Part 12

Only a few birds have been banded in the Pacific, and the knowledge which comes from the recovery of banded birds gives but little aid to the student of movements of birds in the Pacific. The probable flyways for migratory shore birds there have to be deduced from sight records, data from specimens collected, known stations of breeding and wintering (summarized by Peters, 1934:234-293), and from a study of maps of the region. Analysis of information from the above-mentioned sources indicates that there are three routes taken by shore birds which migrate from Micronesia to and from their northern breeding grounds (see figure 6): (1) Asiatic-Palauan Flyway; (2) Japanese-Marianan Flyway; (3) Nearctic-Hawaiian Flyway.

1. ASIATIC-PALAUAN FLYWAY. For shore birds, there appears to be a migration route extending almost due south from the Riu Kiu and the Japanese islands to the Palau Islands. Some birds may migrate via the Philippines and others may pass to the east of the Philippines. This route is considered to be distinct from that used by birds which follow the Asiatic Coast and coastal islands, because the Palau Islands are situated approximately 600 miles east of the Philippines. Moreover, there are fewer species--only 20 recorded from the Palaus as compared with the number recorded from islands closer to the mainland of Asia. Delacour and Mayr (1946:68-74) list 46 species of shore birds from the Philippines; the Hand-list of Japanese Birds (Hachisuka et al, 1942) lists 34 species from the Riu Kiu Islands.

The information available indicates that migrant shore birds which utilize this flyway move east into the Carolines (examples, Tringa nebularia, Charadrius leschenaultii); however, the recording of 20 species from the Palaus as compared with only 12 species in the western Carolines (table 4) indicates that this spread eastward may not be very pronounced. Migrants in autumn probably move from the Palaus in a southerly direction toward the New Guinea area. Eight species of shore birds which reach the Palaus (and adjacent islands in the western Carolines), are not recorded from other parts of Micronesia. Species which apparently utilize the Asiatic-Palauan Flyway are listed in table 5.

2. JAPANESE-MARIANAN FLYWAY. Shore birds from Asiatic, and probably Aleutian and Alaskan, breeding grounds may follow the Asiatic Coast or the adjacent island chains southeast to the Japanese Archipelago. From there some of the birds apparently fly south through the Bonin and Volcano islands to the Marianas, from where they may spread in fanlike fashion to the southeast, south and southwest, even reaching to the Palau Islands (example, Heteroscelus incanus). The number of species of shore birds recorded from the Marianas (see table 4) is greater than that found in the Carolines, but it must be remembered that more intensive investigations have been made by ornithologists in the Marianas, which might account for the recording of more species (especially stragglers, such as Gallinago gallinago). Species which apparently use this flyway are named in table 6.

3. NEARCTIC-HAWAIIAN FLYWAY. Shore birds from breeding grounds in western Canada, Alaska, the Aleutians, the Bering Sea area, and probably northeastern Asia may fly in a southerly direction along a broad front to the Hawaiian Islands. This flyway is probably the one which supplies to central and eastern Oceania the largest wintering populations of shore birds. From the Hawaiian Islands birds may fly directly south through the scattered islands to southern Polynesia, or they may fly in a southwesterly direction and reach the Marshall Islands. The shore birds which visit the Marshall Islands apparently move south through the Gilbert, Ellice and other more southern island groups rather than west into the Carolines as exemplified by the fact that Numenius tahitiensis, a characteristic migrant through the Marshalls from the Hawaiian Islands, is rarely found west of the Marshall Islands in Micronesia. Species which apparently use this flyway are listed in table 7.

Flyways additional to the three suggested above may be utilized by some shore birds on their southward (and northward) migrations. Species reaching Wake and the Marcus Islands may fly directly south from the islands of the North Pacific. Bryan (1903:115, 116) lists four species of shore birds from Marcus (Erolia acuminata, Heteroscelus incanus, Pluvialis dominica, Arenaria interpres).

TABLE 4. LIST OF SPECIES OF SHORE BIRDS KNOWN FROM FIVE GEOGRAPHICAL AREAS OF MICRONESIA

Western Central Eastern Palaus Carolines Marianas Carolines Carolines Marshalls

Number of species 20 12 17 11 10 10

TABLE 5. SHORE BIRDS WHICH MAY USE THE ASIATIC-PALAUAN FLYWAY

Regular Visitors Uncommon? Visitors

Pluvialis dominica fulva Charadrius dubius curonicus Charadrius mongolus stegmanni Charadrius alexandrinus Charadrius leschenaultii Calidris tenuirostris Numenius phaeopus variegatus Erolia ferruginea Numenius madagascariensis Erolia subminuta Limosa lapponica baueri Limicola falcinellus sibirica Tringa nebularia Tringa glareola Actitis hypoleucos Heteroscelus brevipes Arenaria i. interpres Gallinago megala Erolia minuta ruficollis

TABLE 6. SHORE BIRDS WHICH MAY USE THE JAPANESE-MARIANAN FLYWAY

Regular Visitors Uncommon? Visitors

Pluvialis dominica fulva Squatarola squatarola Charadrius mongolus stegmanni Numenius tahitiensis Numenius phaeopus variegatus Numenius madagascariensis Limosa lapponica baueri Tringa glareola Actitis hypoleucos Gallinago gallinago gallinago Heteroscelus brevipes Erolia minuta ruficollis Heteroscelus incanus Arenaria i. interpres Gallinago megala Crocethia alba Erolia acuminata

TABLE 7. SHORE BIRDS WHICH MAY USE THE NEARCTIC-HAWAIIAN FLYWAY

Regular Visitors Uncommon? Visitors

Pluvialis dominica fulva* Squatarola squatarola* Numenius tahitiensis* Charadrius hiaticula semipalmatus[+] Heteroscelus incanus* Charadrius v. vociferus Arenaria i. interpres* Limosa lapponica baueri* Crocethia alba* Tringa melanoleuca*[+] Phalaropus fulicarius Gallinago delicata Phalaropus lobatus*? Erolia melanotos* Erolia acuminata*

* Indicates species which are found in Micronesia.]

POPULATIONS OF SHORE BIRDS IN MICRONESIA

Although shore birds have been observed in Micronesia on many occasions, actual counts of numbers of individuals of the different birds have rarely been made. Kubary, Finsch, Marche, Seale and other early collectors and observers record some data of this kind as have the Japanese investigators in later times. William Coultas of the Whitney South Sea Expedition obtained considerable information of this nature at Guam, Saipan, Kusiae, Ponapé, and the Palaus, but it is unpublished. His records were made in fall, winter and spring, when migrants were present in large numbers and these observations offer evidence that many of the migrants are comparatively numerous, especially in the Carolines, throughout the winter months. McElroy's observations made on his trip for NAMRU2 to Truk in December, 1945, offer further evidence of this.

TABLE 8. POPULATIONS OF MIGRATORY SHORE BIRDS SEEN AT GUAM IN 1945

Column headings:

A: Pluvialis dominica B: Charadrius mongolus C: Numenius phaeopus D: Actitis hypoleucos E: Heteroscelus spp. F: Heteroscelus incanus[+] G: Heteroscelus brevipes[+] H: Limosa lapponica I: Arenaria interpres J: Unidentified K: Total No. of individuals L: Total No. of species

=============+====+====+====+====+====+====+====+====+====+====+====+==== | A | B | C | D | E | F | G | H | I | J | K | L -------------+----+----+----+----+----+----+----+----+----+----+----+---- March 11 | x | | | | | | | | | | x | 1 March 17 | 10 | | 1 | | 2 | | | | | | 13 | 3 March 19 | x | | x | | x | | | | x | | x | 5 April 24 | x | | | | | | | | | | x | 1 April 26 | | | | | | | | 1 | | | 1 | 1 May 19 | | | | | 3 | 2 | | | | | 5 | 1 May 21 | | | | | 4 | | | | | | 4 | 1 May 26 | | | | | x | 2 | | | | | x | 1 June 1 | | | 1 | | | | | | | | 1 | 1 June 6* | | 1 | x | | x | | 1 | | | x | x | 4 June 11 | | | 1 | | | | | | | | 1 | 1 June 12 | | | 12 | | 2 | | | | | | 14 | 2 June 22 | | | 2 | | | | | | | 1 | 3 | 2 June 30 | | | | | | | | | | 2 | 2 | 1 July 7 | | | 2 | | | | | | | | 2 | 1 July 8 | 3 | | x | | 1 | | | | | | x | 3 July 16* | 6 | | 3 | 3 | 4 | | 1 | | | | 17 | 4 July 19 | x | | x | | x | | | | | | x | 3 July 24* | 10 | | 6 | | 3 | | 2 | | 3 | 5 | 29 | 5 July 26 | | | 8 | | | | | | | | 8 | 1 August 2 | | | x | | | | | | | x | x | 2 August 3 | | | 1 | | | | | | | | 1 | 1 August 6* | | | 6 | | 12 | | | | | | 18 | 2 September 29 | x | | x | | | | | | x | | x | 2 October 3* | x | | | | x | | | | | | x | 2 October 10 | x | | x | | x | 2 | | | x | | x | 4 October 11 | | | | | | | | | 2 | | 2 | 1 October 23* | x | | x | | x | 1 | 1 | | x | | x | 5 October 24 | x | | | | | | | | | | x | 1 -------------+----+----+----+----+----+----+----+----+----+----+----+----

x Observed but numbers not recorded.

* Observations made on beach at Agfayan Bay area.

None of the above workers, however, obtained very much information on comparative numbers of species.