be biased because 

 most birds were there in late evening (19 birds on South). 

 Perhaps the\ use the relativeh open areas for roosting and 

 foraging at dusk. Certainly the largest concentrations ( 13. 14) 

 were found late in the day. We found our largest flock ( 14. 

 Sands Inlet, Nake) at 1 600 h, foraging on compacted, silt) sand 

 at the lagoonward end of the inlet, while single curlews dotted 

 the interislet channels and shallow tidal reef flats. 



Vegetated Habitats : We found bristle-thighed curlew s on 

 natural herb mats, in Tournefortia scrub. Pisonia forest, and in 



Cocos habitats, both in the healthy peripheral plantations and 

 w ithin the dying Cocos— Ipomoea woodlands ( Subchapter 1.1. 

 Fig. 36. PI. 34). One was captured in a mist net under a dense 

 Cocos canopy. Disintegrating plantations in the center of 

 South (54 ha) held a large population: calculated numbers 

 produced an estimate of 154 curlews. They foraged over the 

 //wwoefl-strewn ground, frequently using broken-topped 

 coconut trunks as lookouts. We also found 5 curlews on 

 transects in Pisonia forests up to 20 m tall on Nake (calculated 

 population, 41 ). They were foraging on the relatively open, 

 although dimly lit, forest floor. 



Numbers : From the 1988 data we estimated a population 

 of ±300 curlews: 41 birds in Pisonia, 154 in Cocos-Ipomoea, 

 43 on the beaches of South Island (29) and the Sandy Inlet of 

 Nake (14), and another 62 scattered over the remainder of the 

 atoll. Because 154 of them were calculated from the sighting 

 of a flock of 7 curlews on one transect on South, there may be 

 a bias in our population estimate. Incidental observations made 

 off-transect did show, however, that curlews were common in 

 the Cocos-lpomoea woodlands, and we believe that the numbers 

 on the 104 ha that compose South Island approximated our 

 estimated density (about 1.5 birds/ha). 



Bill Length : Bristle-thighed curlews show great variation 

 in bill length immediately after the breeding season. Because 

 birds of the year migrate south before their bills reach adult 

 length (R.Gill, personal communication ). the ratio of "long" to 

 "short" bills provides a rough estimate of juvenile survival. Of 

 3 1 curlews seen in September. 20 were clearly adult length. 

 7 were conspicuously shorter, and 4 were "intermediate" 

 (probably young birds). All March and May birds had long, 

 adult-sized bills. 



Some subadults also remain on their Pacific wintering 

 grounds for up to 3 years, during which time they pass through 

 a flightless phase (Gill. 1 990: Marks el ai. 1990). Noflightless 

 birds were seen. 



Foraging : We saw one curlew chase and capture a small 

 Polynesian rat at dusk on the south shore of South Island. The 

 bird bashed the rat on the coral rubble, then ran rapidly about 

 with the rat dangling from its bill. After about 5 minutes, the 

 bird swallowed the rat with vigorous gulps. 



Polynesian rats, abundant on Caroline (especially in 

 Pisonia- and Cocas-dominated habitats), remain within the 

 forest during the day. but many move to the beach crest and tide 

 line at dusk. They provide abundant potential prey for curlews, 

 which can easily capture them on the open rubble. The 

 synchronous appearance of rats and curlews at the beach- 

 woodland interface at dusk may be part of the foraging strategy 

 of this large shorebird. The presence of curlews beneath the 

 forest canopy may also be partly associated w ith this source of 

 food. 



Sanderling (Crocethia alba) 



One sanderling in winter plumage was seen at water's 

 edge on the windward beach of Long Island on 27 September 

 1988. Although Sanderlings arc well-known fall migrants in 

 the Line and Phoenix Islands (Clapp & Sibley. 1967, 1968), 

 this is the first record for Caroline Atoll. 



148 



