Status of candidate endangered bird species on Saipan, Tinian and

184

M icronesica

could be added with the continued presence of qualified observers, particularly in the Northern Marianas.

Subsequent to the completion of this study, I observed on 12 July 1979 one immature Common Ringed Plover (Charadrius hiaticula) on Agana Bay, Guam . The observation represents the first record of this species in Micronesia.

This study was supported primarily by Federal Aid to Wildlife Restoration (Pittman-Robertson Act).

References Cited Baker, R. H . 1951 . The avifauna of Micronesia, its ongm , evolution, and distribution . Univ.

Kansas Pub!. Mus. Nat. Hist. 3(1): 1- 359. du Pont, J . E. 1971 . Philippine Birds. Delaware Mus. Nat. His. Mono . Ser. (2). 480 p.

King, B. F . and E. C . Dickinson . 1975. A Field Guide to the Birds of South-east Asia . Houghton Mifflin Co ., Boston . 380 p .

Mayer, E. 1945. Birds of the Southwest Pacific.

MacMillan Co., New York. 316 p .

Owen , R . P . 1977. A checklist of the birds of Micronesia. Micronesica 13(1 ): 65- 81.

Division of Aquatic & Wildlife Resources, Department of Agriculture, Go vernment of Guam , P.O . Box 23367, GMF, Guam , M.I. 96921

other Mariana Islands. Thus, the present study wa s undertaken to determine the status of candidate endangered species on Saipan , Tinian, and Rota of the Mariana Islands.

Methods Saipan and Tinian were surveyed by two biologists on each island during the third week of January 1979; Rota was surveyed by three biologists 3- 6 April 1979. Two count techniques were employed on each island ; roadside counts and station counts. Roadside counts were conducted at dawn from vehicles traveling between 15-25 kph, primarily in areas of mature forest vegetation . The total kilometers of roadside counts for each island were as follows : Saipan, 215.4 km; Tinian , 34.6 km; Rota , 51 .5 km . Data for each island were equated by computing birds per I 00 km. Station counts were conducted in mature forest habitats and involved the recording of each individual of each species sighted or heard by a stationary observer during a 15 minute count period . Fifteen station counts were conducted on Saipan , 33 counts on Tinian and 19 counts on Rota . Following Shallenberger (1978), data were used to generate three indices of species abundance:

J. MARK JENKINS ,

Species Frequency-Number of count periods during which a species was recorded , divided by the total number of count periods.

Species In cidence-Number of birds of a species recorded , divided by the number of count periods during which the species was recorded .

STATUS OF CANDIDATE ENDANGERED BIRD SPECIES ON SAIPAN, T!NIAN AND ROTA OF THE MARIANA ISLANDS

Because of severely depleted populations and restricted ranges , ten of the native bird species of Guam have been recommended for protection under the Endangered Species Act of 1973. These include two endemic species (Rallus owstoni, M y iagra freycineti) , two endemic subspecies (Halcyon c. cinnamomia , Zosterops c. conspicillata) , and six species which occur on more than one island of the Marianas Archipelago (Gallinula chloropus guami, Gallicolumba x. xanthonura , Ptilinopus roseicapi/lus, Collocalia vanikorensis bartschi, Corvus kubary i, M yzomela cardinalis saffordi). While the status of these candidate endangered species is known on Guam, little is known about the status of the six species which occur on

Relative Abundance- The number of birds of a species recorded , divided by the number of the most abundant species recorded during the same count periods.

Findings and Recommendations The Marianas Gallinule (Gallinula chloropus guami) was not recorded on roadside or station counts during this study due to a concentration of work in forest bird habitats rather than wetlan'ds.

Generally, this species is confined to Lake Susupe on Saipan and Lake Hagoi on Tinian in addition to its Guam range. This species does not occur on Rota and its status on Pagan remains undetermined . Because of the relatively small numbers and restricted ranges exhibited by G. c. guami in the Marianas, we recommend a listing as endangered

Vol. 17. December 1981

185

Table I . Species frequency , species incidence, and relative abundance of five proposed endangered species recorded in 15 station counts on Saipan, 33 counts on Tinian, and 19 counts on Rota.

SAIPAN

White-throated Ground Dove Marianas Fruit Dove Vanikoro Swiftlet Marianas Crow Cardinal Honeyeater

TIN IAN

ROTA

S.F.

S.l.

R.A.

S.F.

S.I.

R .A.

S.F.

S.I .

R .A.

0 0.53 0.20

0 1.6 8.0

0 .03 0.06

.06 0.33 0

1.0 2.0 0

.01 0.08 0

.33

1.0

.01

.39

1.3

0.06

.21 .79 0 0.16 0.89

1.25 2.20 0 1.33 3.0

.04 0.26 0 0.03 0.41

Table 2. Number of five proposed endangered species recorded per I 00 km of travel on roadside counts conducted on Saipan, Tinian and Rota.

SAIPAN

TIN IAN

White-throated Ground Dove Gallicolumba x. xanthonura

0.9

0

1.9

Marianas Fruit Dove Ptilinopus roseicapillus

0.5

0

0

Vanikoro Swiftlet Collocalia vanikorensis

21.2

0

0

Marianas Crow Corvus kubaryi Cardinal Honeyeater Myzomela cardinalis saffordi

ROTA

13.5

3.2

throughout its range.

The White-throated Ground Dove (Gallicolumba x . xanthonura) was not recorded in station counts on Saipan , and was similarly rare on Tinian, and less so on Rota (Table 1). Roadside count data indicated a similar rarity for all three islands (Table 2). G. x . xanthonura may in fact be less abundant on the islands surveyed than on Guam. We recommend a listing of endangered on Saipan, Tinian, Rota and Guam. Populations on Asuncion, Pagan, Alamagen and Yap remain undetermined .

The Marianas Fruit Dove (Ptilinopus roseicapillus) was recorded on half of the station counts on Saipan, one-third of the counts on Tinian, and nearly 80 % of the counts on Rota (Table 1). It was, however, rarely recorded on roadside counts (Table

3.5

57.9

2). Because of this species loud penetrating calls, which may carry for half a kilometer or more, the station count technique effectively censuses a much larger area for fruit doves than for most other species. In 1945, this species was considered numerous to abundant on all islands (Marshall 1949, Baker 1951 ), and data from the present study must therefore be interpreted as representing a general decline for the species. We recommend the following listing: endangered on Guam, threatened on Saipan and Tinian, no listing of the Rota population.

The Yanik oro Swiftlet (Collocalia vanikorensis bartschi) was not recorded on station or roadside counts on Tinian or Rota, but small numbers were recorded on Saipan (Tables I and 2). In view of the

Micronesica

\86

rarity of the species on Guam, C . v. bartschi must be considered one of the most critically endangered species in the Marianas, and we therefore recommend a listing of endangered throughout its range .

The Marianas Crow (Cor vus kubary i) , known only from Guam and Rota , was recorded in only 16 % of the station counts on Rota (Table 1), despite the species' loud, " squawking" calls. It was recorded slightly more frequently on roadside counts (Table 2). The species is best considered uncommon on Rota and rare on Guam, with perhaps less than 300 of these birds left in the world .

We recommend a listing of endangered throughout its range .

The Cardinal Honeyeater (Myzomela cm路dinalis sajfordi) was uncommon on Saipan and Tinian, yet abundant on Rota (Tables I and 2). We recommend the following listings: Endangered on Guam, threatened on Saipan and Tinian, with no listing of the Rota population . Populations on Agiguan, Alamagan , Pagan, Agrihan, and Asuncion remain undetermined .

This study was supported by Federal Aid to Wildlife Restoration (Pittman-Robertson Act, 1937) and was greatly assisted by the cooperation of the Commonwealth of the Northern Marianas.

References Cited Baker, R . H. 1951. The avifauna of Micronesia, its ongm , evolution, and distribution . Univ.

Kansas Pub!. Mus. Nat. Hist. 3(1): 1- 359.

Marshall , J. T. 1949. The endemic avifauna of Saipan , Tinian, Guam and Palau . Condor 51 : 200-221.

Shallenberger, R . J . 1978. Avifauna( survey in the central Ko'olau Range , O'ahu . Ahuimanu Productions. Unpublished. 104 p .

J. MARK JENKINS and C ELESTINO F . AGUON , Division of Aquatic & Wildlife Resources, Department of Agriculture, Government of Guam , P.O . Box 23367, GMF, Guam , M.I. 96921

N Ew BIRD RECORDS FOR MICRONESIA Most of the following are sight records, and as a result, have been screened carefully. We give a brief description of the conditions of the sighting, and note field characters for those species more difficult to identify. Three of the records are represented by collected specimens. These records are by

no means a product of the authors only, but derive from a number of observers in a variety of locations. Due credit should be given to all who assisted . Contributors to the text include Paul Anderson , Pamela and Keith Axelson , Greg Bright, Keith Guthrie, and Warren King. Numerous other observers aided in pointing out new birds or confirming identification of birds.

These include Robert Brownell, Phil Bruner, John Kochi , Douglas Pratt, Dennis Puleston, Thomas Ritchie, Takesi Suzuki , and Sabino Zacharias. Their help was greatly appreciated.

Birds Previously Unrecorded from Micronesia

Pelecanus conspicillatus- A USTRA LIAN PELICAN The most dramatic new record for Micronesia was the arrival in Palau of 50 to l 00 of these birds in mid-July 1978 . Individuals, small groups, and large flocks (up to 52 birds) were reported from all parts of the Palau Archipelago. A wounded bird that eventually died was collected on 27 July 1978.

The skin was identified and filed at the National Museum of Natural History under catalog number USNM 571157. The species is a resident in Australia and normally sedentary, but strays have been recorded from New Guinea, New Zealand , the Solomon Islands, Fiji Islands and Indonesia.

The distance from Australia to Palau, over 1800 km , is one of the greatest the bird has been known to wander. Of the large number that arrived in Palau, only four wild birds remained as of February 1979. The remainder of the flock departed of their own accord , were taken for pets, or were killed .

Haliastur indus- BRAHMINY KITE One bird observed on 29 November 1977 in the Seventy Island Group , Palau (P. Anderson, R. Brownell, and J . Kochi). The bird was an adult, and was flying in an enclosed bay at a distance of approximately 200m from the observers. Several noddy terns pursued and dived at it repeatedly as it skirted the forested edge of an island and disappeared from sight. The white head and breast, and russet back and wings were clearly visible, both with the naked eye and with binoculars, and the shape and manner of flight clearly identified the bird as an accipitrid . The individual seen in Palau was probably a stray from the Philippines or New Guinea, where the kite is resident.