1.2 Ecological Studies on Caroline Atoll, 



Republic of Kiribati, South-central Pacific 

 Ocean 



Part 2. Seabirds, Other Terrestrial Animals, and Conservation 



CAMERON B. KEPLER . ANGELA K. KEPLER and DAVID H. ELLIS* 



' US Fish & Wildlife Service, Patuxent Wildife Research Center, Southeast Research Station. Athens, Georgia, USA 

 I S Fish & Wildlife Service. Patuxent Wildlife Research Center, Laurel, Maryland, USA 



Introduction 



On 26 July 1988. the Soviet research vessel Akademik 

 Korolev sailed from Vladivostok enroute to Dutch Harbor, 

 Alaska. There, Soviet oceanographers joined their American 

 colleagues to invest : gate the Gulf of Alaska and the Chukchi 

 Sea in the Third Joint US-USSR Bering & Chukchi Seas 

 Expedition. When the arctic research was completed in early 

 September, the ship headed toward the central Pacific. A 

 rendezvous for a second contingent of Americans took place in 

 Hilo. Hawaii, on 9 September. Six Americans joined the ship, 

 which set sail on a cruise track of 14.N42 km that terminated 



6 weeks later in Singapore. An important part of the expedition 

 was research in and around little-known Caroline Atoll, at the 

 southeastern edge of the Line Group. On Christmas Island, we 

 picked up Katino Teeb'aki, a conservation officer for the 

 Republic of Kiribati, who represented his government and 

 helped our land-based research efforts. After landing on 

 Caroline on 22 September, we camped in 2 locations for 



7 nights, surveying the terrestrial plants and animals on all 

 39 islets. Caroline is a remarkably pristine atoll with its native 

 plant communities nearly intact on all but three islets, and 

 teeming seabird communities that, collectively, are second in 

 the Line Group only to Christmas Island (Kiribati) in diversity. 

 For several historical reasons, the natural values of this 

 spectacular blend of marine and terrestrial resources have been 

 overlooked. 



Approximately 1,000. 000 seabirds of I I species bred mi 

 Caroline Atoll in November 1988. The most abundant species, 

 with over 900.000 birds in 1988. was the sooty tern (Sterna 

 fuscata). Two species (red-tailed tropicbird [Phaethon 

 rubricauda], blue-gray noddy [Procelsterna cerulea]) are 

 reported breeding for the first time. The known seabird fauna 

 now includes one tropicbird. three boobies, two frigatebirds, 

 and five terns. 



Seabird distribution on Caroline is determined by the 

 distribution of plant communities, rats, coconut crabs (Birgus 

 latro). and the prevailing trade winds. Red-tailed tropicbirds 

 and ground-nesting brown noddies (Anous stolidus) nested on 

 small islets relatively free of rats and coconut crabs, masked 

 and brown boobies (Sula leucogaster) preferred exposed 

 windward beaches, primarily on Long and Nake. The tree- 

 nesting red-footed booby (Sula sula) and the frigatebirds 



attained their highest nest densities in areas with reduced wind 

 speed. The black noddy (Anous minutus) was found in dense 

 colonies, generally high in Pisonia trees in the center of small 

 islets, while the uncommon blue-gray noddy (Procelsterna 

 cerulea) nested solitarily on open coral rubble. Sooty terns 

 nested in large colonies, generally near or under relatively open 

 Tournefortia scrub but also in open areas under Tournefortia 

 and closed-canopy P/.sy»i/« forests. Tree-nesting brown noddies 

 and white terns (Gygis alba) were found throughout the native 

 forests and were the only species that nested in anthropogenic 

 forests. Disturbed forests on South and Nake held the lowest 

 seabird population densities, and no birds nested on inhabited 

 Motu Ana-Ana. 



About 300 bristle-thighed curlews {Numenius tahitiensis). 

 a rare shorebird, overwinter on Caroline, foraging in all terrestrial 

 habitats, including Pisonia and Cocos-Ipomoea forests. We 

 extended the known winter range of the long-tailed cuckoo by 

 discovering a small population on the atoll, the first record for 

 the Southern Line Islands. 



The known lizard fauna was increased from three to six 

 species. Approximately 2.200 coconut crabs inhabited 

 12 islets on Caroline. Although primarily associated with 

 coconut plantations, we also found them in Pisonia and 

 Tournefortia. 



We now know that the populations of seabirds and coconut 

 crabs on Caroline Atoll are of national and international 

 importance. The black noddy (17,000 birds) and white tern 

 (8,000 birds) populations are the largest in the Republic of 

 Kiribati, while the red-footed booby population (7.000 birds) 

 is the fifth largest in the world. 



History of Ornithological Studies 



"There were a great quantity of seabirds of several kinds, 

 and so importunate that they seemed to want to attack the men" 

 (Markham. 1904). So wrote the Portuguese explorer deQuiros 

 on 21 February 1601, the first European to see Caroline Atoll. 



Precisely what seabirds were present remained a mystery 

 until the island was surveyed 364 years later by the Pacific 

 Ocean Biological Survey Program (POBSP) (Clapp & Sibley, 

 1971a). Prior to this expedition, accounts of the avifauna had 

 been incomplete and somewhat confused. Bennett (1840) 

 described red-footed boobies, a frigatebird (species '.'). white 



139 



