Island Life Part 13

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CHAPTER XV

THE SANDWICH ISLANDS

Position and Physical Features--Zoology of the Sandwich Islands--Birds--Reptiles--Land-sh.e.l.ls--Insects--Vegetation of the Sandwich Islands--Peculiar Features of the Hawaiian Flora--Antiquity of the Hawaiian Fauna and Flora--Concluding Observations on the Fauna and Flora of the Sandwich Islands--General Remarks on Oceanic Islands.

The Sandwich Islands are an extensive group of large islands situated in the centre of the North Pacific, being 2,350 miles from the nearest part of the American coast--the bay of San Francisco, and about the same distance from the Marquesas and the Samoa Islands to the south, and the Aleutian Islands a little west of north. They are, therefore, wonderfully isolated in mid-ocean, and are only connected with the other Pacific Islands by widely scattered coral reefs and atolls, the nearest of which, however, are six or seven hundred miles distant, and are all nearly dest.i.tute of animal or vegetable life. The group consists of seven large inhabited islands besides four rocky islets; the largest, Hawaii, being seventy miles across and having an area 3,800 square miles--being somewhat larger than all the other islands together. A better conception of this large island will be formed by comparing it with Devonshire, with which it closely agrees both in size and shape, though its enormous volcanic mountains rise to nearly 14,000 feet high. {311} Three of the smaller islands are each about the size of Hertfordshire or Bedfordshire, and the whole group stretches from north-west to south-east for a distance of about 350 miles. Though so extensive, the entire archipelago is volcanic, and the largest island is rendered sterile and comparatively uninhabitable by its three active volcanoes and their widespread deposits of lava.

[Ill.u.s.tration: MAP OF THE SANDWICH ISLANDS.]

The light tint shows where the sea is less than 1,000 fathoms deep.

The figures show the depth in fathoms.

The ocean depths by which these islands are separated from the nearest continents are enormous. North, east, and south, soundings have been obtained a little over or under three thousand fathoms, and these profound deeps extend over a large part of the North Pacific. We may {312} be quite sure, therefore, that the Sandwich Islands have, during their whole existence, been as completely severed from the great continents as they are now; but on the west and south there is a possibility of more extensive islands having existed, serving as stepping-stones to the island groups of the Mid-Pacific. This is indicated by a few widely-scattered coral islets, around which extend {313} considerable areas of less depth, varying from two hundred to a thousand fathoms, and which _may_ therefore indicate the sites of submerged islands of considerable extent. When we consider that east of New Zealand and New Caledonia, all the larger and loftier islands are of volcanic origin, with no trace of any ancient stratified rocks (except, perhaps, in the Marquesas, where, according to Jules Marcou, granite and gneiss are said to occur) it seems probable that the innumerable coral-reefs and atolls, which occur in groups on deeply submerged banks, mark the sites of bygone volcanic islands, similar to those which now exist, but which, after becoming extinct, have been lowered or destroyed by denudation, and finally have altogether disappeared except where their sites are indicated by the upward-growing coral-reefs. If this view is correct we should give up all idea of there ever having been a Pacific continent, but should look upon that vast ocean as having from the remotest geological epochs been the seat of volcanic forces, which from its profound depths have gradually built up the islands which now dot its surface, as well as many others which have sunk beneath its waves. The number of islands, as well as the total quant.i.ty of land-surface, may sometimes have been greater than it is now, and may thus have facilitated the transfer of organisms from one group to another, and more rarely even from the American, Asiatic, or Australian continents. Keeping these various facts and considerations in view, we may now proceed to examine the fauna and flora of the Sandwich Islands, and discuss the special phenomena they present.

[Ill.u.s.tration: MAP OF THE NORTH PACIFIC WITH ITS SUBMERGED BANKS.]

The light tint shows where the sea is less than 1,000 fathoms deep.

The dark tint ,, ,, ,, more than 1,000 fathoms deep.

The figures show the depths in fathoms.

_Zoology of the Sandwich Islands: Birds._--It need hardly be said that indigenous mammalia are quite unknown in the Sandwich Islands, the most interesting of the higher animals being the birds, which are tolerably numerous and highly peculiar. Many aquatic and wading birds which range over the whole Pacific visit these islands, twenty-five species having been observed, but even of these six are peculiar--a coot, _Fulica alai_; a moorhen, _Gallinula galeata_ var _sandvichensis_; a rail with rudimentary wings, _Pennula millei_; a stilt-plover, _Himantopus knudseni_; and {314} two ducks, _Anas Wyvilliana_ and _Bernicla sandvichensis_. The birds of prey are also great wanderers. Four have been found in the islands--the short-eared owl, _Otus brachyotus_, which ranges over the greater part of the globe, but is here said to resemble the variety found in Chile and the Galapagos; the barn owl, _Strix flammea_, of a variety common in the Pacific; a peculiar sparrow-hawk, _Accipiter hawaii_; and _Buteo solitarius_, a buzzard of a peculiar species, and coloured so as to resemble a hawk of the American subfamily Polyborinae. It is to be noted that the genus Buteo abounds in America, but is not found in the Pacific; and this fact, combined with the remarkable colouration, renders it almost certain that this peculiar species is of American origin.

The Pa.s.seres, or true perching birds, are especially interesting, being all of peculiar species, and, all but one, belonging to peculiar genera. Their numbers have been greatly increased since the first edition of this work appeared, partly by the exertions of American naturalists, and very largely by the researches of Mr. Scott B. Wilson, who visited the Sandwich Islands for the purpose of investigating their ornithology, and collected a.s.siduously in the various islands of the group for a year and a half. This gentleman is now publishing a finely ill.u.s.trated work on Hawaiian birds, and he has kindly furnished me with the following list.

Pa.s.sERES OF THE SANDWICH ISLANDS.

MUSCICAPIDae (Flycatchers).

1. _Chasiempis ridgwayi_ Hawaii.

2. ,, _sclateri_ Kauai.

3. ,, _dolei_ Kauai.

4. ,, _gayi_ Oahu.

5. ,, _ibidis_ Oahu.

6. _Phaeornis obscura_ Hawaii.

7. ,, _myadestina_ Kauai.

MELIPHAGIDae (Honeysuckers).

8. _Acrulocercus n.o.bilis_ Hawaii.

9. ,, _braccalus_ Kauai.

10. ,, _apicalis_ (extinct) Oahu or Maui.

11. _Chaetoptila angustipluma_ (extinct) Hawaii.

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DREPANIDIDae.

12. _Drepanis pacifica_ (extinct) Hawaii.

13. _Vastiaria coccinea_ All the Islands.

14. _Hiniatione vireus_ Hawaii.

15. ,, _dolii_ Maui.

16. ,, _sanguinea_ All the Islands.

17. ,, _montana_ Lanai.

18. ,, _chloris_ Oahu.

19. ,, _maculata_ Oahu.

20. ,, _parva_ Kauai.

21. ,, _stejnegeri_ Kauai.

22. _Oreomyza bairdi_ Kauai.

23. _Hemignathus obscurus_ Hawaii.

24. ,, _olivaceus_ Hawaii.

25. ,, _lichtensteini_ Oahu.

26. ,, _lucidus_ Oahu.

27. ,, _stejnegeri_ Kauai.

28. ,, _hanapepe_ Kauai.

29. _Loxops coccinea_ Hawaii.

30. ,, _flammea_ Molokai.

31. ,, _aurea_ Maui.

32. _Chrysomitridops coeruleorostris_ Kaui.

33. ,, _anna_ (extinct)

FRINGILLIDae (Finches).

34. _Loxioides bailleni_ Hawaii.

35. _Psittirostra psittacea_ All the Islands.

36. _Chloridops kona_ Hawaii.

CORVIDae (Crows).

37. _Corvus hawaiiensis_ Hawaii.

Many of the birds recently described are representative forms found in the several islands of the group.

Taking the above in the order here given, we have, first, two peculiar genera of true flycatchers, a family confined to the Old World, but extending over the Pacific as far as the Marquesas Islands. Next we have two peculiar genera (with four species) of honeysuckers, a family confined to the Australian region, and also ranging over all the Pacific Islands to the Marquesas. We now come to the most important group of birds in the Sandwich Islands, comprising seven or eight peculiar genera, and twenty-two species which are believed to form a peculiar family allied to the Oriental flower-p.e.c.k.e.rs (Diceidae), and perhaps remotely to the American greenlets (Vireonidae), or {316} tanagers (Tanagridae). They possess singularly varied beaks, some having this organ much thickened like those of finches, to which family some of them have been supposed to belong. In any case they form a most peculiar group, and cannot be a.s.sociated with any other known birds. The last species, and the only one not belonging to a peculiar genus, is the Hawaiian crow, belonging to the almost universally distributed genus Corvus.

On the whole, the affinities of these birds are, as might be expected, chiefly with Australia and the Pacific Islands; but they exhibit in the buzzard, one of the owls, and perhaps in some of the Drepanididae, slight indications of very rare or very remote communication with America. The amount of speciality is, however, wonderful, far exceeding that of any other islands; the only approach to it being made by New Zealand and Madagascar, which have a much more varied bird fauna and a smaller _proportionate_ number of peculiar genera. The Galapagos, among the true oceanic islands, while presenting many peculiarities have only four out of the ten genera of Pa.s.seres peculiar. These facts undoubtedly indicate an immense antiquity for this group of islands, or the vicinity of some very ancient land (now submerged), from which some portion of their peculiar fauna might be derived. For further details as to the affinities and geographical distribution of the genera and species, the reader must consult Mr. Scott Wilson's work _The Birds of the Sandwich Islands_, already alluded to.

_Reptiles._--The only other vertebrate animals are two lizards. One of these is a very widespread species, _Ablepharus poecilopleurus_, ranging from the Pacific Islands to West Africa. The other is said to form a peculiar genus of geckoes, but both its locality and affinities appear to be somewhat doubtful.

_Land-sh.e.l.ls._--The only other group of animals which has been carefully studied, and which presents features of especial interest, are the land-sh.e.l.ls. These are very numerous, about thirty genera, and between three and four hundred species having been described; and it is remarkable that this single group contains as many species of {317} land-sh.e.l.ls as all the other Polynesian Islands from the Pelew Islands and Samoa to the Marquesas. All the species are peculiar, and about three-fourths of the whole belong to peculiar genera, fourteen of which const.i.tute the subfamily Achatinellinae, entirely confined to this group of islands and const.i.tuting its most distinguishing feature. Thirteen genera (comprising sixty-four species) are found also in the other Polynesian Islands, but three genera of Auriculidae (Plecotrema, Pedipes, and Blauneria) are not found in the Pacific, but inhabit--the former genus Australia, China, Bourbon, and Cuba, the two latter the West Indian Islands. Another remarkable peculiarity of these islands is the small number of Operculata, which are represented by only one genus and five species, while the other Pacific Islands have twenty genera and 115 species, or more than half the number of the Inoperculata. This difference is so remarkable that it is worth stating in a comparative form:--

Inoperculata. Operculata. Auriculidae.

Sandwich Islands 332 5 9 Rest of Pacific Islands 200 115 16

When we remember that in the West Indian Islands the Operculata abound in a greater proportion than even in the Pacific Islands generally, we are led to the conclusion that limestone, which is plentiful in both these areas, is especially favourable to them, while the purely volcanic rocks are especially unfavourable. The other peculiarities of the Sandwich Islands, however, such as the enormous preponderance of the strictly endemic Achatinellinae, and the presence of genera which occur elsewhere only beyond the Pacific area in various parts of the great continents, undoubtedly point to a very remote origin, at a time when the distribution of many of the groups of mollusca was very different from that which now prevails.

A very interesting feature of the Sandwich group is the extent to which the species and even the genera are confined to separate islands. Thus the genera Carelia and Catinella with eight species are peculiar to the island of Kaui; Bulimella, Apex, Frickella, and Blauneria, to Oahu; Perdicella to Maui; and Eburnella to Lanai. {318} The Rev. John T. Gulick, who has made a special study of the Achatinellinae, informs us that the average range of the species in this sub-family is five or six miles, while some are restricted to but one or two square miles, and only very few have the range of a whole island. Each valley, and often each side of a valley, and sometimes even every ridge and peak possesses its peculiar species.[73] The island of Oahu, in which the capital is situated, has furnished about half the species already known. This is partly due to its being more forest-clad, but also, no doubt, in part to its being better explored, so that notwithstanding the exceptional riches of the group, we have no reason to suppose that there are not many more species to be found in the less explored islands. Mr. Gulick tells us that the forest region that covers one of the mountain ranges of Oahu is about forty miles in length, and five or six miles in width, yet this small territory furnishes about 175 species of Achatinellidae, represented by 700 or 800 varieties. The most important peculiar genus, not belonging to the Achatinella group, is Carelia, with six species and several named varieties, all peculiar to Kaui, the most westerly of the large islands. This would seem to show that the small islets stretching westward, and situated on an extensive bank with less than a thousand fathoms of water over it, may indicate the position of a large submerged island whence some portion of the Sandwich Island fauna was derived.