6. The Patagonian Subregion, consisting of Antarctic America up to the Brazilian wood-districts and the highlands of Bolivia on the eastern side of the Andes, and apparently extending as far as the Gulf of Guayaquil on the west.
It is, of course, impossible to draw a precise line between these six Subregions, and any boundaries assigned to them can only be regarded as approximative; but it is obvious that nearly, if not quite, the whole of the Argentine Republic, the Avifauna of which we are now considering, comes within the limits of the Patagonian Subregion. It is possible that the birds of the Territory of Misiones and of some parts of Northern Corrientes may be more nearly akin to those of Brazil, but we may say generally that the Argentine Republic belongs to the Patagonian Subregion.
As shown in the succeeding pages, the number of species of Birds as yet ascertained to be found within the Argentine Republic[2] is about 430. We will now take the leading groups of the Neotropical Ornis, one after another, and consider the rôle they play in the Argentine Avifauna, so as to get some general ideas as to its peculiarities.
The subjoined Table contains in the first column the number of Neotropical species assigned to each of the 20 different Orders of Birds in the ‘Nomenclator Avium Neotropicalium.’ In the second column is given the corresponding number of Argentine species of each order according to the present work. The total number of Neotropical species will be seen to be about eight times as many as those of the Argentine Avifauna; so that where this average is exceeded in the individual orders the particular group may be considered to be over-represented, and where it is not reached to be under-represented in the Argentine Avifauna. This is of course a very rough-and-ready mode of calculation, because it assumes that every species has an equal area of distribution, which is not ordinarily the case; but it will serve to give us some general ideas on the subject. We will now proceed to consider the principal groups one after another, and to point out their comparative importance in the Argentine Avifauna.
The known Argentine Passeres, according to the present work, are 229 in number; those of the Neotropical Region, according to the ‘Nomenclator,’ are 1976; so that the species of Argentine Passeres, according to the ratio which we have adopted, would be very little short of the average numbers. If, however, we divide the Passeres up into the three suborders of Oscines, Oligomyodæ, and Tracheophonæ, we shall find that the Oligomyodæ are rather in excess of the estimated average, while the species of the two other groups are deficient. This arises mainly from the large number of Tyrannidæ belonging to the Argentine Ornis. Not less than 63 species of this group have been already discovered within its limits. Besides Tyrants, other prevailing families of Passeres in the Argentine Avifauna are the Finches (Fringillidæ) and the Wood-hewers (Dendrocolaptidæ), both of which have 46 representatives in the Argentine Republic. Both these families are, however, well represented all over the Neotropical Region. But the Tapacolas (Pteroptochidæ) and the Plant-cutters (Phytotomidæ) are both of them families specially characteristic of the Patagonian Avifauna, and both of them are represented in the Argentine Republic. One other Passerine form is also worthy of special mention. The Dippers (Cinclidæ) are essentially an Arctic group diffused all over the Palæarctic and the Arctic Regions. It is singular, however, that this form should reoccur at higher elevations in the Neotropical Region. A Cinclus is found in the mountains of Colombia, another in the Andes of Peru, and a third has lately been discovered in the northern sierras of the Argentine Republic. As regards Passerine birds, therefore, which great order makes up more than one half of the Argentine Ornis, we may say that Finches, Tyrants, and Wood-hewers are remarkable for their abundance, Plant-cutters and Tapacolas for peculiarity of type, and Dippers as an instance of the occurrence of an Arctic form in Antarctic latitudes.
| I. No. of Neotropical Species. | II. No. of Argentine Species. | III. Proportion. | ||
|---|---|---|---|---|
| I. | Passeres. | |||
| Oscines | 1049 | 108 | – | |
| Oligomyodæ | 445 | 67 | + | |
| Tracheophonæ | 482 | 54 | – | |
| II. | Macrochires | 444 | 18 | – – |
| III. | Pici | 116 | 13 | – |
| IV. | Coccyges | 214 | 15 | – |
| V. | Psittaci | 142 | 10 | – |
| VI. | Striges | 37 | 6 | + |
| VII. | Accipitres | 114 | 22 | + |
| VIII. | Steganopodes | 17 | 1 | – |
| IX. | Herodiones | 44 | 19 | + |
| X. | Anseres | 64 | 23 | ++ |
| XI. | Columbæ | 66 | 8 | = |
| XII. | Gallinæ | 90 | 4 | – |
| XIII. | Opisthocomi | 1 | 0 | |
| XIV. | Geranomorphæ | 57 | 16 | ++ |
| XV. | Limicolæ | 73 | 25 | ++ |
| XVI. | Gaviæ | 53 | 9 | + |
| XVII. | Pygopodes | 9 | 5 | + |
| XVIII. | Impennes | 9 | 1 | = |
| XIX. | Crypturi | 36 | 8 | + |
| XX. | Struthiones | 3 | 2 | + |
| 3565 | 434 | |||
As regards the second order, Macrochires, the Argentine Avifauna is notably deficient on account of the comparative scarcity of Humming-birds. Although eleven species of this remarkable group have been met with within our limits, the great mass of the Trochilidæ, which are now known to number some 400 species, belong to the Tropics. The Swifts are also scantily represented by a single species. The Caprimulgidæ are comparatively more abundant, but slightly below the average in number of species.
The Argentine Woodpeckers enumerated in the present work are thirteen in number, but several of those are somewhat doubtful species, and others only occur in the extreme northern limits of the Republic. On the whole we may say that the Pici are decidedly deficient in Argentina.
Nine families of the fourth order, Coccyges, are included in the Neotropical Avifauna, but of these only five are represented in the Argentine Ornis—the Motmots, Todies, Jacamars, and Barbets being entirely wanting. The Trogons, Puff-birds, and Toucans are also essentially Tropical forms, and have but one or two representatives on the northern outskirts of the Republic; so that the Cuckoos and Kingfishers are the only two families of Coccyges which play any material rôle in the Argentine Ornis.
Of the order of Parrots it will be seen from our Table that 142 species are known as belonging to the Neotropical Region, and that only ten of these have been met with within our limits. Of these ten, moreover, several are either doubtful, or only occur on the northern outskirts of Argentina, so that Parrots must be held to be deficient in the Argentine Ornis. As is well known Parrots are mostly inhabitants of the Tropics, and it is quite an exception to the rule that several of these warmth-loving birds should extend into the cold latitudes of Patagonia and Chili. This, however, is paralleled in the Old World by the existence of Parrots in some of the Antarctic Islands south of New Zealand.