DISTKIBUTION OF THE GULLS AND TERNS. 393 



over, it seems to prey ; for Capt. H. W. Feildea found tlie bones 

 and feathers of that species in the stomachs and castings of tha 

 Skuas at the Earoes. In winter it ranges down to the Straits 

 of Gibraltar, and perhaps a little further ; and on the Pacific side 

 it has once been obtained, as recorded by Lawrence, at Monterey, 

 California. It would probably have little chance of overtaking a 

 Tern, but it is quite fast enough to tyrannize over any of the 

 smaller Gulls ; and it is interesting to observe that its range 

 coincides with the winter range of the Kittiwake. As already 

 shown, it has occurred in California ; but descending that coast, 

 we find no trace of a large Skua until we enter the fish-abounding, 

 and therefore gull-frequented, waters of Humboldt's Current, 

 which cools the coasts of Chili and Peru throughout a width of 

 about 300 miles, and sweeps outwards to diminish the natural 

 heat of the equatorial Galapagos Islands. In these productive 

 waters is found a large Skua, ^S*. cMlensis {vide P. Z. S. 1876, p. 

 323, pi. xxiv.), separable from the northern 8. catarrhactes by its 

 brighter and more chestnut underparts and axillaries — differences 

 which are constant, although it is true that they are merely those 

 of colour. Its bill is perhaps a trifle more slender than that of 

 the northern bird, a point which should be borne in mind, because 

 on passing through the Straits of Magellan, where this species 

 appears to stop, we come at once to another large Skua, S. antarc- 

 ticus, which, although in such close geographical proximity to 

 S. cMlensis, yet differs far more from it than 8. chilensis does from 

 S. catarrJiactes ! The Antarctic Skua ranges from the Palkland 

 Islands down to the edge of the pack-ice, the shores of New Zea- 

 land, and up to Norfolk Island, and thence by way of the chain of 

 Kerguelen Island, St. Paul's Island, the Crozets, &c., it reaches 

 the Cape of Good Hope and, as a straggler, Madagascar. From 

 the Cape it works round by Tristan d'Acunha and the South 

 Atlantic islands, till the chain is completed at the Ealklands again. 

 8. antarcticus is a uniformly dusky bird, with stronger and shorter 

 bill than either of its near relatives; but it is interesting to 

 observe certain slight variations in the chain even in the selfsame 

 species. The largest birds are from the Southern Ocean, between 

 New Zealand and the Cape of Good Hope, and they are also the 

 duskiest in colour ; those from the South Atlantic are smaller, and 

 have a tendency to a pale frill of acuminate feathers, similar to 

 that which is more or less marked in all the other Skuas ; whilst 

 the three individuals obtained by the ' Erebus ' and ' Terror ' 



28* 



