Movement Patterns ofHawaiian Petrels and Newell's Sheatwaters on the Island ofHawai'i1 Robert H. Day, 2 Brian A. Cooper, 3 and Richard]. Blaha3 Abstract: We studied movements and distribution and abundance of endan­ gered Hawaiian Petrels ('Ua'u [Pterodroma sandwichensis Ridgway]) and threat­ ened Newell's Shearwaters ('A'o [Puffinus auricularis newelli Henshaw]) on the island of Hawai'i in May-June 2001 and 2002. We recorded radar targets of either species at 14 of the 18 sites but recorded no birds visually at any site. Movement rates of petrels and shearwaters were very low (0-3.2 targets per hour) over all except one of the sites (Waipi'o Valley: 25.8 targets per hour). We saw radar targets moving from shortly after sunset throughout the rest of the sampling, suggesting that both petrels and shearwaters were present. Highest movement rates occurred 1-2 hr after sunset, when primarily Newell's Shear­ waters are flying. Timing of evening movements suggests that Hawaiian Petrels fly over the northern and southern parts of the island and may dominate on Mauna Loa and Mauna Kea. In contrast, timing suggests that Newell's Shear­ waters fly over essentially the entire island (except in the southwestern part, where no birds appear to occur), dominate numerically in the Kohala Moun­ tains, and occur in low numbers on Mauna Loa, in the Puna District, and on the northern slopes of Mauna Kea. Evening flight directions were predominantly inland at all sites except four. The limited radar data suggest that a substantial population change did not occur in the Puna District from 1995 to 2001-2002. WITH THE EXCEPTION of the island of dearth of basic biological information is due Kaua'i, little information is available on primarily to these birds' nocturnal habits and the distribution, abundance, and population the inaccessibility of their remote, mountain­ trends of the endangered Hawaiian Petrel ous nesting colonies. Obtaining accurate in­ ('Ua'u [Pterodroma sandwichensis Ridgway]) formation on distribution, abundance, and and the threatened Newell's (Townsend's) population trends is an objective of the Re­ Shearwater ('A'o [Puffinus auricularis newelli covery Plan for both species (USFWS 1983) Henshaw]) in the Hawaiian Islands. This and is especially important because of the re­ cent, precipitous declines of Newell's Shear­ waters on Kaua'i: in 2001, the number of shearwaters and petrels recorded on ornitho­ I The u.s. Fish and Wildlife Service, Pacific Islands Ecoregion, Honolulu, funded the 2001 research, and the logical radar around this island averaged only U.S. Coast Guard, Civil Engineering Unit, Honolulu, 38-40% of that recorded in June 1993 (Day funded the 2002 research. Manuscript accepted 14 Au­ et al., in press). gust 2002. The Hawaiian Petrel formerly was com­ 2 AER, Inc.-Environmental Research & Services, mon on the island of Hawai'i (Wilson and P.O. Box 80410, Fairbanks, Alaska 99708-0410 (phone: 907-455-6777; fax: 907-455-6781; E-mail: bday@abrinc. Evans 1890-1899). This seabird reportedly com). nested in large numbers on the slopes of 3 AER, Inc.-Environmental Research & Services, Mauna Loa, in the saddle between Mauna P.O. Box 249, Forest Grove, Oregon 97116-0249. Loa and Mauna Kea, and at moderate to high elevations on Hualalai (Wilson and Evans Pacific Science (2003), vol. 57, no. 2:147-159 1890-1899, Henshaw 1902, Richardson and © 2003 by University of Hawai'i Press Woodside 1954). For example, Munro saw All rights reserved one on the ground in 1891 at ~1370 m 147 148 PACIFIC SCIENCE· April 2003 (4500 ft) in Honaunau, Kona District (Banko (Sincock and Swedberg 1969, USFWS 1983, 1980a). The Hawaiian Petrel was a food Simons 1985). A secondary threat to these source of the ancient Hawaiians, and bones two species is their grounding (either through of this species are common in middens ex­ collision or exhaustion) and subsequent mor­ cavated in numerous locations on the island tality during the annual fallout of birds, pri­ of Hawai'i (Banko 1980a). By the beginning marily juvenile Newell's Shearwaters that are of the twentieth century, however, a decline on their way to the sea for the first time in this species had been noted by local resi­ (Hadley 1961, Telfer 1979, Sincock 1981, dents, and, by the early 1940s, Munro (1960) Reed et al. 1985, Telfer et al. 1987, Cooper feared for its survival in the Hawaiian Islands. and Day 1998, Podolsky et al. 1998, Ainley et However, this species still nests in low num­ al. 2001). Predation by introduced mammals, bers at higher elevations of Mauna Loa however, is thought to be the primary cause (Simons and Hodges 1998, Hu et al. 2001), of decline ofboth species on most islands and if not elsewhere on the island. is considered to be the major threat to the The Newell's Shearwater was thought to surviving populations at this time (USFWS be extinct in the Hawaiian Islands after 1894. 1983, Simons and Hodges 1998, Ainley et al. In 1954, however, a specimen was collected 2001). on O'ahu (King and Gould 1967), and a Ornithological radar, combined with visual breeding colony was found on Kaua'i in 1967 sampling, is useful for studying the move­ (Sincock and Swedberg 1969). Newell's ments and behaviors of these two species of Shearwater also breeds on the island of Ha­ nocturnal seabirds and is especially useful in wai'i, but probably in extremely low numbers: monitoring their populations. This research a few small nesting colonies recently have tool, which has been used in the Hawaiian been found in cinder cones in the Puna Dis­ Islands since 1992, has enabled much to be trict of eastern Hawai'i (Reynolds and Ri­ learned about the basic movements, behavior, chotte 1997). This species nests primarily in distribution, and/or population trends of burrows excavated under thick vegetation, these species around Kaua'i (Cooper and Day especially uluhe fern (Dicranopteris linearis 1995,1998, Day and Cooper 1995, Day et al., [Ainley et al. 1997]). in press), Maui (Cooper and Day in press), Reasons for the declines of both species and Hawai'i (Reynolds et al. 1997; B.A.C. and are numerous. Introduced predators include R.H.D., unpubl. data). Most is known about wild pigs (Sus scrofa), Indian mongooses movements of these species on Kaua'i and (Herpestes auropunetatus), feral cats (Felis catus) Maui. and dogs (Canis familiaris), Barn Owls (Tyto Because of the recent declines of Newell's alba), Common Mynas (Acridotheres tristis) , Shearwaters on Kaua'i and the potential for and Norway (Rattus norvegicus), black (R. rat­ continued development on all of the main tus), and Polynesian (R. exulans) rats, all of Hawaiian Islands, there is a clear need for which prey on both species, their eggs, and/ basic information on the distribution, abun­ or nestlings; in addition, introduced feral dance, and movement patterns of petrels and goats (Capra hircus) trample nesting colonies, shearwaters on all of the Hawaiian Islands. and endemic Short-eared Owls (Asio flam­ This study summarizes the results of radar meus sandwichensis) kill adults (Richardson and surveys for Hawaiian Petrels and Newell's Woodside 1954, Sincock and Swedberg 1969, Shearwaters on the island of Hawai'i during Byrd 1979, Byrd and Telfer 1980, Conant May-June 2001 and 2002. 1980, Byrd and Moriarty 1981, USFWS 1983, Simons 1984, 1985, Simons and Study Area Hodges 1998, Ainley et al. 2001, Hodges and Nagata 2001). Avian malaria and avian poxvi­ Hawai'i is the largest and easternmost of the ruses from introduced birds also may have main Hawaiian Islands. It is ~130 km (~81 negatively affected populations of both spe­ miles) in an east-west direction and ~ 145 km cies, particularly in low-elevation populations (~90 miles) in a north-south direction and Seabirds on Hawai'i . Day et at. 149 has a total area of ~1O,41O km 2 (~4021 ditions (daytime, crepuscular [twilight]' dark­ square miles). The island is dominated by ness), and moon phase/presence (i.e., whether four mountains: the enormous Mauna Loa the moon was above or below the horizon). (4170 m [13,679 ft] high) in the southern part When a volunteer was available (11 of the 21 of the island, Mauna Kea (4206 m [13,796 ftl) nights), we also conducted visual sampling in the northeast, Hualalai (2522 m [8271 ftl) (lOx binoculars or 5x Noctron night-vision in the west, and the Kohala Mountains (1671 scope) for species identifications and flight m [5480 ftl) in the northwest. Mauna Loa, altitudes. Mauna Kea, and Hualalai are classic shield volcanoes, whereas the Kohala Mountains are Data Collection characterized by numerous steep valleys on their northern sides, much like northern We collected information on flying birds with Kaua'i. Habitats range from palm trees at sea a Furuno FCR-1510 MKIII (in 2001) or a level to rain forest (on windward slopes) or Furuno FCR-1411 (in 2002) surveillance ra­ xeric/mesic shrubs (on leeward slopes) at dar, which was an X-band radar transmitting moderate elevations and to snow and alpine at 9410 MHz with a peak power output of 12 vegetation near the summits of Mauna Loa kW (10 kW for the FCR-1411). The range of and Mauna Kea. this radar was set at 1.5 km (1.4 km for the FCR-1411), the pulse setting was 0.07 Ilsec (0.08 Ilsec for the FCR-1411), and the plot­ MATERIALS AND METHODS ting function was set to "continuous" (every We collected data on the movements of 15 sec for the FCR-1411). A similar surveil­ Hawaiian Petrels and Newell's Shearwaters lance radar is described in Cooper et al.